Research highlights 2016-2017

During 2016–17 staff from Forest Research have made important contributions to studies ranging from measuring forest canopy cover to monitoring pests and diseases. Some of the highlights are described below and further information is available on this website.

 

Estimating changes in woodland canopy cover

LOOKING UP INTO THE CROWNS OF SILVER BIRCH TREES. AUTUMN. LOCHABER FDIn April 2016, Forest Research took on responsibility for the National Forest Inventory (NFI), a programme that monitors woodland and trees within Great Britain. In August 2016 we produced an NFI report providing preliminary estimates of the changes in canopy cover in British woodlands between 2006 and 2015. As well as reporting net changes in canopy cover, this report, for the first time, separately identified gains and losses in canopy cover, which provide us with a much more detailed picture of what is happening to British woods.

Canopy cover is a subset of woodland area and excludes recently clearfelled and newly replanted sites. Changes in canopy cover can be permanent or temporary in nature and it is important to recognise and distinguish between these. Temporary changes in canopy cover arise from sustainable forest management practices where restocking follows clearfelling and natural events such as windblow. Permanent changes in canopy cover or type of cover result from converting woodland to other land uses such as built developments, restoring open habitat and creating new native broadleaved woodlands. Changes in the levels of canopy cover are complex, interrelated and take place over a number of years.

Britain’s woodlands have been going through a period of restructuring and diversification. As the plantations created in the 20th century came to maturity and were clearfelled, the opportunity has been taken to adjust the balance between conifer and broadleaved species and open habitats. Taken alongside a broadening of forest management objectives and evolving forest management practices, the rate and type of canopy cover change has increased in recent years.

The process of producing the 2016 report used the 2006 NFI woodland map as a base (which shows the extent of woodland of over 0.5 hectare throughout Britain, and which was created from the interpretation of aerial photography). Changes in canopy cover were identified and quantified from satellite imagery from 2006, 2009, 2011, 2012, 2014 and 2015. This was supported by a network of 15,000 field sample assessments carried out between 2009 and 2015.

Highlighting risks and impacts of climate change on forestry

Forest Research led the forestry sector input for two important climate change publications in 2016. The publications were an independent report to government called the UK climate change risk assessment 2017 evidence report and the Living With Environmental Change (LWEC) Agriculture and forestry climate change impacts report card 2016.

The evidence report reviews and summarises the main risks and opportunities for the UK from climate change. It identifies priority risks where there is a need for more coordinated action within the next five years, including extreme weather, water shortages and risks to soils and biodiversity. The report also highlights the need to assess the threats from new and emerging pests and diseases, and invasive non-native species. The report was used by government to inform the second UK climate change risk assessment published in January 2017.

The LWEC report card summarises for a more general audience the evidence of how climate change is affecting and is likely to impact agriculture and forestry in the UK. The report card was supported by several detailed reviews written by scientists at Forest Research. The card assesses the level of scientific confidence in the predictions and, in the section on forestry, changes in biodiversity and changes in timber yield potential in the next 20–30 years are picked out as being very probable (yield is likely to increase in the cooler, wetter uplands of the UK but, in areas or for species that are sensitive to drought, there will be reduced growth).

Forest Research is continuing to investigate the risks, opportunities and impacts of our changing climate for the forestry sector and to develop evidence and advice that will help policymakers and land managers as they adapt to the changing climate. For example, through our work with ClimateXChange we are supporting the Scottish Government as it develops and implements policies to help Scotland adapt to the changing climate.

Early detection of tree health

Observatree volunteerMany of the benefits that society derives from woods and forests depend upon the health of the trees. Studying tree health and helping trees become more resilient to many threats – including climate extremes – are important parts of Forest Research’s work. Recently, attention has focused on the unwelcome increase in outbreaks of new pests and diseases arriving through pathways involving plant movements.

Early detection gives the best possible chance of eradication and control. This requires maximising the number of people seeking to detect the organisms as well as improved diagnostics. Our tree health specialists have been engaged in many events to raise awareness amongst those working in the woodland sector and wider publics. Training has been provided to volunteers in the collaborative citizen science project Observatree, supported by a new set of field identification guides. Refinements to our online portal TreeAlert, our preferred reporting mechanism, also help respondents provide essential diagnostic information.

Enquiries to our Tree Health Diagnostic and Advisory Service have increased substantially in the past year. Reports in the nine months to 31 December 2016 were a third more than in the whole year 2015–16. Half of these reports came via TreeAlert, resulting in a noticeable improvement in data quality. The top host tree in the reports was ash (associated with concerns over ash dieback) and the second was cedar (due to the high incidence of Sirococcus blight).

The reporting led to early identification of, and action to control, a quarantine pathogen Cryphonectria parasitica (which causes chestnut blight), as well as several other unwanted organisms. Our briefings help inform decisions over appropriate actions and, by sharing understanding with colleagues in the UK and overseas, also help preparedness. We have participated in a number of technical workshops and led a diagnostic training event on the bacterium Xylella fastidiosa, organised in collaboration with SASA (Science and Advice for Scottish Agriculture) with funding from Defra.

The reports and detections also provide material for further research to understand the mode of action, life cycle and extent of new threats, and for the development of management or eradication strategies.

Remote monitoring of forest decline

Climatic change and trade have increased the number of pests and diseases threatening forests in Britain, and monitoring methods need to be timely and cost-effective to allow for effective management practices. Therefore, Forest Research set up a research programme to look at the use of earth observation techniques such as aerial or satellite imagery to detect early stress in trees which can then be investigated further on the ground.

The programme is focused on three main areas of work.

The first of these is using thermal sensor imagery to monitor stomata activity. Stomata are the organs in the leaf that exchange water and carbon dioxide with the atmosphere. When plants are under stress they close their stomata earlier and this leads to less water loss and an increase in temperature. Work started with the EU-funded THERMOLiDAR project in 2013, and Forest Research has developed a model linking the imagery and tree stress, which can create a digital map for further investigation. Early but very promising results were presented at the ForestSAT 2016 conference in Santiago, Chile.

Plants under stress also increase the carotenoid composition of their leaves. Carotenoids regulate temperature and in sufficient quantity they lead to orange/red colouring, such as when they naturally increase each autumn. However, smaller increases may not be visible to the naked eye. We have therefore set up experiments with quarantined Japanese larch (Larix kaempferi) seedlings artificially inoculated with the pathogen Phytophthora pseudosyringae – chosen because it creates similar levels of stress to Phytophthora ramorum but its use is not restricted – and are monitoring and calibrating their stress levels using non-visible wavelengths of light such as near and short-wave infrared. These experiments are continuing and we hope later in 2017 to publish results on using remote imagery to provide early detection of anomalous carotenoids as a proxy for plant stress.

Forest Research has also been involved, together with Swansea University and the US Forest Service, in time-series analysis of more than 40 years of Landsat satellite imagery. By processing the Landsat images in the super-computers at Google Earth Engine we can use vegetation indices such as water content and defoliation to identify changes in the vegetation over time. These results can also be used to update the National Forest Inventory data. This work will be supplemented with additional Sentinel-2 satellite earth observation images in 2017.

Partnership working for land management

view of Loch lomondOver the last year, Forest Research has been working as part of a multi-partner project (with Scottish Environment Protection Agency, Forest Enterprise Scotland, Scottish Natural Heritage, Loch Lomond & The Trossachs National Park Authority and the Community Partnership) to trial an approach for developing sustainable and resilient land and water management solutions for Strathard, a rural area in the Loch Lomond & The Trossachs National Park, Scotland.

Within the project ‘Strathard – a landscape to live, work & play’ we collected, collated and analysed detailed local knowledge and information required to model and map opportunities for a number of land management actions, such as flood management. We took account of different stakeholder and local community group views which the partnership has collected through interviews, local events, workshops, an online survey, and an innovative interactive participatory mapping tool called Map-Me. Alongside this, we modelled ecosystem condition and ecosystem service provision, using recognised international criteria.

The modelled outputs were combined and used to target areas for priority management actions. For example, we identified candidate sites for natural flood management measures, such as leaky woody dams and flood storage areas. The modelling enables us to combine local knowledge and concerns with hydrological models and expert opinion in a quantifiable way. The opportunity maps will help partners and the community better understand catchment processes and where potential measures may be targeted to provide the most benefit to the community. We plan to set up a natural flood management demonstration site and to present the results of our wider analysis to the community via workshops and an online ArcGIS Story Map.

Encouraging tree planting for water quality benefits

PINES BESIDE THE RIVER AFFRIC. FORT AUGUSTUS FD CALEDONIAN FOREST RESERVE.Diffuse pollution from agriculture is a major problem, putting significant pressure on more than 40% of Europe’s river and coastal water bodies. While there is evidence that recent improvements to agricultural practices are helping to improve water quality, changes made are unlikely to be sufficient to meet legal targets for water quality.

There is growing support for the use of tree planting in areas where it can intercept and reduce the flow of diffuse pollutants (such as nitrate, phosphate and pesticides) from agriculture into water. However, the costs to landowners and uncertainty about the effectiveness of tree planting in providing water quality benefits have limited its use.

Since autumn 2016, Forest Research has led the creation of a European-wide network (PESFOR-W) to understand better the impacts of woodlands on water quality and to investigate how ‘payments for ecosystem services’ (PES) schemes can be developed to provide cost-effective solutions. PES schemes are flexible, incentive-based mechanisms that could play an important role in encouraging landowners and managers to plant trees to help improve water quality.

PESFOR-W is drawing on expertise from 37 countries in forestry, agriculture, water and environmental economics to collate case studies and learning from existing ‘woodlands for water’ PES schemes. It is also creating a European-wide network through which such PES schemes can be encouraged, extended and improved, for example by linking existing payment schemes for other ecosystem services such as carbon storage.

Forest Research is leading the work to assess the effectiveness of woodland creation measures to reduce diffuse pollution and to provide a methodology and guidance on the data and models that will inform assessments of the cost-effectiveness of woodlands for water PES schemes. We are also considering the possible wider impacts of tree planting on water resources, particularly the ability of woodland creation to affect water use and storage, and how these might be influenced by climate change.

Studying effect of afforestation on soil carbon sequestration

Growing trees can help to mitigate climate change by sequestering carbon not only in the wood, but also in soil, making a significant contribution to meeting the UK Government’s greenhouse gas emission reduction targets. However, different soil types have different properties and levels of carbon, and respond differently to forest establishment. As a result, more information is needed to know where best to focus efforts on future afforestation for carbon balance purposes, and to shape policies that support woodland creation targets.

To date, there are insufficient measurements to be able to confidently quantify the soil carbon changes during past afforestation and subsequent forest rotations, partly because of the difficulties of detecting relatively slow changes in heterogeneous soils. Measurements during the whole life span of forest ecosystems are usually not possible, so quantification of carbon storage changes following afforestation is often carried out using a chronosequence approach (studying forests of different ages and rotations).

Over the past year, soil scientists at Forest Research have been carrying out soil carbon measurements across two large forest chronosequences on mineral-heavy clay soils under oaks (Quercus robur) at Alice Holt in Surrey and on organo-mineral soils under Sitka spruce (Picea sitchensis) at Kielder Forest, Northumberland. Combined with an assessment of soil carbon stocks from the previous land use, these studies have quantified the effects of changing the land use to forestry.

The study on mineral soils confirmed the positive increase of soil carbon under forest over approximately 200 years. Meanwhile the evidence from the study conducted on upland peaty gley soils under Sitka spruce suggested that afforestation over approximately 100 years (two rotations) conducted according to sustainable forestry principles will not have a negative impact on overall soil carbon stocks. A separate, longer-term study is underway at Llyn Brianne in Wales to check the impact of recent conifer harvesting and subsequent restocking on soil carbon.

Forest Research has also commissioned collaborative projects with Cranfield University and the James Hutton Institute on resampling the soils at sites from the English, Welsh and Scottish soil surveys which changed land use to forestry over the last 30–40 years. The results of these two projects are available online and provide further insights into the sequestration potential of woodland soils.