Net exchanges of CO₂, CH₄, and N₂O between China's terrestrial ecosystems and the atmosphere and their contributions to global climate warming

Abstract

[1] China's terrestrial ecosystems have been recognized as an atmospheric CO 2 sink ; however, it is uncertain whether this sink can alleviate global warming given the fluxes of CH 4 and N 2 O. In this study, we used a process-based ecosystem model driven by multiple environmental factors to examine the net warming potential resulting from net exchanges of CO 2 , CH 4 , and N 2 O between China's terrestrial ecosystems and the atmosphere during 1961-2005. In the past 45 years, China's terrestrial ecosystems were found to sequestrate CO 2 at a rate of 179.3 Tg C yr −1 with a 95% confidence range of (62.0 Tg C yr −1 , 264.9 Tg C yr) while emitting CH 4 and N 2 O at rates of 8.3 Tg C yrwith a 95% confidence range of (3.3 Tg C yr −1 , 12.4 Tg C yr −1 ) and 0.6 Tg N yr −1 with a 95% confidence range of (0.2 Tg N yr −1 , 1.1 Tg N yr −1 ), respectively. When translated into global warming potential, it is highly possible that China's terrestrial ecosystems mitigated global climate warming at a rate of 96.9 Tg CO 2 eq yr −1 (1 Tg = 10 12 g), substantially varying from a source of 766.8 Tg CO 2 eq yr −1 in 1997 to a sink of 705.2 Tg CO 2 eq yr −1 in 2002. The southeast and northeast of China slightly contributed to global climate warming; while the northwest, north, and southwest of China imposed cooling effects on the climate system. Paddy land, followed by natural wetland and dry cropland, was the largest contributor to national warming potential; forest, followed by woodland and grassland, played the most significant role in alleviating climate warming. Our simulated results indicate that CH 4 and N 2 O emissions offset approximately 84.8% of terrestrial CO 2 sink in China during . This study suggests that the relieving effects of China's terrestrial ecosystems on climate warming through sequestering CO 2 might be gradually offset by increasing N 2 O emission, in combination with CH 4 emission.

Preindustrial nitrous oxide emissions from the land biosphere estimated by using a global biogeochemistry model

“…The DLEM is characterized of cohort structure, multiple soil layer processes, coupled carbon, water, and nitrogen cycles, multiple GHG emissions simulation, enhanced land surface processes, and dynamic linkages between terrestrial and riverine ecosystems (Liu et al, 2013;Tian et al, 2010. The previous results of GHG emissions from DLEM simulations have been validated against field observations and measurements at various sites (Lu and Tian, 2013;Ren et al, 2011;Tian et al, 2010Tian et al, , 2011. The estimates of water, carbon, and nutrient fluxes and storage were also compared with the estimates from different approaches on regional, continental, and global scales (Pan et al, 2014;Yang et al, 2015).…”

“…In this study, uncertainties in the simulated N 2 O emission were evaluated through a global sensitivity and uncertainty analysis as described in Tian et al (2011). Based on sensitivity analyses of key parameters that affect terrestrial N 2 O fluxes, the most sensitive parameters were identified to conduct uncertainty simulations with the DLEM.…”

Present state of global wetland extent and wetland methane modelling: methodology of a model inter-comparison project (WETCHIMP)

“…The mechanisms and algorithms for simulating CH 4 fluxes have been described in Tian et al (2010Tian et al ( , 2011b; Xu et al (2010). DLEM requires input datasets for daily climate (average, maximum, and minimum air temperature, precipitation, gross radiation, and relative air humidity), atmospheric composition ([CO 2 ], nitrogen deposition and ozone), annual land use information, soil condition information (soil texture, pH, and soil depth), and topographic data (elevation, slope, and aspect).…”

Long‐term trends in evapotranspiration and runoff over the drainage basins of the Gulf of Mexico during 1901–2008

“…[22] During the development of DLEM v1.0, field observations and plant physiological data were collected to calibrate the model and evaluate model 0 s performance in simulating GHG emissions and water fluxes [Ren et al, , 2007bLiu et al, 2008Liu et al, , 2012Xu et al, 2010;Tian et al, 2011aTian et al, , 2011b. In DLEM v2.0, most of the parameters related to biogeochemical and plant physiological processes are the same as the previous DLEM simulations on GHG emissions over North America [Xu et al, 2010].…”