Adapting forest management to the changing climate in Alice Holt Forest
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By Dr Gail Atkinson, Scientist: Climate Change Adaptation
Gail Atkinson, Forest Research scientist, explains how researchers are trialling innovative ways to better prepare our woodlands for climate change.
Our climate is changing, and this is affecting our trees, woodlands and forests. If UK woodlands are to thrive in future, we need to take action to enable them to adapt to the future climate. This involves identifying and testing suitable measures, monitoring changes and sharing insights. If we get this right, they will be better able to continue to deliver a wide range of benefits and products.
There are many risks to UK trees, forests and woodlands from climate change and extreme weather events. Recently witnessed impacts of extreme weather include significant storm damage overwinter (2021-22) and severe regional drought this summer. Understanding and managing climate risks to reduce the potential impact on our forests and the many benefits they provide will improve the resilience of UK forest and provide climate change mitigation. The complexity of responses to, and impacts of, weather extremes represent a challenge for forestry policy and practice but in Forestry England’s Alice Holt Forest, on the Surrey/Hampshire border, work began several years ago to increase our understanding of potential solutions. A series of demonstration areas were set up and linked together with several historic research trials to create a Climate Change ‘Adaptation Trail’.
Understanding and demonstrating Climate Change Adaptation
The demonstration areas in Alice Holt Forest have been set up to show the implementation of climate change adaptation measures in a woodland typical of south-east England, where the risk of increasing severity, frequency and duration of drought is a particularly important management concern. The impacts of a suite of adaptation measures are being monitored and the response to these interventions will inform woodland management to sustain wood production and other benefits.
The Adaptation Trail aims to increase and share understanding of evolving best practice in adaptation management. The planning, operations, implementation and monitoring of adaptation measures has already provided key insights into the practicalities of adapting to future changes. By championing the sharing of new management approaches and the impact of implementing adaptation actions in forestry, the Adaptation Trail provides a living resource which can be used to encourage owners and managers to think about what measures might be adopted in their woodlands. It explores different climate risks and the demonstration areas show a range of different measures, tailored in response to the risks and opportunities specific to different woodland types in south-east England.
Why choose Alice Holt?
Alice Holt Forest is an 850 hectare public working forest and has been a research forest since 1943, on the edge of the South Downs National Park. A mix of broadleaf tree species and coniferous woodland support the provision of a range of important benefits, including timber production, habitat for wildlife and recreational activities, and the Forest Park receives in excess of 450,000 day visitors each year.
Predicted future climate scenarios for Alice Holt Forest, include hotter, drier summers along with more frequent extreme weather events, such as droughts. By the 2080’s, the annual likelihood of a drought occurring is projected to increase between 10% and 50%. We know that numerous tree species are susceptible to drought, but the impact of changes in drought frequency, severity and duration are of particular concern. More frequent severe droughts could lead to significant loss of tree growth, biodiversity and benefits such as carbon sequestration.
How were the demonstration areas set up?
The project is a collaboration between Forest Research and Forestry England. Both organisations are keen to better understand and prepare for climate change and share knowledge.
Following a review of the management objectives for the forest, projected local changes in climate, soil type, current management and analysis of the potential of nearly 60 different tree species under future climate conditions was undertaken. The UK Forestry Standard (UKFS), and policy and conservation requirements for the public forest estate also informed the project. The demonstration areas were incorporated into the Forest Design Plan for Alice Holt (2016-2026) and subjected to the Forest Design Planning Process which includes public and statutory consultation. The measures implemented include alternative thinning to better understand adaptation to manage drought and pest risks, underplanting to transition to an alternative cover system, use of alternative management approaches, alongside wider actions such as increasing species diversity and the use of alternative establishment methods.
What forest management actions are being demonstrated?
Several adaptation measures are being demonstrated in Alice Holt Forest and some in combination.
Underplanting with different provenances
One area in a mature beech woodland demonstrates underplanting existing trees with trees from different locations (“provenances”) (photo above). Tree provenances from a more southerly climate, matched to the projected future climate for Alice Holt, may be more resilient to drought. The area is situated in mature beech woodland to compare the natural beech regeneration with underplanting with native oak and oak s from a more southerly provenance – in this case, we used trees from the Loire Valley in France.
We anticipate the new planting will, in time, show differences in the growth and performance of local provenance trees with those from further south. This demonstration area will provide new insight on the impacts of diversifying provenance selection, whether positive, for example through improved growth and survival, or negative, such as through increased susceptibility to late spring frost or pest outbreaks. We are monitoring mortality, alongside tree growth and the natural regeneration of beech.
Underplanting with a species pair
In one area, a stand of mature Corsican pine growing on a sandy soil has been thinned and under planted with two broadleaved species. In one part of the stand (“woodland current”), beech accounts for 70% of the planting and hornbeam accounts for 30%. In the other part (“woodland future”), the planting ratio is reversed, so that hornbeam dominates the planting. This demonstration will provide evidence of species response to changes in drought frequency in a ‘living lab’. Hornbeam is expected to perform better than beech in the future because it has a higher drought tolerance. Adaptation measures which increase the structural and species diversity of the stand are key components of the new approach. We are monitoring mortality, tree growth, vegetation and soils to better understand its effectiveness. We will also monitor how the mature stand is affected by any high winds.
Different thinning intensities
In another area we are interested in changing the management of a young Corsican pine stand. The stands were thinned in 2018 at two intensities, in two adjacent forest blocks, to compare how the trees and the stand as a whole grow. Hotter, drier summers will increase competition for water but there may be less drought stress in trees where heavier thinning has been undertaken. It is also hoped that the thinning will reduce the incidence of the fungal disease Dothistroma needle blight due to increased airflow through the stand. In this area we are monitoring soil water availability and tree growth to see how the trees respond to changes in drought frequency, severity and duration.
How can I visit the demonstration areas and find more information?
A self-guided ‘Climate Change Adaptation Trail’ takes in the demonstration areas, historic research trials and the Alice Holt Arboretum, which are of interest to those considering how to enhance woodland resilience to environmental change. The self-guided trail guide and associated worksheet are available to download from the Forest Research website Alice Holt Forest climate change adaptation trail - Forest Research. Alternatively, if you would like a hard copy of the guide or to request the file in audio format, contact us at: climate.change@forestresearch.gov.uk
Adaptation case studies accompany the UKFS Practice Guide ‘Adapting forest and woodland management to the changing climate’ and include Bicentenary project: planning 200 years ahead in Gipps Wood (forestresearch.gov.uk).
Information on Forest Research’s work on climate change adaptation demonstration areas.
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