Conference Speakers 2026

Abstract

Reading tree architecture in formative pruning: Identifying future scaffold limbs in young trees

Formative pruning is often approached as a practical operation aimed at creating clearance, correcting defects and guiding young trees towards a functional urban form. However, young trees do not all build their crowns in the same way. Their architectural development determines which branches are temporary, which axes remain subordinated, and which branches may later become permanent scaffold limbs.

This presentation links the principles of the European Tree Pruning Standard to a practical morphological reading of young trees. Using the three growth models described in the standard, the presentation explores how different tree species organise their main axis, lateral branches and temporary or persistent forks during early development.

The central question is: which branches are likely to become future scaffold limbs, especially at an undesirable height within the clearance profile? By recognising these potential low scaffold limbs early, arborists can make better decisions about timing, pruning intensity and branch removal. This is particularly important in species where temporary codominance or plagiotropic (more or less horizontal) growth can be misread as a structural defect, leading to unnecessary or poorly timed pruning.

The aim is not to replace existing pruning standards, but to make them more practical by connecting them to tree architecture and developmental stage. Formative pruning should not only shape a tree for its surroundings; it should guide the tree through its natural architectural development with minimal disruption.

Abstract

Structural root adaptations in an ancient holotype Chiranthodendron pentadactylon

In Toluca, Mexico, stands a remarkable specimen of Chiranthodendron pentadactylon (macpalxóchitl or Mexican hand-flower tree) estimated to be over 300 years old. This tree is historically significant, having been studied by Alexander von Humboldt, and it represents the holotype by which the species was originally described.

In recent years, the tree has experienced a decline in vitality due to water stress, adverse environmental conditions and extreme spatial restriction within a densely confined urban setting. Age-related degradation, combined with site-specific mechanical constraints, has significantly compromised its biomechanical stability.

Management interventions by the Mexican Association of Arboriculture and the Municipality of Toluca have included pruning and the installation of structural supports. However, sonic tomography identified a critical loss of structural integrity at the base of the trunk, indicating that the tree is no longer self-supporting. A non-invasive morphophysiological assessment was conducted to investigate internal adaptive responses. The findings suggest the development of a concealed adaptive strategy within the organism, challenging conventional interpretations of structural support in senescent trees.

This presentation will examine these structures through the framework of root wood. The findings will be discussed in relation to contemporary models of tree architecture and morphophysiology, highlighting the adaptive capacity of ageing trees under extreme urban constraints

Abstract

Tree ring allometry, Harry Potter and his magic handsaw

Biophysical laws influence the ability of plants to exchange energy and mass with their external environments, which is influenced by the size and spatiotemporal display of surface area. In turn, energy–mass exchange rates affect plant growth and thus the consumption of resources and plant vitality.

For trees to grow in height there must be an optimised hydraulic network of vessels that maintains hydraulic resistance by adjusting the rate of conduit widening and coalescence. This economises the carbon employed in developing an energy-efficient vascular system that combines transport and diffusive functions. Examination of tree ring allometry shows an inverse relationship between the widening of conduits from tip to base and the tapering of branch volume base to tip.

Jon will share magnified images of stem base core samples of tree ring distribution together with disks of small branch wood and their ring distribution from the same veteran trees. These samples show:

• tree ring allometry and vessel size change throughout the height of the tree
• even very small-diameter branches can be of considerable age with an intricate vessel network
• remarkable proportionality in tree ring profiles between stem base and branch tips and a history of tree vitality

Jon will show how we must ask if such a small diameter branch has been on the tree for decades, why are we cutting it off? How will removal affect the hydraulic system? Can the stress response of epicormic growth replace such a perfectly dimensioned and intricate vessel network in the long term? What are the long-term systemic consequences of the damage to this hydraulic network on the plant and to the fungal communities in the plant?

If we do not know the answers to these questions, why are we cutting off branches and expecting positive results?

Abstract

Trees of the Middle East: Observations on urban ecosystems and adaptation

The modern Middle East combines rapid urban growth with extreme climate conditions. Despite this, landscapes flourish through heavy use of TSE (treated sewerage water) and imported subtropical species. This approach has been used since the 1970s, and many created landscapes are now mature. However, horticulture is rarely recognised as a discipline, arboriculture is only emerging, and maintenance practices remain largely traditional and often inappropriate.

Climate change is intensifying heat, storms and heavy rainfall, with summer temperatures in the UAE often exceeding 50°C. Trees grown with irrigation and limited root space are therefore prone to windthrow and damage, but culturing the landscape as an urban ecosystem could enhance resilience.

Mark’s observations draw on 15 years spent working as an arboricultural consultant in the region, including visits to brownfield sites where many introduced species, left unmanaged, are forming novel (or hybrid) ecosystems without irrigation or intervention. Native trees are often absent from these sites, while many so-called ‘invasive’ ornamental species thrive. Their success suggests a new model for unirrigated, resilient landscapes that function as adapted ecosystems – providing shade, urban heat mitigation, stormwater retention, living soils and even urban productive systems for food or coppicing for mulch production.

Recognising trees as keystone elements of the urban ecosystem – and adopting ecological arboriculture – will play a crucial role in fostering a transformation to environmentally attuned, climate adapted and people-friendly landscapes.

Abstract

Veteran walking willows of Cambridgeshire

This presentation will explore veteran and ancient riparian trees, with a particular focus on willows across Cambridgeshire. It draws on over 20 years of hands-on experience of managing these trees, alongside personal observations.

Coe Fen and Sheep’s Green in Cambridge have been central sites of both management and learning for Kenny, alongside wider observational work along the River Great Ouse and the River Nene. Time spent moving through river corridors by canoe, and across meadowland, has offered him a unique perspective on how these willows grow, adapt and sit within their natural wetland landscape. This experience has led him to consider more unconventional approaches that do not align with the management of climax species, as riparian trees often exhibit a fast, dynamic and sometimes chaotic growth habit that can be difficult to keep pace with.

Abstract

Survival strategies of ancient and veteran trees: Morphophysiological life stage 10

Trees have evolved to cope with the forces of nature – high winds, storms, drought, lightning strikes, gravity – in a variety of different ways. We’ve all seen trees that have broken apart, partially collapsed, lay down or even disintegrated and yet retained a functional, living section which keeps the tree alive. These remarkable examples and the process of ‘tree reorganisation’ can be described and understood using the language of tree morphophysiology.

The morphophysiological life stage model includes stage 10 – 'reconstruction of the tree'. Very few trees ever achieve this but those that do illustrate the varying processes by which trees can persist.

In this presentation Russell and James will describe various stage 10 survival strategies, with examples of how different tree species may tend to favour one strategy or another. This is likely to be useful for anyone considering the condition and management of ancient and other veteran trees (AoVTs), the most ecologically valuable trees any of us will ever deal with.

Nature doesn’t necessarily fit into neat categories but learning the language of crown architecture and morphophysiology provides us with vocabulary and concepts to describe what we observe, allowing us to share that information to build understanding of these remarkable trees. Join Russell and James on a fascinating journey into stage 10 and beyond!

Abstract

Protecting trees and woodlands: Thoughts from across the border

The Planning (Wales) Act 2026 obtained Royal assent in April. Once in force (probably in autumn 2027), this will replace the Town and Country Planning Act 1990 and much other legislation – and will introduce the system that has been in place in England since 2012.

Charles will summarise the new legislation as it relates to the protection of trees and woodlands in Wales, including new Regulations and accompanying guidance, highlighting key changes and explaining how the industry has been involved. He will also consider whether those changes might be desirable in England.

Abstract

A toxic afterlife: Trees and the dead

Humans have always sought meaningful ways to return to the earth. From the hanging coffins of the Philippines and Tibetan sky burials to the sacred, untouched groves of ancient India and traditional Islamic and Jewish shroud burials, diverse cultures have long embraced a natural return to the elements.

Today, a surging 'green burial' movement seeks to revive these nature-connected traditions. However, as arboriculturists, we face a hidden conflict: the human desire to rest beneath a beautiful, mature tree can sometimes kill the very canopy we seek to preserve. Modern conventional burials routinely introduce highly toxic embalming fluids, such as formaldehyde, and non-biodegradable vaults directly into critical root zones. Cremation – often mistakenly viewed as an eco-friendly alternative – produces ashes that are surprisingly harmful to vegetation. Human cremains have an extreme pH of up to 11.8 and sodium levels 2,000 times higher than plants can naturally tolerate.

This presentation explores how we can bridge the gap between honouring the dead and protecting tree health. Alex will share practical arboricultural methods including safe excavation distances based on trunk diameter, hand-digging protocols, radial grave positioning to prevent lateral root severance, and soil amendments to neutralise the toxicity of cremains before scattering.

By blending global cultural wisdom with modern tree care, we can ensure that our memorial landscapes remain thriving, living ecosystems for generations to come.

Abstract

Tree equity, benefits and maintenance in Stirling

Trees are good for neighbourhoods – they provide shade, help with stormwater and make places feel more liveable. But not everyone gets the same benefits. This study takes a closer look at Stirling, comparing neighbourhoods that score high on the Tree Equity Score with those that score low. The goal is to go beyond simply counting trees. Instead, the focus is on understanding what is actually happening with the ecosystem services those trees provide and, importantly, how they are being maintained.

Carla’s research focuses on two main aspects. First, the benefits trees offer – for example, cooling an area, absorbing carbon and managing rainwater. Second, the maintenance they receive. Are trees getting regular pruning and care, or are they mostly dealt with only when they become a problem? It is expected that in neighbourhoods with higher tree equity, trees are healthier, better cared for and provide more benefits. In contrast, in lower-equity areas, the expectation is to find fewer trees, more stressed or struggling trees and a pattern of maintenance that only kicks in when something goes wrong – like roots damaging a pavement or a branch becoming a hazard.

What this study tries to understand is whether this creates a cycle. If neighbourhoods with fewer resources also get less proactive tree care, their trees do not thrive and residents do not receive the same benefits. That means achieving tree equity is not just about planting more trees – it is about making sure trees in every neighbourhood get the ongoing care they need to grow and do their job.

Abstract

After the ambulance leaves: What nobody tells you about workplace incidents

When someone gets seriously hurt at work, it’s a tragedy. Our thoughts rightfully go to them and their families. But what comes next? The regulators arrive. The insurers start asking questions. Does work just resume on Monday, as if nothing happened?

Through frank, occasionally eye-watering, and carefully tasteful case-based discussion, this presentation will gently escort us – willing or otherwise – into the uncomfortable.

We shall bravely consider the unthinkable and the frankly absurd: how does one clean a chipper after someone has gone through it, and how does one return it to service? How should you respond when a lawyer – with a very serious expression – asks whether an arborist ties their own knots? And perhaps most philosophically: when is a person working on the ground not a groundsperson?

We'll wade cheerfully – or at least purposefully – into the regulatory investigations, insurance processes and legal inquiries that descend upon a business following a critical incident. We’ll examine what all of this means for the business owner, their staff, trainers and everyone else suddenly reconsidering their career choices.

Mark’s session will not make these topics easy, but it will make them approachable – the dark side of workplace incidents, with a splash of colour. This presentation is not for the faint-hearted or those with a queasy disposition.

Abstract

The accidental framework: Infrastructure projects as a funding model for veteran tree management

Ancient and veteran trees offer one of the most ecologically complex and irreplaceable habitats in the British landscape, yet their long-term management has consistently suffered from a fundamental problem: the absence of a reliable funding model. Without dedicated resource, trees are missed, survey work goes undone, management is deferred and trees of exceptional habitat value are lost through neglect as well as other, perhaps more obvious, pressures such as development, farming and climate change.

This presentation will explore how a major infrastructure project created the conditions for a significant investment in ancient and veteran tree management across the North Kent landscape, and will make the case for this model to be replicated wherever large-scale development triggers mitigation obligations.

Drawing on the experience of a VETcert-qualified survey team, the presentation will touch on the challenges of applying robust classification criteria within a legislative framework that offers unclear and conflicting guidance. It will show how individual management plans for 900 veteran trees and 500 ‘future’ veteran trees across 17 public and private sites can generate an evidence base that in this case helped contribute to the declaration of the North Kent Woods and Downs National Nature Reserve in May 2025.

The presentation will examine the findings of the survey. It will also address the broader strategic question: how tree officers and consultants can use the planning process to secure funding for veteran tree management that might otherwise remain unresourced.

Ancient and veteran trees cannot be created within any human timeframe. Whilst development has historically been responsible for tree loss, every project that triggers a mitigation obligation is potentially an opportunity to secure the future of these trees. This presentation will argue that seizing those opportunities is not just good practice. It is a professional responsibility.

Abstract

Creating bat roosts in trees

Fourteen of the UK's 18 bat species live in trees, with some species spending all year in them. Due to their complex ecology, a colony of tree-roosting bats may use up to 50 trees across the year. However, tree habitats don't last forever; trees or their features eventually fall. The longevity of tree-dwelling bats therefore requires a constant supply of new roost sites.

Historically, options for tree roost mitigation have been limited to bat boxes and habitat translocation. However, these are short-term fixes and not without limitations.

Can targeted damage to trees provide an alternative solution to this problem?

Abstract

Crown restoration of heavily mutilated urban trees as an alternative to replacement planting

Veteran urban trees are rapidly declining across many Romanian cities, a trend largely driven by repeated cycles of severe pruning and crown mutilation. When these trees eventually deteriorate, the default response is removal and replacement – yet this approach overlooks a fundamental ecological reality: no newly planted tree can immediately replicate the habitat complexity, microclimate regulation or ecosystem services provided by a mature specimen.

In his presentation Ioan will explore practical and evidence-informed strategies for the restoration of heavily damaged urban tree crowns, situating them within a broader framework of urban biodiversity conservation. Mature and veteran trees serve as irreplaceable ecological anchors – supporting populations of cavity-nesting birds, saproxylic beetles, lichens, fungi and a wide range of other organisms that depend entirely on the structural complexity found only in older trees. Once lost, this habitat continuity cannot be rapidly re-established through replacement planting alone, regardless of species selection or aftercare investment.

Drawing on field examples from Romanian urban landscapes, Ioan’s presentation will demonstrate how crown restoration – where biologically justified and structurally feasible – can meaningfully extend the functional lifespan of compromised trees. It will also challenge prevailing tree management cultures that default to removal, advocating instead for ecologically informed decision-making frameworks that weigh the long-term biodiversity value of retention against the short-term appeal of replacement.

Arboricultural practitioners, urban foresters and municipal decision-makers are encouraged to reconsider the ecological cost of losing mature trees, and to recognise crown restoration as a legitimate, valuable tool within the urban tree management toolkit.

Abstract

Cauterizing pruning cuts and tree wounds: Traditional stewardship in modern arboriculture

Indigenous cultures worldwide have used fire as a tool in forest and tree management for millennia. This presentation will explore the application of fire as a tree care technique to naturally accelerate the Compartmentalisation of Decay in Trees (CODIT) process within fire-adapted Quercus species.

Sprout’s study implements traditional practices through the controlled application of fire using a handheld blowtorch to cauterise pruning cuts and injuries. Thermal cauterisation has demonstrated significant benefits, including the reduction of microorganism and fungal colonisation, improved wound closure and accelerated response wood development at the reaction zone. By blackening but not charring key tissue layers, including the phloem and cambium, burning pruning cuts stimulated the specialised cells in the branch collar, promoting rapid wound closure. Cauterised wounds exhibited significant callus formation, achieving full closure within 2–3 years, depending on soil health and tree vitality. In contrast, untreated wounds exhibited minimal response growth and a substantially higher susceptibility to fungal colonisation.

These findings highlight thermal cauterisation as a sustainable, chemical-free alternative for managing tree wounds, particularly in fire-adapted ecosystems.

By integrating Indigenous cultural practices with modern arboricultural research, this approach offers an innovative solution for mitigating pathogens, enhancing tree health and reinforcing the ecological resilience of fire-prone landscapes.

Abstract

LIFE CoolCity project: AI and remote sensing for evidence-based urban forestry

Urban forests are key elements of urban climate adaptation, addressing impacts such as urban heat islands, extreme rainfall and increasing thermal stress. However, they are also affected by climate change, and their effective management is often hindered by fragmented data and a lack of integrated spatial analyses.

During the workshop, Aleksandra will introduce a multi-scale framework developed within the LifeCoolCity project (since 2023, in partnership with Wrocław City Hall; co-financed by the EU LIFE programme), demonstrating how integrating satellite imagery, high-resolution hyperspectral aerial data and LiDAR – processed using machine learning – can transform raw geodata into practical tools for arboriculture.

The methodology focuses on five key components shaping a city’s adaptive capacity: surface sealing, thermal conditions, hydrological conditions, vegetation condition and biodiversity. In Wrocław, the outputs include a range of spatial products, among them a detailed crown canopy map and biodiversity map for consistent assessment of the city’s vegetation structure, distribution and condition. The system extracts detailed measurements for each tree, including canopy area and volume, estimated trunk diameter, height and classification across 52 classes. Furthermore, the crown health map allows managers to assess crown vigour and hydration levels remotely.

The framework provides a decision support system that identifies ‘hotspots’ – priority areas where interventions, such as planting or enhanced maintenance, can deliver the greatest cooling and hydrological benefits. This will enable data-driven prioritisation of care, including targeted mulching or watering of trees under stress.

Such an approach should empower urban managers to shift from reactive maintenance to evidence-based, strategic management, ensuring that both urban forests and individual trees are optimised to meet the urgent challenges posed by climate change.

Workshop participants will have a chance to test different CoolCity products on their own laptops, compare their potential, as well as limitations, and discuss them.