Spatiotemporal Variation of Vegetation GPP in Subtropical Regions of China and Its Response to GPPmax and Phenology
Vegetation in subtropical regions has strong carbon sequestration capabilities,and its dynamic changes have significant impacts on regional and even global carbon cycling.Based on the gross primary productivity(GPP)of vegetation and sun-induced chlorophyll fluorescence(SIF)data,the curvature derivative and spline interpolation are used to extract the spring and autumn phenology and GPP peak(GPPmax)of subtropical vegetation in China,and combined with MK trend test and partial correlation analysis,the spatiotemporal variation characteristics of annual GPP of subtropical vegetation in China from 2001 to 2018 and its response to phenology and GPPmax are quantitatively analyzed in this paper.The results showed that during the study period,the annual GPP and GPPmax of vegetation in subtropical regions showed a significant increase trend,while the spring phenology and autumn phenology showed no significant advance and significant delay,respectively.The partial correlation analysis results indicate that GPPmax and spring phenology are positively and negatively correlated with annual GPP in the entire study area,respectively;except for the southeastern part of the study area,there is also a positive correlation between autumn phenology and annual GPP.Overall,the annual GPP variation of vegetation in the study area is mainly controlled by GPPmax,followed by spring phenology and autumn phenology.
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