Contribution of climate change and rising CO₂ to terrestrial carbon balance in East Asia: A multi-model analysis

In this study, we use three process-based terrestrial ecosystem models (Lund-Potsdam-Jena Dynamic Global Vegetation Model - LPJ-DGVM; ORganizing Carbon and Hydrology In Dynamic Ecosystems - ORCHIDEE; Sheffield model - SDGVM) to investigate the historical response of ecosystem Net Primary Productivity (NPP) and Net Ecosystem Productivity (NEP) over East Asia to climate change and rising atmospheric CO₂. The results suggest that between 1901 and 2002, the modeled NPP has significantly increased by 5.5-8.5Tg C yr^-1 (15-20% growth). Such increase in NPP has caused an increased cumulated terrestrial C storage by about 5-11Pg C. About 50-70% fraction of this total C sink is located in vegetation biomass. Our modeling results also suggest that 40-60% of the accumulate C uptake of the 20th century is credited to the period of 1980-2002. Although all models tend to agree at the continental scale that East Asia played a role of net C sink (0.14-0.18Pg C yr^-1) during 1980s and 1990s, the trends of NEP are different among the models. Both LPJ and ORCHIDEE estimate a slight but insignificant NEP decrease from 1980 to 2002 (P>0.05), while SDGVM estimates a statistically significant increase in NEP at a rate of 0.005Pg C yr^-2 (P<0.05). Also, there is no consensus among models on the dominant driving factors controlling interannual variation in NPP and NEP at the continental scale, implying that more efforts are needed to investigate the vulnerability of the East Asian terrestrial carbon cycle.