Tree Care and Management in Wood Pasture & Parkland
Open grown trees are one of the key features in any wood pasture or parkland site, critical to their wildlife value. These trees need special care and management to thrive.
Maintaining existing veteran trees
The wood decay inside veteran and ancient trees is the most valuable resource that wood pasture has to offer. In general, ancient trees should be left alone to gracefully mature into old age. The central wood decay and dead wood in the crown support some of the rarest species so should be kept in the tree.
If you have concerns about public safety of the health of the tree, please get advice from an arboriculturalist who specialises in ancient trees.
Any limbs that fall should be left intact and in place. This wood may already contain valuable fungi and invertebrate larvae, some of which require years in the larval form before they develop into adults. Cutting up this wood would cause it to dry out and hasten the decomposition and limit how long it remains valuable for these invertebrates.
When trees reach a certain point of post maturity, they can go through a process known as retrenchment. This is where the largest, tallest limbs die-off, as the tree can no longer support them, in favour of a lower crown. You will often see trees that have been through retrenchment with ‘stags horn’ deadwood in the crown, indicating where the previous crown height used to be. This dead and decaying wood should be retained within the tree as far as possible. Retrenchment is a natural process and not necessarily indicative of poor health (although poor health, especially compaction around the roots can have a similar effect). With a shorter stature, it is important for the future health of the tree that it is not overcrowded, and if there are numerous trees or tall shrubs around the tree it may be wise to thin these out to reduce the competition for water and light.
If you have any concerns about an ancient or veteran tree please seek specialist advice.
More information about ancient and veteran tree care can be found:
- The Ancient Tree Forum website.
- Natural England’s publication, Veteran Trees: A Guide to Good Management
General tree care
Soil compaction can be caused by heavy footfall, congregating cattle or vehicles and machinery. It can damage tree roots which in turn causes tree health to decline and even limb loss in extreme cases. This is essential to be aware of when planning new tracks, car parks or large events. Vulnerable old trees can be fenced to protect them from grazing damage and soil compaction, and this will in turn protect people from any threat from falling branches.
Deadwood is one of the most valuable parts of any wood pasture or parkland site; an increasingly rare habitat home to increasingly rare and endangered species. Any dead and decaying wood in the canopy of a tree should be left. In cases where this might pose a threat to public health please seek specialist advice.
Open grown trees tend to have large limbs low down on the tree trunk. This structure provides a variety of important niches for wildlife. These lower limbs are sometimes removed for agricultural reasons or machinery access. The removal of lower limbs not only takes away a great habitat, but can reduce the life of the tree. This can make it more top heavy and prone to windfall, and may reduce their capacity to survive into ancientness, where their crowns retrench and they rely on branches lower and closer to the trunk
Tree age structure
While the ancient and veteran trees are undoubtedly the most valuable assets in terms of wildlife on wood pasture and parkland sites, it is just as important to have a good range of tree ages on site. Ancient trees do live a very long time, but they do not live forever so it is important that there is a generation of trees growing on to replace them. This will allow the habitat continuity and suitable habitat for specialist dead and decaying wood species to move to when these ancient trees finally perish.
A range of tree ages is essential to the long term continuity of habitat, something that makes these wood pasture sites so rare and valuable.
In some cases, where a site has too few veteran trees to replace the ancient tree habitats, artificial ‘veteranisation’ could be an option. This process deliberately scars and damages a tree to accelerate the processes that lead to the development of dead and decaying wood and veteran features. This work should only ever be undertaken by a specialist tree surgeon, and only after a comprehensive site survey.
For a good tree age structure there should also always be young trees present. The grazing or mowing regimes of some sites may prevent the natural recruitment of young trees, and if this is the case then you will need to take action. This could be in the form of fencing off an area to naturally regenerate, but may be achieved by planting.
Young planted trees should always be protected from grazers, including wild deer or rabbits. This can be in the form of simple tree guards or with the addition of a tree cage or fence.
Consideration should be put into the species of trees planted. You may wish to consider what trees have been planted there historically, perhaps even use a tree on site as a seed source to preserve some of the genetic diversity of the site. You might also want to consider the threats that the site may face in the near or distant future, such as tree diseases or climate change.
Lichen sensitive management
Continuity of light and humidity conditions is vitally important to the future of established lichen communities as their needs can be very specific. Short-term coppicing rotation management is usually damaging as this will remove ecological niches and alter environmental conditions of light and humidity, and such woods are generally poor in lichens.
Rich lichen communities on rocky outcrops and boulders, particularly important in the south and west and may be dependent on the dappled shade and shelter provided by adjacent trees. Any essential management of trees should consider the loss of niches that may result, and the expert advice of a specialised lichenologist should be sought.
Lichens are highly sensitive to changes in light levels and in particular to increased shade which favours replacement by bryophyte communities.
Local air pollutants e.g. ammonia drift from dairy, chicken and pig units can have a serious impact on the lichen communities present, and can lead to the extinction of species. Industrial and vehicular air pollution may have historically influenced what communities remain, and may still impact on those surviving.
Sensitive extensive grazing levels are needed to keep pasture woodland open with dappled light and glades. Overgrazing will erode or remove species, cause soil compaction around tree roots and localised nutrient enrichment.
The scale of a site and opportunities for expansion of lichen communities is vitally important; fragmentation of sites through development impacts directly on species that are not able to disperse spores over distance. Neighbouring riverine, hedgerow and way-side trees are important links in the continuum of diversity.
Further management advice can be provided by lichen specialists, and the British Lichen Society. http://www.britishlichensociety.org.uk/