Soil saturation effects on forest dynamics: scaling across a southern boreal/northern hardwood landscape

Patch modeling can be used to scale-up processes to portray landscape-level dynamics. Via direct extrapolation, a heterogeneous landscape is divided i nto its constituent patches; dynamics are simulated on each representative patch and are weighted and aggregated to formulate the higher level respons e. Further extrapolation may be attained by coarsening the resolution of or lumping environmental data (e.g., climatic, edaphic, hydrologic, topograph ic) used to delimit a patch. Forest patterns at the southern boreal/northern hardwood transition zone ar e often defined by soil heterogeneity, determined primarily by the extent a nd duration of soil saturation. To determine how landscape-level dynamics p redicted from direct extrapolation compare when coarsening soil parameters, we simulated forest dynamics for soil series representing a range of drain age classes from east-central Maine. Responses were aggregated according to the distribution of soil associations comprising a 600 ha area based on lo cal- (1.12,000), county- (1:120,000) and state- (1:250,000) scale soil maps . At the patch level, simulated aboveground biomass accumulated more slowly in poorer draining soils. Different soil series yielded different communit ies comprised of species with various tolerances for soil saturation. When aggregated, removal of waterlogging caused a 20-60% increase in biomass acc umulation during the first 50 years of simulation. However, this early succ essional increase and the maximum level of biomass accumulation over a 200 year period varied by as much as 40% depending on the geospatial data. This marked discrepancy suggests caution when extrapolating with forest patch m odels by coarsening parameters and demonstrates how rules used to rescale e nvironmental data need to be evaluated for consistency.