气候条件对黄土高原水土保持植被结构的影响及其在植被建设中的意义

Influence of Climate on Vegetation Structure for Soil-Water Conservation and Implications in Vegetation Construction

以黄河流域的资料为基础,运用数理统计的方法将描述水土保持植被结构的指标与气候指标相联系,揭示了气候条件对黄土高原水土保持植被结构的影响,在此基础上提出对乔木面积与乔灌草总面积的比率是否合理进行评价的方法。研究表明,年降水量是影响水土保持植被结构的最重要气候因素,乔木、灌木和草地与乔灌草总面积的比率与年降水量的相关系数的显著性水平均大大优于0.01。乔木、灌木和草地与乔灌草总面积的比率与年降水量的相关系数分别为0.72,-0.48,-0.47,逐渐减小,说明乔木、灌木和草类对降水的依赖程度逐渐减小。气温对水土保持植被的结构也有很大的影响,乔木、灌木和草地与乔灌草总面积的比率与年均温和≥10℃活动积温的相关系数显著性水平均大大优于0.01。同时,建立了乔木面积与乔灌草总面积的比率Rt与年降水量Pm、年均气温Ta、年最大雨量与年雨量之比Pmax/Pm、年均大风日数Dw之间的多元回归方程,该方程表明:年降水量越多,年均温越高,大风日数越少,年最大雨量与年雨量之比越低,则乔木面积与乔灌草总面积的比率越高。回归方程还表明,降水对乔木面积与乔灌草总面积的比率贡献最大,年均温的贡献次之,大风日数的贡献率居第3,年最大雨量与年雨量之比的贡献率居第4。基于这一回归方程。

Based on data from the Yellow River basin, the indices describing soil-water conservation vegetation structure have been related to climatic factors using statistical method, thereby to reveal the influence of climate on vegetation structure. The results show that mean annual precipitation (P_m) is the important factor; the correlation coefficients of P_m with the ratios of the areas of trees, shrubs and grasses to the total area of trees, shrubs and grasses are 0.72,-0.48,-0.47, respectively, all significant at a level of <0.01. In this sequence, correlation coefficient decreases, indicating that the precipitation-dependence of trees, shrubs and grasses declines. Mean annual temperature (T_m) also has some influence on soil-water conservation vegetation structure, the correlation coefficients of T_m with the ratios of the areas of trees, shrubs and grasses to the total area of trees, shrubs and grasses are all significant at a level of <0.01. A multiple regression equation has been established between the ratio of tree area to total area of trees, shrubs and grasses and climatic indices such as mean annual precipitation, temperature, strong wind days and the ratio of maximum daily rain to annual precipitation. The equation indicates that the ratio of tree area to total area of trees, shrubs and grasses increases with the increase in annual precipitation and annual temperature, but with the increase in annual strong wind days and the ratio of maximum daily rain to annual precipitation. The regression analysis also indicates that the relative contribution of the variation in precipitation to the variation of ratio of tree area to total area of trees, shrubs and grasses ranks the first, that of temperature the second, that of strong wind days the third, and that of the ratio of maximum daily rain to annual precipitation the fourth. Based on the multiple regression equation, an simple approach is proposed for assessment of existing soil-water conservation vegetation structure.