Findings and Recommendations

There are three reports describing the work and they can be found here. The first two documents are the full report and appendices; the third document is a summary of the work and includes suggested priorities for future research.

There are five main reasons why this work is important:

1. Diversifying the species composition of our forests is a pragmatic way to develop the resilience of the forests throughout the United Kingdom.
2. This study is the first analysis of species diversity of the Public Forest Estate to be published since the formation of the Forestry Commission in 1919.  The analysis focussed on the 20 most common species and, importantly, considered present and future climates.
3. The analysis divides the country into four climate regions (cold-wet; cool-wet; cool-humid and warm-dry) and quantifies that species diversity is much lower in the cold-wet and cool-wet regions, which account for 44% of the area.
4. The report suggests there are two main ways to increase species diversity: (1) use a substitute species from the 20 considered in the analysis or (2) consider another species, which we know less about (i.e. the Emerging Species*). To give one example, based on climate factors Table 3 (of the summary and main report) can be used as a guide to substitution within each climate region. This shows that in the cold-wet region there are six of the 20 species that could be considered as substitutes for Sitka spruce. Of these six species four currently have restricted use because of pest and disease problems and the list is probably much more restricted if site and soil factors are also considered.  A key question for our work is: how many of the Emerging Species* could be considered to increase the available choice?
5. The effects of climate change by 2050 will shift much of the Public Forest Estate to the next warmest temperature zone, hence areas in the cold zone move into the cool zone and much of those in the cool zone shift into the warm zone. The present warm zone also shifts into a new zone for Britain, very warm, and by 2050 this could cover 10-33% of the area.  This is a real challenge for forestry in the warm-dry region and research on species choice for this novel climate should be a priority.

The report identifies three main priorities for research on species and provenance:

1. Identification of species that can be used to diversify forests in the cold-wet and cool-wet regions; specifically, alternatives for Sitka spruce.
2. Evaluate new species and provenances for the warmer climates that will be found throughout Britain with the priority focus being sites that will shift into the very warm zone.
3. Ensure that pests and disease susceptibilities and limitations are considered for all species as well as their silvicultural deployment.

Forest Research will be taking this work forward using a combination of the following methods:

• Evaluation of experience of using all species present in British forests.
• Monitoring the growth and development of trees in arboreta and other tree collections.
• Revisiting existing species and provenance trials established in the period 1950-1980 when there was active establishment of new experiments.
• Matching future climate zones to current climates elsewhere in the world and identifying potential new species with a focus on drought tolerance.
• Establishing new experiments of the most promising species and provenances in selected climate regions.

*Emerging Species – what are they?

In the analysis described in the report tree species were divided into different categories:

Principal tree species are those species where silvicultural knowledge provides confidence to enable successful deployment across Britain. The species are either already widely used or are increasing in usage.  They will continue to be important unless affected by a new pest or disease or become adversely affected by climate change.

Secondary tree species have demonstrated positive silvicultural characteristics in trial plots but gaps in knowledge constrain wider use. The species are being actively evaluated to increase understanding and inform future deployment.

* This is analogous to the third stage of the species introduction process described by MacDonald et al. (1957).

Plot-stage species are a group of species that have demonstrated some positive silvicultural characteristics at the Specimen-stage and are now subject to further testing and development in a limited number of trial plots.

* This is analogous to the second stage of the species introduction process described by MacDonald et al. (1957).

Specimen-stage species are species that have not been trialled for forest potential in experimental plots but have demonstrated, as specimens in tree collections, positive traits of good form, growth rate and hardiness to warrant further testing in plots on a limited scale.

* This is analogous to the first stage of the species introduction process described by MacDonald et al. (1957)

Emerging Species is a collective term used to describe the secondary and plot-stage species.

* Reference

MacDonald, J., Wood, R.F., Edwards, M.V., and Aldhous, J.R. (1957) Exotic forest trees in Great Britain. Forestry Commission Bulletin 30, HMSO, London. [The three stages are described on page 2, paragraph 2]