Wessex Silvicultural Group: Field Meeting Notes
2014 Study ‘Alternative Species in Situ’

Meeting 3: Species Diversification in Adapting to Climate Change

July’s field meeting of the WSG took place at two sites across the New Forest. Forestry Commission Operations Manager Richard Everett led the morning’s visit to Ringwood Forest, where a national trial is underway to look at the potential of several confer species in a changing climate. Vernon Stockton, Nursery Manager from the Forestry Commissions’ Delamere Nursery highlighted some of the challenges faced in supplying suitable stock in light of climate change. The afternoons visit to Bolderwood Arboretum allowed the group to examine and discuss a range of climate-change adapted species.

Morning Session

Ringwood Forest

The trial site at Ringwood Forest is composed of ten different conifer species, planted between 2013 and 2014. Covering 4ha, the site is well drained and has a fairly poor podzol soil type, with a summer rainfall of 319mm and a winter rainfall of 363mm. Prior to planting the site was mulched and lightly scarified. Around 1000 trees of each species were planted, which included Douglas fir, grand fir, western red cedar, cost redwood, wellingtonia, Atlas cedar, Japanese red cedar, Macedonian pine and maritime pine.

Macedonian pine Pinus peuce

One of the most promising species for the future, Macedonian pine suits our changing climate and is resistant to Dothistroma. However, this species has proved hard to grow in the nursery and is slow to establish (taking 2-3 years). This may be due to transplant shock and/or the fact that young trees initially invest heavily in root development. Establishment on weedy sites can be a particular problem, meaning the cost of weed control for several seasons must be factored into management planning. We may simply have to accept the fact that establishment rates of Macedonian pine may not match those of Corsican and Scots pine. There are currently few mature stands of Macedonian pine in the UK, so seed cone production is restricted. The silvicultural requirements of this species raised questions amongst the group as to the financial implications/profitability of its use.

Japanese red cedar Cryptomeria japonica

Young Japanese red cedar trees at the site are performing poorly, showing yellowing which is attributed to lack of moisture.

Atlas cedar Cedrus atlantica

A light demanding species which tolerates exposure, produces good rates of growth and good quality timber. Young trees at Ringwood are performing well, possibly due to the extremely high quality of planting stock. Established stands should be looked at to inform future silvicultural techniques (e.g. site at Queen Elizabeth Country Park).

Wellingtonia Sequoiadendron giganteum

In a sheltered corner of the Ringwood site, the wellingtonia plot is performing very well, showing 100% take. This species is not tolerant of exposed sites, and can often be difficult to establish both in the nursery and planting site. Wellingtonia appears to perform better in shaded conditions, and there is scope to use it as an underplanting species.

Maritime pine Pinus pinaster

A species which seems relatively easy to grow, but with which desirable growth rates can difficult to achieve (either very fast or very slow) and form can be unbalanced. This may be a good choice as a beat up species to increase diversification.

As with any potential future forestry species, a range of provenances will need to be trialed. Species and provenances must be able to tolerate extremes of weather to suit our changing climate. However, we need to not only consider species choice, forest structure and its potential to modify the forest environment should also be taken into account. For example, reducing the density of planting stock can increase stand aeration and reduce the incidence of fungal pathogens, while natural regeneration performs better on northern-facing slopes and in the understory of existing crops (where it is protected from desiccation). In keeping with this consideration, all species trialed in the open at Ringwood Forest will also be trialed as understorey species.

In establishing successful silvicultural methods for potential new forestry species, it may well be prudent to examine the successional stages represented by such species (i.e. pioneer, later successional). Knowing how species have evolved to succeed in their native environment will enable us to make informed and accurate management decisions.

Afternoon Session

The afternoon session began with a discussion of some of the challenges facing the Forestry Commissions’ Delamere Nursery in supplying suitable stock in light of climate change. First and foremost was the issue of supply and demand – the nursery needs to know what species/provenances foresters want (there is a 3 year lead in time). Currently the situation is reversed whereby the nursery grows particular species/provenances, and then supply foresters with what stock they have. This needs to change, and there needs to be better joined up discussions between supplier and buyer. Other challenges encountered by the nursery include sourcing seed and working with an outdated, labour intensive set-up.

Issues associated with specific potential species are as follows:

During the final part of the day, Recreation Ranger Gemma Stride led a tour of Bolderwood Arboretum. Established in the 1860’s, the arboretum is now host to the National Tree Collection Project, led by Richard Jinks at FR, which aims to record and catalogue specimen trees. Comprising 190 specimen trees, of 45 different species, the arboretum has now committed to an accessions policy which aims to plant rare and endangered trees, and trees that will potentially do well in our future climate. Trees of note visited during the afternoon included firstly a Pacific silver fir Abies amabilis - one of the best specimens in the country, relied on heavily in Japan for plywood production, and grows well in the UK climate. Secondly Serbian spruce Picea omorika – despite producing relatively low timber yields, and responding poorly to thinning, this could potentially be an important, climate-proof species for the future, with low susceptibility to Heterobasidion annosum.

Concluding Remarks

The UK must future-proof its forest resource, by producing more resilient forests. We must look at our pool of best stock and from this plant mixed species and mixed provenance stands. The total funds available to Forest Research stands at £35 million, as figure which represents a serious underspend on forestry by the government when compared to other sectors such as agriculture. Sadly, this situation seems unlikely to change in the near future.

Bearing this in mind, allocating resources to the highest priority research questions is crucial. There is currently an online dialogue process taking place in order to help develop more specific research questions from the recently published Forestry Commission Science and Innovation Strategy. You can input your ideas for the future research commissioned by the Forestry Commission via an on-line forum at http://www.forestry.gov.uk/fcsis.