Relationship between extreme climate indices and spatiotemporal changes of vegetation on Yunnan Plateau from 1982 to 2019

Extreme weather events have led to significant changes in vegetation over the past few decades. Extreme climate indices and net primary productivity (NPP) of vegetation on Yunnan from 1982 to 2019 were calculated based on Rclimdex 1.0 software and the Carnegie-Ames-Stanford approach (CASA) model, respectively. The relationship between them was studied on annual and monthly scales. The interaction detector was used to calculate the contribution rate of extreme climate factors and synergistic effect on NPP. The results showed that：(1) Annual NPP showed a significant increasing trend in southeast Yunnan, while it showed a decreasing trend in central and northwest Yunnan. (2) Extreme temperature indices (TXx, TXn, TNx, TNn) showed significant increasing trends (P < 0.01), while cold day index (Tx10p) and cold night index (Tn10p) showed significant decreasing trends (P < 0.01), and the warming trend is more obvious. Individual precipitation intensity increases while the continuous precipitation decreases. (3) The correlation between extreme temperature indices and NPP was lower than that between extreme precipitation factors. Extreme precipitation indices had a significant impact on vegetation NPP and dominated the pattern of spatial distribution. Extreme precipitation indices had the excellent explanatory power for the NPP of shrub, grassland, and agricultural vegetation. NPP of Alpine vegetation was remarkably affected by the maximum Tmin (TNx) (q = 0.868). (4) PD values of interactions between extreme climate factors are higher than that of an individual factor. The synergistic effect of extreme climatic factors on NPP in northeast Yunnan is more significant. The interaction between the two extreme climate factors significantly impacts the NPP of agricultural and alpine vegetation. The results may help deeply understand and predict the impact of extreme climate factors on the different sub-regional ecosystems on Yunnan