利用方式对岩溶山地土壤团粒结构的影响研究

岩溶山地是典型的脆弱生态环境，土壤资源存在先天不足性，其退化恢复受土地利用方式的影响大。以重庆市北碚、黔江、金佛山为代表，研究了6种典型土地利用方式对岩溶山地土壤水稳性团聚体的影响。结果表明：＞0．25mm水稳性团聚体为灌草坡＞原始林地＞次生林地＞果园＞弃耕地＞耕地；林地、草坡的土壤表层团聚体的水稳性较高且水稳性团聚体以＞2mm为主，而果园、弃耕地、耕地土壤团聚体的水稳性较低且＞2mm的水稳性团聚体较少。水稳性团聚体(尤其是＞2mm的水稳性团聚体)以及团聚的水稳性主要受有机质的含量影响，目前有机质是这一地区土壤结构形成的最为重要的胶结物质；林地、草坡开垦后，土壤有机质分解加快或补充减少是土壤团聚体水稳性下降及数量减少的主要原因。坡耕地退耕后，土壤团聚体可得到恢复。

A STUDY OF FEATURES OF WATER-STABLE SOIL AGGREGATE STRUCTURE UNDER DIFFERENT LAND USE IN KARST MOUNTAINS

Karst mountain is a typical fragile ecological environment and its soil resource is congenitally deficient and affected by the land use patterns. Choosing Beibei, Qianjiang and Jinfushan as the representative Karst areas of Chongqing City, the distribution and formation of water-stable aggregates in karst soils under different land use has been studied. The results shows that the contents of >0.25 mm water-stable aggregates changes in the following order:shrub grassland>primitive woodland>secondary woodland >orchard>old field>farmland.The content of >2mm water-stable soil aggregates is more in the surface and subsurface soils of woodland and shrub grassland than that in orchard,old field and farmland. Either the water-stability of aggregates (especially >2mm ) or the content of water-stable aggregates is highly correlated with the contents of soil organic matter.This result shows that organic matter is the cementation of soil aggregate structure. Increased decomposition and decreased input of organic matter after reclamation of shrub grassland and woodland are responsible for the decrease in both the water-stability of aggregates and the amount of water-stable aggregates in karst soils. The soil aggregate structure may be rehabilitated after returning farmland to woodland or grassland.