黄土丘陵区纸坊沟流域近70年农业生态安全评价

在国内外已有研究的基础上,结合黄土丘陵区纸坊沟流域近70a来农业生态经济系统演变过程,参考PSR模型,从生态环境、社会经济和综合功能3方面构建黄土丘陵区流域农业生态安全评价指标体系,基于层次分析法赋权的综合指数评价方法,对纸坊沟流域1938～2005年农业生态安全状况进行评价。结果表明:该流域农业生态安全状况发生了先降后升的变化,1938年处于较安全状况,1958年为极不安全状况,1975年和1985年都处于较不安全状况,1995年处于临界安全状况,2005年属于较安全状况。评价结果表明纸坊沟流域还需要进一步优化农业系统结构,实现农业生态安全。

Assessing the consequence of land use change on agricultural productivity in China

China's cultivated land has been undergoing dramatic changes along with its rapidly growing economy and population. The impacts of land use transformation on food production at the national scale, however, have been poorly understood due to the lack of detailed spatially explicit agricultural productivity information on cropland change and crop productivity. This study evaluates the effect of the cropland transformation on agricultural productivity by combining the land use data of China for the period of 1990-2000 from TM images and a satellite-based NPP (net primary production) model driven with NOAH/AVHRR data. The cropland area of China has a net increase of 2.79 Mha in the study period, which causes a slightly increased agricultural productivity (6.96 Mt C) at the national level. Although the newly cultivated lands compensated for the loss from urban expansion, but the contribution to production is insignificant because of the low productivity. The decrease in crop production resulting from urban expansion is about twice of that from abandonment of arable lands to forests and grasslands. The productivity of arable lands occupied by urban expansion was 80% higher than that of the newly cultivated lands in the regions with unfavorable natural conditions. Significance of cropland transformation impacts is spatially diverse with the differences in land use change intensity and land productivity across China. The increase in arable land area and yet decline in land quality may reduce the production potential and sustainability of China's agro-ecosystems. (C) 2008 Elsevier B.V. All rights reserved.