Simulating net carbon budget of forest ecosystems and its response to climate change in northeastern China using improved FORCCHN

As dominant biomes, forests play an important and indispensable role in adjusting the global carbon balance under climate change. Therefore, there are scientific and political implications in investigating the carbon budget of forest ecosystems and its response to climate change. Here we synthesized the most recent research progresses on the carbon cycle in terrestrial ecosystems, and applied an individual-based forest ecosystem carbon budget model for China (FORCCHN) to simulate the dynamics of the carbon fluxes of forest ecosystems in the northeastern China. The FORCCHN model was further improved and applied through adding variables and modules of precipitation (rainfall and snowfall) interception by tree crown, understory plants and litter. The results showed that the optimized FORCCHN model had a good performance in simulating the carbon budget of forest ecosystems in the northeastern China. From 1981 to 2002, the forests played a positive role in absorbing carbon dioxide. However, the capability of forest carbon sequestration had been gradually declining during the the same period. As for the average spatial distribution of net carbon budget, a majority of the regions were carbon sinks. Several scattered areas in the Heilongjiang Province and the Liaoning Province were identified as carbon sources. The net carbon budget was apparently more sensitive to an increase of air temperature than change of precipitation.