贵州石板桥水库沉积物的矿物磁性特征及其土壤侵蚀意义

对取自贵州省关岭县石板桥水库的岩芯做了矿物磁性测量（lχf、ARM、IRM20mT、SIRM、IRM-100mT）并计算了ARM/SIRM、HIRM、IRM-100mT/SIRM。将这些结果与同时完成的137Cs、粒度、TOC和C/N分析结果相结合,推测了过去的42年（1960²002年）中这一水库的汇水流域内的土壤侵蚀状况。在这一时期,尽管存在着若干次一级的波动,土壤侵蚀总体上呈加剧的趋势。将这些结果与收集的降水和土地利用/土地覆被变化资料数据相结合,探讨了土壤侵蚀状况发生变化的原因。土壤侵蚀的总体加剧可能是由1960年以来林地面积的减小和农田面积的增大以及1990年以来因植树而较强翻动地表物质造成的,而土壤侵蚀的次一级的波动可归结为降水的波动。

Mineral-magnetic characteristics of sediments from Shibanqiao Reservoir,Guanling County,Guizhou Province and their implications on soil erosion

Shibanqiao Reservoir（25°56′56.5″N,105°26′44.5″E,¹400 m a.s.l.） was built in Guanling County which is one of the areas where the worst soil erosion and rocky desertification have been taking place in Guizhou Province,Southwest China.The catchment(6.00 km²,1452-1630 m a.s.l.) of the reservoir is largely underlain with carbonate-rocks,being mainly dolomite.A 24-cm long sediment-core was sampled from the reservoir.Some mineral-magnetic parameters(χ_lf,ARM,IRM_20mT,SIRM and IRM_-100mT) are measured with these sediments and furthermore ARM/SIRM,HIRM and IRM_-100mT/SIRM are calculated for them.Soil-erosion occurring during the past 42 years（1960-2002） in the drainage basin is inferred by interpreting the mineral-magnetic characteristics in combination with results of analyses of ¹³⁷Cs,grain-size,and TOC and C/N simultaneously made and depositional rates calculated for these sediments.Soil erosion seems to have generally intensified in spite of some sub-order fluctuations in its intensity during this period.Causes of the inferred changes in soil erosion are deduced by combining the interpretation with the collected rainfall and land use/land cover change（LUCC） data.The overall intensification of soil erosion may be caused by the decrease of woodland area and the increase of cropland area since 1960 and the occurrence of looser soil scarified in the mass tree-planting initiated since 1990 in the catchment.The minor fluctuations in intensity of soil erosion may be attributed to those in rainfall.In other words,soil-erosion intensity is controlled predominantly by human activities（i.e.land use） while rainfall is likely to influence intensity of soil erosion only relatively moderately,which is generally in agreement with conclusions derived by some other investigators in doing similar studies in other areas.