Impacts of droughts on carbon sequestration by China's terrestrial ecosystems from 2000 to 2011

摘要

In recent years, China's terrestrial ecosystems have experienced frequentdroughts. How these droughts have affected carbon sequestration by theterrestrial ecosystems is still unclear. In this study, the process-basedBoreal Ecosystem Productivity Simulator (BEPS) model, driven by remotelysensed vegetation parameters, was employed to assess the effects of droughtson net ecosystem productivity (NEP) of terrestrial ecosystems in China from2000 to 2011. Droughts of differing severity, as indicated by a standardprecipitation index (SPI), hit terrestrial ecosystems in China extensively in2001, 2006, 2009, and 2011. The national total annual NEP exhibited theslight decline of ?11.3 Tg C yr?2 during the aforementioned years ofextensive droughts. The NEP reduction ranged from 61.1 Tg C yr?1 to168.8 Tg C yr?1. National and regional total NEP anomalies werecorrelated with the annual mean SPI, especially in Northwest China, NorthChina, Central China, and Southwest China. The reductions in annual NEP in2001 and 2011 might have been caused by a larger decrease in annual grossprimary productivity (GPP) than in annual ecosystem respiration (ER). Thereductions experienced in 2009 might be due to a decrease in annual GPP andan increase in annual ER, while reductions in 2006 could stem from a largerincrease in ER than in GPP. The effects of droughts on NEP lagged up to 3–6months, due to different responses of GPP and ER. In eastern China, where ishumid and warm, droughts have predominant and short-term lagged influences onNEP. In western regions, cold and arid, the drought effects on NEP wererelatively weaker but prone to lasting longer.