Fire-induced Reduction in Global Terrestrial Gross Primary Production Varies with Burn Severity and Biomes

Fire is a major disturbance in terrestrial ecosystems worldwide, and can significantly influence the variations in carbon, water and energy fluxes. Previous studies analyzed the fire-induced reduction of terrestrial gross primary production (GPP) by taking fire event as a whole without considering the effect from different burn severity in burnt area. Burn severity can represent the change magnitude of vegetation and soil caused by fire, which is one of the most important factors governing vegetation survival and recovery after fire. However, the response of the terrestrial GPP to fire with the variation of burn severity has not been explored yet. In this study, we analyzed the fire-induced GPP reduction by various burn severity and across biomes from 2001 to 2020 at the global scale. The first MODIS data based global burn severity dataset MOSEV was used to derive the burn severity, pre-burn and post-burn date of different biomes. According to the pre- and post- burn date of the fire, GPP data from the Breathing Earth System Simulator (BESS) were used to determine the GPP pre- and post- the fire, then fire-induced GPP reduction under different burn severity and across different biomes were derived. We found that with the increase of burn severity level, the fire-induced GPP reduction increase across all biomes. Among them, savanna and deciduous broadleaf forests showed highest correlation (r=0.55, p<0.001). Our results highlight the importance of considering burn severity on fire-induced carbon loss estimations and understanding the interactions between fire and terrestrial ecosystems.