Grobner bases, local cohomology and reduction number

生物多样性　1997,5(3):161～167CHIN ESE BIODIV ERSIT Y群落内物种多样性发生与维持的一个假说3张大勇　姜新华(兰州大学生物系干旱农业生态国家重点实验室,　兰州　730000)摘　要　本文根据作者对竞争排除法则的研究而提出了一个新的群落多样性假说。

按照作者的观点,占用相同生态位的物种可以稳定共存;这样,群落内物种多样性将受到4个基本因子所控制。

它们分别是:(Ⅰ)生态位的数量;(Ⅱ)区域物种库的大小;(Ⅲ)物种迁入速率,以及(Ⅳ)物种灭绝速率。

该假说强调区域生物地理过程与局域生态过程共同决定了群落内种多样性的大小及分布模式。

关键词　局域物种多样性,物种分化,区域物种库,生态位,竞争排除法则A hypothesis for the origin and maintenance of within2community species diversity/Zhang Dayong,JiangXinhu a//CHINESE BIODIVERSIT Y.—1997,5(3):161～167This paper formulates a novel hypothesis of community diversity on the basis of rejecting the competitive exclu2 sion principle.Since we accept the view that many species could occupy the same niche,local s pecies diversity is considered to be controlled by four fundamental factors,which are,res pectively,(Ⅰ)the number of niches in the community,(Ⅱ)the size of regional species2pool,(Ⅲ)species immigration rate,and(Ⅳ)species extinc2 tion rate.The hypothesis suggests that both regional biogeographic processes and local ecological processes will play an important role in determining the magnitude and pattern of community diversity.K ey w ords local species diversity,speciation,regional species2pool,niche,competitive exclusion principle Author’s address Department of Biology&State K ey Laboratory of Arid Agroecology,Lanzhou Univer2sity,Lanzhou　7300001 引言由于环境污染和生境破坏等人类活动的影响,大规模物种灭绝已成为当今社会所密切关注的一个焦点。

2024年安徽省“江南十校”高三联考英语试题本试卷分第I卷(选择题)和第II卷(非选择题)两部分,考试结束后,将本试卷和答题卡一并交回。

第I卷留意事项:1. 答第I卷前,考生务必将自己的姓名、考生号填写在答题卡上。

2. 选出每小题答案后,用铅笔把答题卡上对应题目的答案标号涂黑。

如需改动,用橡皮擦干净后,再选涂其他答案标号。

不能答在本试卷上,否则无效。

第一部分听力（共两节，满分30分）做题时,先将答案标在试卷上。

录音内容结束后,你将有两分钟的时间将试卷上的答案转涂到答题卡上。

第一节（共5小题；每小题1.5分，满分7.5分）听下面5段对话。

每段对话后有一个小题，从题中所给的 A、B、C 三个选项中选出最佳选项，并标在试卷的相应位置。

听完每段对话后，你都有10秒钟的时间来回答有关小题和阅读下一小题。

每段对话仅读一遍。

1. Where is Mr. Smith now?A. At home.B. At Sun Valley.C. In the office.2. How many times was the man late?A. 4 times.B. 8 times.C. 7 times.3. How is Steven going to spend this weekend?A. Going fishing.B. Repairing his car.C. Painting the apartment.4. Why is the woman preparing so much food?A. The woman wants to thank the man.B. The man can eat a lot.C. It’s the man’s birthday.5. What can we learn from the conversation?A. They are neighbors.B. They are both students.C. They are from the same country.其次节（共15小题；每小题1.5分，满分22.5分）听下面5段对话或独白。

Evolution through either natural selection or genetic drift is dependent on variation at the genetic and mor-phological levels. Processes that influence the genetic structure of populations include mating systems, effective population size, mutation rates and gene flow among populations. We investigated the patterns of population genetic structure of orchids and evaluated if evolutionary processes are more likely at the indi-vidual population level than at the multipopulation/species level. We hypothesized that because orchid populations are frequently small and reproductive success is often skewed, we should observe many orchids with high population genetic substructure suggesting limited gene flow among pop-ulations. If limited gene flow among populations is a common pattern in orchids, then it may well be an important component that affects the likelihood of genetic drift and selection at the local population level. Such changes may lead to differentiation and evolu-tionary diversification.A main component in evolutionary processes is the necessary condition of isolation. The amount of gene flow among local populations will determine whether or not individual populations (demes) can evolve inde-pendently which may lead to cladogenesis. Usually one migrant per generation is sufficient to prevent populations from evolving independently from other populations when effective population sizes are large. Theoretically, if the gene flow rate, Nm (the effective number of migrants per generation; N = effective pop-ulation size, m = migration rate), is larger than two individuals per generation, then it is sufficient to pre-vent local adaptation while gene flow less than one per generation will likely result in population differen-tiation by selection or genetic drift (Merrell 1981, Roughgarden 1996). If Nm lies between one and two, there will be considerable variation in gene frequen-cies among populations (Merrell 1981). Consequently,populations will have similar genetic structure as if mating were panmictic (Nm >2). Alternatively, if gene flow is low (Nm < 1), populations will have different genetic structures that may result in evolutionary change through either adaptation to the local environ-ments via natural selection or through random effects such as genetic drift.Direct observation of gene flow can be viewed by the use of mark and recapture studies (for mobile organisms, or stained pollen) or tracking marker alle-les (paternity analysis) over a short number of genera-tions. Few orchid studies have attempted to directly observe gene flow and thus far only staining or micro-tagging pollinaria have been used (Peakall 1989, Nilsson et al.1992, Folsom 1994, Tremblay 1994, Salguero-Faría & Ackerman 1999). All these studies examined gene flow only within populations. Indirect methods for detecting gene flow are obtained from allele frequencies and are an estimate of the average long-term effect of genetic differentiation by genetic drift. The alleles are assumed to be neutral so that genetic differentiation based on these markers would be a consequence of drift rather than natural selection. Bohomak (1999) concluded that simple population genetic statistics are robust for inferring gene flow among groups of individuals.The most common approach is the degree of popula-tion differentiation at the genetic level using Wright’s F estimates on data obtained through protein elec-trophoresis or various PCR type approaches. The F statistics separate the amount of genetic variation which can be attributed to inbreeding among closely related individuals in a population: FIS is the inbreed-ing coefficient within individuals; FIT is the result of non random mating within a population and the effect of population subdivision; and a third statistic, FST, is the fixation index due to random genetic drift and the lack of panmixia among populations (Wright 1978).THE GENETIC STRUCTURE OF ORCHID POPULATIONSAND ITS EVO L U T I O N A R Y IMPORTA N C ER AYMOND L. T REMBLAY1,3&J AMES D. A CKERMAN21University of Puerto Rico – Humacao, Department of Biology, Humacao, Puerto Rico, 00791, U.S.A.2University of Puerto Rico – Río Piedras, Department of BiologyP.O. Box 23360, San Juan, Puerto Rico, 00931-3360, U.S.A.3Author for correspondence: raymond@LANKESTERIANA 7: 87-92. 2003.LANKESTERIANA SpeciesReferencesNm(W)Gst Calypso bulbosa (L.) Oakes Alexandersson & Ågren 2000 3.200.072Caladenia tentaculata TatePeakall & Beattie 19967.1010.0346Cephalanthera damasonium (Mill.) Druce Scacchi, De Angelis & Corbo 1991--5--5C ephalanthera longifolia (L.) Fritsch Scacchi, De Angelis & Corbo 1991 2.1510.104Cephalanthera rubra (L.) Rich.Scacchi, De Angelis & Corbo 19910.7610.247Cymbidium goeringii Rchb. f.Chung & Chung 1999 2.300.098Cypripedium acaule Ait.Case 19941.2710.164Cypripedium calceolus L.Case 1993, 1994 1.6310.196Cypripedium candidum Muhl. ex Willd.Case 19943.3710.069Cypripedium fasciculatum Kellogg ex S. Watson Aagaard, Harrod & Shea 1999 6.000.04Cypripedium kentuckiense C. F. Reed Case et al.1998 1.1210.182Cypripedium parviflorum Salisb.var. pubescens (Willd.) O. W. Knight Case et al.19981.2810.163Southern populations Wallace & Case 20000.940.209Northern populations1.570.137var. makasin (Farw.) Sheviak 1.000.199var parviflorum 1.430.149species level0.830.232Cypripedium reginae WalterCase 19940.4710.349Dactylorhiza romana (Sebastiani) SoóBullini et al.2001 3.3210.07Dactylorhiza sambucina (L.) SoóBullini et al.20011.3110.16Epidendrum conopseum R. Br.Bush, Kutz & Anderton 19991.4330.149Epipactis helleborine (L.) Crantz Scacchi, Lanzara & De Angelis 19877.310.033European populations Squirrell et al., 20011.0010.2000.241,40.5064North AmericanHollingsworth & Dickson 19970.09042.5310.2400.791Epipactis youngiana Richards & Porter Harris & Abbott 1997 2.4310.093Eulophia sinensis Miq.Sun & Wong 2001---0.00.1331,30.6533Gooyera procera Ker-Gawl.Wong & Sun 19990.22110.5230.3971,30.3863Gymnadenia conopsea (L.) R. Br.Scacchi & De Angelis 19900.28010.471Gymnadenia conopsea (L.) R. Br. conopsea Soliva & Widmer 19992.960.078Gymnadenia conopsea (L.) R. Br.subsp densiflora (Wahl) E.G. Camus & A. Camus Soliva & Widmer 19990.390.391Lepanthes caritensis Tremblay & Ackerman Carromero, Tremblay & Ackerman 1.300.167(unpublished)Lepanthes rupestris Stimson Tremblay & Ackerman 2001 1.840.170Lepanthes rubripetala Stimson Tremblay & Ackerman 20010.620.270Lepanthes eltoroensis Stimson Tremblay & Ackerman 20010.890.220Lepanthes sanguinea Hook.Carromero, Tremblay & Ackerman 1.450.144(unpublished)Table 1. Estimates of gene flow in orchids. Nm(W) = gene flow estimates based on Wright’s statistics; Gst coeff-cient of genic differentiation among populations. 1Nm calculated by the present authors from Gst or Fst using formula on p. 320 of Hartl & Clark (1989). 2Recalculated using previous formula, original Nm value 3.70. 3Calculated from RAPD markers. 4Calculated from cpDNA. 5No genetic differentiation found among populations. 6Calculated according to Weir and Cockerham’s statistics. 7. Estimated using RAPD’s and AMOVA.88Nº 7T REMBLAY&A CKERMAN- Genetic structure of orchid populationsConsequently, if we make the assumption that the genetic markers sampled are neutral or nearly neutral and that the observed level of FST is a measure of the current gene flow among populations (rather than a historical remnant), then we can evaluate the likelihood that populations are effectively isolated. The scale of FST is from 0 (no population subdivision) to 1.0 (com-plete genetic differentiation among populations).We gathered population genetic data for 58 species of terrestrial and epiphytic orchids from temperate and tropical species. The data are biased toward ter-restrial/temperate species (N = 44). We found only three studies of terrestrial/tropical species and ten epi-phytic/tropical. There is also a bias toward certain taxa: Orchis, Cypripedium, Pterostylis and Lepanthes account for nearly half (30) of the 61 records (Table 1), 10 species of O r c h i s, 7 species each of Cypripedium and Pterostylis, 6 species of Lepanthes,3 species of S p i r a n t h e s, Epipactis, Cephalantheraa n d G y m n a d e n i a, 2 species of D a c t y l o r h i z a, Epipactis, Vanilla and Zeuxine, and one species each of Caladenia, Calypso, Cymbidium, Epidendrum, Eulophia, Goodyera, Nigritella, Paphiopedilum, Platanthera, Tipularia, and Tolumnia.89Mayo 2003Gene flow among populations varies among species ranging from a high of 12 effective migrants per gen-eration in Orchis longicornu(Corrias et al. 1991) to lows of less then 0.2 in Zeuxine strateumatica(Sun & Wong 2001). Assembling the species in groups based on their estimates of gene flow, we note that 18 species have less then one migrant per generation, while 19 species have more than two migrants per generation, and 17 of the species have a migration rates between one and two. No genetic differentiation was found among populations for C e p h a l a n t h e r a d a m a s o n i u m(Scacchi, De Angelis & Corbo 1991) and Spiranthes hongkongensis(Sun 1996). Consequently these two species are excluded from further analysis.O r c h i s species typically have high estimates of gene flow among populations (Scacchi, De Angelis & Lanzara 1990, Corrias et al. 1991, Rossi et al. 1992) whereas Lepanthes and Pterostylis species have much lower gene flow estimates (Tremblay & Ackerman 2001, Sharma, Clements & Jones 2000; Sharma et al.2001). However even within a genus variation in gene flow can be extensive (Table 1).Are there phylogenetic associations with gene flow? The data for O r c h i s(mean Nm = 5.7), L e p a n t h e s(mean Nm = 2.1) and P t e r o s t y l i s( m e a n Nm = 1.0) are suggestive, but much more extensive sampling is needed for both temperate and tropical species. Curiously, L e p a n t h e s and O r c h i s have very different population genetic parameters yet both are species-rich genera and are likely in a state of evolu-tionary flux. It seems to us that orchids have taken more than one expressway to diversification. For the group of species which has more than 2 migrants per generation local populations will not evolve indepen-dently, but as a group, consequently local morpholog-ical and genetic differences among groups will be wiped out, and populations will become homoge-neous if gene flow continues at the level. When gene flow is high, selection studies from different popula-tions should be evaluated together (Fig. 1).For populations that have less than one migrant perLANKESTERIANAFigure 1: Distribution of mean (s.e.) gene flow (Nm) among genera of Orchids. Bars without error bars of single datap o i n t s.90Nº 7T REMBLAY&A CKERMAN- Genetic structure of orchid populationsgeneration, local populations can evolve independent-ly, and evolutionary studies should be done at the local level. In small populations, we may expect genetic drift to be present and selection coefficients should be high to counteract the effects of drift.For species with intermediate gene flow it is proba-bly wise to evaluate evolutionary processes at the local and multi-population/species level. We expect variance in migration rates to be large because of the skewed reproductive success among individuals, time periods and populations. Consequently, the outcome of the evolutionary process will likely depend on the amount and variation of the migration events and consistency in migration rates in time. If variance in gene flow through space and time is small, then the genetic dif-ferentiation will be more or less stable. But, for exam-ple, if variance in gene flow is high, with some periods having high gene flow followed by little or no gene flow for an extended period of time, it is possible that through natural selection and genetic drift local popula-tions might differentiate sufficiently for cladogenesis during the period of reduced immigration.Species with less than one migrant per population are basically unique evolutionary units evolving inde-pendently from other local populations. In popula-tions with large Ne (> 50), it is likely that natural selection will dominate evolutionary processes while if Ne is small (< 50) genetic drift and selection can both be responsible for evolution. Consequently for these species, local adaptation to specific environ-mental conditions is possible.This survey of population genetics studies of orchids shows that multiple evolutionary processes have likely been responsible for the remarkable diver-sification in orchids.L ITERATURE C ITEDAagaard J.E., R.J. Harrod & K.L. Shea. 1999. Genetic vari-ation among populations of the rare clustered lady-slip-per orchid (Cypripedium fasciculatum) from Washington State, USA. Nat. Areas J. 19: 234-238Ackerman J.D. & S. Ward. 1999. Genetic variation in a widespread epiphytic orchid: where is the evolutionary potential? Syst. Bot. 24: 282-291.Alexandersson, R. & J. Ågren. 2000. Genetic structure of the nonrewarding bumblebee pollinated Calypso bul-bosa. Heredity 85: 401-409Arduino, P., F. Verra, R. Cianchi, W. Rossi, B. Corrias, & L. Bullini. 1996. Genetic variation and natural hybridization between Orchis laxiflora and O r c h i s palustris(Orchidaceae). Pl. Syst. Evol. 202: 87-109. Arft, A.M. & T.A. Ranker. 1998. Allopolyploid origin and population genetics of the rare orchid Spiranthes diluvi-alis. Am. J. Bot. 85: 110-122.Bohomak, A.J. 1999. Dispersal, gene flow, and population structure. Quart. Rev. Biol. 74: 21-45.Bullini, L., R. Cianchi, P. Arduino, L. De Bonis, M. C. Mosco, A. Verdi, D. Porretta, B. Corrias & W. Rossi. 2001. Molecular evidence for allopolyploid speciation and a single origin of the western Mediterranean orchid Dactylorhiza insularis(Orchidaceae). Biol. J. Lin. Soc. 72: 193-201.Bush, S.T., W.E. Kutz & J.M. Anderton. 1999. RAPD variation in temperate populations of epiphytic orchid Epidendrum conopseum and the epiphytic fern Pleopeltis polypodioides. Selbyana 20: 120-124. Case, M.A. 1993. High levels of allozyme variation within Cypripedium calceolus(Orchidaceae) and low levels of divergence among its varieties. Syst. Bot. 18: 663-677. Case, M.A. 1994. Extensive variation in the levels of genetic diversity and degree of relatedness among five species of Cypripedium(Orchidaceae). Amer. J. Bot. 81: 175-184.Case, M.A., H.T. Mlodozeniec, L.E. Wallace & T.W. Weldy. 1998. Conservation genetics and taxonomic sta-tus of the rare Kentucky Lady’s slipper: C y p r i p e d i u m k e n t u c k i e n s e(Orchidaceae). Amer. J. Bot. 85: 1779-1779.Chung, M.Y. & M.G. Chung. 1999. Allozyme diversity and population structure in Korean populations of Cymbidium goeringii(Orchidaceae). J. Pl. Res. 112: 139-144.Corrias, B., W. Rossi, P. Arduino, R. Cianchi & L. Bullini. 1991. Orchis longicornu Poiret in Sardinia: genetic, morphological and chronological data. Webbia 45: 71-101.Folsom, J.P. 1994. Pollination of a fragrant orchid. Orch. Dig. 58: 83-99.Harris, S.A. & R. J. Abbott. 1997. Isozyme analysis of the reported origin of a new hybrid orchid species, Epipactis y o u n g i a n a(Young’s helleborine), in the British Isles. Heredity 79: 402-407.Hedrén, M., E. Klein & H. Teppner. 2000. Evolution of polyploids in the European orchid genus N i g r i t e l l a: Evidence from allozyme data. Phyton 40: 239-275. Hollingsworth, P.M. & J.H. Dickson. 1997. Genetic varia-tion in rural and urban populations of Epipactis helle-b o r i n e(L.) Crantz. (Orchidaceae) in Britain. Bot. J. Linn. Soc. 123: 321-331.Li, A, Y., B. Luo & S. Ge. 2002. A preliminary study on conservation genetics of an endangered orchid (Paphiopedilum micranthum) from Southwestern China. Bioch. Gen. 40: 195-201.Merrell, D.J. 1981. Ecological Genetics. University of Minnesota Press, Minneapolis, Minnesota.Nielsen, L.R. & H.R. Siegismund. 2000. Interspecific dif-ferentiation and hybridization in V a n i l l a s p e c i e s (Orchidaceae). Heredity 83: 560-567.91Mayo 2003LANKESTERIANANilsson, L.A., E. Rabakonandrianina & B. Pettersson. 1992. Exact tracking of pollen transfer and mating in plants. Nature 360: 666-667.Peakall, R. 1989. A new technique for monitoring pollen flow in orchids. Oecologia 79: 361-365.Peakall, R. & A. J. Beattie. 1996. Ecological and genetic consequences of pollination by sexual deception in the orchid Caladenia tentaculata. Ecology 50: 2207-2220. Rossi, W., B. Corrias, P. Arduino, R. Cianchi & L. Bullini L. 1992. Gene variation and gene flow in Orchis morio (Orchidaceae) from Italy. Pl. Syst. Evol. 179: 43-58. Roughgarden, J. 1996. Theory of population genetics and evolutionary ecology: An Introduction. Prentice Hall, Upper Saddle River, NJ, USA.Salguero-Faría, J.A. & J.D. Ackerman. 1999. A nectar reward: is more better? Biotropica 31: 303-311. Scacchi, R., G. De Angelis & R.M. Corbo. 1991. Effect of the breeding system ion the genetic structure in C e p h a l a n t h e r a spp. (Orchidaceae). Pl. Syst. Evol. 176: 53-61.Scacchi, R., G. De Angelis & P. Lanzara. 1990. Allozyme variation among and within eleven Orchis species (fam. Orchidaceae), with special reference to hybridizing apti-tude. Genetica 81: 143-150.Scacchi, R. and G. De Angelis. 1990. Isoenzyme polymor-phisms in G y m n a e d e n i a[sic] c o n o p s e a and its infer-ences for systematics within this species. Bioch. Syst. Ecol. 17: 25-33.Scacchi, R., P. Lanzara & G. De Angelis. 1987. Study of electrophoretic variability in Epipactis heleborine ( L.) Crantz, E. palustris(L.) Crantz and E. microphylla (Ehrh.) Swartz (fam. Orchidaceae). Genetica 72: 217-224.Sharma, I.K., M.A. Clements & D.L. Jones. 2000. Observations of high genetic variability in the endan-gered Australian terrestrial orchid Pterostylis gibbosa R. Br. (Orchidaceae). Bioch. Syst. Ecol. 28: 651-663. Sharma, I.K., D.L. Jones, A.G. Young & C.J. French. 2001. Genetic diversity and phylogenetic relatedness among six endemic P t e r o s t y l i s species (Orchidaceae; series Grandiflorae) of Western Australia, as revealed by allozyme polymorphisms. Bioch. Syst. Ecol. 29: 697-710.Smith, J.L., K.L. Hunter & R.B. Hunter. 2002. Genetic variation in the terrestrial orchid Tipularia discolor. Southeastern Nat. 1: 17-26Soliva, M. & A. Widmer A. 1999. Genetic and floral divergence among sympatric populations of Gymnadenia conopsea s.l. (Orchidaceae) with different flowering phenology. Int. J. Pl. Sci. 160: 897-905. Squirrell, J., P.M. Hollingsworth, R.M. Bateman, J.H. Dickson, M.H.S. Light, M. MacConaill & M.C. Tebbitt. 2001. Partitioning and diversity of nuclear and organelle markers in native and introduced populations of Epipactis helleborine(Orchidaceae). Amer. J. Bot. 88: 1409-1418.Sun, M. 1996. Effects of Population size, mating system, and evolution origin on genetic diversity in S p i r a n t h e s sinensis and S. hongkongensis. Cons. Biol. 10: 785-795. Sun, M. & K.C. Wong. 2001. Genetic structure of three orchid species with contrasting breeding system using RAPD and allozyme markers. Amer. J. Bot. 88: 2180-2188.Tremblay, R.L. 1994. Frequency and consequences of multi-parental pollinations in a population of Cypripedium calceolus L. var. pubescens(Orchidaceae). Lindleyana 9: 161-167.Tremblay, R.L & J.D. Ackerman. 2001. Gene flow and effective population size in Lepanthes(Orchidaceae): a case for genetic drift. Biol. J. Linn. Soc. 72: 47-62. Wallace, L.A. 2002. Examining the effects of fragmenta-tion on genetic variation in Platanthera leucophaea (Orchidaceae): Inferences from allozyme and random amplified polymorphic DNA markers. Pl. Sp. Biol 17: 37-39.Wallace, L.A. & M. A. Case. 2000. Contrasting diversity between Northern and Southern populations of Cypripedium parviflorum(Orchidaceae): Implications for Pleistocene refugia and taxonomic boundaries. Syst. Bot. 25: 281-296.Wong, K.C. & M. Sun. 1999. Reproductive biology and conservation genetics of Goodyera procera (Orchidaceae). Amer. J. Bot. 86: 1406-1413.Wright, S. 1978. Evolution and the genetics of popula-tions. Vol. 4. Variability within and among natural pop-ulations. Chicago, The University of Chicago Press.Raymond L. Tremblay is an associate professor at the University of Puerto Rico in Humacao and the graduate faculty at UPR- Río Piedras. He obtained his B.Sc. with Honours at Carleton University, Ottawa, Canada in 1990 and his PhD at the University of Puerto Rico in Rio Piedras in 1996. He is presently the chairman of the In situ Orchid Conservation Committee of the Orchid Specialist Group. He is interested in evolutionary and con-servation biology of small populations. Presently his interest revolves in determining the life history characters that limit population growth rate in orchids and evaluating probability of extinction of small orchid populations. James D. Ackerman, Ph.D., is Senior Professor of Biology at the Univesrity of Puerto Rico, Río Piedras. He is an orchidologist, studying pollination an systematics.92Nº 7。

壤碳氮和微生物群落的影响[J].华中农业大学学报,2022,41（6）：16-26.HU Q L,YANG B J,LIU N,et al.Effects of application rates of nitrogen on rice yield,carbon and nitrogen,microbial community in soil under mixed sowing of green manure[J].Journal of Huazhong Agri⁃cultural University,2022,41（6）：16-26.[3]李忠义,唐红琴,何铁光,等.绿肥作物紫云英研究进展[J].热带农业科学,2016,36（11）：27-32.LI Z Y,TANG H Q,HE T G,et al. Research progress of Chinese milk vetch（Astragalus sinicus）[J].Chi⁃nese Journal of Tropical Agriculture,2016,36（11）：27-32. [4]林新坚,曹卫东,吴一群,等.紫云英研究进展[J].草业科学,2011, 28（1）：135-140.LIN X J,CAO W D,WU Y Q,et al.Advance in As⁃tragalus sinicus research[J].Pratacultural Science,2011,28（1）：135-140.[5]周兴,李再明,谢坚,等.紫云英利用后减施化肥对水稻产量和产值及土壤碳氮含量的影响[J].湖南农业大学学报（自然科学版）, 2014,40（3）：225-230.ZHOU X,LI Z M,XIE J,et al.Effect of re⁃ducing chemical fertilizer on rice yield,output value,content of soil carbon and nitrogen after utilizing the milk vetch[J].Journal of Hunan Agricultural University（Natural Sciences）,2014,40（3）：225-230. [6]张颖睿,杨滨娟,黄国勤.紫云英翻压量与不同施氮量对水稻生长和氮素吸收利用的影响[J].生态学杂志,2018,37（2）：430-437. ZHANG Y R,YANG B J,HUANG G Q.Effects of Chinese milk vetch as a green manure and nitrogen fertilization on rice growth and nitrogen absorption and utilization of rice[J].Chinese Journal of Ecology,2018, 37（2）：430-437.[7]王飞,林诚,林新坚,等.连续翻压紫云英对福建单季稻产量与化肥氮素吸收、分配及残留的影响[J].植物营养与肥料学报,2014,20（4）：896-904.WANG F,LIN C,LIN X J,et al.Effects of continuous turnover of Astragalus sinicus on rice yield and N absorption,distribu⁃tion and residue in single-cropping rice regions of Fujian Province[J].Journal of Plant Nutrition and Fertilizer,2014,20（4）：896-904. [8]ZHOU X,LU Y H,LIAO Y L,et al.Substitution of chemical fertilizer by Chinese milk vetch improves the sustainability of yield and accumu⁃lation of soil organic carbon in a double-rice cropping system[J].Jour⁃nal of Integrative Agriculture,2019,18（10）：2381-2392.[9]鲁艳红,廖育林,聂军,等.紫云英与尿素或控释尿素配施对双季稻产量及氮钾利用率的影响[J].植物营养与肥料学报,2017,23（2）：360-368.LU Y H,LIAO Y L,NIE J,et al.Effect of different incorpo⁃ration of Chinese milk vetch coupled with urea or controlled release urea on yield and nitrogen and potassium nutrient use efficiency in dou⁃ble-cropping rice system[J].Journal of Plant Nutrition and Fertilizers, 2017,23（2）：360-368.[10]颜志雷,方宇,陈济琛,等.连年翻压紫云英对稻田土壤养分和微生物学特性的影响[J].植物营养与肥料学报,2014,20（5）：1151-1160.YAN Z L,FANG Y,CHEN J C,et al.Effect of turning over Chinese milk vetch（Astragalus sinicus L.）on soil nutrients and micro⁃bial properties in paddy fields[J].Journal of Plant Nutrition and Fer⁃tilizers,2014,20（5）：1151-1160.[11]刘春增,常单娜,李本银,等.种植翻压紫云英配施化肥对稻田土壤活性有机碳氮的影响[J].土壤学报,2017,54（3）：657-669.LIUof Chinese milk vetch coupled with application of chemical fertilizer on active organic carbon and nitrogen in paddy soil[J].Acta Pedologi⁃ca Sinica,2017,54（3）：657-669.[12]魏夏新,熊俊芬,李涛,等.有机物料还田对双季稻田土壤有机碳及其活性组分的影响[J].应用生态学报,2020,31（7）：2373-2380. WEI X X,XIONG J F,LI T,et al.Effects of different organic amend⁃ments on soil organic carbon and its labile fractions in the paddy soil of a double rice cropping system[J].Chinese Journal of Applied Ecolo⁃gy,2020,31（7）：2373-2380.[13]LI T,GAO J,BAI L,et al.Influence of green manure and rice straw management on soil organic carbon,enzyme activities,and rice yield in red paddy soil[J].Soil and Tillage Research,2019,195：104428.[14]常单娜,刘春增,李本银,等.翻压紫云英对稻田土壤还原物质变化特征及温室气体排放的影响[J].草业学报,2018,27（12）：133-144.CHANG D N,LIU C Z,LI B Y,et al.Effects of incorporating Chinese milk vetch on redctive material characteristics and green⁃house gas emissions in paddy soil[J].Acta Prataculturae Sinica,2018, 27（12）：133-144.[15]YANG W,YAO L,ZHU M,et al.Replacing urea-N with Chinese milk vetch（Astragalus sinicus L.）mitigates CH4and N2O emissions in rice paddy[J].Agriculture,Ecosystems&Environment,2022,336：108033.[16]聂江文,王幼娟,吴邦魁,等.紫云英还田对早稻直播稻田温室气体排放的影响[J].农业环境科学学报,2018,37（10）：2334-2341. NIE J W,WANG Y J,WU B K,et al.Effect of Chinese milk vetch in⁃corporation on greenhouse gas emissions from early-rice direct-seed⁃ing paddy fields[J].Journal of Agro⁃Environment Science,2018,37（10）：2334-2341.[17]ZHOU Q,ZHANG P,WANG Z,et al.Winter crop rotation intensifica⁃tion to increase rice yield,soil carbon,and microbial diversity[J].Heli⁃yon,2023,9（1）：e12903.[18]唐海明,肖小平,李超,等.冬季覆盖作物秸秆还田对双季稻田根际土壤微生物群落功能多样性的影响[J].生态学报,2018,38（18）：6559-6569.TANG H M,XIAO X P,LI C,et al.Effects of re⁃cycling straw of different winter covering crops on rhizospheric micro⁃bial community functional diversity in a double-cropped paddy field [J].Acta Ecologica Sinica,2018,38（18）：6559-6569. [19]GAO S,CAO W,ZHOU G,et al.Rees bacterial communities in pad⁃dy soils changed by milk vetch as green manure：a study conducted across six provinces in south China[J].Pedosphere,2021,31（4）：521-530.[20]万水霞,唐杉,蒋光月,等.紫云英与化肥配施对土壤微生物特征和作物产量的影响[J].草业学报,2016,25（6）：109-117.WAN S X,TANG S,JIANG G Y,et al.Effects of Chinese milk vetch manure and fertilizer on soil microbial characteristics and yield of rice[J].Acta Prataculturae Sinica,2016,25（6）：109-117.[21]万水霞,朱宏斌,唐杉,等.紫云英与化肥配施对安徽沿江双季稻区土壤生物学特性的影响[J].植物营养与肥料学报,2015,21（2）：387-395.WAN S X,ZHU H B,TANG S,et al.Effects of Astragalus sinicus manure and fertilizer combined application on biological prop⁃River[J].Journal of Plant Nutrition and Fertilizers ,2015,21（2）：387-395.[22]佀国涵,赵书军,王瑞,等.连年翻压绿肥对植烟土壤物理及生物性状的影响[J].植物营养与肥料学报,2014,20（4）：905-912.SI G H,ZHAO S J,WANG R,et al.Effects of consecutive overturning ofgreen manure on soil physical and biological characteristics in tobac⁃co-planting fields[J].Journal of Plant Nutrition and Fertilizers ,2014,20（4）：905-912.[23]王利民,黄东风,何春梅,等.紫云英还田对黄泥田土壤理化和微生物特性及水稻产量的影响[J].生态学报,2023,43（11）：4782-4797.WANG L M,HUANG D F,HE C M,et al.Impacts of theChinese milk vetch （Astragalus sinicus L.）residue incorporation on soil physicalchemical,microbial properties and rice yields in yellow-mud paddy field[J].Acta Ecologica Sinica ,2023,43（11）：4782-4797.[24]CHEN J R,QIN W J,CHEN X F,et al.Application of Chinese milkvetch affects rice yield and soil productivity in a subtropical double-rice cropping system[J].Journal of Integrative Agriculture ,2020,19（8）：2116-2126.[25]WANG L,HE C,HUANG D et al.Co-incorporation of Chinese milkvetch （Astragalus sinicus L.）and chemical fertilizer alters microbial functional genes supporting short-time scale positive nitrogen prim⁃ing effects in paddy soils[J].Pedosphere ,2023.[26]唐海明,程凯凯,肖小平,等.不同冬季覆盖作物对双季稻田土壤有机碳的影响[J].应用生态学报,2017,28（2）：465-473.TANGH M,CHENG K K,XIAO X P,et al.Effects of different winter cover crops on soil organic carbon in a double cropping rice paddy field[J].Chinese Journal of Applied Ecology ,2017,28（2）：465-473.[27]周国朋,曹卫东,白金顺,等.多年紫云英-双季稻下不同施肥水平对两类水稻土有机质及可溶性有机质的影响[J].中国农业科学,2016,49（21）：4096-4106.ZHOU G P,CAO W D,BAI J S,et al.Effects of different fertilization levels on soil organic matter and dis⁃solved organic matter in two paddy soils after multi-years ′rotation of Chinese milk vetch and double-cropping rice[J].Scientia Agricultura Sinica ,2016,49（21）：4096-4106.[28]杨滨娟,黄国勤,王超,等.稻田冬种绿肥对水稻产量和土壤肥力的影响[J].中国生态农业学报,2013,21（10）：1209-1216.YANGB J,HUANG G Q,WANG C,et al.Effects of winter green manure cul⁃tivation on rice yield and soil fertility in paddy field[J].Chinese Jour⁃nal of Eco-Agriculture ,2013,21（10）：1209-1216.[29]龙莉,杨旭初,熊斌,等.冬作物秸秆还田对双季稻产量和土壤肥力的影响[J].作物研究,2019,33（2）：104-109.LONG L,YANGand soil fertility in a double cropping rice paddy[J].Crop Research ,2019,33（2）：104-109.[30]胡安永,孙星,刘勤,等.太湖地区不同轮作方式对稻田氨挥发和水稻产量的影响[J].水土保持学报,2013,27（6）：275-279.HU AY,SUN X,LIU Q,et al.Influence of different rotations on ammonia volatilization and rice yields of paddy fields in Taihu Lake region[J].Journal of Soil and Water Conservation ,2013,27（6）：275-279.[31]BOWLES T M,ACOSTA-MARTÍNEZ V,CALDERÓN F et al.Soilenzyme activities,microbial communities,and carbon and nitrogen availability in organic agroecosystems across an intensively-managed agricultural landscape[J].Soil Biology and Biochemistry ,2014,68：252-262.[32]王光华,刘俊杰,于镇华,等.土壤酸杆菌门细菌生态学研究进展[J].生物技术通报,2016,32（2）：14-20.WANG G H,LIU J J,YUZ H,et al.Research progress of Acidobacteria ecology in soils[J].Bio⁃technology Bulletin ,2016,32（2）：14-20.[33]CHALLACOMBE J F,HESSE C N,BRAMER L M et al.Genomesand secretomes of Ascomycota fungi reveal diverse functions in plant biomass decomposition and pathogenesis[J].BMC Genomics ,2019,20（1）：976.[34]CHEN X,WANG J,YOU Y et al.When nanoparticle and microbesmeet ：the effect of multi-walled carbon nanotubes on microbial com⁃munity and nutrient cycling in hyperaccumulator system[J].Journal of Hazardous Materials ,2022,423：126947.[35]杨胜香,李凤梅,彭禧柱,等.不同碳氮磷源改良剂对铅锌尾矿废弃地土壤微生物群落结构的影响[J].农业环境科学学报,2019,38（6）：1256-1264.YANG S X,LI F M,PENG X Z,et al.Effects ofamendments with different C/N/P ratios on the microbial community structure in Pb-Zn mine tailings[J].Journal of Agro-Environment Sci⁃ence ,2019,38（6）：1256-1264.[36]田程,邱婷,朱菲莹,等.氧化钙对西瓜枯萎病及根际细菌群落的调控[J].湖南农业大学学报（自然科学版）,2018,44（6）：620-624.TIAN C,QIU T,ZHU F Y,et al.Calcium oxide regulation of fusarium wilt and rhizophere bacterial community[J].Journal of Hunan Agricul⁃tural University （Natural Sciences ）,2018,44（6）：620-624.[37]方宇,王飞,贾宪波,等.绿肥配施减量化肥对土壤固氮菌群落的影响[J].农业环境科学学报,2018,37（9）：1933-1941.FANG Y,WANG F,JIA X B,et al.Effect of green manure and reduced chemi⁃cal fertilizer load on the community of soil nitrogen-fixing bacteria[J].Journal of Agro-Environment Science ,2018,37（9）：1933-1941.万欣，张怡，苏鹏程，等.农村水环境政策与污染的时空迁移特征及关系[J].农业环境科学学报,2024,43（4）：886-895.WAN X,ZHANG Y,SU P C,et al.Spatiotemporal migration patterns and relationships between rural water environment policies and pollution[J].Journal of Agro-Environment Science ,2024,43（4）：886-895.农村水环境政策与污染的时空迁移特征及关系万欣，张怡*，苏鹏程，骆心怡，林佳欣（河海大学商学院，南京211100）Spatiotemporal migration patterns and relationships between rural water environment policies and pollutionWAN Xin,ZHANG Yi *,SU Pengcheng,LUO Xinyi,LIN Jiaxin（School of Business,Hohai University,Nanjing 211100,China ）Abstract ：In order to reveal the temporal and spatial evolutional relationships between rural water pollution and the corresponding governance policies,the migration paths of gravity centers for the two indicators were plotted based on measurements of policy strength and pollution intensity.Then,various provinces were classified into different “policy-pollution ”types by using the Shapley value decomposition method,and the causal relationship between policy and pollution under each type was analyzed based on the Granger causality test method.The results showed that both the gravity centers of policy and pollution located in southeast China,but their migration paths were not aligned with each other.The former exhibited a “south-west-north-east ”directional trend,whereas the latter consistently demonstrated a propensity for migration towards the south.In terms of the link between policy and pollution,it was observedthat the reduction in pollution intensity contributed to an enhancement in policy strength in “growth-reduced ”type provinces.However,the drivers for this enhancement differ between eastern and western provinces.As for provinces classified as “reduced-reduced ”,the decrease in policy effectiveness was found to be a result of reduced pollution intensity;however,there were instances of policy deviationevident in specific dimensions of pollution.At last,the provinces falling under the "pollution growth"category did not exhibit Granger causality between policy and pollution.Therefore,it was recommended that future policy-making incorporates its association with pollution outcomes and enhances the precision,synergy,and foresight of policies,which is beneficial to the elevation of efficiency and effectiveness of policy formulation.Keywords ：rural water pollution;gravity center migration;policy strength;pollution intensity;“policy-pollution ”type收稿日期：2023-04-13录用日期：2023-08-03作者简介：万欣（1985—），女，吉林通化人，博士，副教授，主要从事城乡可持续建设与治理研究。

Plant Molecular Biology53:383–397,2003.©2003Kluwer Academic Publishers.Printed in the Netherlands.383Molecular characterization of Brassica napus NAC domain transcriptional activators induced in response to biotic and abiotic stressDwayne Hegedus∗,Min Yu,Doug Baldwin,Margaret Gruber,Andrew Sharpe,Isobel Parkin, Steve Whitwill and Derek LydiateMolecular Genetics Section,Agriculture and Agri-Food Canada,107Science Place,Saskatoon,S7N0X2Canada (∗author for correspondence;e-mail hegedusd@em.agr.ca)Received22July2003;accepted in revised form9October2003Key words:Brassica napus,NAC domain,stress,transcriptional activation,yeast2-hybridAbstractSubtractive expressed sequence tag analysis and screening of cDNA libraries derived from Brassica napus leaves subjected to mechanical wounding,flea beetle feeding or cold temperatures revealed eight genes encoding NAC-domain transcription factors.The genes were found to be differentially regulated in response to biotic and abiotic stresses including wounding,insect feeding,Sclerotinia sclerotiorum infection,cold shock and dehydration.Five BnNAC proteins were orthologous to Arabidopsis thaliana ATAF1or ATAF2and gave rise to developmental abnormalities similar to the A.thaliana nam and cuc mutants when expressed ectopically in A.thaliana.Trans-genic lines expressing BnNAC14,exhibited large leaves,thickened stems and hyper-developed lateral root systems similar to that observed with A.thaliana NAC1,but also were delayed in bolting and lacked an apical dominant tap root.Several of the BnNAC proteins were capable of activating gene expression in yeast and recognized an element within the CaMV35S promoter.A yeast two-hybrid screen revealed that BnNAC14interacted with other select BnNAC proteins in vitro and identified an additional BnNAC gene,BnNAC485.The protein interaction and transcriptional activation domains were mapped by deletion analysis.IntroductionPlants are under constant threat from environmental stress and attack from pathogens and vertebrate and invertebrate herbivores.To cope with this onslaught, they have evolved elaborate mechanisms to perceive the attack and a responsive signaling language to tie the reception of information to the induction of appro-priate defense strategies.These mechanisms encom-pass direct physical and chemical defenses,as well as indirect defenses,such as the release of predator-attracting volatiles(Dicke and Van Poecke,2002). Specific metabolites,proteins and carbohydrates shed by the pathogen or insect(Hammond-Kosack and Jones,1996;Baker et al.,1997)and polygalac-turonide fragments derived from damaged plant cell walls(Thain et al.,1990)interact with specific plant receptors.These serve to initiate signaling cascades leading to local and systemic defense responses that typically consist of changes to plant architecture(e.g. wax accumulation,trichome formation)and the in-duction of defense proteins,hyperoxidized chemicals and secondary metabolites(Walling,2000).One of the least understood resistance mechanisms is toler-ance,the ability to compensate for herbivore attack by sustaining and re-growing damaged tissue(Strauss and Agrawal,1999;Stowe et al.,2000).The plant alters its developmental pattern,establishing an eco-physiological equilibrium with the attacker to limit any decrease infitness(Baldwin and Preston,1999; Kessler and Baldwin,2002).Indeed,one of the larger groups of genes affected by herbivore and pathogen interactions are those involved in plant primary meta-bolism and growth(Reymond et al.,2000;Stotz et al., 2000;Schenk et al.,2000;Hermsmeier et al.,2001).The regulation of defense gene expression is largely governed by specific transcription factors.A384common theme that has emerged with the sequen-cing of whole plant genomes is that these factors often belong to large gene families of more than100 members.Members of the ERF,bZIP,WRKY(Singh et al.,2002)and MYB(Jin and Martin,1999)fam-ilies are the best characterized of the plant defense response activators.While some members of these families are specifically involved in the regulation of defense responses to biotic and environmental stress, others appear to coordinate plant developmental path-ways(Jin and Martin,1999;Chen and Singh,1999; Robatzek and Somssich,2001).Another such family of transcription factors are the NAC-domain proteins.The name derives from a conserved domain originally associated with the NO APICAL MERISTEM(NAM)gene in Petunia(Souer et al.,1996)and the ATAF1,ATAF2and CUP-SHAPED COTYLEDON(CUC)genes of Arabidopsis thaliana(Aida et al.,1997).NAC-domain proteins are unique to plants and comprise large gene families (Kikuchi et al.,2000);103members are present within the A.thaliana genome and have been implicated in various aspects of plant development.In Petunia,NAM was expressed at the primordia and meristem boundar-ies and mutants failed to develop apical shoots(Souer et al.,1996).However,additional NAM genes were be-lieved to be involved since co-suppression studies gave rise to plants with further defects including thicker stems,larger leaves and the absence of axillary mer-istems(Souer et al.,1998).Similarly, A.thaliana cuc1and cuc2double-mutant lines lacked shoot apical meristem development and also exhibited fused coty-ledons,sepals and stamens(Aida et al.,1997,1999). NAC1,another A.thaliana NAC-domain gene,was found to be involved in the auxin-dependent formation of the lateral root system(Xie et al.,2000).More re-cently,NAC-domain genes have been implicated in the plant defense response as the potato StNAC gene and A.thaliana ATAF1and ATAF2genes were induced by pathogen attack and wounding(Collinge and Boller, 2001).Moreover,the geminivirus DNA replication protein,RepA,was found to interact with two NAC-domain proteins,GRAB1and GRAB2;however,their effect on viral DNA replication or plant development has not been determined(Xie et al.,1999).All NAC-domain proteins have a common config-uration consisting of a conserved amino-terminal NAC domain region proceeded by a highly variable carboxy terminus.Two lines of evidence support the notion that NAC proteins are involved in transcriptional reg-ulation.First,A.thaliana lines over-expressing NAC1exhibited up-regulation of the auxin-responsive genes, AIR3and DBP,and a corresponding decrease was ob-served in anti-sense lines.NAC1also localized to the nucleus(Xie et al.,2000).Second,early reports indic-ated that ATAF1and ATAF2were able to trans-activate the CaMV35S promoter(Hirt,original GenBank annotation).This was substantiated by Duval et al. (2002)who showed that the A.thaliana NAM NAC domain recognized a7bp region within the CaMV 35S as-1(activation sequence1)element.In an effort of better understand plant defenses and regulation of such we conducted subtractive ex-pressed sequence tag analysis of B.napus subjected to mechanical wounding,flea beetle feeding or cold temperatures.Here we report the isolation and char-acterization of nine members of the B.napus NAC (BnNAC)gene family and show that they are differ-entially regulated in response to biotic and abiotic stress,form heterodimers and give rise to develop-mental abnormalities when expressed ectopically in A.thaliana.Materials and methodsPlant,fungal and insect materialsBrassica napus line DH12075and Arabidopsis thali-ana ecotype Columbia were grown in soil under a16h photoperiod with a daytime temperature of 22◦C and a night temperature of16◦C.Root de-velopment in transgenic A.thaliana lines was as-sessed in MS medium with3%sucrose according to Xie et al.(2000). A.thaliana Columbia line SALK030702.55.50.X containing a T-DNA inser-tion in the At5g63790locus encoding ATAF2was obtained from the Arabidopsis Biological Resource Center(Columbus,OH).Insertion mutant inform-ation was obtained from the SIGNAL website at .The insertion was verified by PCR using the ATAF2-specific primer SALK030702 (5 -TGGCGTTGTACGGTGAGAAAG-3 )and either one of two T-DNA specific primers,LBa1(5 -TGGTTCACGTAGTGGGCCATCG-3 )or LBb1(5 -CGCTGGACCGCTTGCTGCAACT-3 )as well as by Southern blotting.A line homozygous for the insertion was used for phenotypic assessment.Sclerotinia sclerotiorum isolate‘100’was origin-ally collected on B.napus.Fungal mycelia were grown on potato-dextrose agar(PDA)at20◦C and stored at −80◦C in25%glycerol.385Adultflea beetles were collected in sweep nets from a winter canolafield(B.napus cv.Casino)at the Saskatoon Research Centre farm.Beetles were maintained on a diet of cabbage leaves in mesh cages in a controlled environment chamber(23◦C,16h photoperiod withfluorescent lighting).Beetles were starved for48h prior to conducting the feeding bioas-says.Construction of normal and subtractive cDNA librariesTotal RNA was extracted from8-week old B.napus DH12075leaves2h after crushing with forceps,after 30h of constantflea beetle feeding as described below or from plants that had been grown at5◦C until they reached the expanded six-leaf stage.Poly(A)+RNA was isolated with Oligotex(Qiagen)following the manufacturer’s instructions.cDNA subtraction was performed with the PCR-Select cDNA Subtraction Kit (Clontech).The PCR products were inserted directly into pGEM-T Easy(Promega)and ca.1500expressed sequence tags(EST)generated from each library.Nor-mal cDNA libraries were constructed with the ZAPII cDNA synthesis kit(Stratagene).An EST corres-ponding to the amino-terminus of B.napus NAC1-1 (BnNAC1-1)was used to screen the cDNA libraries to isolate additional full-length BnNAC cDNAs.The BnNAC cDNAs were excised in vivo from the lambda ZAP Express vector as pBluescript SK phagemids using ExAssist helper phage(Stratagene). Expression analysisB.napus leaves were infected with S.sclerotiorum according to the method of Li et al.(2003).To simu-late wounding,leaves were mechanically damaged by crushing with sterile forceps.Forflea beetle feeding, plants were placed in cages with starvedflea beetles at a density of100–150insects per plant.To examine the effect of low temperature and dehydration,8-week old plants were placed at5˚C for24h or had moisture withheld until the point of wilting.Tissues were collected at various time intervals and immediately frozen in liquid nitrogen upon re-moval.Total RNA was isolated by dispensing200mg (wet weight)of ground plant tissue into a1.5ml microcentrifuge tube containing1ml Trizol Reagent (Invitrogen)and RNA extracted according to the man-ufacturer’s protocol.The RNA pellet was washed with 70%ethanol,dried for5min and re-suspended in 50µl RNase-free double-distilled H2O.To detect Bn-NAC mRNA,20µg of total RNA was separated on 1.2%agarose gels in10mM phosphate buffer(pH7.0) and blotted onto a nylon membrane with10×SSC. Hybridizations were conducted in0.5M phosphate buffer(pH7.2)with7%SDS,1%bovine serum albu-min and1mM EDTA at65◦C overnight.Membranes were washed twice with2×SSC at65◦C for10min, twice with1×SSC/0.5%SDS at65◦C for20min andfinally with0.1×SSC at20◦C for10min.DNA probes consisted of PCR-amplified fragments corres-ponding to either the conserved amino-terminal region of BnNAC1-1or carboxyl-terminal regions unique to each BnNAC and labeled with[α-32P]dCTP with the Prime-A-Gene Labeling System(Invitrogen). Computational analysisEST sequences were annotated according to BLAST nucleotide and protein alignments(www.ncbi.nlm.nih. gov).Multiple peptide sequence alignments were per-formed with ClustalW1.2and100permutations of the multiple alignment generated using Seqboot.Distance matrices were calculated from the permutated align-ment with the PAM method in Protdist.Unrooted, neighbor-joined trees were generated with Neighbor and a consensus tree was determined with Consense. Sequence assembly,analysis and phylogenetic tools were accessed through the Canadian Bioinformatics Resource(www.cbr.nrc.ca).Protein secondary struc-ture was determined by SSPRO,PSIpred version2.4, PFRMAT SS and PHDsec available in the PredictPro-tein server(/predictprotein) and COILS(/software/COILS). Determination of nuclear localization sequences was performed by PredictNLS(/ predictNLS)with the method described by Cokol et al. (2000).Peptide sequences common to proteins that are targeted for rapid turnover were identified with PEST-FIND(/embnet/tools/bio/ PESTfind).Plant transformationThe entire coding regions of six BnNAC cDNAs(1-1, 5-1,5-7,5-8,5-11and14)were amplified by PCR with PWO DNA polymerase(Stratagene)and oligo-nucleotide primers containing restriction enzyme sites suitable for cloning into pBI121(Clontech)down-stream of the CaMV35S promoter.Sense and anti-sense BnNAC5-1were inserted into the Bam HI/Sac I sites,BnNAC5-7,5−8and5−11into the Xba I/Sac I386sites and BnNAC1-1and14into the Bam HI/Eco ICRI sites.Plant transformation was carried out according to thefloral dip procedure(Clough and Bent,1998). Mapping of BnNAC transcription activation domainsThe entire coding regions of nine BnNAC cDNAs(Bn-NAC1-1,3,485,5-1,5-7,5-8,5-11,8and14)were amplified by PCR with PWO DNA polymerase and inserted into the Sal I and Not I sites of pDBLeu(In-vitrogen)which fused the BnNAC open reading frame to the GAL4DNA-binding domain(DB).Each con-struct was introduced into Saccharomyces cerevisiae MaV203and tested in a one-hybrid system for the ability to activate transcription of the LacZ reporter. The BnNAC genes were divided into regions encod-ingfive NAC subdomains according to the scheme of Duval et al.(2002)and two carboxyl-terminal sub-domains.Various combinations of the subdomains derived from BnNAC14,BnNAC5-8and BnNAC485 were amplified by PCR,inserted into pDBLeu and examined for transcriptional activation of the LacZ reporter gene.Identification of BnNAC-interacting proteins with a yeast2-hybrid screenA yeast two-hybrid cDNA library was construc-ted from poly(A)mRNA isolated from the above-ground parts of four-leaf stage seedlings of B.napus DH12075and cloned into the GAL4activation do-main(AD)vector,pPC86,using the SuperScript Plasmid System(Invitrogen).The entire coding re-gions of the BnNAC5-1and BnNAC14,which encoded the only two BnNAC proteins that do not activate transcription directly,were used as a bait to screen the B.napus cDNA library with the PROQUEST Two-Hybrid System(Invitrogen).About 1.8×106 S.cerevisiae transformants were subjected to two-hybrid selection on synthetic complete(SC)medium lacking leucine,tryptophan and histidine but con-taining15mM3-amino-1,2,4-triazole(3AT).Putative His+(3AT-resistant)transformants were tested for the induction of two other reporter genes,URA3and LacZ, and reassessed by a second transformation into yeast.Regions involved in protein interaction were mapped by fusing the NAC or carboxyl-terminal do-mains of BnNAC5-7,BnNAC5-8and BnNAC485to the GAL4AD in pPC86.These were tested for interaction with whole BnNAC14or constructs en-coding various combinations of BnNAC14NAC and carboxyl-terminal domains in pDBLeu.Interaction of BnNAC proteins with CaMV35S promoter elementsPlasmid pFL759-1containing the CaMV35S pro-moter,and resident as-1element,fused toβ-glucurondiase(GUS)was obtained from P.Fobert (NRCC,Saskatoon,Canada)and has been de-scribed by Stonehouse(2002).Three independent S.cerevisiae MaV203colonies transformed with pD-BLeu or pDBLeuBnNAC and pFL759-1were as-sessed.Total protein in each sample was determined using Bradford reagent(BioRad Laboratories)and GUS specific activity expressed in units equivalent to pmol umbelliferyl released perµg protein per hour. The data were normalized by log(x+1.0)trans-formation,analysis of variance was performed with general linear models(Proc GLM)and the differences between means were determined with the Waller-Duncan K-ratio t-test(P<0.05)(SAS Institute Inc. 2000,version8.2.0).ResultsIsolation of B.napus NAC domain-containing genes About1500ESTs were generated from each of three subtractive cDNA libraries developed from plants that had been grown at5◦C,mechanically wounded or subjected to herbivory byflea beetles.About5%of the ESTs encoded proteins involved in signal transduction pathways(G-proteins,MAP kinases and transcription factors)or contained domains indicative of DNA inter-action(helix-turn-helix and zincfinger).Proteins con-taining a NAC domain similar to the wound-inducible ATAF1and ATAF2were encoded by a small pro-portion of these and were investigated further.Since the PCR-based subtractive library procedure generated only small cDNA fragments,BnNAC1-1was used to screen normal cDNA libraries derived from B.napus leaf tissue treated as above.cDNAs encoding eight distinct types of BnNAC proteins ranging in size from 252to285amino acids were identified in this man-ner and denoted BnNAC1-1,3,5-1,5-7,5-8,5-11, 8and14.Each protein possessed a160amino acid amino-terminal NAC domain consisting offive highly conserved regions,denoted A–E as per Kikuchi et al. (2000),which were interspersed by short,variable, spacers(Figure1A).The region encoding subdomainC and extending through thefirst half of subdomainD contained a high proportion of conserved basic387Figure1.Multiple sequence alignment of B.napus NAC domain-containing proteins.Residues that are identical in all(white on black back-ground)or most(black on gray background)proteins are highlighted.A.Translated amino acid sequence of nine BnNAC cDNAs showing residues(∗)within the amino-terminal NAC domains comprisingfive subdomains denoted N A−E.A common Pro residue(#)used to divide the variable carboxy-terminal domain into two subdomains V A−B and a putative nuclear localization signal(underline)are shown.Consensus secondary structure prediction of BnNAC NAC domains as determined using SSPRO,PSIpred,PFRMAT SS and PHDsec is shown above and consists ofα-helix(h),extendedβ-sheet(e)and coiled/loop(c)regions.All BnNAC NAC domains had essentially the same secondary structure.B.Alignment of translated BnNAC variable carboxy-terminal domains with corresponding regions of the most closely related plant homologue.Amino acid residues that may contribute to transcription activation and that are present in all(capitals)or most(lower case) proteins are shown above each alignment.These include Asp(D),Glu(E),Gln(Q),Pro(P),Ser(S)and Thr(T).Predicted PEST domains (boxed)associated with protein turnover are also shown.B1.Alignment of BnNAC14(AY245885),A.thaliana AtGRAB1(AC010704_4)and Triticum sativa TrGRAB1(AJ010829).B2.Alignment of BnNAC5-11(AY245884),BnNAC18(AY245886)and A.thaliana ATAF1(X74755). B3.Alignment of BnNAC1-1(AY245879),BnNAC3(AY245880),BnNAC5-1(AY245881),BnNAC5-7(AY245882),BnNAC5-8(AY245883) and A.thaliana ATAF2(AK118910).B4.Alignment of BnNAC485(AY245887)and A.thaliana NAC domain proteins at locus At4g27410 (NM_118875)and locus At1g52890(NM_104167).388Figure1.(Continued.)389 Figure2.Phylogenetic relationship between B.napus(BnNAC)and other plant NAC-domain proteins.The translated sequences used for alignment were as follows:BnNAC1-1,BnNAC3,BnNAC5-1,BnNAC5-7,BnNAC5-8,BnNAC5-11,BnNAC14,BnNAC18,BnNAC485, A.thaliana AtGRAB1and Triticum sativa TrGRAB1,A.thaliana ATAF1,A.thaliana ATAF2,A.thaliana NAC-domain proteins at locus At4g27410and locus At1g52890,A.thaliana AtNAC1(AF198054)and A.thaliana AtNAM(AF123311).Groups were assigned based on similarity to ATAF2(Group I),AtGRAB1(Group II),ATAF1(Group III)and BnNAC485(Group IV).The tree is a consensus of100 neighbor-joined trees and numbers at the nodes indicate bootstrap values.amino acids.Previously,a nuclear localization sig-nal was proposed to reside in subdomain C(Kikuchu et al.,2000);however,neither this region nor any other sequence in the NAC domain conformed to ca-nonical monopartite and bipartite nuclear localization elements as determined with PredictNLS software. The latter portion of subdomain A was predicted to form anα-helix,while the remainder of the NAC domain consisted of alternatingβ-sheet andβ-strand (loop)structures.All of the BnNAC carboxy-terminal domains were predicted to lack extensiveα-helix andβ-sheet struc-ture and consisted primarily of loops.These do-mains contained regions that were rich in either ser-ine/threonine,acidic and proline/glutamine residues (Figure1B).The carboxyl-terminal regions of the Group IB(ATAF2-like)and Group III(ATAF1)Bn-NAC proteins were predicted to contain PEST do-mains common to regulatory proteins that are rapidly targeted for degradation by the ubiquitin-26S proteo-some pathway(Rechsteiner and Rogers,1996).A BLASTX scan of the A.thaliana genomic DNA sequence identified103open reading frames that could encode NAC domain proteins.The highly vari-able carboxy-terminal regions of the BnNAC proteins were compared to the corresponding regions of these A.thaliana proteins to identify homologues or related gene families(Figure1B).BnNAC14was closely re-lated to the AtGRAB1-like protein but neither bore much similarity to the Triticum aestivum TrGRAB1 (Figure1B.1).BnNAC5-11and BnNAC18exhibited a high degree of identity to one another and ap-peared to be homologues of ATAF1(Figure1B.2). Two regions within the variable carboxyl domains of BnNAC1-1,3,5-1,5-7and5-8were identical to ATAF2(Figure1B.3).Phylogenetic analysis con-firmed these relationships with distinct nodes for the ATAF2(Group IA and IB),AtGRAB1(Group II)and ATAF1(Group III)related genes(Figure2).The Bn-NAC485cDNA isolated during a yeast two-hybrid screen(discussed later)encoded a300amino acid protein,the largest of the BnNAC reported here. Analysis of the variable domain identified a putative A.thaliana homologue of BnNAC485residing at locus At4g27410with a related gene at At1g52890(Fig-ure1B.4).Phylogenetic analysis revealed that these three proteins formed a single clade denoted Group IV(Figure2).Other well-characterized NAC domain proteins,such as TrGRAB1,TrGRAB2,AtNAC1, AtCUC2and AtNAM were not closely related to the BnNAC groups.Expression of BnNAC genesWe identified several B.napus NAC domain genes amongst ESTs enriched for induction in response to wounding,growth at a reduced temperature and in-sect feeding.Northern blot analysis with the conserved amino terminus of the BnNAC1-1cDNA as a probe390Figure3.Northern blot analysis of individual B.napus NAC gene expression in response to biotic and abiotic stress.Leaves from 8-week old B.napus DH12075plants were sampled at30min and 2h after mechanical wounding by crushing with forceps,being fed upon byflea beetles for7and30h,being infected with Sclerotinia sclerotiorum for18h,being subjected to5◦C for10h or dehyd-rated to the point of wilting.DNA probes used corresponded to the carboxy-terminal region unique to each BnNAC gene.A5µg portion of total RNA was loaded and each blot was probed with the B.napus actin cDNA to verify loading uniformity.revealed that BnNAC gene expression was induced rapidly(within30min)in response to mechanical wounding.This response was transient,returning to basal levels of expression within10h.Damage caused byflea beetle herbivory or infection with S.sclero-tiorum also induced gene expression;however,the level did not dissipate with time as damage to the tis-sue was continuous.Transferring plants from22◦C to5◦C induced expression within4h of exposure; however,levels continued to increase for the initial 24h period and then remained elevated.Conversely, dehydration to the point of wilting did not appear to affect expression.DNA probes specific to the variable carboxyl-terminal domains were used to determine the expres-sion profiles of six BnNAC genes or gene families (Figure3).BnNAC1-1expression was induced by in-sect and pathogen attack and to a lesser extent by mechanical wounding.Insect,pathogen and mechan-ical damage also induced the expression of BnNAC5-1 and BnNAC5-7,but both responded more strongly to mechanical wounding than BnNAC1-1.BnNAC14ex-pression was induced by mechanical wounding,and to a lesser degree byflea beetle damage,but not by pathogen infection,cold or dehydration.BnNAC5-8and BnNAC5-11were the only genes found to be highly induced by exposure to lower temperature and were responsive to other forms of tissue damage as well.While the basal levels of BnNAC expression var-ied among the individual genes,only BnNAC5-1was definitively induced by dehydration.Expression of BnNAC genes in A.thalianaSix BnNAC genes,as well as a BnNAC5-1anti-sense construct,were introduced into A.thaliana and expressed under the control of the constitutive CaMV35S promoter.Plants transformed with the an-tisense BnNAC5-1construct did not exhibit any phen-otypic difference from either untransformed plants or lines transformed with vector alone.Transgenic plants expressing BnNAC1-1,5-1,5-7,5-8and5-11sense constructs and representing the ATAF1and ATAF2 groups were difficult to isolate.Transformed plants, as confirmed by PCR and growth under kanamycin se-lection,failed to develop adequate root systems.These plants did not generally progress beyond thefirst true leaf stage and exhibited punctate chlorotic patterns on thefirst true leaves prior to death.Those lines that survived antibiotic selection exhibited severe develop-mental abnormalities(Figure4),with BnNAC5-7,5-8 and5-11being more pronounced than BnNAC1-1or BnNAC5-1.The plants generally formed tight rosettes consisting of small curled or cup-shaped leaves.Buds developed in tight clusters in close proximity to the rosette,bolts were rare and if present were usually less than1cm long.The inflorescence possessed poorly developed or fused sepals and petals causing the pistil and stamen to protrude.Siliques formed very rarely and gave rise to small seed that failed to germinate. Due to the small plant size and sterility of the trans-formed lines,it was not possible to isolate sufficient amounts of mRNA for transcript analysis.As such,it could not be determined if the observed phenotypes were due to ectopic expression of the BnNAC genes or co-suppression of the ATAF1and ATAF2homologues. However,a homozygous A.thaliana ATAF2T-DNA insertion line did not exhibit any of the aforementioned abnormalities indicating that the phenotype is likely due to ectopic BnNAC expression.391 Figure4.Ectopic expression of BnNAC genes in A.thaliana.Expression of BnNAC5-7,BnNAC5-8and BnNAC5-11typically resulted in underdeveloped and fused sepals and petals leading to protrusion of the pistil(A,B,E–H)and curled or cup-shaped cotyledons and true leaves (C,D,G and H).Expression of BnNAC14typically resulted in delay in bolting(I),larger leaves(J)and hyper-developed lateral root formation and absence of root apical dominance(K).Conversely,plants confirmed to express BnNAC14 by northern blot analysis exhibited a‘robust’pheno-type.Leaves from these lines grew to approximately twice the normal width and were wrinkled or undu-late in appearance(Figure4).In time course exper-iments,the BnNAC14lines germinated and grew at the same rate as non-transformed plants until they reached the rosette stage.At this point,the untrans-formed plants proceeded to bolt while the BnNAC14 lines remained in the rosette stage for an additional 3–10days before thefirst bolt appeared.During this period leaf size,leaf number and root mass continued to increase.These plants generally possessed thicker stems,althoughflower development,silique formation and seed set were not affected.The BnNAC14lines also lacked an apical-dominant taproot present in un-transformed lines and exhibited extensive lateral root system development near the surface(Figure4). BnNAC proteins as transcriptional activatorsRecent studies demonstrated that a transcription activ-ation domain resided within the carboxy-terminal re-392gion of two A.thaliana NAC domain proteins,namely AtNAM and NAC1(Xie et al.,2000;Duval et al., 2002).Since the carboxy terminus is highly variable among the NAC domain proteins,we used a yeast-one-hybrid system to examine whether the nine BnNAC proteins could also function as transcriptional activ-ators.Each of the BnNAC open reading frames were fused to the GAL4DNA-binding domain and the chi-mera placed under the control of the ADH1promoter. These constructs were introduced into S.cerevisiae MaV203that contained a LacZ reporter gene under the control of the GAL1promoter with an associated GAL4DNA binding site.Beta-galactosidase activ-ity was detected with lines expressing members of the ATAF1(BnNAC5-11and BnNAC18)and ATAF2 (BnNAC1-1,BnNAC3,BnNAC5-7and BnNAC5-8)groups,as well as with BnNAC485(Figure5). Yeast lines expressing BnNAC14,belonging to the At-GRAB1group,exhibited only a very small amount ofβ-galactosidase activity,whereas BnNAC5-1was the only ATAF2-like protein that did not activate tran-scription of the reporter gene.Transcripts correspond-ing to the BnNAC5-1fusion were detected in this yeast line.Deletion analysis of BnNAC5-8and BnNAC485 revealed that the variable carboxy-terminal domain was responsible for transcriptional activation,whereas the conserved NAC domain was unable to promote transcription.With BnNAC5-8,the region compris-ing the acidic and proline/glutamine-rich elements (Figure1B)was alone responsible for transcription ac-tivation,while the serine/threonine-rich region did not function in this regard(Figure5).Neither of the Bn-NAC485carboxy-terminal subdomains was capable of promoting transcription when examined alone.Dele-tion analysis of BnNAC14revealed that the slight tran-scription activation activity observed resided within thefirst two conserved NAC sub-domains,N A−B. However,this activity was lost or reduced when N A−B was associated with additional NAC subdomains or in the context of the entire protein and may be merely an experimental artifact.Interaction of BnNAC proteins with the CaMV35S promoterThe region comprising the N D−E subdomains of At-NAM and NAC1was shown to recognize the AGG-GATG within the as-1activation element of the CaMV 35S promoter(Xie et al.,2000;Duval et al.,2002). The N D−E subdomains exhibit a high degree ofse-Figure5.Determination of B.napus NAC protein transcription activation potential and mapping of activation domains with the yeast one-hybrid system.The BnNAC proteins were subdivided intofive NAC subdomains(N A−E)and two carboxy-terminal variable domains(V A−B)and fused to the GAL4DNA-binding domain(B).The constructs were introduced into S.cerevisiae MaV203which contained a LacZ reporter gene under the control of the GAL1promoter with an associated GAL4DNA-binding site. Beta-galactosidase activity(units)was indicative of transcription activation.quence similarity;however,the region separating the two subdomains of the BnNAC Group I(ATAF2) and Group III(ATAF1)proteins differs extensively from that present in AtNAM,NAC1,BnNAC14or BnNAC485.The ability of the BnNAC proteins to bind to and trans-activate the CaMV35S promoter was assessed in yeast using a GUS gene fused to a minimal CaMV35S promoter but containing the as-1activation element.Each of the Group I and Group III BnNAC proteins,with the exception of BnNAC5-1,was able to activate transcription of the minimal CaMV35S promoter(Figure6).The amount of GUS activity did not correlate with the strength of the resid-ent activation domain as determined earlier(Figure5) suggesting that the degree of trans-activation could be a consequence of both the avidity of DNA bind-ing and the efficiency of activation.Neither BnNAC14。

第7章种群原理Population PrinciplesA population can be defined as a group of individuals of the same species inhabiting an area。

Some important ways in which populations differ include natality （birthrate），mortality (death rate)，sex ratio, age distribution， growth rates， density, and spatial distribution。

In human populations， natality is usually described in terms of the birthrate，the number of individuals born per l000individuals per year。

In human population studies， mortality is usually discussed in terms of the death rate, the number of people who die per 1000 individuals per year.The population growth rate is the birthrate minus the death rate.The sex ratio refers to the relative numbers of males and females.The age distribution, the number of individuals of each age in the population，greatly influences the population growth rate。

a r X i v :c o n d -m a t /9505151v 1 30 M a y 1995Hohenberg-Kohn theorem is validIn a recent paper,Gonze et al (GGG)[1],claim that the Hohenberg-Kohn theorem (HKT),which is the ba-sis of the widely used density functional theory(DFT),is incorrect for periodic solids in an external field,and pro-pose an alternative “density-polarization functional the-ory”.While the proposed method itself is correct,and may become useful in practice,the statement about inva-lidity of the HKT is wrong,and the useful technical point of Ref.[1]is wrapped into a set of formally incorrect and misleading statements.First it is necessary to separate inaccuracies of the local density approximation (LDA)and fundamental problems with the DFT which are confused in GGG.GGG state that the DFT fails to describe static dielectric response for semiconductors.In reality,accurate DFT calculations for dielectric response,even in the LDA,are very compli-cated,because the dielectric function strongly depends on the local field corrections in form of Umklapp pro-cesses and exchange-correlation (XC)corrections.Exist-ing calculations give the results accurate within ≈10%(GGG,Ref.5),which is not bad,in view of the crudeness of LDA.Note that the XC interaction,I xc ,which defines the local fields,is the second variation of the XC energy,and thus very sensitive to the LDA.The discontinuity of of the XC potential,leadind to adifference between the DFT band gap,E DF Tg ,and thereal gap,E expg ,is the reason why the DFT and the many body theory,which treat XC prinicipally differently,must give the same static dielectric function.To the contrary,GGG mention the difference between E DF T gand E expg as an argument that DFT is not able to describe the static response.Taking this alleged failure of the exact DFT for granted,the authors proceed with the statement that the HK theorem does not apply to periodic solids in an external field.Their argument is that an infinite solid in a spatially unlimited homogeneous field does not have a ground state,and thus the HK theorem,whose ob-jects are ground states only,does not apply.This argu-ment is equivalent to the statement that neither infinite solids nor unlimited fields exist in nature.As soon as periodic boundary conditions are applied,this argument fails.Rather what is necessary is to use the method of long waves and treat a potential wave of wavelength q ,and one must make clear distinction between the wave vectors q <1/L ,and q ≫1/L ,where L is the size of the system [2]as one takes the infinite size limit.Since the HK theorem applies to any physical system,like a macroscopically large crystal,L ≫a (a is the lattice pa-rameter),in a flat capacitor with the plates much larger than L ,or to a system subject to an external field with finite q ,it can be used to treat any real physical problem.The next misleading step in GGG is after making an argument applicable only (with the reservation above)to the homogeneous field,the authors consider a fi-nite q field,for which the HK theorem holds without any reservation.What they actually prove is a theo-rem which holds in addition to ,but not instead of ,the HK theorem,namely that the total energy of a peri-odic solid is a functional of the periodic density,n G =G =0exp((i (q +G )r )n (q +G ),n (r )=exp(i qr )n (q )+n G ,and macroscopic polarization.HK theorem states that the same energy is a functional of the total den-sity,including exp(i qr )n (q ),and this is correct.Eq.8in GGG which purports to disprove HK,instead simply shows a separation of the long wave and local parts of the problem,both of which must be included in HK since HK deals with the whole system,not its parts.The example given by GGG illustrates this:Using pe-riodic potential ∆V eff,2they reproduced the correct den-sity within one cell,while the correct,non-periodic poten-tial ∆V eff,1gives correct density for the whole supercell.There is nothing counterintuitive in this result,nor is it “in contrast to a naive application of DFT”.Finally,discussion of the “scissor correction”is also misleading.A scissor correction enlarges the gap,bring-ing the RPA polarizability of the Kohn-Sham particles closer to the RPA polarizability of real one-electron ex-citations.Fully renormalized polarizability,however,in-cludes the local field corrections (note that Eq.11of GGG is just the long-wave part of the XC local field).The latter are principally different in the DFT and in the many-body theory (e.g.,they have qualitatively dif-ferent behaviour at q +G →0).Of course,the fact that I xc in LDA is a contact interaction,may constitute a large difference between LDA and exact DFT,reflectedin a difference of E LDAg from E DF T g,which probably may be corrected by a scissor-like technique.It should notbe mixed with the difference between E DF Tgand E exp g ,which should not be corrected at all,since this difference is to be cancelled by the appropriate difference in the XC corrections.To conclude,the claim of Gonze et al that DFT is in-valid for dielectric response,and should be substituted by a density-polarization functional theory,is incorrect,but the theorem they have proven (that the total energy is a functional of polarization and periodic part of den-sity)is correct and may become useful in the future.We also would like to thank J.Serene for discussion of this Comment.I.I.Mazin and R.E.CohenCarnegie Institution of Washington5251Broad Branch Rd.,Washington,DC 2001530May 1995。

Resources,Conservation and Recycling 54 (2010) 1074–1083Contents lists available at ScienceDirectResources,Conservation andRecyclingj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /r e s c o n r ecPhysical geonomics:Combining the exergy and Hubbert peak analysis for predicting mineral resources depletionAlicia Valero ∗,Antonio ValeroCentre of Research for Energy Resources and Consumptions,CIRCE,University of Zaragoza,María de Luna 3,Zaragoza 50018,Spaina r t i c l e i n f o Article history:Received 14May 2009Received in revised form 19January 2010Accepted 24February 2010Keywords:ExergyHubbert peak ScarcityFuel mineralsNon-fuel mineralsa b s t r a c tThis paper shows how thermodynamics and in particular the exergy analysis can help to assess the degradation degree of earth’s mineral resources.The resources may be physically assessed as its exergy content as well as the exergy required for replacing them from a complete degraded state to the con-ditions in which they are currently presented in nature.In this paper,an analysis of the state of our mineral resources has been accomplished.For that purpose an exergy accounting of 51minerals has been carried out throughout the 20th century.This has allowed estimating from geological data when the peak of production of the main mineral commodities could be reached.The obtained Hubbert’s bell-shaped curves of the mineral and fossil fuels commodities can now be represented in an all-together exergy–time representation here named as the “exergy countdown”.This shows in a very schematic way the amount of exergy resources available in the planet and the possible exhaustion behaviour.Our results show that the peak of production of the most important minerals might be reached before the end of the 21st century.This confirms the Hubbert trend curves for minerals obtained by other authors using a different methodology.These figures may change,as new discoveries are made.However,assuming that these discoveries double,most of the peaks would only displace our concern around 30years.This is due to our exponential demand growth.The exergy analysis of minerals could constitute a universal and transparent tool for the management of the earth’s physical stock.© 2010 Elsevier B.V. All rights reserved.1.IntroductionThe 20th century has been characterized by the economic growth of many industrialized countries.This growth was mainly sustained by the massive extraction and use of the earth’s mineral resources.For instance,only in the US over the span of the last century,the demand for metals grew from a little over 160mil-lion tons to about 3.3billion tons (Morse and Glover,2000).The tendency observed worldwide in the present,is that consumption will continue increasing,especially due to the rapid development of Asia,the desire for a higher living standard of the developing world and the technological progress.But the physical limitations of our planet might seriously restrain world economies.However,inter-national worries are still very far removed from this fact.Currently,most attention is focused rather on the consequences of the use of natural resources,such as climate change,loss of biodiversity or pollution of soils and rivers,than on the depletion of minerals.Obvi-ously the former problems need and are slowly being solved with international agreements,dissemination campaigns,etc.Further-more,the huge amount of energy received every day from the sun (1353J/m 2s)helps restoring at least partially the damages caused∗Corresponding author.E-mail address:aliciavd@unizar.es (A.Valero).to the biosphere,atmosphere and hydrosphere.On the contrary,the natural reposition of the geosphere,which comes mainly from the earth’s interior energy (0.034–0.078J/m 2s—Skinner et al.,1999),is close to zero when compared to that of the other external earth’s spheres.As discussed in Valero and Valero (2010),during millions of years,nature has formed and concentrated minerals through a large number of geological processes such as magmatic separation,hydrothermal,sedimentary,residual,etc.(Chapman and Roberts,1983)forming the currently existing natural stock.The concen-trated mineral deposits serve as a material and fuel reservoir for man.And the more concentrated is a mineral deposit,the less effort is required for extraction.The mining of materials implies an obvious reduction of the natural stock in terms of the min-erals extracted from the mines and the fossil fuels required for the mining processes.Those extracted minerals are concentrated and further refined to obtain the desired raw materials,for which additional quantities of fuels and minerals are required.This way,the natural stock stored in the earth’s crust goes into the hands of society as man-made stock.When the useful life of products finishes,they become dispersed,ending up as wastes (either as pol-lution or disposed of in landfills).As Gordon et al.(2006)argue,the relative sizes of the remaining stock in the lithosphere and the stock transferred to wastes at any given time are measures of how far we have progressed toward the need for total reliance0921-3449/$–see front matter © 2010 Elsevier B.V. All rights reserved.doi:10.1016/j.resconrec.2010.02.010A.Valero,A.Valero/Resources,Conservation and Recycling54 (2010) 1074–10831075on recycling rather than on virgin ore to provide material for new products.Unfortunately,the Second Law of Thermodynamics reflected in Eq.(2),tells us that as the concentration of the resource in the earth’s crust tends to zero,the energy required to extract the min-eral tends to infinity.Consequently,from a practical point of view, it is impossible to recover resources again when they become dis-persed.In a not very distant future,it will be easier to extract metals from landfills than from the crust.This is why recycling is so important to society.But fossil fuels or many additives like Cr,Mo,Mn in steel or in paints,or the new age of high-tech metals such as In,Ge,Ta,etc.included in nanotechnol-ogy and microelectronics are impossible or extremely difficult to recycle.Georgescu-Roegen,1father of ecological economists,states that we can only recycle“carbojunk”.That means that we cannot recycle completely.Furthermore,the worldwide rush for strate-gic materials is causing dramatic consequences in less developed countries such as irreversible environmental damage,corruption and even wars.This effect is named by Humphreys et al.(2007)as the“natural resources curse”.Our technology is quite inefficient in the use of energy and mate-rials,since there is a lack of awareness of the limit.If resources are limited,their management must be carefully planned.But it is impossible to manage efficiently the resources on earth,if we do not know what is available and at which rate it is being depleted.Hence, we need management tools,accountability and political will to accomplish this.The Extractive Industries Transparency Initiative (2006)is becoming an internationally accepted standard for eco-nomic transparency in the oil,gas and mining sectors.But it is still insufficient,since physical and objective information about the remaining resources such as ore grades,quantity of energy and water required for extraction,the amount of waste rock and other physical parameters that would allow an objective analysis of our mineral capital is rarely published.Rational management tools for the efficient use of resources require a theoretical basis,naturally provided by thermodynamics. For a thermodynamicist,this is so obvious,that it is hard to believe that very little systematic effort has been devoted to it.The use of the Second Law through the exergy concept,allows to progress into something more than words.Concepts can be converted into num-bers,and then into objective and universal indicators.The objective of this paper is to contribute to put Second Law numbers to the natural resources depletion and in particular to mineral resources.Georgescu-Roegen was one of thefirst authors in realizing the links between the economic process and the Second Law of thermo-dynamics.In his seminal work The Entropy Law and the Economic Process(Georgescu-Roegen,1971),he states that“the entropy law itself emerges as the most economic in nature of all natural laws[...] and this law is the basis of the economy of life at all levels”.More authors such as Berry et al.(1978),Ruth(1995)or Roma(2006)and Roma and Pirino(2009)state that economic production processes should consider thermodynamic limits on material and energy use in order to be optimal in the long-run.Berry et al.(1978)developed a theorem forfixing the economically-efficient level of thermody-namic efficient production systems.As an example,Ruth(1995) determined the optimal extraction path and production of iron ore at each period of time,taking into account thermodynamic limits on material and energy efficiency,the treatment of technical change through the theory of learning curves and the evaluation of alterna-tive time paths from an economic and thermodynamic perspective. Roma(2006)and Roma and Pirino(2009)developed different mod-els for production processes,imposing energy rather than standard 1See the interview of Antonio Valero with Nicholas Georgescu-Roegen under: http://habitat.aq.upm.es/boletin/n4/aaval.html.monetary terms as a mean of exchange.As a result,the authors state that resources will be more efficiently used,reducing thereby entropic wastes.Parallelly,concerned environmentalists search for alternate indicators closer to nature or social descriptions.A plethora of measuring units(or numeraires)appear,almost one per indica-tor.In particular,those who account for minerals and fossil fuels, have a spectrum of definitions and measurement units that actu-ally impede to make a systematic and universally accepted account of what the earth’s crust provides annually and what remains.On the other side,it is obvious that money cannot be the best unit of measure for the assessment of resources,since currency changes from one country to another,its value depends on dif-ferent factors and moreover,it is impossible to quantify nature in monetary terms,without opening the door to arbitrariness.Nature does not sell anything that we could buy with money.It only can be compensated with counteractions like recovering,restoring and replacing techniques which obviously have an associated cost. These arguments are solid and obvious.However they are difficult to admit,due to the familiarity and omnipresence of money.The argument the cost is not measured with money or everything costs more than the money we pay should be placed over everything can be bought.So,which should be the unit of measure of cost?The answer to this question is in the Second Law of Thermodynamics:if the cost is a sacrifice of resources,and the already consumed resources have been consumed forever,one can deduce that we should see this fact as the base of the physical accountability.In thisfield,Thermody-namics provides tools such as energy,entropy or exergy,among others.The problem with energy is that it does not distinguish quality.Although exergy is also one-dimensional,it is sensible to quantity and quality of the interchanged energy and has energy dimensions.In fact,exergy measures the minimum quantity of use-ful energy required to provide a system for building it from its constituent elements found in the reference environment(R.E.). The reference environment is a hypothetical and homogeneous earth,where all substances have been reacted and mixed,without kinetic or potential energy and at ambient pressure and tempera-ture.Once the R.E.has been defined,the minimum thermodynamic cost or exergy of any material or energyflow can be calculated.This is very important,as exergy takes into account all physical manifes-tations that differentiate the system from its environment:height, velocity,pressure,temperature,chemical composition,concentra-tion,etc.And this is not a function of how much we appreciate things,but on the useful energy that can be released until its deple-tion.On the other hand,the exergy concept participates in all properties of the cost concept:it is additive and can be calculated from the production process.But the process should be considered as reversible in all its steps.The most important contribution of the exergy concept is in its ability to objectify all the physical manifestations in energy units, independently of the economic value.Any product,natural or arti-ficial resource,productive process or polluting emission can be valued from an exergy point of view.This is why a good number of researchers believe that exergy can contribute to the assessment of certain environmental concerns(Szargut,2005,Brodianski,2005, Wall,1977,Sciubba,2003,or Ayres et al.,2004).2.Theoretical backgroundThe most important features thatfix the value of a mineral resource are on one hand its chemical composition and on the other hand its concentration—both characteristics which can be assessed with the single indicator of exergy.1076 A.Valero,A.Valero /Resources,Conservation and Recycling 54 (2010) 1074–1083The chemical composition of a substance is the key factor for fixing the final use of the resource.Furthermore,it has a direct influence on the energy required for processing the mineral (Valero and Valero,2010).For instance,the energy required to extract pure copper from a sulphide is significantly smaller than from an oxide,therefore copper sulphides such as chalcopyrite (CuFeS 2)are pre-ferred as copper ores (see Gerst,2008).The chemical exergy in kJ/mol can be calculated using the following well known expression (Szargut et al.,1988):b ch =v k b 0chel,k+ G mineral(1)where b ch el,k is the standard chemical exergy of the elements that compose the mineral and can be easily found in tables,v k is the number of moles of element k in the mineral and G is the Gibbs free energy of the mineral.The minimum amount of energy –exergy –involved in con-centrating a substance from an ideal mixture of two components is given by the following expression (see for instance Faber and Proops,1991):b c =−RT 0ln(x i )+(1−x i )x iln(1−x i )(2)where b c is the concentration exergy,x i is the molar concentration of substance i,R is the gas constant (8.3145J/mol K)and T 0is the reference temperature (298.15K).The difference between the con-centration exergies obtained with the mineral concentration in a mine x m and with the average concentration in the earth’s crust x c is the minimum energy (kJ/mol)that nature had to spend to bring the minerals from the concentration in the reference state to the concentration in the mine.A more comprehensive expression of the reversible separation energy of an ideal mixture of components is provided by Tsirlin and Titova (2004).In their finite-time thermo-dynamics model,linear kinetics is additionally taken into account.However,in the timeless limit,Tsirlin and Titova’s model converges to Eq.(2).This way,the total replacement exergy (b t —kJ/mol),i.e.its natu-ral exergy,representing the minimum exergy required for restoring the resource from the R.E.to the initial conditions in the mineral deposit,is calculated as the sum of the chemical and concentration exergy components (Eq.(3)).b t =b ch +b c(3)Specific exergies (b t )are converted into absolute exergies (B t )by multiplying the quantities by the moles of the substance con-sidered.However,a study based only on reversible processes (minimum replacement exergies)would ignore technological limits.Results show that,in general,the real energy requirements are tens or even thousands of times greater than the exergy content of the mineral (Valero and Botero,2002).The calculation of the exergy replacement costs b ∗t of the resource,representing the actual exergy required to replace the resource from the R.E.to its initial conditions,with current available technology commonly have two contributions,b ∗t =k ch ·b ch +k c ·b c(4)its chemical cost (k ch ·b ch ),accounting for the chemical produc-tion processes of the substance,and its concentration cost (k c ·b c ),accounting for the concentration processes.Variable k (dimension-less)represents the unit exergy replacement cost of a mineral.It is defined as the relationship between the energy invested in the real obtaining process (E real process )for either refining (k ch )or concen-trating the mineral (k c ),and the minimum energy (exergy)required if the process from the ore to the final product were reversibleTable 1Unit exergy costs of seven base-precious metals (updated from Valero and Botero,2002).Metal k ck ch Ag 7041.81Au 422,879.01Cu 343.180.2Fe 97.4 5.3Ni 431.858.2Pb 218.825.4Zn125.913.2( b mineral ).k =E realprocessb mineral(5)The exergy cost concept developed by Valero et al.(1986)and Lozano and Valero (1993)is also named embodied exergy or cumulative exergy consumption (Szargut et al.,1988).Valero and co-workers focused on the physical roots of cost as well as on pro-viding the concept with a theoretical framework.Table 1shows as an example,the unit exergy replacement costs of some important minerals considered in this paper.These values have been updated by the authors from Valero and Botero (2002).A key study pointing out the actual relationship between ther-modynamic limits and the extraction of mineral resources is that of Chapman and Roberts (1983).These authors developed a com-prehensive treatise on the relationship between the abundance of resources and the energy required to extract them,models for the prediction of non-renewable resource depletion,thermodynamic limits for the exploitation of metals and the effect of recycling on the availability of materials.They observed a relationship between the cut-off ore grade,g ,expressed in weight percentage and the his-torical cumulative production of a given metal,T .This relationship can be expressed as,ln T =−m ln g +c,(6)where c reflects the relative abundance of the metal considered and m the degradation velocity.Values estimated from historical data for constant m can be found in Nguyen and Yamamoto (2007).According to Chapman and Roberts (1983),the energy (approxi-mately equal to its exergy cost b*)required for mining and milling may be expressed as:b ∗=e g(7)where e is the specific energy consumption for mining and milling the metal.A typical value for e is 0.4MJ/kg for open pit mining,and 1.0MJ/kg for underground mining.Eqs.(6)and (7)show empirically what Second Law tells us about the natural exponential behaviour of the exergy needed for extract-ing a material from a mixture as a function of its ore grade (Eq.(2)).The lower the ore grade,the more effort per unit of material is needed to extract it.Even if the earth’s crust is plenty of ele-ments and minerals,its concentration may be so low that the exergy required to extract them from the bare rock becomes economically prohibitive,making it impossible in practice.Following this behaviour,it is natural to resort to the well known Hubbert peak (traditionally used for estimating the peak of produc-tion of fossil fuels—Hubbert (1962))for its application to minerals.Basically,Hubbert (1962)found that the production of fossil fuel trends had a strong family resemblance.The curves started slowly and then rose more steeply tending to increase exponentially with time,until finally an inflection point was reached after it became concave downward.The observed trends are based on the fact that no finite resource can sustain for longer than a brief period such aA.Valero,A.Valero/Resources,Conservation and Recycling54 (2010) 1074–10831077Fig.1.The exergy replacement cost loss of the main non-fuel mineral commodities on earth in the20th century. rate of growth of production;therefore,although production ratestend initially to increase exponentially,physical limits prevent theircontinuing to do so.So for any production curve of afinite resourceoffixed amount,two points on the curve are known at the outset,namely that at t=0and again at t→∞.The production rate will bezero when the reference time is zero,and the rate will again be zerowhen the resource is exhausted,after passing through one or sev-eral maxima.The second consideration is that the area under theproduction curve must equal the quantity of the resource available(R).In this way,the production curve of a certain resource through-out history takes the ideal form of a bell-shaped curve representedby Eq.(8).f(t)=Rb0√e−(t−t0)/b0(8)where parameters b0and t0are the unknowns and R the economic proven reserves of the commodity.The model was successful in predicting the peak of oil extraction in the US lower48states and the subsequent decline in produc-tion.Recently,several authors used Hubbert’s model to predict the evolution of crude oil extraction at the planetary level(Deffeyes, 2001;Bentley,2002;Campbell and Laherrere,1998).According to these estimates,the corresponding production peak could take place within thefirst decade of the21st century or not much later. And as Campbell and Laherrere(1998)argue,from an economic perspective,when the world runs completely out of fuels is not directly relevant:what matters is when production begins to taper off.Beyond that point,prices will rise unless demand declines com-mensurately.Bardi and Pagani(2008)examined the world production of57 minerals reported in the USGS database.They came to the conclu-sion that the bell-shaped curve can be used globally and for most minerals,not only for oil extraction.Moreover,we think that the bell-shaped curve is better suited to minerals,if it isfitted with exergy over time instead of mass pro-duction of the metal commodity over time.Oil quality keeps nearly constant with extraction,whereas other non-fuel minerals do not (mineral’s concentration decreases as the mine is being exploited). Therefore exergy is a much better unit of measure than mass,since it accounts not only for quantity,but also for ore grades and mineral composition.Furthermore,if the Hubbert model is applied to the exergy replacement costs explained before,the technological factor of extracting and refining the mineral is also taken into account.In short,the well known bell-shaped curve can befitted to the exergyor exergy replacement cost consumption data provided,in order to estimate when mineral production will start declining.With our proposal,the yearly exergy replacement cost loss of the commodity calculated with Eq.(5)is represented versus time f(t).With a least squares procedure,the points are adjusted to the curve given by Eq.(8).The maximum of the function is given by parameter t0,and it verifies that f(t0)=R/b0√.3.The exergy loss of world’s mineral reserves in the20th century3.1.Non-fuel mineralsWith the help of historical data compiled by the USGS(2007), and the equations presented above,we have calculated the exergy(B t)and exergy replacement cost(B∗t)destroyed due to non-fuel mineral extraction throughout the20th century of the51most important mineral commodities(see Table2).Furthermore,the average degradation velocities and the latest degradation velocities in minimum exergy and exergy cost terms(˙B t and˙B∗t)registered (from1996to2006)are calculated.The concentration factor has been assumed to be constant and equal to the average ore grades estimated in Valero(2008).Obviously,a better approximation would take into account the evolution of the ore grades with his-tory.But unfortunately this information is generally not compiled and there is only available data for Australia(Mudd,2007).The depletion degree of the commodities shown in Table2(%R and% R.B.)has been obtained as the ratio between the exergy destroyed due to extraction,and the total exergy of the reserves or reserve base of the considered commodity.The latter are obtained as the published reserves or reserve base of the commodity in2006,plus the exergy destroyed from1900to2006.2Finally,the resources to production ratio R/P with exergy units is provided,as a measure of the years until depletion of the commodity.It has been assumed that production remains as in year2006,and that reserves do not increase after that year.****2According to the USGS,reserve base is defined as that part of an identified resource that meets specified minimum physical and chemical criteria related to current mining and production practices,including those for grade,quality,thick-ness,and depth.The reserve basefigure is larger than that of the“reserves”one, which is defined as that part of the reserve base which could be economically extracted or produced at the time of determination.1078 A.Valero,A.Valero/Resources,Conservation and Recycling54 (2010) 1074–1083Table2The exergy and exergy replacement cost loss of the main mineral commodities in the world and average degradation velocities(Valero et al.,2010). Mineral1900–20061996–20062006B t B∗t ˙B t˙B∗t˙B t˙B∗t%R loss%R.B.loss R/P,years R.B./P,yearsAluminium 5.64E+05 1.22E+07 5.27E+03 1.14E+05 1.85E+04 4.01E+0514.912.0135173 Antimony 5.13E+02 5.71E+03 4.80E+00 5.34E+01 1.18E+01 1.31E+0272.856.61632 Arsenic 5.75E+027.23E+03 5.37E+00 6.76E+01 6.91E+008.70E+0174.666.22030 Barite 1.53E+03N.A. 1.43E+01N.A. 3.47E+01N.A.61.025.224111 Beryllium 6.88E−01 3.60E+01 6.43E−03 3.37E−017.97E−03 4.17E−01N.A.N.A.N.A.N.A. Bismuth7.61E+00 1.24E+027.12E−02 1.16E+00 1.54E−01 2.50E+0041.124.756119 Boron oxide 4.04E+03N.A. 3.78E+01N.A. 1.69E+02N.A.39.221.14096 Bromine 2.41E+02N.A. 2.26E+00N.A.7.96E+00N.A.N.A.N.A.N.A.N.A. Cadmium 6.51E+01 3.54E+03 6.08E−01 3.31E+01 1.28E+00 6.98E+0166.845.12562 Cesium 6.62E−02N.A. 6.18E−04N.A.N.A.N.A. 1.20.8N.A.N.A. Chromium 4.53E+04 1.03E+05 4.23E+029.62E+02 1.32E+03 3.00E+03N.A.N.A.N.A.N.A. Cobalt 2.20E+02 1.10E+04 2.05E+00 1.03E+02 5.70E+00 2.86E+0219.511.5104193 Copper 2.96E+04 3.07E+06 2.76E+02 2.87E+047.94E+028.24E+0450.334.53262 Feldspar8.77E+02N.A.8.20E+00N.A. 3.51E+01N.A.N.A.N.A.N.A.N.A. Fluorspar9.95E+03N.A.9.30E+01N.A. 2.03E+02N.A.48.632.14590 Gallium 2.75E−01N.A. 2.57E−03N.A. 1.31E−02N.A.N.A.N.A.N.A.N.A. Germanium 6.52E−01N.A. 6.09E−03N.A. 1.24E−02N.A.N.A.N.A.N.A.N.A. Gold9.98E−018.17E+049.33E−037.64E+02 1.93E−02 1.58E+0375.458.91737 Graphite 3.26E+04N.A. 3.05E+02N.A.7.13E+02N.A.31.015.583204 Gypsum 1.40E+04N.A. 1.30E+02N.A. 3.51E+02N.A.N.A.N.A.N.A.N.A. Helium 1.32E+02N.A. 1.23E+00N.A. 4.11E+00N.A.N.A.N.A.N.A.N.A. Indium 5.45E−01N.A. 5.10E−03N.A. 3.35E−02N.A.34.326.41928 Iodine 1.12E+01N.A. 1.05E−01N.A. 3.86E−01N.A. 3.8 2.26001080 Iron 4.60E+06 3.22E+07 4.30E+04 3.01E+05 1.04E+057.26E+0527.714.984185 Lead 6.01E+03 2.35E+05 5.62E+01 2.19E+038.99E+01 3.51E+0372.555.12349 Lithium9.32E+03 3.49E+048.71E+01 3.26E+02 3.26E+02 1.22E+0362.338.11233 Magnesium 1.01E+04 1.01E+049.45E+019.45E+01 2.96E+02 2.96E+02N.A.N.A.N.A.N.A. Manganese 1.08E+05 1.04E+06 1.01E+039.75E+03 1.82E+03 1.76E+0451.98.739437 Mercury9.24E+00 3.16E+038.63E−02 2.95E+01 2.75E−029.40E+0092.269.431162 Molybdenum9.58E+02 1.80E+048.95E+00 1.68E+02 2.62E+01 4.92E+0237.521.447103 Nickel 4.48E+03 3.55E+05 4.18E+01 3.32E+03 1.31E+02 1.04E+0440.022.94295 Niobium 1.57E+02N.A. 1.46E+00N.A. 6.90E+00N.A.19.818.16167 Phosphate rock 5.47E+047.08E+04 5.12E+02 6.62E+02 1.19E+03 1.54E+0326.111.3127352 PGM 2.41E−01N.A. 2.25E−03N.A.8.35E−03N.A.14.413.0137154 Potash 1.30E+05 2.02E+05 1.22E+03 1.89E+03 2.94E+03 4.56E+0312.8 6.3285619 REE 6.65E+01N.A. 6.22E−01N.A. 2.85E+00N.A. 2.4 1.47151220 Rhenium 6.10E−027.43E+00 5.70E−04 6.95E−02 2.71E−03 3.30E−0124.27.453212 Selenium8.72E+00N.A.8.15E−02N.A. 1.77E−01N.A.48.231.053110 Silver 1.76E+01 1.69E+04 1.65E−01 1.58E+02 3.24E−01 3.11E+0278.563.41328 Strontium 1.83E+03N.A. 1.71E+01N.A.8.52E+01N.A.56.041.91221 Tantalum 4.71E+00 1.31E+03 4.41E−02 1.22E+01 2.30E−01 6.38E+0114.210.794130 Tellurium 4.65E−01N.A. 4.35E−03N.A.7.03E−03N.A.25.813.5159356 Thorium 1.58E+00N.A. 1.47E−02N.A.N.A.N.A. 1.2 1.0N.A.N.A. Tin 2.11E+03 1.08E+05 1.97E+01 1.01E+03 2.92E+01 1.51E+0375.262.72036 Uranium 2.47E+027.29E+04 2.31E+00 6.81E+02 4.68E+00 1.38E+0334.829.996120 Vanadium 4.40E+02 4.96E+03 4.11E+00 4.64E+01 1.56E+01 1.76E+028.9 3.2231675 Wolfram 3.01E+02 2.28E+04 2.81E+00 2.13E+02 6.02E+00 4.56E+0248.530.23269 Zinc 4.98E+049.09E+05 4.65E+028.49E+03 1.13E+03 2.06E+0468.144.41848 Zirconium 3.03E+02 2.91E+05 2.83E+00 2.72E+038.52E+008.18E+0343.829.23261 TOTAL 5.68E+06 5.11E+07 5.31E+04 4.78E+05 1.34E+05 1.29E+0625.614.292191Values are expressed in ktoe and ktoe/year for the degradation velocities.As shown in Table2,in reversible exergy terms,the exergy degradation of the non-fuel mineral capital on earth is clearly dom-inated by the extraction of two commodities:iron and aluminium, representing around81and10%of the total exergy consumption, respectively.The exergy destroyed due to non-fuel mineral extrac-tion between1900and2006is at least5.68Gtoe.As expected, the general consumption pattern has followed an exponential-like behaviour.This is reflected in the drastic change of the exergy degradation velocity(˙B),passing from around10Mtoe/year in 1910,to180Mtoe/year in2006.In irreversible terms,i.e.analyzing the exergy replacement costs (actual exergy)of the commodities,we observe in Fig.1that copper acquires a more important role.Copper is responsible for6%of the total exergy degradation costs on earth,while iron and aluminium, 63and24%,respectively.The irreversible exergy destruction of all analyzed commodities is at least51Gtoe.This means that with current technology,we would require a minimum of a third of all current fuel oil reserves on earth(178Gtoe(BP,2007))for the replacement of all depleted non-fuel mineral commodities. Excluding iron and aluminium,which eclipse the rest commodi-ties,we observe in Fig.2that in decreasing order,the production of manganese,zinc,nickel,zirconium,lead,chromium,uranium, tin and gold contribute also significantly to the planet’s non-fuel mineral capital degradation.Again,an exponential behaviour of the exergy costs of all commodities is observed.The average exergy cost degradation velocity in the20th century is at least0.5Gtoe/year.However in the last decade,this velocity increased to1.3Gtoe/year.According to the depletion ratios(%R loss and%R.B.loss)in Table2,man has depleted in just one century around26%of its world non-fuel mineral reserves,and around14%of its reserve base. The estimated years until the depletion of the total reserves and reserve base are around92and191years,respectively.It must be pointed out that these are only minimum numbers,as it has been。

Transitional time of oceanic to continental subduction in the Dabie orogen:Constraints from U –Pb,Lu –Hf,Sm –Nd and Ar –Ar multichronometric datingHao Cheng a ,b ,⁎,Robert L.King c ,Eizo Nakamura b ,Jeffrey D.Vervoort c ,Yong-Fei Zheng d ,Tsutomu Ota b ,Yuan-Bao Wu e ,Katsura Kobayashi b ,Zu-Yi Zhou aaState Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,ChinabInstitute for Study of the Earth's Interior,Okayama University at Misasa,Tottori 682-0193,Japan cSchool of Earth and Environmental Sciences,Washington State University,Pullman,Washington 99164,USA dCAS Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China eState Key Laboratory of Geological Processes and Mineral Resources,Faculty of Earth Sciences,China University of Geosciences,Wuhan 430074,Chinaa b s t r a c ta r t i c l e i n f o Article history:Received 22August 2008Accepted 9January 2009Available online 8February 2009Keywords:Continental subduction Dabie EclogiteGeochronologyOceanic subduction Tectonic transitionWe investigated the oceanic-type Xiongdian high-pressure eclogites in the western part of the Dabie orogen with combined U –Pb,Lu –Hf,Sm –Nd and Ar –Ar geochronology.Three groups of weighted-mean 206Pb/238U ages at 315±5,373±4and 422±7Ma are largely consistent with previous dates.In contrast,Lu –Hf and Sm –Nd isochron dates yield identical ages of 268.9±6.9and 271.3±5.3Ma.Phengite and amphibole Ar –Ar total fusion analyses give Neoproterozoic apparent ages,which are geologically meaningless due to the presence of excess 40Ar.Plagioclase inclusions in zircon cores suggest that the Silurian ages likely represent protolith ages,whereas the Carboniferous ages correspond to prograde metamorphism,based on the compositions of garnet inclusions.Despite weakly-preserved prograde major-and trace element zoning in garnet,a combined textural and compositional study reveals that the consistent Lu –Hf and Sm –Nd ages of ca.270Ma record a later event of garnet growth and thus mark the termination of high-pressure eclogite –facies metamorphism.The new U –Pb,Lu –Hf and Sm –Nd ages suggest a model of continuous processes from oceanic to continental subduction,pointing to the onset of prograde metamorphism prior to ca.315Ma for the subduction of oceanic crust,while the peak eclogite –facies metamorphic episode is constrained to between ca.315and 270Ma.Thus,the initiation of continental subduction is not earlier than ca.270Ma.©2009Elsevier B.V.All rights reserved.1.IntroductionSubduction zones are essential to the dynamic evolution of the earth's surface due to plate tectonics.Subduction of oceanic and continental crust eventually leads to closure of backarc basins and arc-continent and continent-continent collisions (O'Brien,2001;Ernst,2005;Zheng et al.,2008),forming various types of high-pressure (HP)and ultrahigh-pressure (UHP)metamorphic rocks.Subduction of oceanic lithosphere causes a complex continuum of diagenetic and metamorphic reactions;many kilometres of oceanic lithosphere are ultimately consumed prior to the subsequent continental slab subduction and collision.Subducted continental slabs that detach from the oceanic lithosphere that was dragging them into the mantle are expected to rapidly rise to Moho depths because of their positive buoyancy.Thus,studying subducted oceanic crust in subduction zones can provide clues to the incorporation rate of supercrustal materialinto the mantle and can shed light on the initiation of successive continental subduction.Determining a geochronological framework for determining the sequence and duration of oceanic to continental subduction and HP and UHP metamorphism plays an essential role in this respect.Zircon has long been recognized as a promising geochronometer of the U –Pb decay system because of its refractory nature,commonly preserved growth zones and mineral inclusions within a single grain.Recent developments in analytical techniques allow us to unravel a wealth of information contained in zircons with respect to their growth history and thus the prograde and retrograde metamorphic evolution of the host rock (Gebauer,1996;Wu et al.,2006;Zheng et al.,2007).The Lu –Hf garnet technique has been applied to constrain the prograde and high-temperature histories of metamorphic belts (e.g.,Duchêne et al.,1997;Blichert-Toft and Frei,2001;Anczkiewicz et al.,2004,2007;Lagos et al.,2007;Kylander-Clark et al.,2007;Cheng et al.,2008a )because of its high closure temperature (Dodson,1973;Scherer et al.,2000)and the fact that garnet strongly partitions Lu over Hf,resulting in a high parent/daughter ratio (Otamendi et al.,2002).Combined with Sm –Nd age determination,the Lu –Hf garnet geochronometer can potentially be used to estimate the duration ofLithos 110(2009)327–342⁎Corresponding author.State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China.Tel.:+862165982358;fax:+862165984906.E-mail address:chenghao@ (H.Cheng).0024-4937/$–see front matter ©2009Elsevier B.V.All rights reserved.doi:10.1016/j.lithos.2009.01.013Contents lists available at ScienceDirectLithosj ou r n a l h o m e pa g e :ww w.e l s ev i e r.c o m/l o c a t e /l i t h o sFig.1.Simpli fied geologic map of the Huwan mélange area (b)in southern Dabie orogen (a),modi fied after Ye et al.(1993)and Liu et al.(2004b),showing the sample localities for the Xiongdian eclogite.References:asterisk,this study;[1],Ratschbacher et al.(2006);[2],Jahn et al.(2005);[3],Liu et al.(2004a);[4],Eide et al.(1994);[5],Webb et al.(1999);[6],Xu et al.(2000);[7],Ye et al.(1993);[8],Sun et al.(2002);[9],Jian et al.(1997);[10],Jian et al.(2000);[11],Gao et al.(2002);[12],Li et al.(2001);[13],Wu et al.(2008).amp —amphibole;brs —barroisite;phen —phengite;zrn —zircon.328H.Cheng et al./Lithos 110(2009)327–342garnet growth,which either reflects early prograde metamorphism (Lapen et al.,2003),exhumation(Cheng et al.,2009)or a particular garnet growth stage(Skora et al.,2006).Dating the exhumation of high-pressure(HP)and ultra-high-pressure(UHP)metamorphic rocks by conventional step-heating Ar–Ar technique was largely hampered and discredited due to the presence of excess/inherited argon(Li et al.,1994;Kelley,2002).However,the Ar–Ar geochron-ometer remains irreplaceable in constraining the exhumation of HP/ UHP metamorphic rocks because of its intermediate closure tempera-ture.Nevertheless,timing must be integrated with textures and petrology in order to quantify the dynamics of geological processes, whichever geochronological method is used.During the past two decades,considerable progress has been made in constraining the prograde metamorphism and exhumation of HP/ UHP metamorphism of the Dabie–Sulu orogen by a variety of geochronological methods,indicating a Triassic collision between the South China and North China Blocks(e.g.,Eide et al.,1994;Ames et al., 1996;Rowley et al.,1997;Hacker et al.,1998;Li et al.,2000,2004; Zheng et al.,2004).The initiation of continental subduction is pinned to ca.245Ma(Hacker et al.,2006;Liu et al.,2006a;Wu et al.,2006; Cheng et al.,2008a),but the exact time is poorly constrained.On the other hand,thefingerprints of early continental subduction may not be preserved in continental-type metamorphic rocks due to the succes-sive high-temperature prograde and retrograde overprints.Alterna-tively,the timing of initiation of continental subduction subsequent to the termination of oceanic subduction may be registered in the HP/ UHP eclogites,whose protoliths are of oceanic origin.Currently,the only outcropping candidate is the Xiongdian HP eclogite in the western part of the Dabie orogen(Li et al.,2001;Fu et al.,2002).However,U–Pb zircon ages ranging from216±4to449±14Ma have been obtained for the Xiongdian eclogite(Jian et al.,1997;Sun et al.,2002;Gao et al., 2002);the geological significance of this age spread is controversial. Efforts to clarify the geochronological evolution of the Xiongdian eclogite were hampered by a much older Sm–Nd garnet-whole-rock isochron of533±13Ma(Ye et al.,1993)and the fact that further Sm–Nd and Rb–Sr analyses failed to produce mineral isochrons(Li et al., 2001;Jahn et al.,2005),although oxygen isotopic equilibrium was largely attained(Jahn et al.,2005).Here,we present a combined U–Pb,Lu–Hf,Sm–Nd,Ar–Ar and oxygen multi-isotopic and mineral chemical study of the Xiongdian eclogite.The differences in these systems,in conjunction with chemical profiles in garnet porphyroblasts and zircons,provide a window into the time-scales of the oceanic subduction and sub-sequent exhumation.2.Geochronological background and sample descriptionsThe Qinling–Dabie–Sulu orogen in east-central China marks the junction between the North and South China Blocks(Cong,1996; Zheng et al.,2005).The western part of the Dabie orogen,usually termed the West Dabie and sometimes the Hong'an terrane,is separated from the Tongbaishan in the west by the Dawu Fault and from the East Dabie by the Shangma fault in the east(Fig.1a).It contains a progressive sequence of metamorphic zones characterized by increasing metamorphic grade,from transitional blueschist–greenschist in the south,through epidote–amphibolite and quartz eclogite,to coesite eclogite in the north(e.g.,Zhou et al.,1993;Hacker et al.,1998;Liu et al.,2004b,2006b).The Xiongdian eclogites crop out in the northwestern corner of the West Dabie,in the Xiongdian mélange within the Huwan mélange after the definition of Ratschba-cher et al.(2006),in analogy to the terms of the Sujiahe mélange(Jian et al.,1997)and Huwan shear zone(Sun et al.,2002).The Huwan mélange consists of eclogite,gabbro,amphibolite,marble,and quartzite.The eclogitic metamorphic peak for the Xiongdian eclogite is estimated at600–730°C,1.4–1.9GPa(Fu et al.,2002),550–570°C,∼2.1GPa(Liu et al.,2004b)and540–600°C,∼2.0GPa(Ratschbacher et al.,2006),followed by retrogression at530–685°C and∼0.6GPa (Fu et al.,2002).Except for the Xiongdian eclogite,consistent Triassic metamorphic ages have been obtained for other eclogites across the West Dabie (Webb et al.,1999;Sun et al.,2002;Liu et al.,2004a;Wu et al.,2008). This indicates that West Dabie is largely a coherent part of an HP–UHP belt elsewhere in the Dabie–Sulu orogenic belt.Geochronological debate is limited to the Xiongdian eclogite(Fig.1b).U–Pb zircon ages ranging from ca.216to ca.449Ma have been obtained for the Xiongdian eclogite.Jian et al.(1997)reported ca.400,ca.373and 301±0.6Ma ages by ID–TIMS method.Weighted-mean SHRIMP ages range from335±2to424±5Ma(Jian et al.,2000).The Silurian U–Pb zircon ages were interpreted as the age of the protolith,while the Carboniferous ages mark high-pressure metamorphism(Jian et al., 1997,2000).Weighted-mean206Pb/238U SHRIMP U–Pb zircons ages of 433±9,367±10and398±5Ma were interpreted as the protolith age,while323±7and312±5Ma likely date the high-pressure metamorphism(Sun et al.,2002).A Triassic age of216±4Ma together with449±14and307±14Ma weighted-mean206Pb/238U SHRIMP U–Pb zircon ages appear to argue for the involvement of the Triassic subduction in the Xiongdian eclogite(Gao et al.,2002).A garnet-whole-rock Sm–Nd isochron of533±13Ma(Ye et al.,1993)was interpreted to reflect the high-pressure metamorphism age.Several Table1Chemical compositions of the Xiongdian eclogite from the western Dabie.Sample number DB17DB18(Major oxides in%)SiO254.5452.45 TiO20.370.43 Al2O314.6212.35 Fe2O38.7710.15 MnO0.150.16 MgO 6.669.91 CaO10.3510.26 Na2O 2.88 2.65 K2O0.600.28 P2O50.060.05 Cr2O3⁎6601118 NiO⁎137247 L.O.I0.87 1.28 Total99.95100.11 (Trace elements in ppm)Li27.627.0 Be0.560.47 Rb9.7813.8 Sr178130Y12.612.7 Cs0.89 3.67 Ba86552.4 La 2.21 1.77 Ce 5.97 5.12 Pr0.880.80 Nd 4.35 4.10 Sm 1.25 1.26 Eu0.470.39 Gd 1.53 1.52 Tb0.280.29 Dy 1.83 1.91 Ho0.410.42 Er 1.14 1.19 Tm0.190.19 Yb 1.31 1.34 Lu0.200.20 Pb 6.44 1.85 Th0.050.07 U0.110.06 Zr28.828.2 Nb 1.19 1.77 Hf0.870.88 Ta0.050.08⁎In ppm.329H.Cheng et al./Lithos110(2009)327–342Sm –Nd and Rb –Sr analyses failed to produces isochrons (Li et al.,2001;Jahn et al.,2005),which was believed to be due to unequilibrated isotopic systems despite the fact that oxygen isotopic equilibrium was largely attained (Jahn et al.,2005).Phengite 40Ar/39Ar ages of ca.430–350Ma have been explained as the retrograde metamorphic age (Xu et al.,2000).The 310±3Ma phengite 40Ar/39Ar age (Webb et al.,1999)is likely geologically meaningless due to the concave-upward age spectrum,indicating the presence of excess argon.Collectively,existing geochronology provides an apparently con flicting picture for the Xiongdian eclogites.The timing of the oceanic crust subduction and exhumation essentially remains to be resolved.The two eclogites examined in this study were selected based on their mineral assemblages,inclusion types and geological context (Fig.1).The one (DB17)from the east bank of the river to the east of Xiongdian village is a coarse-grained and strongly foliated banded eclogite,composed mainly of garnet,omphacite and phengite.A second (DB18)eclogite was sampled about 50m to the north of DB17and is strongly foliated with a similar mineralogy assemblage but smaller garnet grains.3.MethodsSample preparation,mineral separation and chemical procedures for isotope analysis,instrumentation and standard reference materials used to determine whole rock and bulk mineral compositions,in situ major and trace element analyses (Institute for Study of the Earth's Interior,Okayama University at Misasa,Japan),zircon U –Pb isotope and trace element analyses (China University of Geosciences in Wuhan),Lu –Hf and Sm –Nd isotope analyses (Washington State University),Ar –Ar isotope analyses (Guangzhou Institute of Geo-chemistry,Chinese Academy of Sciences)and oxygen isotope analyses (University of Science and Technology of China)are described in the Appendix .4.Results4.1.Bulk chemical compositionThe Xiongdian eclogites are mainly of basaltic composition,but they show a wide range of major and trace element abundances.Despite the high SiO 2(52–58%)and low TiO 2(0.32–0.43%)contents,Fig.2.Whole rock chemical analysis data.(a)Chondrite-normalized REE distribution patterns of the Xiongdian eclogites.(b)Primitive-mantle-normalized spidergrams of the Xiongdianeclogites.Fig.3.Backscattered-electron images and rim-to-rim major-element compositional zoning pro files of representative garnets in the matrix and as inclusions in zircon.Amp —amphibole;Ap —apatite;Cal —calcite;Cpx —clinopyroxene;Zo —zoisite;Phen —phengite;Omp —omphacite;Qtz —quartz;Zrn —zircon.330H.Cheng et al./Lithos 110(2009)327–342they have MgO=5.1–9.9%,Cr=430–1118ppm,Ni=88–247ppm (Table 1;Li et al.,2001;Fu et al.,2002;Jahn et al.,2005).In contrast to existing LREE-enriched chondritic REE patterns,our samples have rather flat REE patterns around ten times more chondritic abundances with small,both negative and positive Eu anomalies (Fig.2a).Rubidium is depleted and Sr displays enrichment with respect to Ce.Both negative and no Nb anomalies relative to La were observed (Fig.2b).The N-MORB-normalized value of Th is around 0.5,lower than previous reported values of up to 25(Li et al.,2001).4.2.Petrography and mineral compositionThe Xiongdian eclogites occur as thin layers intercalated with dolomite –plagioclase gneiss and phengite –quartz schist (Fu et al.,2002),mainly consisting of garnet,omphacite,epidote (clinozoisite),phengite and minor amphibole,quartz and kyanite (Fig.3).Zircons were observed both as inclusions in garnet porphyroblasts and in the matrix.The samples have similar mineral assemblages,but differ in modal compositions.Omphacite (X Jd =0.46–0.48)is unzoned.Phengite has 3.30–3.32Si apfu and ∼0.4wt.%TiO 2.Garnets range in size from 0.5to 5mm in diameter,either as porphyroblasts or as coalesced polycrystals,mostly with idioblastic shapes with inclusions of quartz,calcite,apatite and omphacite (Fig.3).Garnet is largely homogeneous (Prp 24–25Alm 49–50Grs 24–25Sps 1.5–1.9),but shows a slightly Mn-enriched core (Fig.3d;Table 2).HREEs in large garnet porphyroblasts,such as Yb and Lu,display weak but continuous decreases in concentration from core to rim (Fig.4a),mimicking the MnO zoning pattern,which could be explained by their high af finity for garnet and likely arises from an overall Rayleigh distillation process during early garnet growth (Hollister,1966;Otamendi et al.,2002).However,the limited variation in MREE concentrations,such as Sm and Nd,in garnet with respect to the weak zoning in HREE (Fig.4a)might be explained by growth in an environment where MREEs are not limited and continuously supplied by the breakdown of other phases.Hafnium has a fairly flat pro file (Table 3),re flecting its incompatible character in garnet and absence of Hf-competing reactions involved in garnet growth.Two distinct domains can be de fined in the large garnet porphyroblasts based on the chemical zoning and the abundance of inclusions.These zones are an inclusion-rich core with richer Mn and HREE and an inclusion-free rim with poorer Mn and HREE (Fig.3d).The inclusion-free rim for individual garnet has a rather similar width of 200–250μm (Fig.3).Although concentrations of Nd (0.22–0.41ppm)and Sm (0.33–0.48ppm)vary within single garnet grains,the Sm/Nd ratios (0.8–2.2)are consistentTable 2Representative major-element data of the garnets,omphacites,phengites,amphiboles and zoisites.(wt.%)Grt Omp RimCore Inclusions-in-zircon Rim Core SiO 238.6838.6438.6638.5338.6538.6637.8637.7555.9356.1256.1356.20TiO 20.050.060.050.050.050.050.050.080.120.110.110.11Al 2O 321.9221.9422.0721.9921.9921.8421.6821.8611.2611.2211.3311.26FeO ⁎22.9823.0523.0623.1623.0523.1124.4224.33 4.25 4.23 4.32 4.27MnO 0.680.720.790.880.750.680.990.930.030.020.030.02MgO 6.37 6.38 6.28 6.31 6.36 6.35 4.23 4.748.158.027.968.13CaO 9.108.949.028.929.038.9910.579.5013.2213.3613.3213.34Na 2O 0.030.030.030.030.030.030.020.01 6.65 6.41 6.39 6.42K 2O 0.000.000.000.000.000.000.000.000.000.000.000.00Total 99.8099.7799.9699.8799.9199.7199.8299.2199.6099.6099.7099.87O.N.12121212121212126666Si 2.986 2.984 2.981 2.975 2.980 2.988 2.958 2.962 1.996 2.010 2.010 2.007Al 1.994 1.997 2.006 2.001 1.999 1.990 1.997 2.0210.4740.4730.4780.474Ti 0.0030.0030.0030.0030.0030.0030.0030.0050.0030.0030.0030.003Fe 2+ 1.486 1.491 1.489 1.499 1.489 1.496 1.596 1.5990.1270.1270.1290.128Mn 0.0440.0470.0520.0580.0490.0440.0660.0620.0010.0010.0010.001Mg 0.7330.7350.7220.7260.7310.7320.4930.5540.4340.4280.4250.433Ca 0.7530.7400.7450.7380.7460.7440.8850.7980.5060.5130.5110.511Na 0.0040.0050.0050.0050.0050.0050.0030.0020.4600.4450.4430.445K0.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.0000.000Phn Amp Zo RimCore Rim Core Mantle Core SiO 248.8649.0949.3349.0147.0847.0746.7246.7539.0538.9239.0239.02TiO 20.400.410.410.400.220.220.220.220.130.130.130.12Al 2O 329.0328.6829.0129.1912.6612.8112.5812.6228.5528.2128.7328.62FeO ⁎ 1.99 1.99 2.00 1.9711.6011.4811.4611.36 6.01 6.01 6.03 6.07MnO 0.000.000.000.010.100.090.090.090.050.050.060.05MgO 2.79 2.77 2.78 2.8012.2012.4712.4412.300.070.060.070.07CaO 0.010.010.010.019.9710.0910.0710.1024.1023.8624.1324.14Na 2O 0.930.920.920.91 2.79 2.77 2.82 2.830.000.000.000.00K 2O 10.009.919.819.780.480.470.470.470.000.000.000.00Total 94.0293.7894.2894.0997.0997.4996.8896.7697.9697.2498.1698.09O.N.111111112323232312.512.512.512.5Si 3.302 3.323 3.318 3.304 6.831 6.800 6.799 6.809 3.008 3.019 3.000 3.003Al 2.313 2.288 2.300 2.319 2.164 2.182 2.158 2.167 2.592 2.579 2.603 2.596Ti 0.0200.0210.0210.0200.0240.0240.0240.0240.0070.0070.0070.007Fe 2+0.1120.1130.1130.111 1.407 1.387 1.394 1.3830.3870.3900.3880.390Mn 0.0000.0000.0000.0000.0120.0120.0120.0120.0040.0040.0040.004Mg 0.2820.2800.2790.282 2.639 2.686 2.699 2.6700.0070.0070.0070.008Ca 0.0010.0010.0010.001 1.550 1.562 1.570 1.577 1.989 1.983 1.988 1.990Na 0.1220.1210.1200.1190.7840.7770.7950.7980.0000.0000.0000.000K0.8620.8550.8420.8410.0890.0870.0880.0880.0000.0000.0000.000⁎Total iron;concentrations reported as wt.%.331H.Cheng et al./Lithos 110(2009)327–342with those obtained by ID-MC-ICPMS (1.9–2.4)within error (Fig.5a),indicating that the Nd isotopic analyses in this study are essentially unaffected by MREE-rich inclusions,likely due to ef ficient mineral picking and/or concentrated H 2SO 4pre-leaching.The consistent Hf concentrations of 0.10–0.13ppm within single grains with those (0.11–0.13ppm)by ID-MC-ICPMS indicates the Hf-rich phases were essentially removed during digestion (Fig.5b).The overall Lu concentration slightly skews towards the garnet rim because of the weak zoning pattern and the spherical geometry effect,i.e.,the outershells dominate the volume of Lu (Cheng et al.,2008a ).The 0.90–0.93ppm Lu contents by ID-MC-ICPMS apparently resemble those of the garnet rim,which could be readily explained by the spherical geometry effect.However,we interpret this with caution because individual garnet porphyroblasts could have different zoning patterns and the individual Lu pro file might not be representative of the population of garnet grains,although the chemical zoning center (nucleation site)coincides with the geometric center (Fig.3d),suggesting asymmetric garnet growth.In addition,biased mineral hand-picking should be considered (Cheng et al.,2008a,b ).Moreover,since the thin-section preparation method for this study cannot ensure that the real center of the garnet was exposed,the observed zoning here likely only represents a minimum zoning of particular garnet porphyroblasts.4.3.Estimation of P –T conditionsMetamorphic peak P –T conditions of 2.2GPa and 620°C for the DB17Xiongdian eclogite (Fig.6)are evaluated on the basis of recent cali-brations of the assemblage garnet+omphacite+phengite+kyanite+quartz,according to the dataset of Holland and Powell (1998).Higher P –T values of 2.4GPa and 650°C are calculated with the calibrations of Krogh Ravna and Terry (2004).While a temperature of 620±29°C is estimated by quartz –garnet O isotope thermometer (Zheng,1993),Ti-in-zircon thermometer (Watson et al.,2006;Ferry and Watson,2007)gives similar value of 695±22°C.Zr-in-rutile thermometer (Watson et al.,2006;Ferry and Watson,2007)yields a lower value of 634–652°C and a similar temperature of 683–701°C (Fig.6)when using the pressure-dependent calibration of Tomkins et al.(2007)at 2.2GPa.Calibration 1uses updated versions of the thermodynamic dataset and activity models in the programs THERMOCALC3.26and AX (Holland,Powell,1998;latest updated dataset;Powell et al.,1998)by using an avPT calculation in the simpli fied model system NCKFMASH with excess SiO 2and H 2O.Calibration 2uses thermobarometry based on the database of Holland and Powell (1998)and activity models for garnet (Ganguly et al.,1996),clinopyroxene (Holland and Powell,1990)and phengite (Holland and Powell,1998).Analyses of garnet,omphacite and phengite (Table 2)were processed according to the two calibrations.Calibration 3uses mineral O isotope compositions (Table 4)to estimate temperature based on the quartz –garnet O isotope thermometer (Zheng,1993).Calibrations 4and 5use Ti contents in zircon by LA-ICPMS and Zr concentration of rutile by SIMS (Table 5)to temperature estimations based on the Ti-in-zircon and Zr-in-rutile thermometers,respectively (Watson et al.,2006;Ferry and Watson,2007;Tomkins et al.,2007).The assemblage of garnet –omphacite –kyanite –phengite –quartz is representative of metamorphic peak conditions of theXiongdianFig.4.Chondrite-normalized REE patterns (Sun and McDonough,1989)of zircons,garnets and omphacite from Xiongdian eclogite (a)and REE distribution patterns between zircon and garnet (b).The equilibrium D REE(Zrn/Grt)values of Rubatto (2002),Whitehouse and Platt (2003)and Rubatto and Hermann (2007)are presented for comparison.Table 3SIMS Sm,Nd,Hf and Lu concentration pro files of the garnets in Figs.4and 5.(ppm)RimCore Cpx Li 0.93 1.140.880.840.890.980.750.520.990.580.690.870.670.7522.1Sr 0.100.130.120.120.100.100.100.120.110.120.130.100.110.1033.5Y 45.646.846.647.346.447.148.350.052.053.553.155.354.657.80.92Hf 0.110.130.120.120.110.110.120.120.120.100.110.100.100.100.41La 0.010.020.020.010.000.000.010.010.010.010.010.010.020.010.02Ce 0.040.050.050.060.050.040.040.040.050.030.040.040.050.030.12Pr 0.010.020.030.020.020.020.020.020.020.020.030.020.020.020.03Nd 0.390.330.280.380.350.270.220.280.340.310.270.410.280.260.36Sm 0.450.360.380.440.470.410.480.450.450.410.340.330.420.410.31Eu 0.270.270.270.280.300.240.280.280.250.300.290.240.250.220.22Gd 1.85 1.96 1.75 1.80 1.85 1.78 1.85 1.84 1.93 1.82 1.57 1.92 1.69 1.530.65Dy 5.68 5.86 5.58 6.18 5.87 5.84 5.79 6.19 6.46 6.40 5.50 6.91 6.09 6.400.26Er 3.74 4.13 4.04 4.25 4.23 4.16 3.76 4.15 4.65 4.99 4.53 4.98 4.63 5.200.06Yb 4.10 4.18 4.01 3.86 4.23 4.11 4.49 4.34 4.97 5.19 5.19 5.65 5.10 5.690.12Lu0.900.910.880.840.840.891.131.151.281.261.261.331.321.420.01332H.Cheng et al./Lithos 110(2009)327–342eclogite.A partly-calibrated thermobarometer is de fined by the three reactions of 3Celadonite +1Pyrope +2Grossular =3Muscovite +6Diopside,2Kyanite+3Diopside =1Pyrope +1Grossular +2Quartz,and 3Celadonite +4Kyanite=3Muscovite +1Pyrope +4Quartz.An intersection point of 2.2GPa and 620°C is de fined and therefore independent of commonly-used Fe –Mg exchange thermometers.This offers an advantage with regards to garnet –clinopyroxene,which is prone to retrograde reactions and problems stemming from ferric iron estimation of omphacite (Li et al.,2005).Results are plotted according to the calibrations mentioned above.The three reactions and intersection points are shown according to programs of calibrations 1–5in Fig.6.4.4.Oxygen isotopic dataThe O isotope compositions of minerals for the two eclogites are presented in Table 4.When paired with quartz for isotope geothermo-metry,garnet,omphacite,phengite,kyanite,zoisite and amphibole yield temperatures of 620±29,563±35,567±43,508±31,404±28and 685±39°C for eclogite DB17,respectively.Because these temperatures are concordant with rates of O diffusion and thus closure temperatures in the mineral assemblage garnet +omphacite +kyanite+phengite+quartz (Zheng and Fu,1998),representative of metamorphic peak conditions,a continuous resetting of O isotopes in the different mineral-pair systems is evident during cooling (Giletti,1986;Eiler et al.,1993;Chen et al.,2007).Quartz –garnet pairs from eclogite DB17give temperatures of 620±29°C,which are consistent with those calibrated by the THERMOCALCmethod,indicating that O isotope equilibrium was achieved and preserved during eclogite –facies recrystallization (Fig.7a).This is also evidenced by the apparent equilibrium fractionation between garnet and omphacite (Fig.7b).In contrast,equilibrium fractionation was not attained between garnets and omphacites in eclogite DB18.The calculated quartz –amphibole pair temperature of 685±39°C is distinctly higher than the 508±31°C from the quartz –zoisite pair.Because oxygen diffusion in amphibole is faster than in zoisite and kyanite (Zheng and Fu,1998),amphibole exchanges oxygen isotopes with water faster than zoisite during retrogression.Consequently,the O isotope temperature increases for the quartz –amphibole pair,whereas the quartz –zoisite temperature decreases relative to the formation temperature.In this regard,the retrograde metamorphism of amphibolite –facies should take place at a temperature between ∼685and ∼508°C.On the other hand,the low quartz –kyanite pair temperature (404±28°C)could be interpreted as a result of in fluence by retrogressive metamorphism without a clear geologicalmeaning.Fig.5.Sm/Nd versus Nd and Lu/Hf versus Hf plots for garnet and whole rock.ID:data obtained by the isotope dilution method using MC-ICPMS.IMS:data obtained by ion microprobe.bombWR —whole rock by bomb-digestion,savWR —whole rock by Savillex-digestion.Error bars for both IMS and ID methods are signi ficantly smaller than thesymbols.Fig.6.Peak P –T estimates of the Xiongdian eclogite.Reactions of py +2gr +3cel =6di +3mu;3di+2ky =py+gr +2q;and 3cel +4ky =py +3mu +4q and intersection points are plotted according to the calibrations of Holland and Powell (1998,latest updated dataset)in solid lines and Krogh Ravna and Terry (2004)in dashed lines.Coesite quartz equilibrium is also shown (Holland and Powell,1998).Abbreviations:alm —almandine,gr —grossular,py —pyrope,cel —celadonite,mu —muscovite,di —diopside,jd —jadeite,coe —coesite.Temperatures estimated by quartz –garnet oxygen isotope thermometry (Zheng,1993),Ti-in-zircon and Zr-in-rutile thermometries (Watson et al.,2006;Tomkins et al.,2007)are also shown.Table 4Oxygen isotope data of minerals for the Xiongdian eclogite.Sample number Mineral δ18O (‰)Pair Δ18O (‰)T 1(°C)T 2(°C)DB17Quartz 12.86,12.66Phengite 10.26,10.14Qtz –Phn 2.57567±43Garnet 8.83,8.85Qtz –Grt 3.93620±29605±22Omphacite 9.64,9.56Qtz –Omp 3.17563±35574±28Zoisite 9.31,9.43Qtz –Zo 3.40508±31494±21Amphibole 9.83,9.60Qtz –Amp 3.06685±39Kyanite 9.36,–Qtz –Ky3.41404±28WR 9.85,9.91DB18Garnet 9.74,9.59Omphacite 8.58,8.48Omp –Grt −1.14WR10.15,9.99T 1and T 2were calculated based on the theoretical calibrations of Zheng (1993)and Matthews (1994),respectively,with omphacite (Jd 45Di 55).Uncertainty on the temperature is derived from error propagation of the average reproducibility of ±15‰for δ18O (‰)values in the fractionation equations.333H.Cheng et al./Lithos 110(2009)327–342。