Description

Reviews our current understanding of the impact of fires typical of eastern oak forests on soil properties, soil organisms, and water quality. Most oak ecosystem fires are dormant-season fires whose intensity falls at the low end of the range of wildland fires. Direct heating of the mineral soil generally is minor except where accumulations of woody debris smolder for lengthy periods. Considerable proportions of nitrogen, phosphorus, and cations may be lost during fire through a combination of volatilization and ash convection. Post-fire precipitation events govern the return of nutrients in ash to the mineral soil, and the interaction of the soil exchange capacity, geomorphology, and weather control the proportion of nutrients from ash that will be retained for later plant use. Exposure of mineral soil by fire may lead to increased sheet erosion, but soil hydrophobicity does not seem to be important in oak ecosystems. Nitrogen availability and organic carbon content of soils may increase after fire, though both appear to be lesser in magnitude and duration than in other ecosystems. Impacts on fungi, bacteria, and microarthropods in the mineral soil are small, whereas those in the forest floor are proportional to the degree of consumption and the extent of heating due to smoldering woody fuels. Microbial activity and microarthropod populations recover quickly except after repeated annual burning. Little is known of effects of fire on other groups of soil organisms (e.g., nematodes and earthworms). The geomorphology of much of the eastern oak region is complex and heterogeneous. In such terrain, the difficulties inherent in scaling up plot-based studies to land areas of management scale are considered in the context of demonstrated landscape-scale variations in belowground effects of fire. GIS-derived landscape-scale metrics can be used to help generate management-scale recommendations from smaller scale research studies.