Potential Environmental Impacts of Bioenergy Harvesting on Soils

Potential Environmental Impacts of Bioenergy Harvesting on Soils

Aspect	Potential Issues	Contributing activities	Examples of mitigating practices
Physical properties:   Moisture   Temperature   Structure   Erosion	Removal of slash and litter layer and disturbance of forest floor leads to exposure of soil surface and drying of surface layers and soil temperature extremes   Changes in soil microclimate   Compaction leads to decreased soil aeration and soil porosity and decreased water infiltration and waterlogged ruts   Clearcutting leads to a loss of evapotranspiration and increased water content and rise of water table and saturation of soil   Exposure of soil surface layers by wind and water leads to erosion	Downed woody debris (DWD) and litterfall removal   Removal of protective roadbed for feedstock   Time of year and soil conditions during operations   Clearcutting and whole-tree harvesting (WTH)   Multiple-pass harvesting   Increased road networks   Heavy mechanized equipment	Maintain protective slash and litter layer on forest floor   Restrict interventions to seasons when soil moisture is low   Use specialized equipment such as high flotation tires and boom-forwarding   Utilize best management practices for road building, as prescribed by the USDA   Orient skid trails and site preparations along slope contours   Minimize interventions by practicing one-pass harvesting   Ameliorate soil compaction through ripping and cultivation
Chemical properties   Nutrients   Toxic substances   pH   Redox potential	Maintaining total capital and availability of nutrients   Increased leaching from the forest floor and mineral soil   Accumulation of toxic substances   Decrease in pH   Anaerobic conditions mobilizing toxic forms of some elements/compounds; altered chemical transformations	Removal of forest biomass throughout the rotation (e.g., WTH, removal of dead wood)   Rotation length and species chosen   Improper use of herbicides, pesticides, fertilizers and wood ash   Oil and hydraulic fluid spills from harvesting machinery	Develop site-specific nutrient management regimes   Avoid windrowing/root raking that results in soil organic matter depletion   Retain nutrient-rich crown biomass on site (e.g., needles, bark, branches, tops)   Harvest deciduous trees in winter, after leaves have fallen   Apply recycled wood ash or fertilizers where needed according to guidelines
Biological properties:	Soil biota is decreased through:   Loss of soil organic matter Compaction Drying Waterlogging Accumulation of toxic elements Temperature extremes	See related activities described above	See mitigation strategies above   When using pesticides and fertilizers, follow guidelines established by the USDA

Permission of Use: Used with permission of Brenna Lattimore and C. T. Smith 1/22/08