GEOGRAPHICAL RESEARCH ›› 2006, Vol. 25 ›› Issue (5): 865-876.doi: 10.11821/yj2006050012

• Earth Surface Processes • Previous Articles     Next Articles

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

WANG Hong-ya,HUO Yu-ying,WU Xiu-qing,CAI Yun-long   

  1. Department of Resources,Environments and Geography,School of Environmental Sciences,Peking University,Beijing 100871,China
  • Received:2005-12-02 Revised:2006-05-17 Online:2006-10-15 Published:2006-10-15

Abstract:

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(χlf,ARM,IRM20mT,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.

Key words: Guizhou, carbonate rocks, soil erosion, reservoir sediments, mineral magnetism