欧亚大陆不同生态区植被生长对降水响应的季节变化规律

欧亚大陆是"一带一路"战略规划的核心区域,了解欧亚大陆植被生长对降水的响应机制是该战略顺利实施的科学与生态基础。采用1982—2015年的归一化植被指数NDVI(Normalized Difference Vegetation Index)和全球气象格点数据,通过计算偏相关系数,排除温度及日照辐射的共同作用,分析植被对降水的响应关系(R_(NDVI-Prep))在不同季节、不同生态区的分异特征。在夏季,R_(NDVI-Prep)为显著正相关的地区广泛地分布在35°—60°N之间的欧亚大陆干旱、半干旱地区以及南亚次大陆西北和南部地区;在春季和秋季,R_(NDVI-Prep)为显著正相关的地区分布则相对于夏季显得更为集中,某些显著相关的区域的边界和现有的生态区划边界有很好的一致性。使用17年为一个周期的时间滑动窗口,分析不同季节上R_(NDVI-Prep)从1982至2015的变化规律,发现夏季植被呈现对降水依赖的地区所处纬度要高于春、秋两季。中亚干旱、半干旱生态区的植被在春、夏两季对降水依赖较强;南亚次大陆西北部地区的干旱、半干旱及东南亚的雨林地区在夏、秋两季对降水依赖较强,且秋季的分布最为集中。以生态区为视角,对欧亚大陆的植被与降水的关系有了更为深入的了解,可以为不同区域应对和适应气候变化提供决策依据。

Seasonal changes in vegetation response to precipitation across eco-regions over Eurasia

Eurasia is the core region of Belt and Road strategic planning. A good understanding of the response of vegetation to precipitation is the scientific and ecological foundation for the implement of this strategic plan. This study used the Normalized Difference Vegetation Index (NDVI) and the global gridded climatic datasets for the period from 1982 to 2015 to analyze the different seasonal and spatial response of vegetation growth to precipitation (R_NDVI-Prep) by using the partial correlation coefficient method, which removes the combined influence of temperature and solar radiation on vegetation. In summer, we found the regions with positive R_NDVI-Prep were in the arid and semi-arid regions of Eurasia with the latitudes from 35°N to 60°N and in the northwestern part and southern part of the South Asia Sub-Continent. In spring and autumn, the area with significant positive R_NDVI-Prep relationship was more concentrated distributed than that in summer. The boundaries for some regions with significant R_NDVI-Prep correlation were consistent with the current eco-region map. We applied 17-year moving windows to analyze the patterns of R_NDVI-Prep in different seasons from 1982 to 2015 and found that the latitude of the pixels where vegetation showed strong dependency on water in summer was higher than those in spring and autumn. In arid and semi-arid regions of central Asia, the vegetation showed greater dependency on water in spring and summer than in autumn. Meanwhile, in the arid and semi-arid regions of the northwestern parts of South Asia Sub-Continent and in the rainforest regions of southeastern Asia, the vegetation showed greater dependency on water in summer and autumn than in spring, especially in autumn with a more concentrated distribution. The results will improve the understanding of vegetation response to precipitation across different eco-regions in Eurasia, and also provide a base theory for policy making for regional development.