The requirement to reduce carbon emissions has led to the development of alternative energy sources, including biomass for fossil fuel substitution. Forest harvesting residues are increasingly being used to supply biomass for heat and power generation in the UK and attention is now turning to the utilisation of tree stumps. Some private sector forestry companies in South Scotland have begun to extract stumps from harvested conifer plantation sites to provide biomass for local power plants.
Maintaining sustainable forest management
Stump harvesting poses a number of risks to the forest environment that can threaten sustainable forest management. However, where these risks can be reduced to a low level, the benefits of increasing the use of biomass may outweigh the potential disadvantages. Forest Research has worked with the Forestry Commission and the forest industry to develop interim guidance to minimise the risks through careful site selection and good practice.
The four principal risks to soil sustainability from stump harvesting are:
- Increased soil damage due to compaction, rutting and disturbance leading to erosion and increased turbidity and siltation of local watercourses.
- Removal of essential major and micronutrients (e.g. nitrogen, phosphorus, potassium and boron), leading to lower soil fertility, and potential loss of tree growth in subsequent rotations.
- Removal of base cations (calcium, magnesium, sodium and potassium) reducing soil buffering capacity and leading to increased soil and stream water acidification.
- Increased carbon loss from disturbed soil after stump harvesting leading to reduced soil carbon stock.
The guidance addresses these risks based on a knowledge of main soil types, slope and other relevant constraints. Recommendations on good practice will help to protect sites from damage.
The guidance is largely based on expert judgement of the scientific issues informed by practical experience of managing forest soils. Uncertainties remain about the long-term sustainability of stump harvesting on certain soil types, which will require new research to quantify impacts and check that the guidance is fit for purpose.
Stump harvesting guidance
Guidance to assist the forest industry in identifying sites where stumps may be harvested without compromising long-term sustainability, and on any environmental safeguards that must be applied.
- Site planning to facilitate stump harvesting
- Stump harvesting systems
- Ongoing research work and publications relevant to stump harvesting
Further information on Forest Research work that is relevant to issues related to stump harvesting and brash removal is available from Tom Nisbet (email@example.com) and Bruce Nicoll (firstname.lastname@example.org).