Stump Harvesting for Bioenergy - A Review of the Environmental Impacts

Abstract

Stump harvesting signifi es an intensifi cation of forest management compared with conventional stem-only or aboveground biomass-only harvesting. There are many practical and perceived benefi ts 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 infl uences the forest soil carbon balance and forest nutrient stocks.

Phosphorus nutrition of beech (Fagus sylvatica L.) is decreasing in Europe

“…Instead, a better understanding of P levels and cycles in forest ecosystems, including the role of root dynamics and mycorrhizal symbioses, is needed as a basis for sustainable P management (Binkley and Fisher 2013). This is especially important now when more intensive biomass removals are applied in European forests to meet the growing demand for bioenergy (Matthews et al 2014;Walmsley and Godbold 2010). Intensive biomass removals, such as whole-tree harvest, will reduce P reserves of forest ecosystems (Mann et al 1988), while P demand of trees is already high due to increased growth as a consequence of anthropogenic N deposition and climate change.…”

Impact of Tree Stump Harvesting on Soil Carbon and Nutrients and Second Rotation Tree Growth in Mid-Wales, UK

“…The disturbance of forest soils during normal harvesting operations is known to result in mineralisation of soil organic matter, leading to carbon loss as carbon dioxide, and potential elevated leaching of Dissolved Organic Carbon (DOC) (Reynolds, 2007;Walmsley & Godbold, 2010). The extra practice of stump harvesting has thus been questioned, as the benefits of fossil fuel substitution may be outweighed by soil carbon loss to the atmosphere (Walmsley & Godbold, 2010;Moffat et al, 2011).…”

“…The extra practice of stump harvesting has thus been questioned, as the benefits of fossil fuel substitution may be outweighed by soil carbon loss to the atmosphere (Walmsley & Godbold, 2010;Moffat et al, 2011).…”

“…Poor stump removal practice can result in detrimental effects on soil structure, increasing the risk of soil erosion, and depletion of soil nutrient and carbon capital (Pitman, 2008;Walmsley & Godbold, 2010;Moffat et al, 2011;Collison et al, 2015). There are four principal threats: 1) machine trafficking causing physical soil damage such as compaction, rutting and erosion, leading to increased water turbidity and siltation of local watercourses; 2) removal of essential nutrients (nitrogen (N), phosphorus (P), potassium (K) and carbon (C)) in residues, leading to lower soil fertility, potential loss of tree growth in subsequent rotations, and reduced soil carbon storage; 3) removal of base cations (calcium (Ca 2+ ), magnesium (Mg 2+ ), sodium (Na + ) and potassium (K + )) reducing soil buffering capacity and leading to increased soil and stream water acidification and 4) soil dis-turbance resulting in CO 2 release, soil organic carbon loss and soil structural damage.…”

Short-term impacts of energy wood harvesting on ectomycorrhizal fungal communities of Norway spruce saplings

“…However, combined impacts of residue and stump harvesting, especially on soil processes and biota, are still poorly understood. Compared with stem harvest only, collecting also stumps and logging residues intensifies the loss of both soil nutrient and carbon (C) stocks (Palviainen et al, 2010;Walmsley and Godbold, 2010), which may have cascading effects on soil microbiota and further on the new regenerating tree cohort.…”