DEVELOPING A LAND-USE MODELING FRAMEWORK TO SUPPORT ANALYSES OF CARBON SEQUESTRATION AND FLUX

The goal of the LandCarbon project is to conduct a comprehensive and scientifically credible assessment of the nation’s ecosystems for present and future potential sequestration capacities and fluxes of three greenhouse gases, including carbon. A comprehensive and integrated land-use and land-cover (LULC) modeling framework is required to support this work, as LULC change is an extremely important factor controlling carbon flux. The FOREcasting SCEnarios of land-cover change (FORE-SCE) model (Sohl and Sayler; 2008; Sohl and others, 2007) will be utilized to provide 1) forecasts of multiple potential futures under different socioeconomic and climatic scenarios 2) LULC forecasts at relatively high spatial resolutions (250m) at a national scale, and 3) forecasts of sufficient thematic detail to examine carbon sequestration and flux implications.

The FORE-SCE model utilizes distinct but linked “Demand” and “Spatial Allocation” components as a means to handle driving forces of LULC operating at scales from global to local. Demand provides aspatial proportions of LULC change for a given region, i.e., annual “prescriptions” for regional LULC change. Demand for the LandCarbon project corresponds to LULC change stories constructed within the framework of Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenarios (SRES) storylines. SRES storylines describe global driving forces of LULC change. The primary elements of scenario construction are: 1) qualitative interpretation and translation of SRES storylines to national and regional scales, 2) downscaling of SRES quantitative land use projections, and 3) development of linkages between SERS products and regional land-use histories. An integration of these elements will be used to construct regionally specific LULC scenarios for each EPA Level II ecoregion, including annual prescriptions of LULC change.

Regional prescriptions of LULC change from the Demand component are used to inform the Spatial Allocation component, which spatially distributes prescribed LULC change on the landscape. The primary component of the Spatial Allocation component are probability surfaces, constructed through the analysis of empirical relationships between LULC patterns and an array of spatially explicit biophysical and socioeconomic data. FORE-SCE then utilizes a unique methodology to place LULC “change” on suitable site locations, patch-by-patch, utilizing historical LULC data from the USGS Trends project to regionally parameterize realistic patch sizes and configurations for each modeled LULC transition. Forest stand age is established from Forest Inventory and Analysis (FIA) data and tracked to enable more realistic modeling of forest cutting cycles. A Protected Areas Database of the United States (PAD-US) is utilized to restrict unrealistic LULC change in protected regions. FORE-SCE will provide LULC projections for each scenario on an annual basis from 2001 through 2050, utilizing the 2001 to 2010 time period to calibrate the model and validate model performance.

References Cited:

Sohl, T.L. and Sayler, K.L., 2008. Using the FORE-SCE model to project land-cover change in the southeastern United States: Ecological Modelling, v. 219, p. 49-65.

Sohl, T.L., Sayler, K.L., Drummond, M.A., and Loveland, T.R., 2007. The FORE-SCE model: a practical approach for projecting land cover change using scenario-based modeling: Journal of Land Use Science, v. 2, p. 103-126.