SPATIAL-TEMPORAL CARBON SEQUESTRATION UNDER LAND USE AND LAND COVER CHANGE

In this research carbon (C) sequestration of the Blue Ridge ecoregion of North America was investigated using the General Ensemble biogeochemical Modeling System (GEMS). GEMS assimilated historical land use and land cover change (LUCC) data within ten 20km by 20-km sampling blocks in the ecoregion and performed biogeochemical C simulations for the period of 1973 – 2000. The LUCC data were derived from both low spatial resolution census and survey data (forest structure and agricultural cropping practices), and from high spatial resolution sequential land cover maps. The land cover maps were derived from Landsat remote sensing data at 60-meter resolution. GEMS used Monte Carlo approaches to deal with some spatial and temporal LUCC scaling issues such as initialization of forest age and crop species. It also prescribed the land use activities such as forest selective cuttings that were not reflected in the land cover change maps. Results showed that this ecoregion was a C sink during the simulation period. The sink averaged 100 – 120 g C m -2 yr -1 with a major portion (50-80%) attributed to living biomass and smaller portions attributed to soil and harvested C. Net primary productivity (NPP) in Blue Ridge ecoregion was about 600 to 800 g C m -2 yr -1 . Based on the 10 sample blocks, estimation error of C sequestration at 95% confidence level is about 15 to 45 g C m -2 yr -1 , varying by year. Model simulations also indicated that LUCC played a significant role in determining the magnitude of carbon sink strength in the region. Without considering the dynamics of LUCC, the C sink strength would be underestimated by 30 to50 percent.

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