关键词: 杨树人工林, 生产力衰退, 细根根序, 碳氮分配格局

Abstract: Water and soil loss is the main cause of soil degradation, and one of the most serious ecological environmental problems. Many achievements have been obtained in the study of soil erosion in Karst region, but few studies are conducted on the mercury (Hg) translocation induced by soil erosion in seriously Hgpolluted areas of typical Karst regions. Selecting the Wanshan Hg mining area (167.4 km²) of Southwest China as study area and by using geographic information system (GIS) and a revised universal soil loss equation (RUSLE), this paper assessed the intensity of soil erosion and the surface soil Hg translocation via soil erosion. In the mining area, soil erosion modulus was in the range of 0-600884 t·km^-2·a^-1, and the areas with slight and severe erosion occupied 76.6% of the total, among which, the area with severe erosion made up 90.5%. On annual basis, the surface soil Hg loss was up to 505 kg·a^-1, and the Hg loss rate was 3.02 kg·km^-2·a^-1. Land use type and slope gradient were the main factors affecting the Hg loss, and Hg loss easily occurred on the farmland and shrub land in steep zones, with an amount of 175 and 319 kg a^-1, respectively. This study not only provided scientific basis for the control of water and soil erosion in the study area, but also supplied data support for the management of Hg pollution of local ecosystems.

Key words: poplar plantation, productivity decline, fine root order, carbon and nitrogen allocation.