Impressions made at a ProSilva Ireland Seminar by Prof. Hans-Jürgen Otto
Between the 20th and 22nd of October, 2000, Pro Silva Ireland, the most recently founded national group of Pro Silva Europe, held its first Seminar at Spanish Point, Co. Clare on the Atlantic coast. This group increases the number of countries with ProSilva branches to 23 with around 7000 members.
In the tradition of near to nature groups, where the major points are learnt directly from the existing forests, the Irish seminar was concentrated on excursions. Despite this, a half-day was reserved for presenting papers, to which around 40 forest owners and foresters came. The first initiatives to develop an Irish near to nature forestry were presented. Insights and conclusions for near to nature forestry that have been learnt from true natural and virgin forests were described and the economic advantages as well as possibilities of this system explained.
The Irish forestry industry, along with the British forestry industry, is subject to specific natural restrictions, which are distinctly different to temperate Eastern, Central and Western Europe. It is probably helpful to the development of concepts for ProSilva Ireland to observe this situation from a Pan European view.
So how is Irish forestry to be viewed in regard to near to nature forestry in the European context?
The author, who accepted the invitation to the seminar and returned home with much thought provoking impressions, would like this article to be understood as a small contribution to the development of Pro Silva Ireland. He does that with a feeling of heartfelt gratitude at being so welcomed, over the years, by Irish, Welsh and English foresters and for the varied and very personal hospitality he was given. He is also aware that these impressions are those of an outsider and that many details will need correcting or addition.
As far as was seen the most severe problem for Ireland is the lack of variety of native tree species. This presents a fundamental problem, for one intending to practice near to nature forestry. The low numbers of species, caused by the last Ice Age, is also considered a problem in Central and Western Europe. Already in Great Britain this number of native tree species has fallen, and the post glacial migration of species back across Europe left Ireland with even less. A central or West European forester would find it almost impossible to imagine forest management if he did not have Beech at his disposal.
As a consequence British and Irish foresters in the 20th century have turned to foreign species, in particular species from the Western coast of North America. So today we find large areas of Sitka Spruce plantations and to a lesser degree Douglas Fir. This is no different to other parts of Europe such as Holland, Germany, and Denmark which also suffered extensive deforestation: where pioneer forests were established using robust species on open and often degraded ground. These were national achievements, which should never be underestimated. The question, which should be asked, is if Pioneer Forests are acceptable, if they are healthy, stable and have the capacity to meet our expectations.
Can Pioneer Forests be expected to be acceptable in the future? Are their alternatives? Improvements? Must Pioneer Forests continue to be Pioneer Forests?
Before one can approach this question one must look at another limiting factor. Ireland is a country similar to the West Coast of Britain, which is also affected by wind. This wind has two forms: firstly large storms, which regularly hit these areas with unstoppable force. These storms are more frequent and cause greater damage than in other parts of Western Europe. Of perhaps greater importance is the consistently strong winds. What, along the Danish and German North Sea coast, causes crown deformation through strong winds, results in Ireland, in the impossibility of establishing a forest above a certain altitude. The more one can hide forests in valleys and hollows, to avoid the kinetic energy of the wind, the better. Irish forestry not only has obstacles such as this, but also has a number of advantages. The rainfall is generally between 1000mm and 2000mm, which is more than enough and is well spread out through the year. The climate is particularly mild. Assimilation is possible for conifers throughout the year. Ireland does not experience the limitations of short growth periods, or damage through late and early frosts, no consistently returning droughts, no damage to crowns by snow. The similarities to the lower altitudes along the pacific coast of North America are obvious. The extremely pronounced Atlantic climate is without a doubt an excellent condition for very good growth of forest trees. This is of course also true of other species such as Rhododendron, Bracken and brambles, increasing their invasive and competitive abilities. Rhododendron in particular is a problem, which will prove hard to overcome.
Where and how, can close-to-nature forestry be practiced under these conditions?
Although the large areas of exotic, but fast growing, conifer species should or could not be questioned, the question still remains whether there are alternatives. Must one grow Sitka Spruce or Douglas Fir or can other species provide variety and an increased range of forest products? As far as can be seen, both Common and Pedunculate Oak along with Ash as native species would probably be interesting from a commercial production viewpoint. Up to now they have only attracted marginal interest from the forestry Industry, along with Red Alder, Birch, Mountain Ash and Willow species. Near Killarney a particularly fast growing stand of Yew was found, which shows the potential to become a high value timber producing species in this area. This would be a very interesting area for development in particular in forests with mixed species. A good knowledge of the site conditions and the optimal suitability of the species used in mixture on the sites most suitable to each, would be an important condition for such Silvicultural diversification.
For some Ecologists the question of exotic tree species includes the role of Hemeroby. This is the attempt to define deferent levels of near-natural conditions and human impact. One way to do this is to view the spread of a species, a short distance outside its natural area, as less severe as those species that have traveled further. The reason for this interpretation is the increased risk of various possible ecological links being made. Many life forms have evolved very closely with each other and the environment they occupy. It is presumed that the ecological network of species can develop and exist better when the species is closer to its native area. If one uses this thinking for the situation in Ireland, one must conclude that the post glacial migration of species across Europe is simply could not finish, because the sea blocked the way and also because of mans early and widespread influence on his environment. If we look at the climatic and site conditions we must ask why Beech, Sycamore and Silver Fir should not be grown in Ireland? If we add to the autecological suitability the concept of Hemeroby, then it would be acceptable to suggest that by planting these species we would only be helping to conclude the post-glacial migration of these species. From a purely ecological view this would be even more acceptable as these species would fit in synecologically more easily as they would be just a short distance from the native area in comparison to exotic species taken from distant parts of the world. Not only European species would be of interest. In County Kerry impressive Thuja plicata and Chamaecyparis lawsoniana were seen by the author, along with very fast growing stand of Abies procera seen at Robert Tottenhams, Mount Callan Tree Farm. Considering the Site conditions one must also think of Abies amabilis (Pacific silver fir).
It should be endeavored to practice close-to-nature forestry, to manage according to site conditions and where possible with native species to that site, to create or maintain mixture, to improve or maintain forest structure, to replace clearfell with the harvesting of large individual trees and groups of trees and to regenerate naturally.
In the Sitka plantations at Mount Callan, they have already begun to identify and encourage the best trees and tree groups through frequent thinning with careful attention to the crowns. Through this the trees will form long crowns which will allow the trees to continue to increase in diameter. This lowers the center of gravity, which reduced the leverage effect of the wind. If one concentrates these thinnings on encouraging the most valuable trees, independent of their distribution within the stand, then uneven structures will begin to form. These will become more defined through storm damage. Irregular openings in the canopy form, creating room for natural regeneration. One could imagine planting broadleaf species in groups into these openings: Ash, Sycamore, Red Alder (& Beech??), or accepting naturally regenerating species such as Mountain Ash, Birch & Willow species.
Sitka Spruce forest with vertical and horizontal structures in groups of various sizes, with broadleaf’s in group mixture would be longer lasting, more stable or better prepared to withstand wind-throw and less susceptible to Butt-rot. The water requirements of the stand would be the same either way. Competing vegetation would be continually suppressed. The breaking down of organic matter would be improved. The affects of storms would be reduced due to the finely structured mosaic nature of the forest, and would only ever affect certain sections of the whole area. This would give the whole stand comparatively more stability and increase the ability of large forested areas to recover through regeneration (Resilience). This is the real reason one should work towards highly structured forests. Structures do not have a value in themselves. They are among other things also good to increase bio-diversity!
Would it be a realistic vision to have structured forests of foreign conifers in continual timber production and self regeneration, enriched and broken up with native broadleaf species or broadleaf species from neighbouring Europe, that could fill ecological and/or production functions?
At Mount Callan the first steps toward increasing structure have already been taken through thinning, along with the effects of smaller windthrow holes in stands and these have allowed us to have a glimpse of possible developments in the future. While respecting the huge achievements of the previous generation of foresters in creating pioneer forests, it is up to the present generation to evaluate these concepts in order to improve on what has been handed to them. They, in turn, may pass on a huge achievement to their grand children.