亚热带丘岗区生态系统水分平衡及农业反应

通过对自然集雨区水分动态10年定位观测研究，初步明确了我国亚热带丘岗区生态系统水资源的分布特征与水平衡状况。该区域雨水丰沛，总量可维持系统水分平衡，但其时空变化大，加之蒸发变化与之错位和土壤持蓄水分性能差等因素作用，导致系统水分盈亏现象发生，水分“高盈期”的湿害和“亏缺期”的伏旱严重制约了丘岗区农业的发展。强化工程、农艺措施调控能力，提高农业水资源管理水平，是促进我国亚热带丘岗区农业持续稳定发展的技术保障。

Water equilibrium in subtropical hilly ecosystems and its impacts on agriculture

Field observations for ten years were carried out in a catchment basin-basic ecological unit to investigate the natures of water equi librium. This unit had been selected as the representative ecosystem of subtropi cal hilly land of South China. Obtained data include the annual variation and d istribution of the rainfalls, evaporation and run off, and irrigation requiremen t in the ecosystem. The results showed that the amount of rainfalls was abundant and able to maintain water equilibrium in the ecosystem. However, the distribut ion of rainfall varied largely in a year. During the rain season(late March to J u ne),the amount of rainfalls was much greater than evaporation(including plant co nsumption), which resulted in water logging.In contrast,during the period from l ate July to late September, the amount of rainfalls was smaller than half of eva poratioin. Over this period, water deficiency dominated the water ecology of the system and resulted in dry environment. With such water environment, crop produ ctions in the subtropical hilly regions suffer seriously from both impacts of water l ogging and drought.Based on the water characteristics in the subtropical hilly e cosystems, the main effort for arising crop production is to reduce harms from both of water logging and drought. The countermeasures are to strenghen the con struction of farmland(engineering and agronomical method) and to improve water m anagement, in order to control water-logging and best use water resource.