Stump Harvesting for Bioenergy – A Review of the Environmental Impacts
AbstractStump harvesting signifies an intensification of forest management compared with conventional stem-only or above-ground biomass-only harvesting. There are many practical and perceived benefits of stump harvesting. These include (1) the production of woodfuel; (2) fossil fuel substitution; (3) additional revenue for forest owners; (4) improved site preparation and (5) potential reduction of Heterobasidion . However, evidence suggests that, in the absence of appropriate precautionary measures, stump harvesting will lead to many undesirable environmental impacts. These include (1) removal of soil organic matter inputs; (2) adverse impacts on forest soil carbon stores and greenhouse gas emissions; (3) increased soil erosion; (4) increased soil compaction; (5) depletion of soil nutrient stocks and changes in nutrient cycling; (6) unknown impacts on future productivity; (7) loss of valuable habitat for fungi, mosses, bryophytes and insects and (8) increase in non-forest vegetation and additional herbicide requirements. To minimize environmental impacts, best practice guidelines should be developed and communicated. Research to date has focussed on the impact of stump removal on the incidence of root diseases and has limited applicability to healthy uninfected stands. Additional research is required to understand fully the environmental impacts, particularly how stump harvesting influences the forest soil carbon balance and forest nutrient stocks.