冯珍 董莉丽 胡丹

摘要 [目的] 研究渭北旱地退耕还林工程在提高土壤质量和改善土壤结构方面的作用。[方法]选取位于渭北旱塬的长武县马坊村人工林地、荒地和农地3种土地利用类型，利用快速湿润法测定表层土壤各粒级水稳性团聚体质量百分含量，并测定全土样和水稳性团聚体各组分的有机质和速效磷含量。[结果]水稳性团聚体平均质量直径、几何平均直径和土壤有机质含量在林地和荒地较农地大。有机质和速效磷含量在粒级<0.05 mm的土壤团聚体中最小，0.5～0.1 mm土壤团聚体有机质含量最高， 0.2～0.5 mm土壤团聚体速效磷含量最高。[结论]农地转化为人工林地后，土壤质量具有不同程度的提高，且小粒级团聚体向大粒级转化。土壤有机质和速效磷含量主要分布在较大粒级的水稳性团聚体中，并随着粒级由小变大，二者先增大后略微减少。

关键词 水稳性团聚体； 土壤有机质； 退耕还林

中图分类号 S153.6+2 文献标识码

A 文章编号 0517-6611（2014）31-10947-03

Effects of Converting Farmland to Forest or Grassland on Soil Organic Matter and Soil Water Stable Aggregates

FENG Zhen，DONG Lili*，HU Dan （College of Tourism and Resource Environment，Xianyang Normal University，Xianyang，Shaanxi 712000）

Abstract [Objective] The functions of returning farmland to forests or grassland on improving soil quality and structure were studied in Weibei dry land.[Method] Selecting three landuses types including planted forest，waste land and crop land from Mafang Village of Changwu County at Weibei dryland， the percentage of water stable aggregates with different sizes was measured by fast wetting and soil organic matter and available phosphorus of whole soil samples and water stable aggregates with different sizes were measured.[Results] Mean weight diameter，geometric mean diameter of water stable aggregates and content of soil organic matter were higher at forest and waste land than those of crop land.The content of soil organic matter and available phosphorus was the least at water stable aggregate whose size was smaller than 0.05 mm and was the highest at 0.5-0.1 and 0.2-0.5 mm water stable aggregate respectively.[Conclusion] Soil quality was improved with different degree and smaller size aggregate was transformed to larger one after crop land converting to forest.Soil organic matter and available phosphorus were distributed mainly in larger water stable aggregates，which were increased firstly and then decreased slightly with the increase of grade size.

Key words Soil water stable aggregates； Soil organic matter； Converting farmland to forest or grassland

土壤是地球表層最大的有机碳库，在全球碳循环中起着关键作用^[1]。土地利用方式影响土壤的功能和性质，能增加或降低土壤碳的数量，并且改变微生物多样性，使得土壤成为碳的源或汇，从而影响大气中CO2浓度。自1950年以来，各级政府开展了大量的退耕还林等生态环境建设工作。研究退耕还林对土壤碳固定及其养分和水稳性的影响，不仅可以丰富土壤科学的研究内容，而且可以评价退耕还林工程在提高土壤质量、增加水分入渗、减少土壤流失等方面产生的效益。

土壤质量是与土壤的各种形成因素及土壤耕作引起的动态变化有关的一种固有的土壤属性^[2]。土壤有机质对土壤结构稳定性和土壤养分状况有多重影响，对土壤资源的可持续利用非常重要^[3]。土壤有机质是土壤质量的核心，也是土壤团聚体与土壤功能体现的基础^[4]。……