黄土高原半干旱区水土保持植被恢复限度——以人工柠条林为例

Limit of vegetation rehabilitation for soil and water conservation in semi-arid region of Loess Plateau:A case study of artificial Caragana korshinskii Kom stand

为了确定水资源不足地区植被恢复潜力和水土保持林建设目标,在黄土丘陵半干旱区宁夏固原上黄试区,对相同立地条件的16年生人工柠条林进行疏伐,建立不同密度林地,进行林分密度、森林植被水土保持效益和土壤水分关系的定位实验。结果表明:平均基径随密度的增加而减少,二者为线性关系;盖度随密度的增加而增大,盖度与密度为对数关系;林冠截留随密度的增加而增大,二者为指数关系;地表径流随密度的增加而减少,二者为对数关系;泥沙含量随密度的减少而增加,二者关系可用倒S形曲线描述。虽然密度增加,盖度增加,森林植被水土保持效益增强,但是受土壤水资源的限制,柠条林有一个最大恢复限度。当超过限度时,势必会引发或加剧土壤旱化。

In order to determine the potential for vegetation rehabilitation and set the goal of soil and water conservation forest in water-shortage region of Loess Plateau, 16-year-old artificial Caragana korshinskii Kom stand grown in a reasonably uniform site was selected and thinned to establish different densities of experimental plots, and the experiments of the relationships between density of a stand, forest benefit to conserve soil and water and soil water was conducted in the Caragana korshinskii Kom stand in Shanghuang Eco-experimental Station of the semi-arid region, Guyuan County, Ningxia Hui Autonomic Region of China. The results showed that the mean basal diameter of Caragana korshinskii Kern stand decreases with increasing density and there is a linear relationship between basal diameter and stand density, the stand coverage increases with increasing density and there is a logarithm relationship between coverage and density; the canopy interception increases with density and both of them is a power relationship; the surface runoff decreases with increasing density and the relationship between them is a logarithm functional relationship, the sediment charge in the runoff increases with reducing density and the relationship between them can be expressed by an ＂inverse-S shape＂curve. Although the canopy closure increase with increasing density, and the effect of Caragana korshinskii Kom stand on soil and water conservation strenthens, but there is a limit in the course of vegetation rehabilitation because of the limit of soil water resources. When the cover degree is more than the limit, soil drying appears or was aggravated in the Caragana korshinskii Kom stand.