Global Fire emissions and its impacts on terrestrial ecosystem carbon budget from 1901 to 2010

As a natural disturbance in the earth system, fire plays a critical role in determining vegetation composition and distribution, atmospheric components, terrestrial carbon budget, and land surface energy balance, which all contribute to climate change. However, the fire regime prior to satellite era (the 1980s) is largely unknown at global level due to the lack of sufficient long-term fire records. Recently, a centurial-scale burned area dataset has been reconstructed at global level based on satellite information and fire model simulation. By incorporating this fire dataset into the Dynamic Land Ecosystem Model (DLEM), we estimated the fire emissions from global fires and analyzed the changes in terrestrial ecosystem carbon budget caused by fire during 1901 - 2010. Our preliminary results indicated that the average global fire emissions is 3.0 Pg C year-1 with a significantly decreasing trend during the study period. The difference between fire-on and fire-off simulations showed that fires reduced both net primary productivity (NPP) and ecosystem heterotrophic respiration (Rh). The immediate post-fire reduction in NPP is stronger than that in Rh, which dampened the Net Ecosystem Productivity; while the long-term post-fire recovery in NPP is much faster than that in Rh. Overall, the post-fire recovery processes sequestrated approximately 50% of the carbon emissions released from fires; the global fire cause a net carbon source at about 1.5 Pg C year-1 during the 110 years. In the 21st century, a large increase in global fire potential and burned area has been reported by previous studies according to climate projections. Our results imply that the future fires regime could produce more GHG emissions and reduce carbon sink size, which in turn cause positive feedbacks to global warming.