Abstract:
In the context of global warming, the carbon process of alpine wetland ecosystems is complex and sensitive. However, the long-term dynamics and driving mechanisms of carbon balance in alpine wetland ecosystems are still unclear. In this study, the carbon dioxide (CO2) flux measured by eddy covariance technique is used to analyze the CO2 exchange flux of the Zoige alpine wetland from 2017 to 2021, as well as the dynamics and driving mechanisms of CO2 exchange flux. The results showed that during the vegetation growing season (June - October), the annual gross primary productivity (Gross Primary Productivity, GPP) and ecosystem respiration (Ecosystem espiration, Re) of the ecosystem showed an unimodal pattern, while the annual net ecosystem CO2 exchange (Net Ecosystem Exchange, NEE) of the ecosystem showed a V-shaped trend. The Zoige alpine wetland ecosystem is a carbon sink during the growing season, which is a carbon exchange process between land and air that absorbs more than releases. The daily average NEE, GPP, and Re over the years reached -3.10±4.61, 4.78±5.61, and 1.65±1.56 umol(m2·s), respectively. On the monthly scale, the effects of air temperature (Air Temperature, Ta), soil temperature (Soil Temperature, Ts), photosynthetic photon flux density (Photosynthetic Photon Flux Density, PPFD), precipitation (Precipitation, PPT), air relative humidity (Air Relative Humidity, RH) and vapor pressure deficit (Vapor Pressure Deficit, VPD) on NEE, GPP and Re were analyzed by the regression analysis. The results showed that Ta, Ts and PPT were the main determinants of monthly NEE changes, and NEE was negatively correlated with them. Ts and Ta largely determined the monthly variation of GPP, which is positively correlated with it. Ts ,Ta and PPT are the main determinants of monthly Re variation, and Re is positively correlated with them. The Classification and Regression Tree (Classification and Regression Tree, CART) algorithm was used to analyze the effects of various factors on carbon exchange flux in the daily scale. The results showed that soil temperature had a great influence on daily GPP and Re, and temperature is the main controlling factor for daily NEE. The results of this study provide important data and reference for understanding the carbon budget of alpine wetland ecosystems.