Impacts of climate extremes on ecosystem metrics in southwest China

摘要

Due to global warming, climate extremes are increasing significantly, which is greatly impacting ecosystems dynamics. Identified as a key ecological area, southwest China (SWC) has experienced frequent extreme climatic events. Using daily meteorological data and Moderate-Resolution Imaging Spectroradiometer data, we analyzed the spatio-temporal variations of 21 extreme climate indices (ECIs) and 3 ecosystem metrics, namely, normalized difference vegetation index (NDVI), leaf area index (LAI), and gross primary production (GPP), as well as the responses of these metrics to ECIs during 2000-2018. Our results showed that the regionally averaged NDVI, LAI, and GPP increased significantly in this period with annual rates of 0.003, 0.04 m~2 m~(-2), and 10.58 g C m~2, respectively (P ＜ 0.001). Cold-related ECIs and consecutive wet days decreased, while warm-related ECIs, heavy precipitation days, and extreme precipitation intensity displayed the opposite trend. The sums (22.48%, 12.98%, and 32.70%, respectively) of the relative contribution proportions of the sensitive temperature-related ECIs (T-ECIs) to NDVI, LAI, and GPP were higher than that those (14.60%, 12.75%, and 16.37%, respectively) of the sensitive precipitation-related ECIs (P-ECIs). Ecosystem metrics were significantly correlated with most ECIs with time lags of 2-3-month. The correlation coefficients between large-scale atmospheric circulation indices and T-ECIs were significant (P ＜ 0.05). The Atlantic Multidecadal Oscillation had a greater influence on T-ECIs than any other large-scale climatic oscillations. Our study indicated that T-ECIs had a greater impact on ecosystems than P-ECIs in SWC and that more attention should be paid to increasingly heavy precipitation and extreme high temperatures in the region.