干旱区生态环境知识资源中心

Since Sorensen first proposed the definition of ecotope in 1936, the stratified feature and distinct management of ecosystems has received extensive consideration worldwide. We chose the Loess Plateau of China as a case study to quantitatively establish a potential model system entitled the Stratified Strategies for Ecosystem Management (SSEM). The Loess Plateau is geographically dominated by hilly and gully topography. Intense rainfall during summer erodes the bare topsoil from the hill tops to the valleys, which leads to serious soil and water loss, land degradation and social poverty. Since the 1980s, four big national programs have been initiated and implemented to reduce the erosion and improve livelihoods, including the Grain for Green Program (GFGP), the Natural Forest Conservation Program (NFCP), the Terraced Field Construction Program (TFCP), and the Integrated Rain-harvesting Agriculture (IRHA). Our statistical analysis shows that these strategies have played positive roles in harmonizing ecosystem conservation with human development. Vegetation cover has been increased by 27.0% and total farmland area has been reduced by 23.6% at four typical sites. Soil organic carbon has increased by 1.59 g/kg, while annual topsoil loss has been reduced by 650 Kt. In addition, terracing has significantly improved soil water storage, sediment trapping and soil quality on the Loess Plateau. On the other hand, the IRHA system in the valley areas has brought about a significant increase in the productivity of summer crops. Based on the IRHA model, the grass-crop rotation system has led to considerable improvement in agricultural cropping patterns, and promoted modern agricultural and animal husbandry systems. The population of farmers growing crops has been reduced 20% but the regional GDP has increased 800%. Human productive activities have tended to transfer from the tops of the hills to the side of the hills and valleys. We therefore propose an integrated model of SSEM, which provides a novel strategy to conserve endangered ecosystems in semiarid and arid areas.