Assessment of Carbon Dynamics of Forest Ecosystems in the Poyang Lake Basin Responding to Afforestation and Future Climate Change

Afforestation projects were applied in the Poyang Lake Basin of China at the beginning of 1980s. The large-scale plantation may dramatically influence the changes in carbon storage of forests in this basin. Therefore, climate-induced variations in the carbon balance of the Poyang Lake Basin＇s forests may play an important role in the carbon cycle of China. However, we have little understanding of their long-term behavior, especially the future trend of carbon sink/source patterns under climate change and rising atmospheric CQ. The annual carbon budget of the Poyang Lake Basin＇s forests during 1981-2050 was estimated by using the Integrated Terrestrial Ecosystem Carbon-budget model （InTEC） coupled with projected climate change simulated by Regional Integrated Environmental Model System （RIEMS 2.0）. During 1981-2000, the rapid increment of annual NPP in this basin was possible due to large plantation. Soil organic carbon storage （0-30cm） of forests generally decreased by 1.0% per year at the beginning of plantation. Moreover, forests in this basin converted from carbon source in 1980s to carbon sink in 1990s. By 2040-2050, total carbon stocks of forest ecosystems will increase by 0.78Pg C, compared to recent years （2001-2010）. Under future climate and CQ concentration in AIB scenario, NEP of forests in Poyang Lake Basin lean to keep relative stable （20-30Tg C y-i） because of old forests except for some years induced by extreme droughts. Our results also showed that prediction of NEP of forests in Poyang Lake Basin was controlled by water limitation; in contrast, temperature was the main factor on inter- annual variability of NPP.

The current and future of terrestrial carbon balance over the Tibetan Plateau

The contemporary carbon balance over the Tibetan Plateau is highly uncertain with a ten-fold difference between various estimates.In a warming world,the potential exists for a large carbon release from its permafrost which could compromise China’s 2060 carbon-neutral goal.Here,we used a satellite-and inventory-based approach,ecosystem models,and atmospheric inversions to estimate that the carbon sink was 33.12–37.84 TgC yr^(–1)during 2000–2015.The carbon sink induced by climate change and increasing CO_(2) levels largely overcompensated for a livestock grazing-induced carbon source of 0.38TgC yr^(-1).By 2060,the carbon sink is projected to increase by 38.3–74.5% under moderate to high emissions scenarios,with the enhanced vegetation carbon uptake outweighing the warming-induced permafrost carbon release.The restoration of degraded grassland could sequestrate an additional 9.06 TgC yr^(-1),leading to a total carbon sink of 57.78–70.52 TgC yr^(-1).We conclude that the Tibetan Plateau’s ecosystems absorbed two-and-a-half times the amount of its cumulative fossil CO_(2) emissions during 2000–2015 and that their carbon sinks will almost double in strength in the future,helping to achieve China’s pledge to become carbon neutral by 2060.

The effects of multiple environmental factors on global carbon allocation

Background The allocation of photosynthate among the parts of plants(e.g.,leaves,wood tissues and roots)strongly regulates their growth,and this conditions the terrestrial carbon cycle.Recent studies have shown that atmospheric CO_(2)and climate change dominate the changes in carbon allocation in plants,but the magnitude and mechanism of its effects remain unclear.Methods The Community Atmosphere Biosphere Land Exchange(CABLE)model can accurately simulate the responses of carbon allocation to environmental changes.This study quantifies the contributions of four environmental factors-atmospheric CO_(2),temperature,precipitation,and radiation-on resource availability and carbon allocation from 1979 to 2014 by using the CABLE model.Results The results of the CABLE model showed that rising CO_(2)significantly reduced carbon allocation to the leaves of plants at a global scale,but the other three environmental factors exhibited contrasting effects that dominated the rise in carbon allocation to the leaves.The increased precipitation and CO_(2)significantly reduced the light availability and increased carbon allocation to the wooden parts of plants.By contrast,the rising temperature reduced the water availability,resulting in a decrease in carbon allocation to the wooden parts.All four environmental factors consistently exhibited negative effects on carbon allocation to the roots,with rising precipitation causing the largest reduction in carbon allocation to them.Moreover,except for CO_(2),the effects of the other three environmental factors were heterogeneous owing to their variable interactions in different regions.Conclusions The CABLE model can accurately represent the mechanisms of response of resource availability and carbon allocation to environmental changes.Our study highlights the substantial environmental regulation of global carbon allocation.The responses of carbon allocation to global environmental changes need to be extensively studied through ecosystem models based on different hypotheses.