Meeting the threat of Climate Change and diseases
Ash - Fraxinus excelsior
It is widely believed that we will lose 90% of all ashes across the UK. Only a small minority have a natural resistance to the Hymenoscyphus fraxineus fungus that arrived around 2004.
Our response to this threat is flexible. When the disease takes hold in Toll Wood, we can leave trees standing unless they threaten users' rights of way (Granny Stile's footpath and Toll Lane). It may be enough, in these circumstances, to only remove branches to leave a stump. This approach allows diseased trees an opportunity to recover (if they can), and help us recognise any trees with resistance (we can but hope!). Dead/rotting trees can still be useful to invertebrates, birds, and fungi. [Objective 4 (p6 of the Ten-year Woodland Management Plan].
Miyawaki planting method and woodland resilience. The answer to Ash Dieback?
As part of our succession-planting for Ash - we may consider this method of VERY close planting of a variety of trees. The species interact and compete until the most suited trees win through. Taking our dry situation with rich soil over chalk, we could plant together - field maple, hornbeam, sessile oak, whitebeam, service tree/wild service tree, copper beech, and aspen. Also blackthorn and hawthorn (which we are building up in the boundary lanting).
Elms - Wych, English, and Field/Smooth-leaved
The case of elm species is more complicated (perhaps more simple!). Elms spread mostly through root suckers (seed is unreliable). This has led to elm species being identical clones. When disease hits one elm, the others of that species are vulnerable to the same diseases. This has led to wholesale felling when disease appears. Ashes do have genetic variety that is worth looking for and promoting in the wild.
Ophiostoma novo-ulmi fungus is spread by elm bark beetles that arrived from Canada in the 1960s. With clones, when disease strikes, the only option is felling. However, that does not mean we give up.
Several 100% DED-resistant hybrids have been bred in Europe that include close genetic parents to our own elms. The most important thing we can do now is to start with succession planting of these new varieties. Decades of poor management of Toll Wood means there are many invasive sycamore that need reduction to open the canopy and allow new elm varieties to become established. Today, the woodland floor is starved of light, water and nutrients. Reducing sycamore in the wood will bring opportunities to plant resistant varieties for future generations to enjoy. Only time will tell whether our rich mixture of trees makes our elms 'invisible' to the elm-bark beetles.
Risks to Toll Wood from DED-resistant elms. One of our greatest concerns is that planting of disease-resistant elms close to stands of native elms (like Toll Wood) risks bringing elm bark beetles close to our own native elm species. Managed woodlands may take this threat into account when making stocking decisions. But individuals may inadvertently create an additional risk to Toll Wood by planting nearby.
Possible Responses. (1) As part of our succession-planting strategy, plant DED-resistant elms inside Toll Wood to retain biodiversity into the future.
(2) Leave any diseased elms standing to see if regeneration takes place. Leave standing stumps for other uses by nature (insects, birds, mammals, fungi).Our current shortlist includes:
- Morfeo Elm - FL 509 - Hybrid [U. chenmoui x [(U. glabra x U. minor) x U. minor]]. Istituto per la Protezione delle Piante, Florence, Italy;
- FL 493 - [[((U. wallichiana x U. minor) x (U. pumila x U. minor)) o.p.] x (U. x hollandica “Vegeta” x U. minor)] o.p. Istituto per la Protezione delle Piante, Florence, Italy;
- Columella - [(U. glabra var Exoniensis x U. wallichiana) x (U. minor 1 x U. minor 28)] selfed. Dorschkamp Research Institute, Wageningen, NL;
- Ulmus laevis - European White Elm - Unpalatable to Scolytus beetle due to Alnulin;
- Ulmus glabra – Wych Elm - Unpalatable to Scolytus beetle due to Alnulin. Already present in Toll Wood.
An alternative approach by Brighton and Hove Council was to introduce annual inoculations. Subsequent felling suggests only moderate success.
Climate Change and Toll Wood succession planting
Our ten-year Woodland Management Plan (WMP), Appendix 4, lists trees suited to our conditions as climate change bites. Succession-planting is designed to improve resilience into the future. That future promises more violent storms, wetter winters and drier summers.
Toll Wood sits on the dip-slope of the Lyn Valley. Our site is free-draining deep loam on chalk. The Lyn Valley is reputed to have a 'nailbourne'. That underground stream emerges as two springs near Osier Farm and Teynham Levels to the north.
The Forestry Commission and Forest Research are a rich source of expert advice on managing the Climate Emergency. Forest Research has created a Climate Change Hub, that focusses on the impacts of climate change on woodlands. The Royal Horticultural Society (RHS) includes descriptions of species and their tolerance of soil, drought, disease.
