试论我国北方地区人工植被的土壤干化问题

我国北方地区以人工林为代表的人工植被建设中正面对一个严峻问题－土壤干化。土壤干化是北方少雨地区人工植被土壤退化的主要表现形式，其显著特征是因植物蒸腾过量耗水造成的植物根系作用范围内土壤水分长时间持续地严重亏缺，天然降水已不能有效予以补偿，土壤表层板结．土壤紧实度增大，从而导致植物生长明显衰退以至大面积干枯死亡。土壤干化已成为这一地区人工植被建设的严重隐患。造成人工植被土壤干化的直接原因是植被类型选择不当，群落密度过大和群落生产力过高。人工植被土壤干化的防治对策是，在正确的植被建设思想指导下，依据当地的生物气候生产力因地制宜地选择植被类型，大幅度降低群落密度，合理调控群落生产力，以保持植物蒸腾耗水与土壤水分补偿之间的水分平衡，从而维持群落的持续稳产与高产。

THE PRELIMINARY DISCUSSION ON SOIL DESICCATION OF ARTIFICIAL VEGETATION IN THE NORTHERN REGIONS OF CHINA

The serious soil drification, which is being confronted in the course of construction of artificial vegetation represented by artificial plantation in the northern regions of China, is put forward in this paper. Soil desiccation is the mainly expressive form of soil deterioration of artificial vegetation in northern regions where there is less precipatation,the principal characteristic of soil desiccation is critical deficit of soil water continuously for a long time in the affecting scope of plant root system because of extra transpration of plant. The precipitation cannot compensate for water consumption effectively, surface soil crusts and soil compactness increases, which results in obvious declination of plant growth, even make plant shivelled and dead in the range of large area. The soil desiccation has become seriously potential danger of the construction of artificial vegetation in tills region. In my opinion, the direct reason, which causes soil desiccation of artificial vegetation, is the improper selection of vegetation type, too high community density and too high community productivity. The prevention and control strategy is as the follows:In the guidance of correct thought of vegetation construction, according to local bio-climatic productivity, vegetation type is selected in the light of local condition, community density is decreased subtantially,community productivity is adjusted and controled rationally, the final purpose is to keep balance between water consumption by plant transpiration and compensation of soil water, to further keep continuous stability and high yield of community.