黄土高原全新世以来土壤侵蚀强度的定量分析初探

A Preliminary Quantitative Analysis of Soil Erosion Intensityon Loess Plateau since the Holocene

黄土高原全新世以来可划分出5个侵蚀阶段,其起始年龄分别为11,7.0,0.7,0.3,0.15kaBP。根据高原现代河流沉积物的粒度组成、河流输沙量、径流量和年降水量等数据建立了各个指标的回归方程。根据各方程和全新世不同时期阶地沉积物的实测数据,计算了各个阶段的平均古侵蚀强度和流域输沙量。结果表明,不同时期水土流失的主要控制因素是不同的:在11000～7000aBP时期以构造活动因素为主,在7000～2000aBP期间以气候因素为主,在2000～700aBP和300aBP以来以人为活动因素为主,而在700～300aBP是构造活动、气候变迁和人类活动的共同作用因素。自然因素的突变作用一般大于人类活动的作用,而现代人类活动的加剧程度大约是自然侵蚀强度的45.5%。

Since the Holocene the soil erosion process in the Loess Plateau can be divided into 5 stages, of which starting times are 11, 7.0, 0.7, 0.3 and 0.15 ka B P. The regression equations of some parameters of modern rivers in the plateau are established by using the data of grain size of sediments, sediment discharge of river, annual runoff and precipitation. Based on the measured data of the samples in each terraces the paleoerosion intensity and paleosediment discharge in various stage of the Holocene are calculated from the regression equations. The study result indicate the difference of the factor forcing soil erosion: tectonic forcing during 11 000~7000 a BP, climatic forcing during 7 000~2 000 a BP, manmade forcing during 2 000~700 and in the past 300 a BP, and coupled forcing during 700~300 a BP. Clipping change of natural process is stronger generally than that of human activity, but the soil erosion intensity caused by human is bigger by 45.5% than that by natural factors at present. 