晋西黄土高原水资源植被承载力分析及对策建议

干旱缺水始终是黄土高原地区林业水资源管理面临的难题. 为了探究造成黄土高原地区林水失衡的主要原因,以2009—2012年晋西黄土高原蔡家川流域油松人工林树干液流量与土壤水分长期连续定位观测数据为基础,采用土壤有效水与单株油松耗水量的比值来衡量该区域水资源植被承载力. 结果表明:①在油松人工林实际密度(1 300株/hm2)下,油松人工林过度耗水是深层土壤干化的主要原因；降水量是决定水资源植被承载力的主要环境因子,降水量越大,油松人工林地的水资源植被承载力就越高. ②根据构建的降水量-水资源植被承载力拟合方程,在当地年均降水量为576 mm条件下,研究区20 a林龄油松人工林地水资源植被承载力为1 084株/hm2,而油松人工林地的实际密度远大于该水资源植被承载力. 在黄土高原地区,人工林密度过高是造成深层土壤干化、植被退化等生态恶化的主要原因. 因此,将人工林密度控制在当地水资源植被承载力范围之内,是减少林地深层土壤水分消耗、调节林地水平衡的重要措施. 

Analysis and Countermeasures of the Carrying Capacity of Water Resources for Vegetation on the Loess Plateau, Western Shanxi Province, China

Abstract: Forestry water resources management to solve drought and water shortage at the Loess Plateau is a big problem in environmental management. In order to investigate the causes of the imbalance of water resources in plantations, the carrying capacity of water resources for vegetation (CCWRV) was measured by the ratio between available soil water and water consumption of a single Chinese Pine. The data were obtained through long-term continuous in situ simultaneous monitoring of soil water content and measurements of stem sap flow in Chinese Pine at the Loess Plateau in Western Shanxi Province during 2009-2012. The results showed that the water consumption of Chinese Pine plantations is one of the factors deteriorating soil water deficit under the conditions of the actual stand density (1300 trees per hectare). Precipitation is one of the key environmental factors determining the CCWRV. The higher the precipitation was, the higher the CCWRV. A curve-fitting equation to calculate the reasonable density for Chinese Pine stands based on annual precipitation was created in the present study. The CCWRV in a 20 years-old Chinese Pine plantation in the experimental area was estimated as 1084 trees per hectare, using the equation based on an average annual precipitation of 576 mm. The CCWRV in Chinese Pine plantation was far less than the actual stand density. It is the basic reason for ecological deterioration, such as deep soil water deficit, vegetation degradation, etc., on the Loess Plateau. Therefore, keeping the stand densities of vegetation within the limits of CCWRV is an important measure to reduce deep soil water consumption and maintain the soil water balance on the Loess Plateau.