Water availability control the seasonal and inter-annual variability of CO2 fluxes in an alpine meadow on the eastern Tibetan Plateau
Shaoying Wang, Yu Zhang, Xianhong Meng, Lunyu Shang, Zhaoguo Li, Suosuo Li
Abstract
Alpine ecosystems may be contribute to increasing atmospheric carbon dioxide (CO2) concentrations under intensified climate change on the Tibetan Plateau (TP). The eddy covariance technique was used in this research to examine how net ecosystem CO2 exchange (NEE) and its component fluxes, gross primary production (GPP), and ecosystem respiration (ER) varied over 10 years (from 2010 to 2019) in an alpine meadow on the eastern TP. This alpine meadow acted as a sink of CO2, with a mean of –92.5 ± 54.9 g C m–2 year–1 during the measurement period. The exponential ER response model is unsuitable for water stress conditions, potentially resulting in an overestimation of ER and GPP. The intra-annual variations of daily GPP and ER were more related to photosynthetic active radiation (PAR), soil temperature (Ts) and normalized difference vegetation index (NDVI), but the daily NEE during growing seasons shifts between PAR-dependent and NDVI-dependent with changes in soil water content (SWC). At monthly and seasonal scales, the sensitivity of GPP to NDVI and water conditions was higher than that of ER. The inter-annual variability in NEE was significantly related to the SWC. These findings are critical for understanding the response mechanism of carbon dynamics to the changing biotic and abiotic conditions in the TP.