等高反坡阶对坡耕地土壤碳库的影响

目的]研究坡耕地等高反坡阶措施的蓄水保土和固碳减排效应,为改善云南山区红壤坡耕地土壤侵蚀状况提供科学依据。方法]自然降雨条件下,通过松花坝迤者小流域1a的野外径流小区定位观测,对有、无等高反坡阶措施条件下的坡面产流产沙和土壤有机碳流失进行对比分析。结果](1)泥沙作为土壤有机碳流失的重要载体,因其流失所致的流失量占总有机碳流失量的85%以上,最高达95.38%;(2)等高反坡阶具有显著的蓄水减流和保土减沙效应,其减流率在5.56%~53.91%,减沙率在18.84%~83.11%,产沙调控作用更优;(3)雨季前后,原状坡面小区土壤碳储量减少率达9.90%,明显高于等高反坡阶小区土壤碳储量的减少率3.99%;(4)通过相关分析发现,2个小区土壤有机碳的流失率与降雨量均未达到显著相关,但与降雨侵蚀力显著相关(p0.05)。径流、泥沙与2个小区有机碳的流失率均达到了显著正相关(p0.05)。结论]等高反坡阶通过改变地表微地形,减少了坡耕地有机碳的输出。

Effects of Reverse-slope Level Terrace on Soil Carbon Stock of Sloping Farmland

Objective] In order to provide a scientific basis for prevention of soil erosion on slope farmlands in mountainous area of Yunnan Province, the effects of reverse-slope level terraces on soil and water conservation and soil carbon stock of slope farmland were studied.Methods] A comparative experiment was conducted in a fixed 1 year run-off observation plot located in Yizhe watershed of Kunming Songhuaba reservoir under natural rainfall condition. Surface runoff, sediment quantity and the loss of soil organic carbon from slope farmland with and without reverse-slope level terraces(act as control) were measured.Results] (1) As an important carrier of soil organic carbon, the loss of sediment-bonded soil organic carbon accounted for over 85% of the total organic carbon lost with runoff, and the maximum bonded loss proportion could reach 95.38%.(2) The reverse-slope level terrace performed significant effects on promoting soil and water conservation and on reducing runoff and sediment. The reduction rates of runoff and sediment by the reverse-slope level terrace were 5.56%~53.91% and 18.84%~83.11%, respectively, showing that the sediment reducing effect of reverse-slope level terrace was more prominent than that of carbon reducing effect.(3) The reduction rate of soil carbon storage of slope farmland with reverse-slope level terrace was 3.99% during the rainy season, which was significantly less than that of the control of 9.90% reduction.(4) Correlation analysis by the observations from treatment with reverse-slope level terrace and the control showed that the loss rate of soil organic carbon from slope farmland was not significantly correlated with rainfall, it was significantly correlated with erosion capacity of the rainfall(p<0.05). The runoff and sediment quantities were significantly and positively correlated with the loss rate of soil organic carbon in both of the two observation plots(p<0.05).Conclusion] Mainly by changing micro-topography of land surface, reverse-slope level terrace had remarkable effect on reducing the output of soil organic carbon from slope farmland.