Quantification of terrestrial ecosystem carbon dynamics in the conterminous United States combining a process-based biogeochemical model and MODIS and AmeriFlux data

摘要

Satellite remote sensing provides continuous temporal and spatialinformation of terrestrial ecosystems. Using these remote sensing data andeddy flux measurements and biogeochemical models, such as the TerrestrialEcosystem Model (TEM), should provide a more adequate quantification ofcarbon dynamics of terrestrial ecosystems. Here we use Moderate ResolutionImaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI), LandSurface Water Index (LSWI) and carbon flux data of AmeriFlux to conduct sucha study. We first modify the gross primary production (GPP) modeling in TEMby incorporating EVI and LSWI to account for the effects of the changes ofcanopy photosynthetic capacity, phenology and water stress. Second, weparameterize and verify the new version of TEM with eddy flux data. We thenapply the model to the conterminous United States over the period 2000–2005at a 0.05° × 0.05° spatial resolution. We find that the newversion of TEM made improvement over the previous version and generallycaptured the expected temporal and spatial patterns of regional carbondynamics. We estimate that regional GPP is between 7.02 and 7.78 Pg C yr?1and net primary production (NPP) ranges from 3.81 to 4.38 Pg C yr?1and net ecosystem production (NEP) varies within 0.08–0.73 Pg C yr?1over the period 2000–2005 for the conterminous United States.The uncertainty due to parameterization is 0.34, 0.65 and 0.18 Pg C yr?1for the regional estimates of GPP, NPP and NEP, respectively. The effects ofextreme climate and disturbances such as severe drought in 2002 anddestructive Hurricane Katrina in 2005 were captured by the model. Our studyprovides a new independent and more adequate measure of carbon fluxes forthe conterminous United States, which will benefit studies of carbon-climatefeedback and facilitate policy-making of carbon management and climate.