The impacts of forest harvest and wildfire on soils and hydrology in temperate forests: A baseline to develop hypotheses for the Boreal Plain

This component of the Forest Riparian and Watershed Disturbance (FORWARD) project evaluates soils in burned, harvested, and undisturbed watersheds to quantify effects of disturbance on forest soils in the Boreal Plain. The current knowledge of disturbance effects on soils is reviewed, with a focus on temperate ecosystems, to generate the following hypotheses to be tested in field studies. Harvest and fire should affect surface horizons more than mineral horizons. Forest harvest should affect soils most through compaction, the degree being mediated by soil texture, soil moisture, and harvest operations. Nutrient export will likely increase from logged watersheds, with changes in microbial processes being more strongly associated with nitrogen (N) losses and erosional processes more strongly linked to phosphorus (P) losses. Effects of fire on Boreal Plain soils will increase with fire severity. Coarser soils after fire should be subject to hydrophobicity, erosion, and low infiltration rates. Chemical changes should include increased solubility of oxidized cations. N losses should exceed P losses and be due to volatilization and leaching of mineralized N compounds. Particulate P should comprise P loss; although P availability may increase after fire, soluble P movement from the forest environment will be limited by P uptake by soils.