四川紫色土退化的分类与分区

CLASSIFICATION AND REGIONALIZATION OF PURPLE SOIL DEGRADATION IN SICHUAN PROVINCE

四川紫色土耕地面积406.1万公顷,占全省耕地面积的36.5％,属全省农业生产的主体区域。四川紫色土普遍退化。退化分为物理性(含构造性)、化学性、营养性三类。用模糊综合评判方法,评价了四川(主要为盆地丘陵区)紫色土退化的程度和状况。同时又建立了退化紫色土的分区原则,将四川紫色土退化分布区域划分为6个退化亚区,10个退化小区。

The three types: physical (including constitutional), chemical and nutritive clagradation had been classed according to the forms of soil dagradation and the principles, process of degradation formation in the purple soils.Taking advantage of the experts scoring and the standards related to assess soil degradation, the Index System to Evaluate the Purple Soil Degradation was set up. Meanwhile, the status and degree of the purple soil dagradation in the hilly region of Sichuan Basin had been evaluated, by means of Fuzzy Comprehensive Evaluation. The results showed that the slight and moderate physical (containing constitutional), nutritive degradation are the major forms of purple soil degradation, and the occurrence frequency of the physical, nutritive degradation is 54. 3, 64. 8(%), respectively, and the slight and moderate degradation reaches 84. 2, 89. 8(%) of the occurrence frequency of the physical, nutritive degradation, separately.Determined by the division principles and Index Systen to Evaluate the Purple Soil Degrada-tion as well as the results of Fuzzy Comprehensive Evaluation, the distribution region of thepurple soils was divided into 6 degradation subregions. The subregions are as follows Ⅰ. the slight physical and nutritive degradation subregion of the purple soils in northern Sichuan Basin; Ⅱ . the moderate physical and nutritive degradation subregion of the purple soils in central Sichuan Basin; Ⅲ. the slight chemical degradation subregion of the purple soils in southern Sichuan Basin; Ⅳ. the slight physical degradation subregion of the purple soils in eastern Sichuan Basin ,Ⅴ . the slight physical degradation subregion of the purple soils in western Sichuan Basin;Ⅵ. the moderate physical degradation subregion of the purple soils in Panzhihua-Xichang.