By Vanessa Burton, Woodland Trust.

​A sunny August midweek found an unusual collection of woodland ecologists, advisers and practitioners coming together in the National Forest. We weren’t the usual clientele for the Deer Barn, which usually hosts weddings or kids for the adventure park (although some of us had to resist the temptation of the huge bouncy slide). The aim: to share knowledge around integrating more natural processes into woodland creation practice, and all made possible by a collaboration between the Woodland Trust conservation training programme, the TreE PlaNat research project and the National Forest.

This two-day knowledge exchange and training event aimed to: 

• disseminate the latest evidence from the TreE PlaNat (and other relevant) research projects 

• enable practitioners and advisers to network and share knowledge, and  

• develop the latest in a series of woodland creation training events run by the Woodland Trust across the UK

We kicked off hearing from Elisa Fuentes-Montemayor, TreE PlaNat’s principal investigator, about the learnings from the long-term natural experiment, WrEN, or “Woodland creation and Ecological Networks” which has been running since 2013. This project has set up a replicated chronology of woodland creation sites in Scotland and England and has carried out numerous field surveys on these sites over time.  ​

The WrEN project has given us a great understanding about how planted woodland creation sites develop over time. We know that habitat development is slow, and that it takes from 80-160 years for characteristics similar to that of an ancient woodland to develop. Most sites also show a significant lack of natural regeneration in the understory. In terms of biodiversity outcomes, creating new woodland adjacent to existing ones (i.e. close proximity) is really beneficial for several taxa including moths, small mammals and plants. We also know that more complex woodland habitat structure (e.g. gaps, fallen trees, variety of tree sizes) is associated with greater abundance and/or diversity in many taxa. 

So, we know a decent amount about planted woodlands - that they can lack some of the features of a ‘good’ habitat, and that it takes a long time for these features to develop. Because of the urgency of the nature and climate crises, there’s therefore a lot of interest in (and expectations of) natural processes such as natural regeneration and natural colonisation, to help us meet national creation targets. It’s often assumed that these processes will create woodlands with more complex structure (therefore benefiting biodiversity) and be more resilient than planted woodlands. 
 
However, as highlighted by Kevin Watts on the day, to date there’s been a limited evidence base for the outcomes of woodland created via natural processes, because of a small number of studies, highly variable results & possible survivorship bias, where results are only reported when they’re positive (i.e. where natural colonisation successfully resulted in a new woodland). We have some limited knowledge about what to expect from recent research (see Bauld et al. 2023), but research gaps remain, and TreE PlaNat has been aiming to fill some of these.  
 
Laura Braunholtz talked the group through some early results from the ecology work package of the project, where new woodland creation sites created by planting, natural colonisation, and a hybrid of the two have been compared. Structure came through as an important variant between the three methods, and often correlated with biodiversity measures. Planted sites were predominantly uniform, while higher ‘gappiness’ in hybrid sites with a mixture of planting and natural colonisation was associated with higher floral species richness and moth species riches & abundance. 
 
If you’re keen to find out more, take a look at Laura’s blog https://www.wren-project.com/tree-planat-blog/notes-from-the-field, Thiago & Sam’s blog on structural measurements of the field sites using LiDAR https://www.wren-project.com/tree-planat-blog/lasering-trees-for-science-how-we-use-lidar-technology-to-understand-woodland-ecology and the ecology webinar https://www.youtube.com/watch?v=cAN-ylzGgWE.  ​

On day two, the groups took pre-prepared woodland creation designs for the site and discussed the appropriate woodland communities (species composition) and method choices for the site, making use of the Woodland Trust Tree Species Handbook. ​

We finished by discussing four possible trajectories for natural colonisation sites that have been highlighted in work by Forest Research. We explored how natural processes might result in: 

1. A woodland community similar to source woodland 
2. Unpalatable vegetation (e.g. bracken, bramble) dominating 
3. A single tree or shrub species dominating 
4. Very few trees establishing at all 

 
The groups had valuable discussions about how to respond in each of these situations. A recurring theme was that good monitoring and adaptive management are essential to respond appropriately, but that these are currently hard to do in practice due to time, resource and guidance limitations. ​

Big thanks to Heather and Simon at the National Forest for hosting us.​

By Laura Braunholtz, University of Stirling

When it comes to new areas of woodland, questions remain about the extent to which the way they are created plays a role in shaping their structure, biodiversity, and functioning. Is it always true that woodlands that are created through planting will have a more homogeneous form and structure compared to naturally colonised ones? Are trees within naturally colonised woodlands more resistant to disease than those in planted areas? Do woodlands formed through different processes provide habitat for the same species of wildlife?
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In trying to answer these questions and more, myself and two field researchers, Megan Layton and Billy Dykes, found ourselves crouched in a thicket of blackthorn under the blazing mid-June sun, tape measures and clipboards in hand. It was unfortunate that the random number generator had directed us to this particular location, but as we quickly learned, in young naturally colonised woodlands you’re never too far from spiky vegetation. This was during the summer of 2023, and our team of three was carrying out the ecological fieldwork for the TreE PlaNat project. We conducted a range of surveys across our study woodlands, involving multiple trips to each site between May and September.

Preparation is key

Getting to the point of carrying out the surveys had taken considerable preparation. Risk assessments, protocols, purchasing equipment, and, of course, the all-important site selection process. Selecting the woodlands that made up our study locations involved months of reviewing the long list of potential sites, poring over maps and satellite images, consulting Woodland Grant Scheme datasets, comparing notes with colleagues at Forest Research, and the challenge of tracking down landowners and managers to gain permission to carry out our surveys. The resulting list of 28 sites was spread across central and southern England.
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We kept a number of properties consistent across our sites; they were all relatively young woodlands, ranging from 15-30 years old, adjacent to areas of established woodland and on land that had previously been arable or improved grassland. Seven of our woodlands had been planted, nine were sites of natural colonisation, and twelve came under our “mixed” category, having a combination of planting and natural colonisation processes at play. 

Into the wilderness we go

Now we were carrying out our surveys, collecting data on several metrics that we had chosen to represent the structure, ecological function and biodiversity of woodlands.
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This included setting out five 20m diameter plots at each site, within which we were identifying trees, measuring their diameter at breast height (DBH) and counting seedlings and saplings to assess tree biomass and habitat complexity. We also assessed the trees for signs of disease or pests, focusing on those of highest concern (further information: Observatree). We checked a sample of leaves from ten trees in each plot for signs of damage by insect herbivores and recorded the number of seedlings and saplings that had been browsed by mammal herbivores. Using 20 plasticine caterpillars at each site, we quantified predation pressure on insect herbivores.
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To quantify the biodiversity value, we were assessing several different taxonomic groups. In small quadrats, we looked at herbaceous vegetation, poring over keys and guidebooks to identify species of grass, ferns and other flowering plants. We set out camera traps to document sightings of mammal species and placed acoustic recorders in trees to capture the sounds of passing insects, birds and bats. On two different nights during the summer months, two moth traps were set up at each site and Billy had some very early morning starts to check the traps, identify the species within, and release all moths on site. For the final surveys in August, Dr Thiago Silva flew a drone mounted with a LiDAR sensor over all the sites to capture information about the structure of the woodlands.

Data, data, data

Reflecting on the field season now, summer seems a distant past, and November’s short, cold days see me sitting at my laptop writing code to crunch the numbers and try to answer our research questions. We collected an impressive amount of data, measuring over 5000 trees from 36 different species, as well as counting over 1000 seedlings and saplings from 24 tree species. We captured nearly 2500 moths from 398 species and identified over 130 species of herbaceous ground flora. The camera trap and AudioMoth data files are still being processed; soon, we’ll know more about the mammals and bird species using our woodland sites.

Data analysis might not sound as glamorous as frolicking among the trees, but it's the key to understanding the intricate ecological dynamics at play within these ecosystems. Spoiler alert: nature's spreadsheet is a lot messier than Excel.
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Check back soon to find out what we’ve learned!

By Susannah Fleiss, University of Edinburgh

How can landowners try something new, when little information is available? Stimulated by conversations among foresters, farmers, land agents and ecologists, the TreE PlaNat team have put together a number of case studies on woodland creation through natural colonisation to address this issue.

When creating woodland, land managers (such as farmers, foresters, estate owners and their land agents) usually plant trees, designing the planting scheme according to their local context, reasons for creating the woodland, planned uses, and desired species. However, allowing trees to establish through natural processes can create locally-adapted, resilient woodlands, of high biodiversity value [1]. When creating woodland through ‘natural colonisation’, seedlings germinate from local seed sources that arrive at the site naturally, some of which survive and develop into trees. A key difficulty for land managers is that the outcome of this process is not guaranteed: it is very difficult to predict the timeframe it takes to create a closed-canopy woodland, and the species which will colonise the area and survive [2,3,4].

Our project, TreE PlaNat (Treescape Expansion through Planting and Natural colonisation), is examining how, where and for whom natural colonisation might be used to create new woodlands, including in combination with tree planting. As part of this project, researchers at the University of Edinburgh are facilitating a ‘Knowledge User Board’ of land managers, who provide feedback on the research directions and findings, and help guide the project to produce useful outputs for those working on the ground. Early in the project, the group highlighted the importance of having case studies to provide land managers with examples and basic knowledge to consider using natural colonisation to create woodland. In a collaborative effort with the Knowledge User Board, we created a collection of case studies and one-page summary factsheet, available through the Edinburgh Research Archive and the TreE PlaNat website.