雨强对红壤坡耕地泥沙流失及有机碳富集的影响规律研究

EFFECT OF RAINFALL INTENSITY ON SOIL LOSS FROM SLOPE FARMLAND OF RED SOIL AND ORGANIC CARBON ENRICHMENT IN SEDIMENT

在典型红壤丘陵区平均坡度为10°的坡耕地径流小区(2 m×5 m)上进行降雨强度为1.69mm min-1(大雨强)、1.31 mm min-1(中雨强)和0.64 mm min-1(小雨强)的模拟降雨试验,并对模拟降雨过程中泥沙的迁移规律和土壤有机碳的流失富集规律进行了研究。结果表明:侵蚀作用下土壤流失量随着降雨强度的增大而增加,并与径流量呈显著的立方关系,径流量是坡耕地土壤流失的重要影响因素;土壤有机碳流失以泥沙结合态为主,泥沙态有机碳流失量占总有机碳流失量的84%以上,最高达97.6%;泥沙中有机碳富集比随着降雨强度的增大而减小,有机碳的选择性迁移在低强度降雨条件下表现更为明显;中雨强和小雨强下有机碳的富集比与黏粒的富集比分别呈极显著和显著正相关,而大雨强泥沙有机碳富集比与黏粒富集比没有显著的线性关系。雨强是影响泥沙流失和泥沙有机碳迁移的重要因素。

Simulated rainfalls, 1.69 mm min-1 （high）, 1.31 mm min-1 （moderate） and 0.64 mm min-1 （low） in intensity, were performed on plots of farmland, 2 m×5 m each in area and 10° in average slope gradient, on a red soil hill typical of hilly regions, to study on rules of migration,of sediments and enrichment of organic carbon therein. Results show that soil loss increased with rainfall intensity, and demonstrated a significant cubic relationship with volume of runoff, which is an important factor influencing soil loss on slope farmland; Sediment-bonded soil organic carbon is the mainly form of organic carbon lost with runoff, accounting for more than 84% and even 97.6% of the total loss of organic carbon. Organic carbon enrichment ratio of the sediments decreases gradually with increasing rainfall intensity, and selective migration of organic carbon was more evident in rainfalls low in intensity. In rainfalls, high in intensity, no significant linear relationship was observed between organic carbon enrichment ratio and clay enrichment ratio, but in rainfalls, moderate or low in intensity, an extremely significant or significant positive relationship was observed, respectively. Therefore, it can be concluded that rainfall intensity is an important factor that affects soil loss and migration of organic carbon with sediments.