白云岩喀斯特侵蚀坡地的^(137)Cs法研究

RESEARCH ON ERODED SLOPE LAND OF KARST DOLOMITE USING ^(137)Cs TRACING METHOD IN MAOLAN CLUSTERED PEAK DEPRESSION AREA

在黔南峰丛洼地区林间白云岩坡地应用137Cs法研究土壤侵蚀。4个坡面采样样方的137Cs面积浓度都低于137Cs本底值浓度;表土样137Cs浓度随着坡长增加而增大,全样137Cs面积浓度的顺坡变化呈逐步下降趋势;应用137Cs农耕地侵蚀模型计算获得样点土壤侵蚀量后,加以坡长加权平均计算获得的坡长权重土壤位移量为2.045 t/(km2·a)。同时在坡脚的土壤分层剖面中的137Cs浓度峰值在土壤次表层出现,随着深度增加呈指数递减变化,属于未受耕作扰动的无侵蚀非农耕地,但表层含有相对低浓度137Cs是坡面侵蚀泥沙的搬运堆积结果,估算距1963年以来侵蚀泥沙年平均堆积厚度为0.0682~0.1364 cm/a。坡地土壤侵蚀速率远小于以往贵州喀斯特地区典型喀斯特小流域和坡地的观测结果,但坡脚泥沙堆积速率远大于坡地土壤侵蚀速率。表明季节性暴雨、坡面降雨汇流和耕作侵蚀等侵蚀作用使喀斯特坡地土壤颗粒出现微距离位移,长期则在坡脚出现显著的侵蚀泥沙堆积。

The research select one karst dolomites slope in peak cluster depression area of southern Guizhou to research karst slope soil erosion and accumulation using^137 Cs tracing method.^137 Cs concentration among 4 slope soil sampling quadrates all are lower than the137 Cs reference value.^137 Cs concentration of slope surface soil samples increase but^137 Cs concentration of slope soil samples decrease along with the slope length. Using137 Cs cultivation newimproved model to calculate the soil erosion rate in the sampling sites,and the slope soil erosion rate of slope length weighted average is 2. 045 t / km^2. a. At the same,the profile at the slope foot has bigger area activity and the activity value decreased along with the depth increased and the peak value emerged at the sub- surface layer at which it could infer that the profile belong to undisturbed uncultivated land,the lower activity at the surface layer meant that the sediment accumulation at the slope foot,and hence infer that the sediment accumulation depth rate are among 0. 0682 cm / a and 0. 1364 cm / a,which are smaller than the reported observation data in small catchments and the cultivated slope land. There the sediment accumulation rate at the slope foot was far bigger than the erosion rate of the slope. The research results showthat the soil particle had occurred micro- distance movement driven by the seasonal rain and the slope stream and the agriculture activity,and sustainable eroded sediment accumulated at slope foot in longer time.