生态工程背景下西南喀斯特植被变化主导因素及其空间非平稳性

Factors impacting on vegetation dynamics and spatial non-stationary relationships in karst regions of southwest China

我国西南喀斯特地区石漠化面积已实现净减少,植被状况具有明显改善。为了更清晰的了解该区植被变化情况及其影响因素的区域差异,采用长时间序列遥感数据,综合运用空间自相关分析、主成分分析(PCA)和地理加权回归(GWR)等研究方法,分析生态工程实施以来滇桂黔喀斯特植被变化及其主要影响因素的空间非平稳性。结果表明:与1982—2000年相比,2001—2011年生长季归一化植被指数(GSN)在整个研究区域都有增加且具有显著的空间集聚性(Ig为0.90),但增加程度在空间上具有差异性(变异系数为43%);影响滇桂黔植被变化的主要因素包括气候因子、土壤质地、人类活动、水分有效性、土壤养分和社会经济条件,且对植被变化的影响程度随地理位置的变化而变化。不同工程地貌类型区内,影响植被变化的主导因素不同,且存在显著的空间差异性,需综合考虑植被变化主导因素的区域差异来调整或改进后续生态工程措施。

With the implementation of ecological restoration, the net area of rocky desertification has been reduced and vegetation coverage significantly improved in karst areas, southwest China. It is crucial to explore the trends in vegetation change and distinguish the driving forces under different karst terrain conditions. Based on the long-term time-series of GIMMS NDVI 3g images, the present study aimed to identify the vegetation changes at different spatial and temporal scales and non-stationary relationships between vegetation changes and driving forces in karst regions of Ynnnan, Guangxi, and Guizhou Provinces with a combination of spatial autocorrelation, principal component analysis （PCA）, and geographically weighted regression. The results showed that from 2001 to 2011 the growing season normalized difference vegetation index （GSN） significantly increased compared to that from 1982 to 2000 in the three regions. The GSN appeared spatially assembled （the Moran＇s index/was 0.90）, while the extent of increase was significantly diverse for different areas （the variable coefficient was 43%）. The PCA indicated that the main driving forces of vegetation change were climatic factors, soil texture, human activities, water availability, soil nutrients, and the level of social and economic conditions. The extent of impacts of the driving forces on vegetation change varied with different geographic positions. In addition, the main driving forces were spatially different under different karst landforms. Our study indicated that the differences of vegetation driving forces should be taken into consideration during future implementation of ecological restoration under different karst landforms.