黄土高原人工混交林土壤肥力及混交效应研究
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黄土高原人工混交林土壤肥力及混交效应研究*
董建辉1, 薛泉宏2, 张建昌3, 冯 浩2(1.陕西职业技术学院,陕西西安710100;2.西北农林科技大学,陕西杨陵712100;3.杨凌职业技术学院,陕西杨陵712100)摘 要:测定了沙棘+侧柏,刺槐+侧柏及其对应侧柏纯林土壤80cm土层32个土样的8项肥力指标和人工林生长量,对2个混交林的土壤肥力特征及混交对侧柏的促生效应进行了初步探讨。结果表明:(1)供试混交林80cm土层土壤有机质、全氮、速效氮含量及其剖面变异和氮素贮量表现为沙棘>侧柏及刺槐>侧柏,沙棘、刺槐人工林对土壤的培肥效应大于侧柏;(2)沙棘+侧柏混交林不同树种根区土壤pH、碳酸钙、全磷及速效钾含量差异很小。关键词:混交林肥力;混交效应;黄土高原人工林;沙棘;刺槐中图分类号:S724 文献标识码:A 文章编号:1001-7461(2005)03-0031-05SoilFertilityCharacteristisandMixedEffectofPlantationForestsonLoessPlateauDONGJian-hui1, XUEQuan-hong2, ZHANGJian-chang3, FENGHao2(1.ShaanxiVocational&TechnologicalInstitute,Xi'an,Shaanxi710100,China;2.CollegeofForestry,NorthwestA&FUniversity,Yangling,Shaanxi712100,China;3.YanglingVocationalandTechnologicalCollege,Yangling,Shaanxi712100,China)Abstract:Fertilityof32soilsamplesfrom80cmsoilhorizoninmixedplantationsofHippophaerhamnoides+Platycladusorientalis,Robiniapseudoacacia+P.orientalisandpureplantationofP.orientalisweredetermined.Thesoilfertilitycharacteristicandthegrowth-promotingeffectofthetwomixedplantationstoP.orientaliswerein-vestigated.Theresultsindicatedtha:t¹Contentandvariationofthesoilorganicmatter,totalnitrogen,availablenitrogenandthesoilnitrogenstorageunderat80cmsoilhorizonofthemixedplantationswereH.rhamnoides>P.orientalisandR.pseudoacacia>P.orientalis.TheimprovementoftheH.rhamnoidesandR.pseudoacaciatosoilfertilityweremoreobviousthanP.oricntalis.ºThegrowthpromotingeffectofthemixedplantationsoftheH.rh-amnoides+P.orientalisisrelatedwiththeincreasingofthesoilnitrogenstoragesintherootregionofPlatycladusorientaliscausedbyH.rhamnoides.»TherewaslittledifferencesamongpH,CaCO3,totalphosphorusandavaila-blepotassiumofthedifferenttreesrootregioninmixedplantations.Keywords:soilfertilityofmixedplantations;mixedeffects;plantationsontheLoessPlateau;Hippophoerham-noides;Robiniapseudoacacia 混交林研究是/三北0防护林建设模式研究的重要内容之一,一直受到有关学者关注[1~12]。在黄土高原渭北试验区,沙棘+侧柏及刺槐+侧柏混交林中,侧柏生长优于纯林,这与地上光照、通风等生态因子改变有关,同时也可能受混交林中伴生树种引起的土壤肥力改变的影响,但目前对供试混交林不同树种根区土壤肥力的分布了解不多[14~17,9,11,12]。定量研究混交林树种间及各树种根区,混交林与纯林相同树种根区土壤肥力的差异,对于了解混交林内土壤肥力分布状况,从肥力角度探讨混交的促生效应及进行黄土高原混交林树种选择配置有重要的理论与应用价值。1 采样点概况与研究方法1.1 采样点概况供试人工林位于黄土高原渭北生态经济型防护林体系建设模式试验区(永寿县马莲滩)。1.2 研究方法西北林学院学报 2005,20(3):31~35JournalofNorthwestForestryUniversity
*收稿日期:2005-02-01 修回日期:2005-03-17基金项目:国家/八五0重点科技项目(85-019-02-02)。作者简介:董建辉(1962-),男,山西定襄人,副教授,主要从事资源环境方面的研究与教学工作。1.2.1 采样人工林选择 在马莲滩试区选5年生沙棘+侧柏及刺槐+侧柏混交林各一块,并在混交林旁各选侧柏纯林及地形相近、土壤类型相同的无林地各一块,以无林地为对照采样区。1.2.2 土壤样品采集 在混交林及纯林中,供试林木各选代表性样树2株,在其根区采样,并在不同树种间选过渡性采样点。在样树侧挖长@宽@深为60㎝@60㎝@90㎝土坑,整修得长@深为60㎝@90㎝断面,然后在距树50㎝处向下采0~20、21~40、41~60㎝及61~80㎝4层土样,采样土柱高@宽@厚为20㎝@10㎝@5㎝,将重复样树相同部位土样混匀取1kg装袋。过渡性样点及无林对照各挖一剖面,按相同方法采样。将对照剖面4层土样各项测值的均值作为造林前土壤该性质的背景值,林木根区土壤各项测值与相应背景值之差为增量。1.2.3 树木生长量调查 测定2种混交林及对应侧柏纯林内采样树及其周围10株同一种树的树高,基径和新梢生长量。1.2.4 土壤肥力测定 全氮:半微量开氏法;有效氮:康维皿法;有机质:K2Cr2O7容量法;速效钾:1mol/LNH4Ac浸提,火焰光度法;阳离子代换量(CEC):HC-lCa(Ac)2法;CaCO3:气量法;pH:1B1水浸,pH计测定[7]。
表1 混交林土壤养分测值Table1 Nutrienscontentsinthesoilofthemixedforests测定项目深度/cm沙棘、侧柏沙棘侧柏沙棘-侧柏间侧柏纯林刺槐、侧柏刺槐侧柏沙棘-侧柏间侧柏纯林
pH0~208.848.588.568.418.168.248.218.2421~408.598.578.628.598.248.268.248.2741~608.598.568.648.568.328.248.258.2561~808.598.598.598.598.278.348.258.
25有机质g#kg-10~2013.910.911.012.214.48.512.410.721~4010.78.59.48.77.05.25.66.241~608.28.18.88.16.04.85.66.061~806.97.37.07.56.03.05.24.
3全氮g#kg-10~201.311.101.200.921.211.041.040.6121~401.201.081.051.040.880.970.880.4041~601.100.710.500.510.860.850.800.3361~800.470.500.460.410.890.750.870.
30速效氮/Lg#g-10~2070.338.832.239.552.627.739.543.721~4029.225.626.713.222.924.720.218.541~6023.224.926.313.616.315.217.318.761~8017.925.331.211.213.815.915.913.
5速效钾/Lg#g-10~2014012512313221214816515221~4010711311311311315016011341~6010610410510711713112211261~8010010199108112122127
108全磷/g#kg-10~201.351.351.201.341.431.341.391.3521~401.411.371.371.251.291.271.271.2541~601.331.271.321.301.231.221.291.0161~801.301.281.211.211.151.221.260.
92碳酸钙g/#kg-10~2012311914712911914713413521~4012914714311314714315014041~6013213913911613913914114361~8013013815994138159147
139CEC/cmol#kg-10~207.908.838.4010.2211.209.8011.2011.1521~407.449.309.1012.5510.207.409.3010.2241~607.4410.209.109.7611.707.408.8010.2261~806.519.309.308.8311.207.909.809.99
2 结果与讨论2.1 混交林内土壤养分分布2.1.1 不同树种根区土壤养分垂直变化 从表1、表2看出,土壤各肥力随深度变化,且各测值的变化大小不同,不同树种同一测值的变化大小各不相同。32 西北林学院学报 20卷供试地区黄土母质土层深厚,质地均一,各化学组分比较一致。成土作用使剖面上下各层养分发生变化,林木生长加快了上下层养分差异。故树木根区土壤剖面不同层次养分测值变异系数愈大,表明树木对土壤肥力的影响愈显著。从表2可知,沙棘+侧柏混交林及对应侧柏纯林各树种土壤根区剖面8种测值变异系数的平均值排序为:速效氮(42.9%)>全氮(40.5%)>有机质表2 供试混交林80cm土层土壤养分均值及变异系数Table2 Theaverageandcoefficientofvariationofsoilnutrientatthedepthof80cmofthemixedforests测定类型项 目树种pHCEC/cmol#kg-1有机质/g#kg-1全氮/g#kg-1全磷/g#kg-1碳酸钙/g#kg-1速效氮/Lg#g-1速效钾/Lg#g-1
沙棘[侧柏平均值变异系数/%混交林纯林混交林纯林平均沙棘侧柏沙棘+侧柏间侧柏沙棘侧柏沙棘+侧柏间侧柏8.568.588.608.540.630.150.411.000.557.39.49.010.37.96.14.315.38.49.98.79.19.131.317.218.723.122.61.020.850.800.7237.334.147.543.140.51.341.321.281.283.53.86.54.54.61241241291134.27.83.012.87.035.228.729.119.467.923.610.469.542.9113.3110.8110.0115.016.09.79.510.111.