Quantifying the variability and changes in phenology and gross primary production (GPP) of alpine wetlands in the Qinghai–Tibetan Plateau under climate change is essential for assessing carbon (C) balance dynamics at regional and global scales. In this study, in situ eddy covariance (EC) flux tower observations and remote sensing data were integrated with a modified, satellite-based vegetation photosynthesis model (VPM) to investigate the variability in climate change, phenology, and GPP of an alpine wetland ecosystem, located in Zoige, southwestern China. Two-year EC data and remote sensing vegetation indices showed that warmer temperatures corresponded to an earlier start date of the growing season, increased GPP, and ecosystem respiration, and hence increased the C sink strength of the alpine wetlands. Twelve-year long-term simulations (2000–2011) showed that: (1) there were significantly increasing trends for the mean annual enhanced vegetation index (EVI), land surface water index (LSWI), and growing season GPP (R² ≥ 0.59, p < 0.01) at rates of 0.002, 0.11 year⁻¹ and 16.32 g·C·m⁻²·year⁻¹, respectively, which was in line with the observed warming trend (R² = 0.54, p = 0.006); (2) the start and end of the vegetation growing season (SOS and EOS) experienced a continuous advancing trend at a rate of 1.61 days·year⁻¹ and a delaying trend at a rate of 1.57 days·year⁻¹ from 2000 to 2011 (p ≤ 0.04), respectively; and (3) with increasing temperature, the advanced SOS and delayed EOS prolonged the wetland’s phenological and photosynthetically active period and, thereby, increased wetland productivity by about 3.7–4.2 g·C·m⁻²·year⁻¹ per day. Furthermore, our results indicated that warming and the extension of the growing season had positive effects on carbon uptake in this alpine wetland ecosystem.

Potential changes in both the intensity and frequency of extreme drought events are vital aspects of regional climate change that can alter the distribution and dynamics of water availability and subsequently affect carbon cycles at the ecosystem level. The effects of extreme drought events on the carbon budget of peatland in the Zoige plateau and its response mechanisms were studied using an in-field controlled experimental method. The results indicated that the peatland ecosystem of the Zoige plateau functioned as a carbon sink while under the control (CK) or extreme drought (D) treatment throughout the entire growing season. Maximum fluxes of methane (CH₄) emissions and the weakest carbon sink activity from this ecosystem were in the early growth stage, the most powerful carbon sink activity was during the peak growth stage, while the absorption sink activity of carbon dioxide (CO₂) and CH₄ was present during the senescence stage. Extreme drought reduced the gross primary productivity (GPP) and ecosystem respiration (R_e) of the peatland ecosystem by 14.5% and 12.6%, respectively (p < 0.05) and the net ability to store carbon was reduced by 11.3%. Overall, the GPP was highly sensitive to extreme drought. Moreover, extreme drought significantly reduced the CH₄ fluxes of the ecosystem and even changed the peatland from a CH₄ emission source to a CH₄ sink. Subsequent to drought treatment, extreme drought was also shown to have a carry-over effect on the carbon budget of this ecosystem. Soil water content and soil temperature were the main driving factors of carbon budget change in the peatland of the Zoige plateau, but with the increase in soil depth, these driving forces were decreased. The findings indicated that frequent extreme drought events in the future might reduce the net carbon sink function of peatland areas, with an especially strong influence on CO₂.