川中丘陵区紫色土坡耕地土壤侵蚀特征

Characteristics of soil erosion on sloping farmlands in a purple hilly region of the Sichuan Basin

利用137Cs示踪方法与耕作侵蚀模型评价了川中丘陵区紫色土坡耕地土壤侵蚀速率,并通过比较分析方法探讨了2种典型坡耕地-短陡坡与缓长坡耕地-土壤侵蚀特征差异。结果表明,短陡坡耕地土壤侵蚀速率高达52.6 t.hm-2.a-1,是缓长坡耕地土壤侵蚀速率(26.7 t.hm-2.a-1)的2倍。耕作侵蚀是短陡坡耕地的主要侵蚀过程,它整体性搬运土壤,其对土壤总侵蚀的贡献高达74%。水蚀是缓长坡耕地的主要侵蚀过程,其分选性搬运土壤,对土壤总侵蚀的贡献为55%。短陡坡耕地与缓长坡耕地土壤侵蚀速率均沿着向下坡方向逐渐降低,但短陡坡耕地土壤侵蚀速率下降梯度明显高于缓长坡耕地。耕作侵蚀导致两种坡耕地的坡顶土壤损失最为严重。因此,川中丘陵区的耕作侵蚀风险应该引起重视。

In this study,soil erosion rates of slope farmlands in a purple hilly region of the Sichuan Basin were assessed using 137Cs technique and tillage erosion model.The difference in soil erosion between two types of representative slope farmlands,i.e.,the short-steep slope farmland and the gentle-long slope farmland,was also investigated by using comparative analysis.It was found that soil erosion rate of the short-steep slope farmland reached 52.6 t.hm-2 a-1,approximately two times of the erosion rate of gentle-long slope farmland（26.7 t.hm-2.a-1）.On the short-steep slope farmland,soil erosion processes were dominated by tillage erosion,which entirely transported soil along the downslope transect,with a contribution rate of 74% to the total erosion.In contrast,the major erosion process on the gentle-long slope farmland was water erosion,which selectively transported soil along a downslope transect,with a contribution rate of 55% to the total erosion.Whilst soil erosion rate decreased downslope on both farmlands investigated,a higher decrement was found on the short-steep slope farmland in comparison with the gentle-long slope farmland.Tillage erosion resulted in severe soil loss,especially at the top of the two farmlands.Thus,tillage erosion risk should arise more attention in hilly areas of the Sichuan Basin.