Increasing ecosystem respiration in Tibetan Plateau alpine grasslands under recent climate warming and wetting

Ecosystem respiration (ER) is the second-largest carbon flux in terrestrial ecosystems after photosynthesis and plays a critical role in regulating regional carbon balance and carbon–climate feedbacks. Alpine grasslands are the dominant vegetation type on the Tibetan Plateau; however, under the ongoing warming and wetting climate, the spatiotemporal patterns and controlling mechanisms of ecosystem respiration in these grasslands remain poorly understood. To address this gap, we integrated eddy covariance observations from 35 flux sites widely distributed across the Tibetan Plateau with multi-source satellite remote sensing and reanalysis data, and applied machine learning approaches to upscale ecosystem respiration of alpine grasslands from 2000 to 2023, enabling a comprehensive assessment of its spatiotemporal variations and driving factors. 
Our results show that the multi-year mean ecosystem respiration of alpine grasslands on the Tibetan Plateau during 2000–2023 was 259.8 ± 7.4 g C m⁻² yr⁻¹ and exhibited a significant increasing trend, rising from 245.9 g C m⁻² yr⁻¹ in 2000 to 268.2 g C m⁻² yr⁻¹ in 2023, with an average growth rate of 0.96 g C m⁻² yr⁻¹. Spatially, ecosystem respiration displayed pronounced east–west contrasts, with high respiration rates exceeding 700 g C m⁻² yr⁻¹ in eastern alpine meadows, while much lower values, generally below 150 g C m⁻² yr⁻¹, occurred in western alpine desert steppes. Trend analyses indicate that ecosystem respiration increased significantly in more than 90% of the study area , with enhancement rates reaching up to 3 g C m⁻² yr⁻¹ in eastern alpine meadows, whereas the increasing trend was considerably weaker in western alpine desert steppes, remaining below 0.5 g C m⁻² yr⁻¹. Further analyses suggest that vegetation growth improvement under a warming and wetting climate was a key factor driving the sustained increase in ecosystem respiration across alpine grasslands on the Tibetan Plateau.