^137Cs技术研究岩溶高原湿地小流域土壤侵蚀特征

Study on Soil Erosion Features of Small Catchment of Karst Plateau Wetland by ^(137)Cs Tracing Technology

运用137Cs技术研究了威宁草海沙河小流域不同土地利用方式和地貌部位的土壤侵蚀特征。结果表明:研究区137Cs的背景值为879Bq·m2;农耕地土壤剖面中137Cs中呈均匀分布,非农耕地土壤剖面中呈指数递减分布;不同土地利用方式下,137Cs的面积活度值从大到小为灌丛地>人工草地>农耕地,土壤侵蚀模数值为农耕地>草地>灌丛地;不同地貌部位土壤中,137Cs面积活度值从大到小为下坡>中坡>上坡,侵蚀模数值变化为上坡>中坡>下坡。小流域年均侵蚀模数为:1254.9t·(km2·a)-1,灌丛地侵蚀模数为462.6t·(km2·a)-1,人工草地为630.4t·(km2·a)-1,农耕地为3311.8t·(km2·a)-1。因此,在小流域水土流失综合治理过程中,农耕地是治理的重点。

The ^137Cs tracing technology was used to study the soil erosion features for different land usage patterns and landform positions in Shahe small catchment of Caohai, Weining. The results showed that the ^137Cs background value was estimated to be 879Bq.m^-2. Most of the ^137Cs in the plow layer of the cultivated sites is distributed uniformly, and it showed exponentially decline distribution in the non-cultivated land vertical section; the values of ^137Cs activity per unit area for different land use patterns followed the order of shrub land 〉 artificial pasture 〉 agricultural land, and soil erosion modulus size was accorded withthe order of agricultural land 〉 artificial pasture 〉 shrub land. The values of ^137Cs activity per unit area was down slope 〉 middle slope 〉 up slope for the different landscape positions and soil erosion modulus size followed the sequence of up slope 〉 middle slope 〉 down slope. The average erosion modulus of the small watershed was 1254.9 t· （km^2 ·a） ^-1, the shrub land was 462.6 t· （km^2 ·a） ^-1, the artificial pasture was 630.4 t· （km^2 ·a） ^-1 and the farmland was 3311.8 t· （km^2 ·a） ^-1Therefore, the farmland is the fist and foremost task in the comprehensive management of the small watershed.