灌丛分布与坡度的关系: 京津冀山地实例研究
Relationship between Shrubs Distribution and Slope: A Case Study in Mountains of the Beijing-Tianjin-Hebei Region

摘要 以京津冀山地暖温带灌丛为研究对象, 基于网格化的坡度、气候和植被类型的数据, 利用分段线性回归模型, 分析灌丛的面积百分比与坡度之间的关系。结果显示, 网格内灌丛的百分比与坡度的关系之间存在一个拐点, 而不是单调的线性关系。在缓坡上, 灌丛的百分比随坡度增加而增加, 可能是因为坡地在一定程度上屏蔽了人类活动的干扰。在陡坡上出现两种格局: 除荆条酸枣以外的灌丛的百分比随坡度升高而降低, 主要体现陡坡对资源的限制作用; 荆条酸枣灌丛的百分比没有下降趋势, 可能是因为荆条酸枣灌丛在海拔分布上的差异导致。此外, 研究还发现, 当不考虑气候条件的空间差异时, 除荆条酸枣灌丛以外的类型均分布在15°附近; 在不同的气候条件下, 拐点的位置不同。
Abstract Shrublands in the Beijing-Tianjin-Hebei region were selected to unveil relationships between the area percentage of shrubland and the slope angle. Gridded data of vegetation and slope angle were correlated for the whole region as well as different climatic regimes with piecewise regression analysis. The results show that there is a tipping point on the fitted curve between percentage of shrubs and slope angle, instead of a monotonous linear fit. On gentle slopes, percentage of shrubs increases with the increase of slope angle, which might be caused by the decrease of human cultivation. On steep slopes, there are divergent patterns, percentage of shrublands except that dominated by Vitex negundo var. heterophylla and Zizyphus jujuba var. spinosa decreases with the increase of slope angle, which might be caused by resource limitation. Percentage of this shrubland type does not show trend of decline with slope angle increase, which might be caused by its distribution on low elevations and its adaptation to varied habitats. In addition, the tipping point mostly fixes around 15 degree of slope angle when the region is taken as a whole; it changes under different climatic regimes.