半干旱黄土高原退化生态系统的修复与生态农业发展

首先分析了半干旱黄土高原区域生态系统的特点，指出：这里地带性植被极度退化，土壤质量严重恶化，治理难度大，可持续发展受到严重威胁。然后，进行生态系统退化关键驱动力的分析，认为，在不同时期，农民的利益驱动始终是土地利用格局和生态系统演化／退化的关键驱动力。在寻求分析退化生态系统修复的突破口时，认为提高作物产量和经济效益，解决农民的需求是具有可操作性的途径。而实现这一途径必须提高单产，以减轻更广大土地面积上的生产力需求压力。通过集水、覆盖等措施改善农田水分条件，再配合地膜、化肥，在对农田进行合理管理的情况下，粮食单产可获得持续大幅度的提高。在此基础上，提出了实现区域可持续发展的途径——集水型生态农业及其景观配置模式。在这一模式中，经济作物、粮食作物、人工草地和天然草地在一个完整的景观单元内合理配置，形成完整的景观复合生态系统。对这一模式的深人研究和正确实施将推动半干旱黄土高原退化生态系统的修复，并为西部开发中经济建设和生态建设并举提供理论与实践指导。

Restoration of degraded ecosystems and development of water-harvesting ecological agriculture in the semi-arid Loess Plateau of China

The natural regional vegetation and soil quality in the semi arid Loess Plateau of China have been degraded extremely due to over grazing and frequent reclamation of natural grassland. Functions of the ecosystems and regional sustainable development were seriously threatened. The analysis of the current ecological environmental situation suggests that transformation of natural vegetation to farmlands in the process of frequent reclamation of natural grassland results in water loss, soil erosion and land degradation. Repeated reclamation of wasteland due to the great pressure of food demand resulted from population growth is the key driving force to the degradation of these ecosystems. To restore natural vegetation and soil quality, we have to find a way to meet the requirement of food for the local farmers in a small portion of the land to reduce the pressure of food production for the rest of the land of a region. In semi arid areas, many studies have shown that the key step for increasing grain yield per unit area is to improve field environmental conditions, including soil moisture supply, topsoil temperature and soil nutrient level. This can be accomplished through the combination of water harvesting technology with plastic film mulching and fertilizer application, which can generally increase the unit grain yield twice or more. Based on these technologies, we propose an approach of water harvesting ecological agriculture (WHEA) and associated landscape configuration in the paper. Unit yield of cash and grain crops can be increased greatly through limited irrigation, and the irrigated cropland can be interspersed with improved pastures and restored natural vegetation in a continuous landscape (a typical hill) in WHEA. Further research and dissemination of WHEA can help supply local farmers with sufficient food and higher income. Various types of grasslands will replace cropland and cover a large proportion of the landscape; animal feeding will be mainly dependent upon pen feeding in order to decrease grazing pressure. These strategies closely follow the ecological patterns of natural vegetation and landscape, as well as the planning pattern of regional industrial arrangement. The coexistence of multiple ecological and economic systems in a landscape helps to improve both biodiversity and industrial diversity, and enhance the flexibility and stability of these systems. Therefore, WHEA, an innovative approach for regional development, can lead to significantly improvement in both the restoration of degraded ecosystems and regional sustainable development simultaneously in the semi arid Loess Plateau.