Welsh forestry relies heavily on introduced tree species; what do you consider as the major challenges and opportunities of introduced tree species?
The greatest risk posed by introduced species to Welsh forestry is the overdependence on a small number of species with a heavy concentration of the productive capacity on one introduced conifer species. The opportunity, on the other hand, is that introduced species increase species and genetic diversify creating more resilient and adaptive woodlands to face up to the effects of accelerating climate change. The major challenge is to reconcile short term commercial objectives, that are generally confined to softwood timber production, with longer term sustainability and adaptive strategies incorporating wider forestry outputs.
What are the major drivers or using introduced as opposed to native tree species in Wales?
Major historic deforestation and one of the lowest levels of forest cover in Europe has driven forestry policy in the United Kingdom (UK) to establish new areas of forest. Wales has contributed to the UK strategy and has supplied larges areas of upland forest managed by both the state and the private sectors. Many introduced species are able to withstand high levels of exposure and tend to develop rapidly on sites that may not have supported forest for several thousand years. They have in this way contributed to recreating forest conditions but this has to be weighed up against loss of habitats and potentially biodiversity. Introduced species have become established in spite of the difficult and degraded site conditions, and rapid and concentrated timber production has enabled the timber industry to attract substantial amounts of capital to create a home grown timber industry. Native species have different site requirements and provide different benefits to introduced species in Wales. They struggle to compete within the present framework of the forest industry, however their role must not be ignored and they must be incorporated within integrated forest management practices.
Bearing in mind climate change, do you think the proportion of introduced tree species in Welsh forests will change over time or remain similar?
The effects of climate change may be to reduce the number of species, both native and introduced, as is already happening with attacks of Chalara fraxinea in the native ash, and Phytophthora ramorum in introduced larch. Strategic responses to climate change may mean that a further mix of species is introduced or that foresters may have to deal with the existing mix as intimate mixtures rather than as monocultures.
Do you think introduced tree species can be used in close-to-nature forest management? What is your experience with this?
Introduced species can work extremely well in close-to-nature forest management in Wales. Wales has a small number of native species because of the separation from the continent that halted species migration, so introduced species have provided good opportunities for foresters. Irregular or close-to-nature forest management can quite easily incorporate a range of species without threatening native habitats, which is not the case in even-aged stands or monocultures. Irregular forest management is best for managing natural regeneration that can be perceived as a threat coming from introduced species. Because close-to-nature forest management makes use of silvicultural advantage by harnessing natural processes the forester can modify prescriptions and reduce threats while also allowing stands to be adaptive and respond to changing environmental conditions. Close-to-nature forest management has great potential for integrating the benefits of native and introduced species and minimising threats.
Do you think that invasive potential of introduced tree species in general is considered at the time of their introduction?
The invasive potential was generally ignored or never considered as a threat because the focus of the foresters who established exotic species monocultures was on the single objective of timber production. The invasive nature of some introduced species may have been considered as being useful demonstrating a good site match and ecological fit at the time.
Philippe Morgan BSc FICFor
Wales, United Kingdom
Pro Silva Europe
Association Futaie Irrégulière (AFI)