Mike Perks - Academia.edu (original) (raw)

Papers by Mike Perks

establishment advice for UK uplands: promoting good silviculture via a

Challenges and Opportunities for the World's Forests in the 21st Century

Temperate and boreal forests represent substantial stocks of carbon as biomass and organic matter... more Temperate and boreal forests represent substantial stocks of carbon as biomass and organic matter. Depending on the extent of climate change and the nature of future management practices, these forests may lose, retain or accumulate carbon in future decades. We review data on the impact of management on forest carbon, and we lay out some management options including longer rotations, lower disturbance, nitrogen fertilization and the afforestation of new land. We ask whether the carbon gains made possible by such practices will be at the expense of timber production and also we examine the impact of these practices on a range of environmental services (nature conservation, watershed protection, public amenity value, bio-fuel production). We look forward to a period of warming, which favours more rapid growth of trees in northern regions, but predictions from ecosystem models must be tempered by the likelihood that there may be more extremes, including droughts, storms and outbreaks of new pests and diseases.

Forest tree nurseries rely on tight scheduling of operations to deliver vital seedlings to the pl... more Forest tree nurseries rely on tight scheduling of operations to deliver vital seedlings to the planting site. Cold storage is required to: (1) prevent winter damage, especially in container seedlings; (2) to maintain planting stock in an inactive condition; and (3) to ensure plant supply for geographically distinct planting sites, a definite requirement for large-scale or internationally operating nurseries. Cooler storage has become common practice, but poses a dilemma for nursery managers. Efficient management requires that the handling of seedlings, such as transfer to cold storage, be carried out at the earliest possible time. However, lifting and storage of insufficiently hardened plants reduces vitality and may lead to cold damage, dehydration, and fungal infection. To prevent this kind of damage and its adverse economic effects on nurseries and end-users, it is of vital importance to accurately determine the peak physiological condition for lifting or transfer. Despite the ec...

The effect of clear-fell harvesting on soil greenhouse gas (GHG) fluxes of carbon dioxide (CO 2),... more The effect of clear-fell harvesting on soil greenhouse gas (GHG) fluxes of carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2 O) was assessed in a Sitka spruce forest growing on a peaty gley organo-mineral soil in northern England. Fluxes from the soil and litter layer were measured monthly by the closed chamber method and gas chromatography over 4 years in two mature stands, with one area harvested after the first year. Concurrent measurements of soil temperature and moisture helped to elucidate reasons for the changes in fluxes. In the 3 years after felling, there was a significant increase in the soil temperature, particularly between June and November (3 to 5 • C higher), and in soil moisture, which was 62 % higher in the felled area, and these had pronounced effects on the GHG balance in addition to the removal of the trees and their carbon input to the soil. Annual soil CO 2 effluxes reduced to almost a third in the first year after felling (a drop from 24.0 to 8.9 t CO 2 ha −1 yr −1) and half in the second and third year (mean 11.8 t CO 2 ha −1 yr −1) compared to before felling, while those from the unfelled area were little changed. Annual effluxes of N 2 O more than doubled in the first two years (from 1.0 to 2.3 and 2.5 t CO 2 e ha −1 yr −1 , respectively), although by the third year they were only 20 % higher (1.2 t CO 2 e ha −1 yr −1). CH 4 fluxes changed from a small net uptake of −0.03 t CO 2 e ha −1 yr −1 before felling to a small efflux increasing over the 3 years to 0.34 t CO 2 e ha −1 yr −1 , presumably because of the wetter soil after felling. Soil CO 2 effluxes dominated the annual net GHG emission when the three gases were compared using their global warming potential (GWP), but N 2 O contributed up to 20 % of this. This study showed fluxes of CO 2 , CH 4 , and N 2 O responded differently to clear-felling due to the significant changes in soil biotic and abiotic factors and showed large variations between years. This demonstrates the need for multi-year measurements of all GHGs to enable a robust estimate of the effect of the clear-fell phase on the GHG balance of managed forests. This is one of very few multi-year monitoring studies to assess the effect of clear-fell harvesting on soil GHG fluxes.

The EGU General Assembly, 2013

Climate change impacts resulting from fossil fuel combustion and concerns about the diversity of ... more Climate change impacts resulting from fossil fuel combustion and concerns about the diversity of energy supply are driving interest to find low-carbon energy alternatives. As a result bioenergy is receiving widespread scientific, political and media attention for its potential role in both supplying energy and mitigating greenhouse (GHG) emissions. It is estimated that the bioenergy contribution to EU 2020 renewable energy targets could require up to 17-21 million hectares of additional land in Europe (Don et al., 2012). There are increasing concerns that some transitions into bioenergy may not be as sustainable as first thought when GHG emissions from the crop growth and management cycle are factored into any GHG life cycle assessment (LCA). Bioenergy is complex and encapsulates a wide range of crops, varying from food crop based biofuels to dedicated second generation perennial energy crops and forestry products. The decision on the choice of crop for energy production significant...

ABSTRACT The greatest contributors to global greenhouse gases (GHG's) are CO2 emissions f... more ABSTRACT The greatest contributors to global greenhouse gases (GHG's) are CO2 emissions from fossil fuel use and following land use change (LUC). Globally, soils contain three times more carbon than the atmosphere and have the potential to act as GHG sources or sinks. A significant amount of land may be converted to bioenergy production to help meet UK 2050 renewable energy and GHG emissions reduction targets. This raises considerable sustainability concerns with respect to the effects of LUC on soil carbon (C) conservation and GHG emissions. Forests are a key component in the global C cycle and when managed effectively can reduce atmospheric GHG concentrations. Together with other dedicated bioenergy crops, Short Rotation Forestry (SRF) could be used to meet biomass requirements. SRF is defined as high density plantations of fastgrowing tree species grown on short rotational lengths (8-20 years) for biomass (McKay 2011). As SRF is likely to be an important domestic source of biomass for energy it is imperative that we gain an understanding of the implications for large-scale commercial application on soil C and the GHG balance. We utilized a paired-site approach to investigate how LUC to SRF could potentially alter the underlying processes of soil GHG production and consumption. This work was linked to a wider soil C stock inventory for bioenergy LUC, so our major focus was on changes to soil respiration. Specifically, we examined the relative importance of litter, soil, and microbial properties in determining potential soil respiration, and whether these relationships were consistent at different soil temperatures (10 ° C and 20 ° C). Soils were sampled to a depth of 30 cm from 30 LUC transitions across the UK and incubated under controlled laboratory conditions, with gas samples taken over a seven day enclosure period. CO2, N2O and CH4 gas fluxes were measured by gas chromatography and were examined together with other soil properties measured in the field and laboratory. LUC to SRF resulted in a significant reduction in CO2 fluxes overall at 0-15 cm (on both a soil mass and carbon mass basis). Furthermore, this response of CO2 flux to LUC was similar at both 10 ° C and 20 ° C. Reductions in CO2 flux at 0-15 cm are significantly related to decreased bacterial biomass, as measured by Phospholipid Fatty Acids (PLFA), soil pH and bulk density. These patterns suggest that changes in the quality and quantity of organic inputs under SRF may drive a reduction in soil respiration. While changes in soil C were limited, reduced respiration was supported by the increase in litter C stock under SRF. These findings indicate that LUC to SRF can strengthen the soils potential as a C sink whilst contributing successfully towards meeting GHG emissions reduction targets. This work is based on the Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial (ELUM) project, which was commissioned and funded by the Energy Technologies Institute (ETI)

A trial of six cold-tolerant eucalypt species, planted in 1981 near Exeter, in south west England... more A trial of six cold-tolerant eucalypt species, planted in 1981 near Exeter, in south west England, was assessed in 2010 for height, diameter at breast height and survival. The predicted soil moisture deficit on the site is low and it is relatively warm (AT 1662.5) and sheltered (DAMS 126), although it experienced a succession of cold winters in the 6 years following planting.The growth of some E. delegatensis was very rapid; the productivity of the seedlot having best survival (48%) was38 m3 ha-1 yr-1 although this seedlot was collected from one mother tree and was unrepresentative of the broader population at that location. Of the closely-related species E. johnstonii and E.subcrenulata, seedlots recorded as E. johnstonii had poor average survival (26%) and growth (7 m3 ha-1 y-1), while E. subcrenulata seedlots from Mount Cattley, Tasmania exhibited both good average survival (68%) and growth (25 m3 ha-1 y-1), with progenies from individual mother trees performing substantially bet...

ABSTRACT Many areas of British conifer forests will be due for felling in the next 10–20 years, w... more ABSTRACT Many areas of British conifer forests will be due for felling in the next 10–20 years, which represents a major opportunity for adapting forests to future climate. Greater use of more southerly provenances is possible for all the major conifers so reducing their vulnerability to climate change. Managers should use a mix of forest management alternatives to obtain the best out-turn in terms of climate change mitigation and adaptation. Intimate species mixtures are only likely to be viable in broadleaved woods and mosaic mixtures should be preferred elsewhere. Current policies seeking to diversify plantation forests through changes in species and structure may cause a decline in carbon sequestration unless this is offset by the use of more productive genotypes. When planning future planting programmes, greater emphasis should be given to species carbon content, and to their rates of carbon sequestration. Forest planning and management must take uncertainty and risk into account. Current policies are resulting in more stands being retained for longer which will increase the risk of windthrow and disturbance to forest and soil carbon stocks. Stands which are currently marginal because of soil moisture requirement are likely to prove vulnerable to climate change adding to the threat from established and new pests and pathogens. Improved methods of forest planning are needed that take uncertainty into account, increase the resilience of British forests to climate change and enhance their role in carbon sequestration. These methods will need to be supported by appropriate training.

for reviewing the 2008 draft and providing many useful comments. 4.4.2 Fossil fuel use 4.5. Stand... more for reviewing the 2008 draft and providing many useful comments. 4.4.2 Fossil fuel use 4.5. Stand establishment 4.5.1 Plant production 4.5.2 Restocking 4.6. Forest harvest 4.6.1 Thinning and harvesting operations 4.6.2 Consequences of clearfelling and harvesting on GHG emissions 4.6.3 Characterising the GHG impacts of forest residue harvesting 4.7. Timber transport and road building 4.7.1 Timber haulage 4.7.2 Road building 4.8. Afforestation 4.8.1 Introduction 4.8.2 Soil C changes with afforestation on mineral soils 4.8.3 Soil C changes with afforestation on organic soils 4.8.4 GHG fluxes and peatland afforestation 4.8.5 Changes in C stocks in other vegetation 4.9. Continuous cover and other management systems 5. Estimating C and GHG fluxes during the management cycle 5.1. Introduction 5.2. Phases in the forest management cycle 5.3. Estimation of forest C and GHG balances using CSORT 5.3.1 Overview 5.3.2 CSORT model description 5.4. CSORT model outputs 5.4.1 The establishment phase 5.4.2 The initial phase 5.4.3 The full vigour phase 5.4.4 The mature phase 5.4.5 The old-growth phase 5.5. Results for example forest management cycles 5.6. Application and interpretation of results for forest management cycles 5.7. Plans to further develop the CSORT model 6. Key conclusions, evidence gaps and research needs 6.1. Forestry, the carbon cycle and carbon stocks 6.2. Woodland stand C dynamics 6.3. Litter and coarse woody debris C stocks 6.4. Woodland soil C stocks 6.5. Quantifying the role of harvested wood products 6.6. Quantifying the role of material and fuel substitution 6.7. Assessment of forest C and GHG fluxes 6.8. Impacts of forest management 6.9. Forest operations effects 6.10. Use and development of C accounting models 6.11. Concluding points v References Appendices Appendix 1. Table of standing biomass in GB woodland Appendix 2. The FC soil classification system Appendix 3. The C dynamics in harvested wood products Appendix 4. Carbon content of timber Appendix 5. Summary of measured forest soil GHG fluxes Appendix 6. CSORT soil C sub-model Appendix 7. CSORT calculations of forest operations and wood processing Appendix 8. Example CSORT C balances for forest management cycles Notes, symbols and abbreviations and glossary Notes Symbols and abbreviations Glossary vi 1. See Symbols and abbreviations for explanation of global warming potential. 2. For explanation of terms sink, source etc., see Box 1.1. 1.3 Basic terms and definitions Key definitions and the meanings of key terms used in this review are given in Box 1.1; there are also lists of symbols and abbreviations, and a glossary, at the end of the report. the forestry C balance, and discusses the factors affecting them. Chapter 4 examines the fluxes of C and the other two key GHGs (N 2 O and CH 4) in forests and how they are affected by forestry operations. Chapter 5 describes the approach and calculations behind the forest C accounting model CSORT that is used to estimate the effect of different management options on C balance in different woodland types. Chapter 6 summarises key points arising from the review and outlines the major evidence gaps that need to be addressed by continuing Box 1.1 Key definitions and meanings of terms used in forest C and GHG research Carbon flux: the rate of exchange of carbon between different pools, or in and out of the system. Usually expressed as a mass change per unit time per unit land area (tCO 2 ha-1 y-1). Carbon pools: the different components of the system. Carbon sinks and sources: a carbon sink is any system which causes a net C transfer from the atmosphere to the system. A growing forest is normally a sink, but there are situations where a forest can beco me a carbon source, transferring C to the atmosphere (e.g. through deforestation or fires). Carbon sequestration: is said to have occurred if C is removed from the atmosphere and adds to C stock within one or more reservoirs (trees, soil etc). In its legal usage it refers to temporary seizure, thus the C removal can be reversed; in climate science 'sequestration' usually implies periods of years. Carbon stock: the amount of carbon in the system or its components at a given time. Either expressed as mass per unit land area (e.g. tC ha-1), or as a mass for a defined area (e.g. MtC). In order to compare stocks with CO 2 emissions, they can be expressed as mass CO 2 , as used here, by multiplying by the ratio of the molecular masses of CO 2 and C (44/12); thus 1 tC @ 3.667 tCO 2. CO 2 e (CO 2 equivalents): To express the emissions of other GHGs as well as CO 2 , it is conventional to use 'tonnes CO 2 equivalent' (tCO 2 e) which combines the effect of various GHGs with a weighted sum taking into account their differing warming effect, or 'global warming potential' (GWP). For CH 4 (methane) and N 2 O (nitrous oxide) these are 25 and 298 times, respectively, the GWP of CO 2 (IPCC, 2007). In this review we use CO 2 e only where other GHGs have been included. Forest: a landscape which has a high proportion of woodland, but which may also include other land cover types and uses. Litter: consists of all debris and material on the ground under woodland that has come from the trees and other vegetation: branches, twigs, leaves, growth and decay of vegetation. In soil science 'litter' on the surface of the soil is part of the organic or O horizon (see Box 3.1). Soil: consists of the inorganic and organic matter forming the ground under trees (not including litter), above the bedrock or other parent material. Soil carbon: is an abbreviation for soil organic carbon (SOC) as it should be noted that soil also contains inorganic C in minerals and the soil solution. SOC is the C content of organic matter derived from decomposing plant, microbial and animal material. It does not include live roots, nor the litter which is present on the soil surface. Stand (forest stand, or stand of trees): a measurable unit of trees with some form of homogeneity, often managed in the same way. For example, a stand of trees may be formed of one species, or several species evenly mixed. A stand may also contain trees all of the same age.

Quarterly Journal of Forestry, 2011

Usage of any items from the University of Cumbria's institutional repository 'Insight' must confo... more Usage of any items from the University of Cumbria's institutional repository 'Insight' must conform to the following fair usage guidelines. Any item and its associated metadata held in the University of Cumbria's institutional repository Insight (unless stated otherwise on the metadata record) may be copied, displayed or performed, and stored in line with the JISC fair dealing guidelines (available here) for educational and not-for-profit activities provided that • the authors, title and full bibliographic details of the item are cited clearly when any part of the work is referred to verbally or in the written form • a hyperlink/URL to the original Insight record of that item is included in any citations of the work • the content is not changed in any way • all files required for usage of the item are kept together with the main item file. You may not • sell any part of an item • refer to any part of an item without citation • amend any item or contextualise it in a way that will impugn the creator's reputation • remove or alter the copyright statement on an item. The full policy can be found here.

establishment advice for UK uplands: promoting good silviculture via a

Challenges and Opportunities for the World's Forests in the 21st Century

Temperate and boreal forests represent substantial stocks of carbon as biomass and organic matter... more Temperate and boreal forests represent substantial stocks of carbon as biomass and organic matter. Depending on the extent of climate change and the nature of future management practices, these forests may lose, retain or accumulate carbon in future decades. We review data on the impact of management on forest carbon, and we lay out some management options including longer rotations, lower disturbance, nitrogen fertilization and the afforestation of new land. We ask whether the carbon gains made possible by such practices will be at the expense of timber production and also we examine the impact of these practices on a range of environmental services (nature conservation, watershed protection, public amenity value, bio-fuel production). We look forward to a period of warming, which favours more rapid growth of trees in northern regions, but predictions from ecosystem models must be tempered by the likelihood that there may be more extremes, including droughts, storms and outbreaks of new pests and diseases.

Forest tree nurseries rely on tight scheduling of operations to deliver vital seedlings to the pl... more Forest tree nurseries rely on tight scheduling of operations to deliver vital seedlings to the planting site. Cold storage is required to: (1) prevent winter damage, especially in container seedlings; (2) to maintain planting stock in an inactive condition; and (3) to ensure plant supply for geographically distinct planting sites, a definite requirement for large-scale or internationally operating nurseries. Cooler storage has become common practice, but poses a dilemma for nursery managers. Efficient management requires that the handling of seedlings, such as transfer to cold storage, be carried out at the earliest possible time. However, lifting and storage of insufficiently hardened plants reduces vitality and may lead to cold damage, dehydration, and fungal infection. To prevent this kind of damage and its adverse economic effects on nurseries and end-users, it is of vital importance to accurately determine the peak physiological condition for lifting or transfer. Despite the ec...

The effect of clear-fell harvesting on soil greenhouse gas (GHG) fluxes of carbon dioxide (CO 2),... more The effect of clear-fell harvesting on soil greenhouse gas (GHG) fluxes of carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2 O) was assessed in a Sitka spruce forest growing on a peaty gley organo-mineral soil in northern England. Fluxes from the soil and litter layer were measured monthly by the closed chamber method and gas chromatography over 4 years in two mature stands, with one area harvested after the first year. Concurrent measurements of soil temperature and moisture helped to elucidate reasons for the changes in fluxes. In the 3 years after felling, there was a significant increase in the soil temperature, particularly between June and November (3 to 5 • C higher), and in soil moisture, which was 62 % higher in the felled area, and these had pronounced effects on the GHG balance in addition to the removal of the trees and their carbon input to the soil. Annual soil CO 2 effluxes reduced to almost a third in the first year after felling (a drop from 24.0 to 8.9 t CO 2 ha −1 yr −1) and half in the second and third year (mean 11.8 t CO 2 ha −1 yr −1) compared to before felling, while those from the unfelled area were little changed. Annual effluxes of N 2 O more than doubled in the first two years (from 1.0 to 2.3 and 2.5 t CO 2 e ha −1 yr −1 , respectively), although by the third year they were only 20 % higher (1.2 t CO 2 e ha −1 yr −1). CH 4 fluxes changed from a small net uptake of −0.03 t CO 2 e ha −1 yr −1 before felling to a small efflux increasing over the 3 years to 0.34 t CO 2 e ha −1 yr −1 , presumably because of the wetter soil after felling. Soil CO 2 effluxes dominated the annual net GHG emission when the three gases were compared using their global warming potential (GWP), but N 2 O contributed up to 20 % of this. This study showed fluxes of CO 2 , CH 4 , and N 2 O responded differently to clear-felling due to the significant changes in soil biotic and abiotic factors and showed large variations between years. This demonstrates the need for multi-year measurements of all GHGs to enable a robust estimate of the effect of the clear-fell phase on the GHG balance of managed forests. This is one of very few multi-year monitoring studies to assess the effect of clear-fell harvesting on soil GHG fluxes.

The EGU General Assembly, 2013

Climate change impacts resulting from fossil fuel combustion and concerns about the diversity of ... more Climate change impacts resulting from fossil fuel combustion and concerns about the diversity of energy supply are driving interest to find low-carbon energy alternatives. As a result bioenergy is receiving widespread scientific, political and media attention for its potential role in both supplying energy and mitigating greenhouse (GHG) emissions. It is estimated that the bioenergy contribution to EU 2020 renewable energy targets could require up to 17-21 million hectares of additional land in Europe (Don et al., 2012). There are increasing concerns that some transitions into bioenergy may not be as sustainable as first thought when GHG emissions from the crop growth and management cycle are factored into any GHG life cycle assessment (LCA). Bioenergy is complex and encapsulates a wide range of crops, varying from food crop based biofuels to dedicated second generation perennial energy crops and forestry products. The decision on the choice of crop for energy production significant...

ABSTRACT The greatest contributors to global greenhouse gases (GHG's) are CO2 emissions f... more ABSTRACT The greatest contributors to global greenhouse gases (GHG's) are CO2 emissions from fossil fuel use and following land use change (LUC). Globally, soils contain three times more carbon than the atmosphere and have the potential to act as GHG sources or sinks. A significant amount of land may be converted to bioenergy production to help meet UK 2050 renewable energy and GHG emissions reduction targets. This raises considerable sustainability concerns with respect to the effects of LUC on soil carbon (C) conservation and GHG emissions. Forests are a key component in the global C cycle and when managed effectively can reduce atmospheric GHG concentrations. Together with other dedicated bioenergy crops, Short Rotation Forestry (SRF) could be used to meet biomass requirements. SRF is defined as high density plantations of fastgrowing tree species grown on short rotational lengths (8-20 years) for biomass (McKay 2011). As SRF is likely to be an important domestic source of biomass for energy it is imperative that we gain an understanding of the implications for large-scale commercial application on soil C and the GHG balance. We utilized a paired-site approach to investigate how LUC to SRF could potentially alter the underlying processes of soil GHG production and consumption. This work was linked to a wider soil C stock inventory for bioenergy LUC, so our major focus was on changes to soil respiration. Specifically, we examined the relative importance of litter, soil, and microbial properties in determining potential soil respiration, and whether these relationships were consistent at different soil temperatures (10 ° C and 20 ° C). Soils were sampled to a depth of 30 cm from 30 LUC transitions across the UK and incubated under controlled laboratory conditions, with gas samples taken over a seven day enclosure period. CO2, N2O and CH4 gas fluxes were measured by gas chromatography and were examined together with other soil properties measured in the field and laboratory. LUC to SRF resulted in a significant reduction in CO2 fluxes overall at 0-15 cm (on both a soil mass and carbon mass basis). Furthermore, this response of CO2 flux to LUC was similar at both 10 ° C and 20 ° C. Reductions in CO2 flux at 0-15 cm are significantly related to decreased bacterial biomass, as measured by Phospholipid Fatty Acids (PLFA), soil pH and bulk density. These patterns suggest that changes in the quality and quantity of organic inputs under SRF may drive a reduction in soil respiration. While changes in soil C were limited, reduced respiration was supported by the increase in litter C stock under SRF. These findings indicate that LUC to SRF can strengthen the soils potential as a C sink whilst contributing successfully towards meeting GHG emissions reduction targets. This work is based on the Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial (ELUM) project, which was commissioned and funded by the Energy Technologies Institute (ETI)

A trial of six cold-tolerant eucalypt species, planted in 1981 near Exeter, in south west England... more A trial of six cold-tolerant eucalypt species, planted in 1981 near Exeter, in south west England, was assessed in 2010 for height, diameter at breast height and survival. The predicted soil moisture deficit on the site is low and it is relatively warm (AT 1662.5) and sheltered (DAMS 126), although it experienced a succession of cold winters in the 6 years following planting.The growth of some E. delegatensis was very rapid; the productivity of the seedlot having best survival (48%) was38 m3 ha-1 yr-1 although this seedlot was collected from one mother tree and was unrepresentative of the broader population at that location. Of the closely-related species E. johnstonii and E.subcrenulata, seedlots recorded as E. johnstonii had poor average survival (26%) and growth (7 m3 ha-1 y-1), while E. subcrenulata seedlots from Mount Cattley, Tasmania exhibited both good average survival (68%) and growth (25 m3 ha-1 y-1), with progenies from individual mother trees performing substantially bet...

ABSTRACT Many areas of British conifer forests will be due for felling in the next 10–20 years, w... more ABSTRACT Many areas of British conifer forests will be due for felling in the next 10–20 years, which represents a major opportunity for adapting forests to future climate. Greater use of more southerly provenances is possible for all the major conifers so reducing their vulnerability to climate change. Managers should use a mix of forest management alternatives to obtain the best out-turn in terms of climate change mitigation and adaptation. Intimate species mixtures are only likely to be viable in broadleaved woods and mosaic mixtures should be preferred elsewhere. Current policies seeking to diversify plantation forests through changes in species and structure may cause a decline in carbon sequestration unless this is offset by the use of more productive genotypes. When planning future planting programmes, greater emphasis should be given to species carbon content, and to their rates of carbon sequestration. Forest planning and management must take uncertainty and risk into account. Current policies are resulting in more stands being retained for longer which will increase the risk of windthrow and disturbance to forest and soil carbon stocks. Stands which are currently marginal because of soil moisture requirement are likely to prove vulnerable to climate change adding to the threat from established and new pests and pathogens. Improved methods of forest planning are needed that take uncertainty into account, increase the resilience of British forests to climate change and enhance their role in carbon sequestration. These methods will need to be supported by appropriate training.

for reviewing the 2008 draft and providing many useful comments. 4.4.2 Fossil fuel use 4.5. Stand... more for reviewing the 2008 draft and providing many useful comments. 4.4.2 Fossil fuel use 4.5. Stand establishment 4.5.1 Plant production 4.5.2 Restocking 4.6. Forest harvest 4.6.1 Thinning and harvesting operations 4.6.2 Consequences of clearfelling and harvesting on GHG emissions 4.6.3 Characterising the GHG impacts of forest residue harvesting 4.7. Timber transport and road building 4.7.1 Timber haulage 4.7.2 Road building 4.8. Afforestation 4.8.1 Introduction 4.8.2 Soil C changes with afforestation on mineral soils 4.8.3 Soil C changes with afforestation on organic soils 4.8.4 GHG fluxes and peatland afforestation 4.8.5 Changes in C stocks in other vegetation 4.9. Continuous cover and other management systems 5. Estimating C and GHG fluxes during the management cycle 5.1. Introduction 5.2. Phases in the forest management cycle 5.3. Estimation of forest C and GHG balances using CSORT 5.3.1 Overview 5.3.2 CSORT model description 5.4. CSORT model outputs 5.4.1 The establishment phase 5.4.2 The initial phase 5.4.3 The full vigour phase 5.4.4 The mature phase 5.4.5 The old-growth phase 5.5. Results for example forest management cycles 5.6. Application and interpretation of results for forest management cycles 5.7. Plans to further develop the CSORT model 6. Key conclusions, evidence gaps and research needs 6.1. Forestry, the carbon cycle and carbon stocks 6.2. Woodland stand C dynamics 6.3. Litter and coarse woody debris C stocks 6.4. Woodland soil C stocks 6.5. Quantifying the role of harvested wood products 6.6. Quantifying the role of material and fuel substitution 6.7. Assessment of forest C and GHG fluxes 6.8. Impacts of forest management 6.9. Forest operations effects 6.10. Use and development of C accounting models 6.11. Concluding points v References Appendices Appendix 1. Table of standing biomass in GB woodland Appendix 2. The FC soil classification system Appendix 3. The C dynamics in harvested wood products Appendix 4. Carbon content of timber Appendix 5. Summary of measured forest soil GHG fluxes Appendix 6. CSORT soil C sub-model Appendix 7. CSORT calculations of forest operations and wood processing Appendix 8. Example CSORT C balances for forest management cycles Notes, symbols and abbreviations and glossary Notes Symbols and abbreviations Glossary vi 1. See Symbols and abbreviations for explanation of global warming potential. 2. For explanation of terms sink, source etc., see Box 1.1. 1.3 Basic terms and definitions Key definitions and the meanings of key terms used in this review are given in Box 1.1; there are also lists of symbols and abbreviations, and a glossary, at the end of the report. the forestry C balance, and discusses the factors affecting them. Chapter 4 examines the fluxes of C and the other two key GHGs (N 2 O and CH 4) in forests and how they are affected by forestry operations. Chapter 5 describes the approach and calculations behind the forest C accounting model CSORT that is used to estimate the effect of different management options on C balance in different woodland types. Chapter 6 summarises key points arising from the review and outlines the major evidence gaps that need to be addressed by continuing Box 1.1 Key definitions and meanings of terms used in forest C and GHG research Carbon flux: the rate of exchange of carbon between different pools, or in and out of the system. Usually expressed as a mass change per unit time per unit land area (tCO 2 ha-1 y-1). Carbon pools: the different components of the system. Carbon sinks and sources: a carbon sink is any system which causes a net C transfer from the atmosphere to the system. A growing forest is normally a sink, but there are situations where a forest can beco me a carbon source, transferring C to the atmosphere (e.g. through deforestation or fires). Carbon sequestration: is said to have occurred if C is removed from the atmosphere and adds to C stock within one or more reservoirs (trees, soil etc). In its legal usage it refers to temporary seizure, thus the C removal can be reversed; in climate science 'sequestration' usually implies periods of years. Carbon stock: the amount of carbon in the system or its components at a given time. Either expressed as mass per unit land area (e.g. tC ha-1), or as a mass for a defined area (e.g. MtC). In order to compare stocks with CO 2 emissions, they can be expressed as mass CO 2 , as used here, by multiplying by the ratio of the molecular masses of CO 2 and C (44/12); thus 1 tC @ 3.667 tCO 2. CO 2 e (CO 2 equivalents): To express the emissions of other GHGs as well as CO 2 , it is conventional to use 'tonnes CO 2 equivalent' (tCO 2 e) which combines the effect of various GHGs with a weighted sum taking into account their differing warming effect, or 'global warming potential' (GWP). For CH 4 (methane) and N 2 O (nitrous oxide) these are 25 and 298 times, respectively, the GWP of CO 2 (IPCC, 2007). In this review we use CO 2 e only where other GHGs have been included. Forest: a landscape which has a high proportion of woodland, but which may also include other land cover types and uses. Litter: consists of all debris and material on the ground under woodland that has come from the trees and other vegetation: branches, twigs, leaves, growth and decay of vegetation. In soil science 'litter' on the surface of the soil is part of the organic or O horizon (see Box 3.1). Soil: consists of the inorganic and organic matter forming the ground under trees (not including litter), above the bedrock or other parent material. Soil carbon: is an abbreviation for soil organic carbon (SOC) as it should be noted that soil also contains inorganic C in minerals and the soil solution. SOC is the C content of organic matter derived from decomposing plant, microbial and animal material. It does not include live roots, nor the litter which is present on the soil surface. Stand (forest stand, or stand of trees): a measurable unit of trees with some form of homogeneity, often managed in the same way. For example, a stand of trees may be formed of one species, or several species evenly mixed. A stand may also contain trees all of the same age.

Quarterly Journal of Forestry, 2011

Usage of any items from the University of Cumbria's institutional repository 'Insight' must confo... more Usage of any items from the University of Cumbria's institutional repository 'Insight' must conform to the following fair usage guidelines. Any item and its associated metadata held in the University of Cumbria's institutional repository Insight (unless stated otherwise on the metadata record) may be copied, displayed or performed, and stored in line with the JISC fair dealing guidelines (available here) for educational and not-for-profit activities provided that • the authors, title and full bibliographic details of the item are cited clearly when any part of the work is referred to verbally or in the written form • a hyperlink/URL to the original Insight record of that item is included in any citations of the work • the content is not changed in any way • all files required for usage of the item are kept together with the main item file. You may not • sell any part of an item • refer to any part of an item without citation • amend any item or contextualise it in a way that will impugn the creator's reputation • remove or alter the copyright statement on an item. The full policy can be found here.