Significance: Cold regions contain vast stores of permafrost carbon. Rapid warming will cause permafrost to thaw and plant respiration to accelerate, with a resultant loss of CO₂, but could also increase the fixation of CO₂by plants. A network of 32 eddy covariance sites on the Tibetan Plateau, which has the largest store of alpine permafrost carbon on Earth, shows that this region functions as a net CO₂sink. Our sensitivity analyses, experiments, and model simulations consistently showed that the fixation of CO₂by plants outpaces the loss of CO₂from permafrost and accelerates plant respiration. This indicates a plant-dominated CO₂balance on the Tibetan Plateau, which could provide a negative feedback to climate warming.

Lakes play an important role in the global carbon cycle, and littoral zones of lakes are potential hotspots of greenhouse gas production. In this study, we measured the partial pressures of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) in the littoral zones of 17 lakes on the Tibetan Plateau. The littoral zones of lakes on the Tibetan Plateau were supersaturated and acted as sources of CO₂, CH₄, and N₂O to the atmosphere. The average partial pressures of CO₂, CH₄, and N₂O in the surface lake water were 664.8 ± 182.5, 139.8 ± 335.6, and 0.3 ± 0.1 μatm, respectively. The average diffusive fluxes (and uncentainty intervals) of these three gases were 73.7 (0.9–295.3) mmol · m⁻² · day⁻¹, 5.2 (0.0008–45.9) mmol · m⁻² · day⁻¹, and 6.5 (0.07–20.9) μmol · m⁻² · day⁻¹, respectively. The diffusive fluxes of CO₂ in lakes were significantly correlated with dissolved organic carbon, dissolved organic nitrogen, salinity, and water temperature. The diffusive fluxes of N₂O were significantly correlated with lake water depth. However, no relationships were found between environmental factors and the CH₄ diffusive flux at the scale of this study. CO₂ exchange with the atmosphere from saline lakes was found to be higher than from freshwater lakes with equivalent CO₂ concentrations by a factor of 2.5 due to chemical enhancement of the gas transfer velocity. Therefore, further study with enhanced spatiotemporal resolution and breadth is needed to better understand the important role played by lakes on the Tibetan Plateau in both regional and global carbon cycles.