Summary of Recent Climate Change Studies on the Carbon and Nitrogen Cycles in the Terrestrial Ecosystem and Ocean in China

This article reviews recent advances over the past 4 years in the study of the carbon-nitrogen cycling and their relationship to climate change in China. The net carbon sink in the Chinese terrestrial ecosystem was 0.19--0.26 Pg C yr-1 for the 1980s and 1990s. Both natural wetlands and the rice-paddy regions emitted 1.76 Tg and 6.62 Tg of CH4 per year for the periods 1995--2004 and 2005--2009, respectively. China emitted ～1.1 Tg N2O-N yr-1 to the atmosphere in 2004. Land soil contained ～8.3 Pg N. The excess nitrogen stored in farmland of the Yangtze River basin reached 1.51 Tg N and 2.67 Tg N in 1980 and 1990, respectively. The outer Yangtze Estuary served as a moderate or significant sink of atmospheric CO2 except in autumn. Phytoplankton could take up carbon at a rate of 6.4×1011 kg yr-1 in the China Sea. The global ocean absorbed anthropogenic CO2 at the rates of 1.64 and 1.73 Pg C yr-1 for two simulations in the 1990s. Land net ecosystem production in China would increase until the mid-21st century then would decrease gradually under future climate change scenarios. This research should be strengthened in the future, including collection of more observation data, measurement of the soil organic carbon (SOC) loss and sequestration, evaluation of changes in SOC in deep soil layers, and the impacts of grassland management, carbon-nitrogen coupled effects, and development and improvement of various component models and of the coupled carbon ～cycle-climate model.