Ecosystem drought recovery and its driving factors in southwest China

Study area

Southwest China.

Study focus

Southwest China, with its karst topography and mismatched soil-water resources, is highly susceptible to drought stress. Drought recovery time, defined as the time required for ecosystems to restore their pre-drought functions following stress, is critical for evaluating impacts of droughts and ecosystem resilience. Previous studies have predominantly focused on the influence of factors such as temperature, precipitation, and gross primary production on ecosystem drought recovery time across large scales, with insufficient attention paid to southwest China: a region prone to frequent droughts and ecologically vulnerable. To investigate the characteristics of drought recovery time in different ecosystems across southwest China under the following two drought recovery trajectories when drought occurs at different time, as well as the impacts of multiple driving factors on drought recovery time: (1) drought recovery was completed prior to the winter of the dry year (R_SGS); (2) drought recovery extended into the winter and the subsequent year following the drought year (R_MGS), this study used Standardized Precipitation Evapotranspiration Index (SPEI) and solar-induced chlorophyll fluorescence (SIF) to identify drought recovery time. It categorized ecosystem drought recovery into two trajectories and utilized the Random Forest (RF) model to assess the importance of various bioclimatic factors, vegetation physiological conditions, and karst landform in influencing ecosystem drought recovery.

New hydrological insights for the regions

The results showed that: (1) The drought recovery time of different ecosystems in southwest China shows significant differences. (2) Precipitation during the drought response lag period significantly influenced drought recovery under R_SGS; according to the feature importance results identified by the RF model, the importance of spring phenology to drought recovery is 78 %-85 % under R_MGS. (3) Precipitation, temperature, vapor pressure deficit (VPD), and spring phenology all have significant impacts on drought recovery in both recovery trajectories. These findings highlight the key role of hydrological conditions and spring phenology in drought recovery and emphasize their importance in accurately quantifying ecosystem resilience and guiding future climate change adaptation strategies.