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During the past year, we have continued our research across a wide breadth of topics. Our research ranges from urgent responses to outbreaks of pests and diseases, including the new findings of Ips typographus and Phytophthora pluvialis, to longer-termclimate change modelling and determining the carbon balances for different types of woodland creation and management. We’ve also been increasing our use of satellite imagery to map changes to our forests, whether from storm damage or to establish the location of larch trees, which are susceptible to Phytophthora ramorum, to help monitor tree health. These projects are summarised here, along with a selection of other work.
Forest Research has completed a new study, ‘Quantifying the Sustainable Carbon Cycle’, which assesses the latest evidence about the carbon balance of woodlands in the UK. The focus is on the potential for the creation of new woodlands and their management to contribute towards mitigation of greenhouse gases (GHGs). The assessment is comprehensive and considers carbon sequestration in woodlands and in wood products, as well as the potential to avoid emissions through increased use of wood products and wood fuel in place of alternative materials and fuels.
As part of this study, we modelled the carbon balances of a large number of options for woodland creation and management, covering many tree species, yield classes, soil types and a range of management prescriptions. These have been included in a software tool that enables us to access and display the results and compare different woodland options. Further model results are presented for a smaller set of more-complex woodland types, consistent with current sustainability criteria such as for tree species composition, habitat conservation and multi-objective woodland management.
A full report on the study describes the modelling methods and shows how the results can be used to evaluate the GHG emissions mitigation potentials of woodland options in different UK localities. The report also explores the sensitivity of woodland GHG balances to a range of site and management factors. In addition, we have reviewed other recent studies and published statements about woodland creation and management to contribute to GHG emissions mitigation in policy-relevant timescales.
We have also prepared a summary report, which concentrates on the key policy-relevant findings of the study. Both reports will be published later this year.
Woodland creation and expansion is an important policy goal and can be achieved in a variety of ways, including by natural colonisation. This is the process by which trees and woodlands establish from seeds (or other propagules) dispersed naturally from local sources. It can be distinguished from natural regeneration by the absence of recent woodland cover at a site.
Use of natural colonisation in recent years has been limited and so may be unfamiliar to many land managers, prompting the need for a review of evidence. We conducted a literature review, on behalf of Natural England, which concluded that where existing mature woodland and hedgerows or isolated trees provide suitable seed sources and the site conditions are favourable, then natural colonisation provides the potential to expand tree cover relatively quickly (within five years). In other circumstances, there is a risk of little apparent colonisation progress in the short to medium term and the result can be a scrubland rather than woodland habitat. Therefore natural colonisation depends primarily on choice of site, ground conditions and suitable seed source.
Natural colonisation by trees and scrub is progressive and, as well as contributing towards increased woodland cover, it can potentially provide complex habitat mosaics of high biodiversity value. The projected biodiversity gains from natural colonisation processes (after first excluding grazers) include highly diverse transitional habitat that could be expected to last for 20 years or more and contribute to the government’s biodiversity targets and ambitions for nature recovery.
There may also be benefits to long-term carbon sequestration or storage. However, these are yet to be quantified so it is difficult to state with confidence what contribution can be made to the government’s 2050 net zero commitments. The unpredictability of natural colonisation may result in it being judged by policy makers and land managers as being less reliable in achieving rapid carbon storage when compared to tree planting or direct seeding systems.
As well as summarising existing knowledge, the review highlighted some important gaps in evidence. We are currently conducting field-based research in partnership with Natural England and the Forestry Commission, funded by Defra, to unpick natural colonisation processes, ecological benefits and carbon balance both above and below ground. Complementary research is examining land-manager attitudes to natural colonisation as a woodland expansion strategy. These investigations will refine understanding and the guidance available to land managers in the near future.
A pivotal technological breakthrough for species detection from DNA has been the advent of next-generation sequencing. This allows multiple species to be rapidly identified from a single sample at relatively low cost with the proviso that DNA sequences can be extracted, sequenced and matched to reference databases. This is ‘metabarcoding’ and, using environmental DNA (eDNA), this method holds particular promise as a non-destructive detection method since it relies on DNA shed by species into the environment. DNA is extracted from an environmental sample (e.g. collected from water, soil, air) with no need for the isolation of target species or species groups.
In 2021, Forest Research was co-funded by Forestry England and Defra’s Natural Capital and Ecosystem Assessment programme to undertake pilot studies of an eDNA approach as a potential means of facilitating forest biodiversity monitoring and increasing the information acquired. Forest Research and Forestry England share a common ambition to increase direct measures of forest species diversity and to move beyond the current reliance on surrogate measures of biodiversity (e.g. indicator species).
One study explored the potential to detect forest mammals from surface soil samples. We set up camera traps in the same area to verify the metabarcoding results. Preliminary results revealed that from a 20-minute soil-sampling effort, eDNA methods detected many mammals frequently observed by the camera traps (e.g. deer, rabbit, hare) as well as some that could not be surveyed using this method (e.g. mole, shrew).
A second study focused on the potential for eDNA to characterise fungal and invertebrate communities in surface organic soil layers across a wide range of forest types and biogeoclimatic zones in England, and explored community associations with forest management intensity. In this study, soil surface layer fungal and invertebrate species identified by eDNA reflected expected community collections for the range of forest types sampled. For example, stands of only Sitka spruce did not contain invertebrate species that are sensitive to the low soil pH (e.g. earthworms, woodlice) that typically develops under a bed of spruce needles. Nematode community composition also reflected the frequent disturbances to soils that occur in this intensively managed forest type. The pilot studies, now being written up for publication, confirm the potential of soil eDNA to provide affordable, accurate biodiversity assessments for use in establishing baselines, conducting surveillance, and monitoring recovery and responses.
Forest Research has been responding to new outbreaks of pests and pathogens discovered in 2021. In June, the eight-toothed spruce bark beetle (Ips typographus) was detected in Kent and East Sussex, while in September the pathogen Phytophthora pluvialis was found for the first time in England, subsequently being identified in Wales and Scotland.
Work on Ips typographus has focused on understanding how these new introductions of the beetle have occurred following a previous finding (which prompted an eradication programme) in 2018. In collaboration with Aberystwyth University, we have carried out pheromone trap studies and molecular research that have provided robust evidence that the new incursions have come from dispersal across the English Channel. Research is under way to investigate the susceptibility of Sitka spruce as a host; Sitka spruce is not a native host for Ips butas our primary forestry species, it is being tested to inform eradication plans in case the pest were to become more widely established. The eradication methods in the Forestry Commission’s Ips Contingency Plan are also being evaluated to confirm that the tools and approaches needed to respond to future incursions are in place and effective. Forest Research is in a unique position to test whether the protocols in our contingency plans are fit for purpose while ensuring that the goals of the eradication programme are met. Research into Ips typographus will better prepare the government and forestry sector to deal with any further incursions of this species, as well as inform plans for dealing with our most serious forestry pest threats.
A diseased stand of western hemlock was detected by the Forestry Commission on a site in Cornwall in September 2021. Decline symptoms were found on mature trees and the naturally regenerated understorey, and Forest Research was sent samples for diagnosis. We found Phytophthora pluvialis from resinous cankers in the branches of diseased trees. This is the first report of the pathogen in the UK and in Europe. It is also the first report of these symptoms on western hemlock. Phytophthora pluvialis was originally reported in Oregon, USA, in 2013 and in New Zealand in 2014. In these countries, Douglas fir, tanoak and several pine species (in particular radiata pine) are susceptible to the pathogen and it causes needle cast, shoot dieback, and occasionally lesions on the stem, branches and roots. It is mainly considered a foliar pathogen. Western hemlock had not been identified previously as a host and the symptoms observed have not been seen before. Pathogenicity tests are ongoing to prove that P. pluvialis is responsible for the symptoms observed in western hemlock.
To investigate the biology and life cycle of the pathogen, we are undertaking monitoring of infected trees, rainwater traps and stream baiting. We have introduced two new real-time molecular diagnostic methods to ensure that P. pluvialis is detected reliably. Following the discovery of P. pluvialis in Cornwall, official surveillance in the UK has identified the pathogen in Scotland, Wales and on a number of sites in England. The pathogen has also been detected on Douglas fir growing among infected western hemlock. We are continuing to test samples from the outbreak and over 600 samples were processed in 2021. A research programme has been developed and collaborations with colleagues in the UK, USA and New Zealand have been initiated to investigate the origin of P. pluvialis in the UK, and to understand the potential impact of this pathogen for UK forestry.
Phytophthora ramorum has the potential to cause significant damage to the natural environment. Larch trees, which are widely grown in the UK for timber, are particularly susceptible to infection. Intervention and control of the disease focuses on minimising its spread by felling infected trees. For this to be most effective, it is imperative that action is taken swiftly and regular surveillance of high-risk larch sites is carried out. Therefore, having up-to-date and complete information of larch locations is highly valuable to enable effective surveys.
Between April and September 2021, Forest Research partnered with tree health practitioners across Natural Resources Wales, the Welsh Government, Scottish Forestry and the Forestry Commission to explore the potential of identifying larch using satellite imagery. This method can be difficult, as variation between species is often masked by environmental conditions, such as meteorological and atmospheric effects. As a deciduous conifer, larch changes colour seasonally, flushing a lime green in spring and a burnt orange in autumn. Our species mapping approach focused on this seasonal variation. A series of satellite images were captured in spring and autumn to enable us to develop a mapping approach that uses this seasonal change to identify likely larch stand locations. We also used control sites identified by forestry experts. We hosted a workshop for tree health teams working across England, Scotland and Wales to identify larch surveying needs and then developed a series of larch likelihood or ‘heat’ map products, with product type and presentation informed by the workshop.
The larch maps produced this year will be field-tested by tree health teams in spring 2022 for practices such as targeting surveying paths. We continue to develop and improve the larch map products, working with our partners to ‘package’ the larch likelihood data in distinct ways for different uses and landscapes. During development, we recognised the potential to identify changes in tree health and further target surveying. We plan to explore this further with partners in a ‘phase 2’ of this work.
Invasive pathogens present a significant threat to the UK forestry industry, most notably the killing of larches by Phytophthora ramorum and severe damage to pines caused by the needle cast pathogen Dothistroma septosporum. These epidemics highlight the risks of over-reliance on a narrow range of plantation forestry tree species.
In the past 10 years, research trials have been established to assess alternative forestry species that have an overseas origin, but which might be suitable for production forestry in the UK. Key to their suitability will be the extent to which these species remain resilient when exposed to endemic pathogens present in the UK. One study investigated pathogen impacts at two replicated trial sites: one in the Scottish Borders and one in Gloucestershire. Health surveys were conducted and analysed by an MSc student from Harper Adams University together with a Forest Research pathologist. Both sites contained between one and three provenances of 14 alternative conifer and broadleaved species, replicated three times in plots of 49 trees. Thirteen trees per plot were scored for a range of health variables. Samples were collected and the causal agents of damage identified using morphological and molecular methods.
All tree species had some form of pathogen damage, with significant impacts of D. septosporum and the shoot pathogen Gremmeniella abietina on exotic radiata pine and maritime pine. In contrast,Weymouth pine, which is native to eastern North America, appeared relatively unaffected. However, this species is highly susceptible to a serious disease known as white pine blister rust. Other pathogens of note included Swiss needle cast of Douglas fir, Sirococcus on Atlas cedar and Pestalotiopsis sp. on Japanese red cedar. We will continue health surveys of other UK trial sites in 2022 to allow a better understanding of the future commercial potential of these alternative forestry species.
As an applied research agency, Forest Research has a unique bridging role between the research community, policy-makers and land managers. Effective knowledge exchange and research impact are critical to our purpose, ensuring our work makes a difference and providing a rationale for our work and the basis of our contracts with key customers. We have developed a new Knowledge Exchange and Impact Strategy covering three broad themes.
The first is stakeholder engagement – to ensure our stakeholders can interact effectively with us and improve the quality, relevance, uptake and impact of our research. We have prepared Knowledge Exchange and Impact Plans for all core-funded projects and programmes, launched a successful new Forest Science Seminar series, and run regular thematic workshops where research findings can be interpreted and their implications discussed with policy colleagues.
The second theme is research capability – to ensure research disciplines and teams work together and have the capacity to deliver high-quality, relevant outputs. We are also collaborating with land managers and the public in our research, through citizen science, reporting pests and diseases, forest monitoring, testing decision-support tools and facilitating networks of practitioners to share insights from innovation.
Finally, evaluation and learning – to elicit feedback from our customers and other stakeholders to monitor, evaluate and communicate our impact, but also to ensure that together we identify and respond to new opportunities to support innovation, resilience and delivery across the sector. We have prepared case studies to highlight our impacts, understand their causes and identify lessons for the future.
Through these actions, we aim to further improve our user experience. Our ambition is to establish and maintain Forest Research’s position at the heart of the forestry and environmental sectors – informing, advising, training, facilitating and collaborating with partners to address the climate and biodiversity crises and other challenges we face together.