Modeling Carbon Fluxes Using Multi-Temporal MODIS Imagery and CO2 Eddy Flux Tower Data in Zoige Alpine Wetland, South-West China

Abstract

An accurate and synoptic quantification of gross primary production (GPP) in wetland ecosystems is essential for assessing carbon budgets at regional or global scales. In this study, a satellite-based Vegetation Photosynthesis Model (VPM) integrated with observed eddy tower and remote sens- ing data was employed and adapted to evaluate the feasibility and dependability of the model for estimating GPP in an alpine wetland, located in Zoige, Southwestern China. Eddy flux data from 2-year observations showed that temperature explained mostof theseasonal variability incarbonfluxesand that warming increased GPP and ecosystem respiration, and hence affected the carbon balance of alpine wetlands. The comparison between modeled and observed GPP fluxes indi- cated that simulated values were largely in agreement with tower-based values (P<0.0001). 12-year long-term simula- tions (2000-2011) found that (1) there was significantly in- creasing trends at rate of 17.01 gCm �2 year �1 for annual GPP (R 2 =0.62, P=0.002); (2) the inter-annual variation in GPP was highly sensitive to climate warming; and (3) a warmer climate can prolong the plant growing season and, by that, increase wetland productivity. Our results demonstrated that the satellite-driven VPM model has the potential to be applied at large spatial and temporal scales for scaling-up carbon fluxes of alpine wetlands.