woodlandheritage.org

Pro Silva is a European federation of foresters who advocate forest management based on natural processes. The Continuous Cover Forestry Group is affiliated to Pro Silva and usually our Chairman or other representatives of the group attend these conferences.

Our thanks to Woodland Heritage for giving financial help for the three authors to attend this conference.

Nat-Man is a four year research programme looking at Nature-based Management of Beech in Europe with Denmark, Britain, Hungary, Slovenia, Netherlands and Germany as the main partners, plus links and contributions from other countries in Europe.

Fourteen work packages were researched with the aims to deliver policy recommendations and management guidelines based on the scientific axiom that nature based management is a powerful tool in achieving sustainable forest management.

The authors: John Everard, Andy Poore (still waiting for his luggage to arrive), and Rik Pakenham.

This was therefore a joint conference where the first day and a half were occupied with the final reporting of the Nat-Man results, plus workshops to help develop the management guidelines. Two and a half days were then spent out in various forests.

Approximately 80 people attended from 14 different countries split equally between research and practice. This proved a good mix, bringing researchers and foresters together from diverse cultures and backgrounds.

On the whole Denmark is an undulating country with the highest point being 173 metres above sea level. This ‘high spot’ has now been topped by a suspension bridge! With one exception the country is a collection of islands, and the close proximity to the sea has a great impact on the woodlands.

Wind-throw occurs frequently, but the number of frost-free days is high. For most of the broadleaved species found there, Denmark is their northern boundary.

Managed forestry goes back very many years, with regulations for state and private forests dating from about 1670. Although initially greatly influenced by German foresters, forestry in Denmark became very forward-looking in the 20th century, particularly so in the use of crown thinning.

For very many years Beech has been the dominant species, and is now regarded as the national tree’. There is a wide range of native broadleaves including, Oak, Ash, Sycamore, Common Alder, Birch and Hornbeam. In contrast only Juniper is considered to be the only truly native conifer, with Scots Pine having been reintroduced in about 1800. Both Douglas Fir and Sitka Spruce, introduced in the second half of the nineteenth century, grow very well on the right sites, as does Larch.

Transformation of spruce and silver fir, now aged 130 years, started in 1993. Beech groups were planted within a deer fence, and the naturally regenerated conifers are accepted as part of the stand.

The woodlands seen in Denmark have been well managed for many years, with both Oak and Beech producing very high quality timber. At the same time, the woods are well used for public recreation, and today there is a high regard for nature conservation. However, as is the case in many parts of Western Europe, the present very difficult financial situation in the home-grown timber industry is beginning to bite. Considerable changes are being made, with sustainability taking the place of financial returns as the main objective. In the state forests, 22% of all woodlands, it has been decided that ‘close to nature’ forestry will be become the basis of management and that private woodland owners will be encouraged to do likewise. Timber production is still an objective but over the long term native broadleaves, in particular Beech, will replace conifers. This development is partly based on the view that climatic conditions for Norway spruce, the dominant exotic species of the last 100 years, are becoming too warm.

Traditionally forest management in Denmark has been even-aged, with plantation management dominating coniferous stands and shelterwood systems with a short regeneration period or plantation being used in Beech dominated stands. The political decision to move towards Continuous Cover Forestry in the State sector therefore represents a major challenge in changing attitudes and working practice within an organisation where foresters are thin on the ground.

A programme designed to address this has been established by the Danish Centre for Forest, Landscape & Planning. A particularly interesting aspect of this approach is the use of the concept of ‘Forest Development Types’. These are a set of stand structures which might develop on different site types with different sets of species given the application of ‘Close to Nature’ management principles. They are represented as a series of drawings of stands moving from even-aged to an irregular structure in order to be able to convey a visual impression of the transformation process. This was one of the key outputs from the Nat-Man project. A further significant aspect of this approach was the way in which foresters and technicians were involved in the development of these images rather than the simple ‘imposition’ of ideas derived from academic forest research.

Suserup is a semi natural, mixed deciduous forest at the northern side of Lake Tystrup, central Zealand, Denmark. Annual mean temperature is 8ºC and an annual mean precipitation is 635 mm with maximum in July to December. The physiographic setting of Suserup is an undulating elevated plateau to the North and some 10-15% downward slopes toward a lower terrace along the lakeside. The low terrace consists of lacustrine soils, developed through a slow land reclamation process along the lakeside, which is caused by accumulation of organic material, inter mingled with pockets of sediments rich in clay. The elevated parts are mainly developed from glacial calcareous till.

The forest comprises 19.2 ha, and consists of three parts (A, B and C) with different management history. Part A (10.7ha) is dominated by Beech (Fagus sylvatica), but Ash (Fraxinus excelsior) and Elm (Ulmus glabra) are also important species. A model for the dynamics occurring in this part of the forest is described below. Part B (4.9 ha) has a history of grazing and the created open conditions resulted in an Oak-dominated (Quercus robur) canopy layer. Sycamore maple (Acer pseudoplatanus) is most abundant in this part of the forest. Part C (3.7 ha) is situated along the lakeside, and is dominated by Alder (Alnus glutinosa) on the wettest conditions and beech on the more elevated sites.

Suserup is probably the most researched forest in Denmark, with many years of scientific work recording and monitoring taking place including several of the work packages for the Nat-Man project.

During our visit we looked at three specific areas of research: Deadwood resource, gap phased dynamics and visual interpretation of the research data. Because natural processes have been allowed to develop without human interference, a fair volume of both aerial and ground deadwood had accumulated, but how much, what sort and how was it functioning within the forest cycle ? These were some of the questions being researched.

Dead wood is one of the most important habitats for biodiversity. Its functions are water retention which contributes to the microclimate of the forest, nutrient storage, erosion control, habitats for birds, mammals, fungi, insects, bryophytes and plants - all part of the forest’s natural cycle. It is also an important indicator for sustainability.

Transformation of spruce and silver fir, now aged 130 years, started in 1993. Beech groups were planted within a deer fence, and the naturally regenerated conifers are accepted as part of the new stand.

Profile diagram, photo documentation and Silva of a 10x120 m transect. Trees with dbh < 5 cm are not shown in the profile diagram and Silva diagram. Dashed lines link the photo documentation to the hand-drawn profile diagram and the Silva diagrams by pointing out individual trees.

In a natural forest all types and ages of the deadwood cycle are present, and the volume is generally one third of the living volume.

In the 1920s A. S. Watt developed a conceptual model of ‘the forest cycle’ based on his work in British Beechwoods. This describes the phases within the forest cycle and has been renamed for the Suserup model shown here with the average duration of each phase. Gap, Regeneration (Innovation 14 yrs), Building (Aggradation 56 yrs), Mature (Early Biostatic 96 yrs), Ageing (Late Biostatic 108 yrs), Degenerating (Degradation 10 yrs). Therefore the whole cycle takes 284 years. These long-term dynamics prompted by natural disturbances were well illustrated at Suserup showing that a forest, although well rooted, is a kinetic structure, creating an ever evolving mosaic of the various phases of the cycle.

One of the plots interestingly had all the research detritus waiting to be cleared up of wires, pipes, pegs, lines, markers etc. used to monitor light, soil, water, nutrients, canopy features, ground vegetation, tree regeneration and gap closure at canopy level for WP3. The research most importantly extended beyond the gap into the closed canopy surrounding it.

Once monitoring of stand structure is completed, whether it be research or forest management, how does one illustrate the results and share the knowledge with others in an easily understood, visual format ? Computers can do the analysis and produce a visualised image. Photographs can be linked to the numbers, but a third way is for an artist to illustrate the structure. All three methods were shown to many practising foresters in Denmark, and they unanimously chose the artist's illustrations as the best and easiest way to understand and disseminate the information. This would be even more relevant when teaching to students or developing demonstration forests.

Trials of converting conifers to broadleaves have been running for some years in the Klosterheden District, in the most westerly part of Jutland, north-west Denmark. Of the total area of 20,000 hectares, 12,000 is forest, with the first purchase, of the poor heathland, being in 1880. The earliest plantings were of pioneer species, in particular Mountain Pine. Later, other species, in particular European Larch and Scots Pine were planted in the shelter of the Mountain Pine, so that by 1924 some 7000 hectares had been planted. Later still, more species, including Douglas Fir, Sitka Spruce, Silver Fir, were tried. Broadleaves were considered unsuitable, other than Oak on the better soils. Today, conifers total 78% of the woodland, but this is gradually changing in favour of broadleaves, in particular, Beech.

Roe and red deer are commonplace. Shooting is an important source of income, and visitors to the forest are very pleased to see the deer. It is therefore necessary to fence all areas being regenerated. There was considerable support from the public when it was proposed to re-introduce beavers, and 34 young have been born over the past four years.

The two main silvicultural systems tried over the last fifteen years are Group Shelterwood and Target Diameter Fellings, both of which have been successful. Of the two, Target Diameter Felling seemed to be favoured by the majority of the visiting Pro Silva foresters. A target diameter of about 60cm diameter at breast height (dbh) was generally preferred, but the problems are arising where sawmills restrict their demands to small diameter logs. Conversion should start at a relatively early age if a good range of size and age classes is to be obtained.

Where opening the stand groups are preferred, 50m by 25m or thereabouts seemed to be preferred coup size, with the narrow face pointing towards the prevailing wind. It was suggested that rather than extending such groups, it is preferable to start new ones. There seemed to be general agreement that in future the silvicultural system should be simple, as the trees to be cut would be selected by the harvester operator.

Where conifers were going to be converted to broadleaves, trials of sowing Beech seed within the stand have, after three years, been successful. The following points were made.

1. The stand should not be opened too much before sowing, otherwise grass will come in strongly.

2. Sow dry pre-treated seed in late April to early May.

3. The system has been used successfully with Oak, Beech and Douglas Fir.

It was interesting to learn that the Jay is a protected bird in Denmark, and as a result Oak seedlings occur scattered throughout the woods.

Grydebjerg Forest is part of the estate owned by the Sorø Academy Trust situated in central Zealand on the western side of the town of Sorø.

The Trust is a private commercial trust, whose main objective is to run the Sorø Academy’s School as well as to fulfill its obligations as owner of Sorø Monastery. It is managed by a board of Directors consisting of five persons; their areas of expertise are agriculture, general commerce and the law.

The stands were in the highest Danish beech quality classes despite relatively low rainfall of 600 mm per year and had produced high quality beech for specialised markets, including Japan. Under these market conditions top quality timber commanded almost 5 times the value of the 3rd class and attained these prices at relatively small diameters of 45 cm plus. Currently low prices have lead to a reduction in harvesting. Concerns were expressed by the managers that ‘close to nature’ forestry would lead to larger dimensions being grown which were seen to economically less advantageous and with a greater potential for red-heart, the severe discolouration which affects beech in Europe.

During the conference Roger Cook raised considerable interest in the problem of grey squirrels in the UK, also Ireland, Italy and probably soon Switzerland. His literature was quickly taken up, and many more foresters throughout Europe are now aware of the possible damage they too might face.