Spatial patterns and climate drivers of carbon fluxes in terrestrial ecosystems of China

Abstract

Understanding the dynamics and underlying mechanism of carbon exchange between terrestrial ecosystems and the atmosphere is one of the key issues in global change research. In this study, we quantified the carbon fluxes in different terrestrial ecosystems in China, and analyzed their spatial variation and environmental drivers based on the long-term observation data of ChinaFLUX sites and the published data from other flux sites in China. The results indicate that gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem productivity (NEP) of terrestrial ecosystems in China showed a significantly latitudinal pattern, declining linearly with the increase of latitude. However, GEP, ER, and NEP did not present a clear longitudinal pattern. The carbon sink functional areas of terrestrial ecosystems in China were mainly located in the subtropical and temperate forests, coastal wetlands in eastern China, the temperate meadow steppe in the northeast China, and the alpine meadow in eastern edge of Qinghai-Tibetan Plateau. The forest ecosystems had stronger carbon sink than grassland ecosystems. The spatial patterns of GEP and ER in China were mainly determined by mean annual precipitation (MAP) and mean annual temperature (MAT), whereas the spatial variation in NEP was largely explained by MAT. The combined effects of MAT and MAP explained 79%, 62%, and 66% of the spatial variations in GEP, ER, and NEP, respectively. The GEP, ER, and NEP in different ecosystems in China exhibited 'positive coupling correlation' in their spatial patterns. Both ER and NEP were significantly correlated with GEP, with 68% of the per-unit GEP contributed to ER and 29% to NEP. MAT and MAP affected the spatial patterns of ER and NEP mainly by their direct effects on the spatial pattern of GEP.

Construction and progress of Chinese terrestrial ecosystem carbon, nitrogen and water fluxes coordinated observation

“…The highest carbon sink appeared in central subtropical forests (550±258 g C m -2 yr -1 ), and followed by warm temperate forests (492±37 g C m -2 yr -1 ) and northern subtropical forests (343 g C m -2 yr -1 ). Yu et al, 2013b;Chen et al, 2014;FLUXNET, 2013;Du et al, 2012;Wang et al, 2008;Liu et al, 2011aLiu et al, , 2011bDong et al, 2011aDong et al, , 2011bZhang et al, 2007 Grassland Yu et al, 2013b;Chen et al, 2014 Cool temperate forests showed lower carbon sink compared to warm temperate and temperate forests. Studies of specific ecosystem suggest that mature forests in Northeast, Southeast, and Southwest (Zhang et al, 2006a;Liu et al, 2014a;Tan et al, 2010Tan et al, , 2012Guan et al, 2006;Zhang et al, 2006b;Yan et al, 2012) and subtropical plantations (Liu et al, 2006;Wen et al, 2010) had strong carbon sequestration capacity.…”

“…Temperate steppes and alpine meadows served as weak carbon sink (24±83, 45±59 g C m -2 yr -1 ). The grasslands in northern China probably served as a weak carbon source after disturbances, which differed substantially among ecosystems and years (Shi et al, 2006;Li et al, 2006;Fu et al, 2006Fu et al, , 2009Yu et al, 2013b).…”

“…To reduce the uncertainty of terrestrial ecosystems in the global carbon budget, it is necessary to understand the spatial variability of carbon flux and its controlling mechanism. ChinaFLUX researchers based on the ecosystem carbon flux data, quantitatively evaluated the spatial variability of ecosystem carbon flux in China (Yu et al, 2013b). GPP, RE and NEP showed obvious latitudinal pattern and mean annual temperature and precipitation and their interaction explained more than 60% of the spatial variation of GPP, RE and NEP in China (Yu et al, 2013b).…”

“…In the past two decades, the ecosystem CO 2 and H 2 O flux observation have been carried out worldwide, and accumulated large amount of scientific data (Luysseart et al, 2007;Reichstein et al, 2014;Baldocchi et al, 2008Baldocchi et al, , 2014Yu et al, 2013b). Recently, continuous observation of CH 4 , NO, NO 2 , N 2 O, NH 3 , HNO 3 and other carbon, nitrogen and water trace gas fluxes is gradually applied in the field (Baldocchi, 2014).…”

Regional representativeness assessment and improvement of eddy flux observations in China

“…Since its establishment, ChinaFLUX has developed rapidly and expanded from the initial eight sites into a national scale network, with observation sites covering most of the terrestrial ecosystem types in China (Fu et al, 2010). The network of flux towers in China provides extensive and reliable measurements of the CO 2 , H 2 O and energy fluxes with high temporal and spatial resolution, which enables the estimation and prediction of the respective spatiotemporal variability of the carbon and water cycles under the global climate change scenario (He et al, 2010;Fu et al, 2010;Yu et al, 2013;Wang et al, 2013). To correctly upscale these fluxes to regional and global level, the representativeness of the current network is an important aspect to consider (Sulkava et al, 2011).…”