Spatiotemporal patterns of fire-driven forest mortality in China

Wildfire is one of the most prevalent natural or human-induced disturbances across the world, which can kill trees directly during the active combustion phase or cause delayed forest mortality through interactions with other disturbance agents. With its diverse range of climate and forest ecosystems, China also has diverse forest fire regimes. However, the spatial and temporal patterns of fire-driven forest mortality on the national scale remain largely unexplored. In this study, we employed satellite observations and statistical models to investigate the spatiotemporal patterns and underlying drivers of fire-induced forest mortality across China. Our results demonstrate pronounced temporal patterns of forest burned area and fire-driven forest mortality. On the seasonal scale, forest fires mostly occurred in the winter and spring, whereas the forest mortality is highest from May to July. Both forest burned area and fire-driven mortality exhibited a significant decreasing trend during 2003–2016. Forest burned areas are mainly distributed in Northeast China, Southwest China and South China. There exists a tight spatial consistency between areas with high mortality and burned area with East China as an exception. Correlation analysis and multiple linear regression analysis show that fire size, fire spread rate, fire duration and drought intensity had significant impacts on postfire forest mortality, with fire size and fire spread rate accounting for 38.3% and 37.1%, respectively, of the model's explanatory power. Our results highlight the importance of fire regime impacts on postfire forest mortality. Future climate change that drives more intense fire regimes might thus lead to enhanced forest mortality and increase the loss of forest ecosystem services.