黄土高原沟壑区小流域不同地形下土壤性质分布特征

地形条件是影响黄土高原地区土壤性质分布的主要因素,研究不同地形条件下土壤性质的分布是合理评价黄土区土壤质量状况的重要前提。论文研究了黄土高原沟壑区小流域地形条件对土壤性质剖面分布的影响,结果表明土壤硝态氮、速效磷、碱性磷酸酶和蔗糖酶为高度变异的土壤性质;pH值和过氧化氢酶为小变异土壤性质。塬面和沟道土壤pH值和过氧化氢酶活性较低,阳离子交换量较高。土壤有机质、全氮、全磷、速效磷、碱性磷酸酶和蔗糖酶活性在土壤剖面随土层深度的增加逐渐降低,且均表现为塬面>梯田>坡地>沟道的趋势。不同地形条件下土壤pH值的变化由地形条件引起的土壤过程及硝态氮在土壤中的累积引起;阳离子交换量的变化由成土过程、pH值和有机质的差异引起;土壤有机质及氮、磷养分的差异由与地形条件对应的土地利用方式引起;土壤酶活性的差异则是有机质的差异引起的。

Distribution of Soil Properties as Affected by Landforms in Small Watershed of Loessial Gully Region

Landform is the most important environmental factor influencing soil properties of the Loess Plateau.The well understanding of the effects of landforms on the distribution of soil properties is an important prerequisite for the estimation of soil quality of the Loess Plateau.This study was therefore conducted in a small watershed of the loessial gully region to reveal the profile distribution of soil properties as affected by landforms.Soil samples distributed into various landforms were collected and soil properties were determined.The results showed that nitrate,available phosphorus,alk-phosphatase and invertase are highly varied properties while soil pH and catalase are lowly varied properties in the study area.Soils of plateau land and gully bottom were characterized by the lower pH and catalase activity but higher cation exchange capacity.The contents of organic matter,total nitrogen,total and available phosphorus and the activities of alk-phosphatase and invertase were decreased gradually with the increase of soil depth in profile.Besides,these properties followed the order of plateau land>terrace land>slopping land>gully bottom.Changes in soil pH at different landforms were caused by the soil-forming processes and the accumulation of nitrate in soils.The differences of soil cation exchange capacity with landforms were derived from the differences in soil formation,soil pH and organic matter.The variance of soil nutrients was led by the landuse conditions corresponded to landforms,while that of enzymatic activities was led by landform induced changes of soil organic matter.