Response of Vegetation NPP to Multiscale Meteorological Drought in Southwest China

[Objective] This study was aimed to explore the response mechanism of vegetation to drought at different times scales and clarify the frequent occurrence of extreme drought events in southwest China on vegetation growth. [Methods] Based on vegetation net primary productivity (NPP) data from 2001 to 2019 and standardized precipitation evapotranspiration index (SPEI) data on a continuous scale from 1-24 months in southwest China, correlation analysis, maximum synthesis method, significance test were used to analyze the responses of NPP of different geomorphic types and vegetation types to multi-scale SPEI in southwest China. [Results] (1) On the annual scale, seasonal scale and growing season, the responses of vegetation NPP and SPEI at 1-24 months were dominated by the January-March scale, vegetation NPP had a good response to short-term drought changes, but a relatively poor response to medium and long-term drought changes. (2) The response of NPP to SPEI at 1-24 month scale showed significant spatial heterogeneity and seasonal differences. The interannual correlation showed a trend of significant positive correlation to significant negative correlation from southeast to northwest. The seasonal correlation showed that significant negative correlation was dominant in summer, significant positive correlation was dominant in spring, autumn, and winter. This indicated that in the southwest China, the summer temperature was high and humid, which limited vegetation growth the area with the largest positive correlation was Guangxi Hills, while the area with the largest negative correlation was Zoige Plateau. (3) The responses of NPP to SPEI from 1-24 months were different among different vegetation types. Although the response characteristics of grassland, scrub and forest land to SPEI were basically similar, the trend of negative correlation between NPP and SPEI became stronger with the scales of SPEI decreased in summer for all types of vegetation. This suggested that all types of vegetation are more susceptible to drought under high temperature and drought conditions in summer. [Conclusion] The research results provide effective scientific support for the protection and restoration of the ecosystem in the southwest China, provide an important theoretical basis for disaster prevention and reduction and coping with climate change, help formulate more targeted policies and measures to promote the sustainable development of southwest China.