关中东部缓坡地面全新世土壤侵蚀与沉积发展演变规律研究

对华县古洪积扇全新世黄土一土壤剖面的磁化率、粒度进行分析研究，揭示了全新世以来缓坡地面面状流水侵蚀和沉积的发生规律。研究结果表明，晚更新世末期，由于黄土土质疏松，植被薄弱，在即将进入全新世时有自然侵蚀沉积发生；在全新世4000aB．P.之前，洪积扇特殊的环境生态条件造成土壤堆积时期土壤水分缺乏，成壤较弱，面状流水侵蚀与沉积活动不明显。自夏商时代以来，农业耕垦活动影响古洪积扇地表，促进了坡面流水侵蚀堆积过程，发生了面状流水侵蚀；从3100aB．P.开始气候干旱，人类活动强烈地影响着当地的生态环境，加速了面状流水侵蚀沉积；隋唐以来人类活动引起的加速侵蚀沉积则更进一步增强，这个过程反映土壤侵蚀呈现阶段性加速的趋势。由此可见，土壤侵蚀的加速是与人类的活动相伴随，随着人类活动强度的增强，土壤侵蚀在自然侵蚀的基础上，呈现加速趋势。

The variation of Holocene soil erosion and re-deposition on gentle slope ground in the eastern Guanzhong basin

A Holocene loess-paleosoil profile was studied on pluvial-alluvial fan in the eastern Guanzhong basin at Huaxian county, Shaanxi province. Analyzed from the soil magnetic susceptibility and grain size, the variation of the Holocene sheet rainwash ero- sion-redepositions was revealed on gentle slope ground. The results showed that, there was the natural erosion and deposition in the end of late Pleistocene because of the loosen loess and the spare vegetation. Before 4 000 a B.P. in Holoence, there was short of soil moisture on pluvial-alluvial fan for the special ecology and environment, the sheet rainwash erosion-redepositions was not notable. Since Xia and Shang dynasties, the human agricultural cultivation activities affected the surface of pluvial-alluvial fan and promoted the slope runoff erosion and deposit process. Beginning from the 3 100 a B.P., the climate became dryer, but the human activities affected strongly the local ecology and environment, and accelerated the sheet rainwash erosion-redepositions. After Sui and Tang dynasties, the intensity of sheet rainwash erosion was intensified caused by the human activities. So the speedup of soil erosion was related to the human activities. With the increasing of the human activities intensity, the soil erosion intensity tended to accelerate.