Response of terrestrial carbon uptake to climate interannual variability in China

Abstract

The interest in national terrestrial ecosystem carbon budgets has been increasing because the Kyoto Protocol has included some terrestrial carbon sinks in a legally binding framework for controlling greenhouse gases emissions. Accurate quantification of the terrestrial carbon sink must account the interannual variations associated with climate variability and change. This study used a process-based biogeochemical model and a remote sensing-based production efficiency model to estimate the variations in net primary production (NPP), soil heterotrophic respiration (HR), and net ecosystem production (NEP) caused by climate variability and atmospheric CO 2 increases in China during the period 1981±2000. The results show that China's terrestrial NPP varied between 2.86 and 3.37 Gt C yr 21 with a growth rate of 0.32% year 21 and HR varied between 2.89 and 3.21 Gt C yr 21 with a growth rate of 0.40% year 21 in the period 1981±1998. Whereas the increases in HR were related mainly to warming, the increases in NPP were attributed to increases in precipitation and atmospheric CO 2 . Net ecosystem production (NEP) varied between 20.32 and 0.25 Gt C yr 21 with a mean value of 0.07 Gt C yr 21, leading to carbon accumulation of 0.79 Gt in vegetation and 0.43 Gt in soils during the period. To the interannual variations in NEP changes in NPP contributed more than HR in arid northern China but less in moist southern China. NEP had no a statistically significant trend, but the mean annual NEP for the 1990s was lower than for the 1980s as the increases in NEP in southern China were offset by the decreases in northern China. These estimates indicate that China's terrestrial ecosystems were taking up carbon but the capacity was undermined by the ongoing climate change. The estimated NEP related to climate variation and atmospheric CO 2 increases may account for from 40 to 80% to the total terrestrial carbon sink in China.

Long‐term record of atmospheric CO2 and stable isotopic ratios at Waliguan Observatory: Background features and possible drivers, 1991–2002

“…A recent model calculation [Cao et al, 2003] on the interannual variations and trends in terrestrial carbon uptake caused by climate variability in China during the period of 1981 -1998 indicated that both temperature and precipitation reached the highest value in 1998, a record for the twentieth century, and resulted in the largest soil heterotrophic respiration (HR) in arid northwest China where WLG is located. In 1992, however, both temperature and precipitation reached the lowest values.…”

Impact of future climate change on terrestrial ecosystems in China

“…The productivity of forest would increase by 1-10% and more significant in higher latitude regions in China (Taskforce on China's National Assessment Report on Climate Change, 2007). China's vegetation NPP increased significantly in humid regions and less in arid and semi-arid regions (Cao et al, 2003). NPP of most steppes in China will decrease by 15-20% and NPP of woodland, shrublands and desert grasslands will increase by 20-115% using a regional model with elevated CO 2 , a 20% increase in precipitation and a 4°C increase in temperature (Gao and Yu, 1998).…”

Remote sensing of ecosystem services: An opportunity for spatially explicit assessment

“…Most studies aiming at estimating NEE using remote sensing employ physiological process based models that are parameterized for a specific location using flux data together with meteorological data; the model output is then scaled up using satellite data (Cao et al, 2003). The NEE can hardly be calculated solely by remote sensing, because spatially explicit respiration rates can not be calculated with remote sensing data (Olofsson et al, 2008).…”