| Introduction |
In June 2005 we were extremely grateful to be accepted (as young foresters), for a Woodland Heritage Garthwaite Travel Bursary allowing us to join the RFS East Anglian Division four day tour of lowland Danish forests organised by Edward Brun. The tour focussed on quality hardwood production on four large private estates, but also provided an insight to the increasingly pertinent topic of green energy production by visiting a woodfuel Combined Heat and Power Plant (CHP). This report aims to convey the rich technical discussions held by the diversity of experienced participants including foresters, landscapers, arborists, woodland owners, timber merchants, sawmillers and cabinet makers.
| Denmark - Forest History Past and Present |
To set the scene, Denmark has a population of 5.7 million with a land area one-third the size of England. 2005 is notable as the 200th anniversary of the first forest law, which served to halt the decline in woodland cover standing then at only 4%. This stated that no cattle, or pigs could graze forest land (allowing the return of vital natural regeneration of seedlings) and that no land could revert to other uses (preventing arable conversion or development). The cover now stands at a more healthy 12%, rising 2% in the last 2 years, one-third of which is state owned with the remainder under the control of some 53,000 private owners. Arable land comprises approximately 70% of land area with pasture at approximately 10% giving Denmark the second largest percentage of farming area of the European countries.
The unfortunate historical effect of deforestation is that very little Ancient Semi-Natural Woodland remains with the majority of ancient sites being replanted. Indeed there appears to be little room for wildlife and biodiversity protection in the economic management of the woods. However, the land which has been used for afforestation is, by English definition, far from marginal. It is largely flat and under 30m with a rainfall of 610mm annually making conditions very similar to East Anglia, but with the added advantage of deep loamy soils. Despite the optimal conditions described on each estate the group were repeatedly amazed to hear that the woodland books only break even. High land taxes are the central and overriding constraint to profitable forestry at £30/ha/year making the maintenance of consistent timber markets, good circulation of alternative forest income ideas and key research into timber quality improvement all the more important.
Of the current forest laws, those for public access are of particular interest. Full access is allowed to woods over 5ha (only on recognised tracks) from 6am to dusk, entirely at the user’s risk. Public damage to valuable timber trees can even be claimed from the government by the owner. With the added knowledge that not only the litigation culture, but crucially, grey squirrels, are absent from the country, the tour became an engaging experience and one highly recommended to any lowland forester.
Day 1 (Robin)
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| Castor Plant - Inside plant - talk by Henrik |
We were taken north through the island of Zealand, stopping for an excellent lunch (typical of the superb catering throughout) including salmon, herring, rye breads and Tuborg, at the outer moat of the Fredriksborg Slot at Hillerod, a spectacular brick built castle dating from the 1600s and reminiscent of Russian architecture. Through predominantly conifer forests, including the Grib Skov, we emerged at Graested 5 miles from the north coast and the ‘Castor’ Plant at Greasted.
| Graested Combined Heat and Power Plant |
Our host Henrik Houmann had designed and engineered the very low rise (the size of a small terraced house) industrial plant as a pilot on behalf of ‘Biosynergi Proces ApS’. They hope to develop and market the system, as an exemplar of the potential of combined energy production from wood chip. This particular unit was part funded by the government.
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| Oak Butt (Day 4) - Mikal's monument- Petergaard estate (145cm dbh, 18.5m of clear butt) |
The gasification process which Henrik is mastering, works by super heating the dried wood chips in the combuster (an upright steel cylinder) to produce a flammable vapour just above their surface which in turn burns to produce massive heat of 550°C. Air is jetted into the combuster at several stages to perpetuate the burning and ensure the maximum energy release from the raw material. The hot gases produced are utilised by passing through a series of water jackets (exchangers) to transfer the energy creating 200 kW/hr of heat. The resulting cooled gases are then filtered and mixed with 20% natural gas (principally methane) to produce a combustion fuel for the electricity generator – a torquey 12 litre V8 Deutz running a 90 kW/hr alternator at 1,500 rpm. The process of energy creation and recycling does not stop there as the hot exhaust gases from the engine are used to heat a rotating metal drum which dries the wood chips to the required 15% moisture.
Questions of waste products arose from the group and Henrik revealed a small hopper of pure carbon filtered from the gases which he hoped could be used for charcoal briquettes in future. Even the main chimney gases were pure water vapour from the chip drying. The process of a complete burn had minimised the byproduct of toxic tars.
Issues of chip supply were also answered with haulage distance not exceeding 30 miles. In addition the plant provides a real incentive for local growers to use waste brash wood from harvesting which cannot be left in-situ for practical reasons. Because of the subsidy the plant still receives, Henrik currently pays a generous price to the growers of £9.40 per loose m3 of chip. Some saw the first chink in the long term viability at this point, but my feeling is, given ambitions of a threefold upscale in electrical output within 10 years, that catalytic and progressive thinking of this type has far more to offer.
Day 2 (Robin)
The trip took us to the south coast of Zealand (Rosenfeldt) and also the north coast of the island of Falster (Orenaes) which faces it across 3 miles of sea. Sycamore (Acer pseudoplatanus L.) silviculture and the Danish skill in exploiting this high yielding species, most notably in the absence of the grey squirrel, were the focus for the day.
| Orenaes Estate |
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| Opera House - outside of auditorium in sycamore |
| Sycamore Quality |
The woods comprise 90% deciduous hardwoods with the main investment being in sycamore as a commercial crop. Sycamore is considered a native species in Denmark and does not therefore suffer from the biodiversity prejudice experienced in the UK. The estate was a proud provider of quality sycamore for the new Opera House in Copenhagen (see photo), visited on Day 5, where a multi-facetted globe of brilliant panels was used to house the main auditorium – a project funded by the Maersk shipping company, responsible for 15% of the Danish Gross National Product !
Nils first showed us a 56 year old stand of plantation sycamore providing a good insight to its practical silviculture. He explained the importance of correct spacing through planting density and more crucially thinning regime, in quality timber production, setting the basis for the day’s discussions.
The 2 x 4m spacing used had allowed too much light onto the stems compared with 2 x 2m now preferred. This had produced notable ‘water sprouts’ (Danish term for epicormic growth) which he thought would degrade the timber and reduce its suitability for quality veneers.
The stand had recently been thinned with the logs being sold in 3m lengths for planking and Nils confirmed that a light (10%) and frequent (10 yearly) thinning regime was key. A further detrimental effect was heavy thinning (unlike beech, oak and ash) causing dieback in the crown with the accompanying loss of health, vigour and timber height. Combining these factors meant that continuous cover management was unviable and clearfell in year 80 was the best option. Nils concluded his review of this first stand by confirming the Danish label for sycamore as the ‘prima donna’ of trees, re-iterating its need for frequent attention and ideal conditions, only under which it can out perform other species in yield and economic viability.
| Sycamore Productivity |
It is rare that empirical data can be added to a woodland visit and we were very pleased to be received at the second stop by scientists from ‘The Danish Centre for Forest, Landscape and Planning’ of which Nils is Chairman.
We stood in the centre of a 1.2 ha plot of 50 year old sycamore, split into 4 quarters and subjected to 5 yearly regimes of moderate, heavy and very heavy thinning plus a control, for the last 30 years. The regimes were visually distinguishable by differences in tree number but to quantify these levels, their current plot basal areas as a percentage of the control 100%, were: moderate 57%, heavy 45% and very heavy 31%.
The key findings of the work were that 1. the increase in diameter growth induced by heavy thinnings (i.e. any heavier than the moderate regime) was very limited and also that 2. very severe thinnings cause a decrease in annual volume increment. Therefore, there was no justification on the basis of productivity for thinning on any more than a moderate regime. Whilst they also suggested that practically this would incur the least labour cost, Peter Goodwin made the point that they could make light thinnings pay, chiefly because such a large forest area is available for harvesting and large attractive sale parcels were still achievable.
Our hosts concluded that the ‘little and often’ programme meant that the crowns of remaining trees were not being over-shaded (suppressed) by others, or over-exposed to the light as both effects can cause damage which cannot be recovered from if severe.
In summary, the over-thinning of sycamore was confirmed as unviable. The experience of the forester justified this on the grounds of quality reduction and the scientific analysis had proved this on the grounds of negligible productivity gain.
| Rosenfeldt Estate |
The owner Peter Oxholm Tillisch and his father Erik Tillisch were our kind hosts for the afternoon and greeted us at the estate mansion (1776) which graces the surrounding lime avenues and Baroque gardens with its intricate brickwork and tall towers. Erik is a leading authority and scientific author on the silviculture of sycamore in Denmark and provided detailed insight to the areas of provenance, light regime, markets and the use of mixtures.
| Sycamore Silviculture |
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| Members dwarfed by the massive Petersgaard Oak |
Walking through the gardens Erik pointed out the groups of three open grown sycamore (typical of the period) planted at either end of the lime avenue on construction of the house. He made the point that despite the excess of light these clearly received, they were magnificent specimens, indicating that only sudden changes in regime are damaging.
At the first stand of 50 year old sycamore grown from natural regeneration Erik identified evidence of over-thinning with stems showing frequent water sprouts, but the second stand of 35 years had been managed far more sensitively exhibiting a fine 9m of clean stem and excellent potential for veneer production. This was attributed to thinning regime and Erik confirmed that a spacing of 4-5 m at 43 years old was quite normal. It was made clear however that over squeezing of the crowns (through under-thinning) could stress the trees in just the same way as opening them too much (over-thinning).
So what, we asked, were the health of the markets for the ‘prima donna’ of trees ? First length veneer material was achieving what was considered an acceptable but not spectacular £160/m3 in sale to Japan, with second length selling well at £33/m3 for use in gymnasium flooring construction. Even the very early thinnings were sold to self-cutters (see Day 3) for firewood at £15/m3.
We also inspected a 93 year old beech stand and Erik explained how the strong natural regeneration of sycamore had been used effectively to supplement the stand and fill the gaps. The two species were described as working well in mixture as the low beech understorey was in turn helping to suppress water sprouts in the sycamore.
Erik’s second key tool in growing quality sycamore was selection of the correct provenance. A large number of cultivars are present in Denmark and he noted its good potential for intensive breeding (as per the British & Irish Hardwood Improvement programme experiments with species such as wild cherry). The importance of assured provenance was emphasised as we closed our visit with a 9 year old stand grown surprisingly from coppice regrowth. On felling, the 100 year old stand had produced good quality stems and with this pedigree in mind, the same individuals were considered well worth testing for a second attempt. Issues of sweep from the stool base were dismissed given the 80-90 years being allowed for this to grow out. The proposed management was of singling stools every 5 years to retain a 2 x 2m spacing.
Our host’s insights to the growing of a species less well known in England were fascinating. A consensus was reached that the physical conditions in England were almost equally favourable and without the grey squirrel we would grow sycamore just as well. Edward Brun confirmed a wish to trial Danish provenances in England, but it would be a waste of time because of grey squirrels, which was echoed by other growers present.
Day 3 (Phil)
| Gjorslev Estate |
The Gjorslev estate is owned by the Tesdorpf family and extends to 850 ha. of farmland and 800 ha. of woods growing 25% beech, 12% oak, 9% ash, 20% sycamore and 25% conifers. Three full time forest workers are employed.
Sloping down to a sea which was remarkable for its calmness and lack of “seasidey” feel the woodlands showed none of the signs of coastal woods in Britain. Here trees grow vertically and healthily right by the sea on good soils.
We were treated to a tour by owner Peter Henrik Tesdorpf and forester Ole Peterson. With a combination of good growing conditions, good provenance, lack of grey squirrels and continuity of skilled management, the quality of the stands we were shown was in excess of anything many of us had experienced.
| Beech Silviculture |
We were shown a towering stand of beech with 8 to 10 metres of clear stem. In Britain this would have been considered good quality, but here they were a little disappointed and the logs are attracting low prices at present. The best logs had been going to the Chinese market at £300/m3, that has now reduced to £140/m3. The 1999 French storm flooded and killed the veneer market so they are not felling beech at present. They are expecting the market to pick up in the next 10 years.
We debated the efficacy of natural regeneration in beech resulting from ground scarification by Danish ploughs in the 1989 mast year. It looked very good to us, but Ole felt planting with a known provenance would have been a better strategy. Great emphasis was placed generally on provenance of planting stock with Dutch origin held in high regard. Could they afford to leave the over storey for longer in the hope of the market picking up ? Would this damage the growth of the regeneration ? As ever we were reminded what an imprecise science forestry is. At Orenaes we had seen less dense beech regeneration in shadier conditions, with the owner confident that they would eventually produce a perfectly acceptable crop! The grant scheme here offers little incentive for persevering with natural regeneration. At present grants range from £4000/ha for oak restocking, to £2000/ha for other broadleaves and £200/ha for natural regeneration.
| Oak Silviculture |
We were then shown a breathtaking stand of superb quality oak dating from 1898 with beautiful straight clean stems and magnificent crowns. The stems were up to 90cm dbh and were at their final spacing of 10-12m. Here some sycamore had been allowed to grow up with the oak to shade the stems and prevent epicormic growth. The sycamore is thinned every 4 years to prevent interference with the crowns of the oak. This area is used as a seed source and can realise 1 tonne/ha. of seed in a mast year which is collected by local children. The seed can attract a value of £2000/tonne. Unlike beech, oak has held its price and also has the advantage that it can be held in reserve for when a substantial income is required. This is in contrast to beech which will stain if retained too long. It is however becoming difficult to sell oak in Denmark due to the reduction in local sawmills and the low wage effect of Eastern Europe.
This stand is a testament to what can be achieved with ongoing management of a high standard.
| Land Tax |
Danish forestry has many advantages over its British counterpart, but one aspect which puts it at a disadvantage is the land tax. Every hectare of the country is subject to a tax of £30-40/ha/yr amounting to £30,000 for this large estate. This means the estate only manages to balance the books from forestry.
We were shown an example of the kind of silviculture that the land tax leads to. A waterlogged area had been ploughed and planted with Norway spruce and receives ongoing pumped drainage at a cost of £1000/year. The decision to plant was driven by the need to produce an income from all of the land. Due to low softwood prices there is now no prospect of producing an income from this stand and they are debating its future. The favoured option is to clear fell the stand and then leave the area to nature. There are moves to provide grants for the creation of nature areas in Danish forests making this option very attractive.
| Markets |
Markets are considered poor at present with softwood unsaleable (felled early due to the threat of windthrow in 20 year interval storms) and beech attracting low prices, despite the quality. The estate is generally felling at a low level compared to increment due to the poor prices. However, small thinnings of sycamore and oak, which may only be firewood grade in the UK, are sold to a flooring plant although there is a market for wood fuel for energy plants. The estate also has income from seed sales from the registered seed stands of beech, oak and sycamore, Christmas trees (4-6000 a year) and foliage (10-30 tonnes a year) as well as minor forest products such as tree tops used in children’s play parks for climbing frames and spring flower bulbs. Other possibilities under consideration include truffle production, protection of ground water (for which the estate could be paid), “the nature experience”, or team building activities in the woodland, permits for horse riding and pet graveyards. As timber values have decreased the development of these alternative markets has become necessary. Shooting is rented at £50/ha as against £10/ha in England.
The presence of large mature trees in the woodland is considered to be very desirable in terms of land values and may even double the value of woodland sales.
| Squirrels and self cutters |
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| The Petersgaard champion beech |
The absence of squirrels enables the growth and natural regeneration of stands of sycamore and beech that would be virtually impossible in many parts of Britain. Self cutting involves the marking of areas of low grade thinnings to be cut by local people for firewood. The people pay a reasonable sum of money for the privilege of cutting their own logs ! When questioned on health and safety matters, we were told that it is entirely the responsibility of the cutters, a situation that could not happen in the UK. This tradition is on the wane as younger people prefer delivered logs and, in response, the estate is beginning to expand that side of operations.
Day 4 (Phil)
| Petersgaard Estate |
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| Edward Brun (second left) and his tour party with Mikal Herlow (arrowed) in beech woods |
After arriving on a glorious sunny day at the immaculate house and gardens we were shown a recently planted avenue of lime down the front drive. Here Mikal has displayed the military precision of his former career and employed a laser to obtain a perfectly straight avenue of trees !
The estate has 1500ha of which 1066ha are woodland of which 37% are beech, 24% oak, 11% spruce and 8% each of ash and sycamore. The stands of trees we were shown here exceeded in quality even those of Gjorslev. The woods have been under management since 1799 with amazingly only 10 foresters in that time. For 135 years they have been cared for by the present family with the directive that the woods should receive the best possible management. This continuity of management is self evident in the forest. Growing again on low lying coastal land, with a mild climate and on fertile soils, these are considered the best conditions in Denmark. The estate has four full time forest workers with outside help from contractors when needed.
| Provenance |
We were shown a remarkable beech provenance trial consisting of stock gathered locally, from Holland and from Czech Republic initiated around 1930. The stand is supervised by the Forest Research Institute and their measurements show the relative growth rates to be very similar. The variation came in the form of the trees with the Czech ones proving to be straighter, but with many showing a pronounced spiral. Overall it was felt that the Dutch provenance was the best. The emphasis on provenance was revealing of the Danish desire not just to grow trees, but to grow quality timber trees which will attract the best markets in future. In addition, seed collection is a lucrative business here with a 3.5 ha stand of beech generating £12000 (2 tonnes) of seed on a 3-4 year mast interval.
| Oak Silviculture |
Several stands of oak were shown to us ranging from relatively newly planted through to mature stands. The thinning regime consists of regular thins throughout the life of the stand, up to a final thin at age 90-100 years to give a final spacing of 14 metres or 55 stems/ha. At this stage they are straight and branch free to about 15 metres, attaining an increment of 10m3/ha/year and a volume of 300m3/ha. It really was a great sight, the aim being to produce as many veneer quality logs as possible. The importance of avoiding water sprouts when growing veneer was emphasised as these can seriously reduce the value of the logs. Despite this, it is not considered cost effective to have them removed as several interventions would be required. There was then a suggestion from our group of a time-honoured method involving removing the sprouts on 1st June and 1st August for 3-4 years after which they will not return. Mikal had never heard of this method and he agreed he would give it a try, showing that the trip was of value to both hosts and visitors alike.
We also saw a stand of 94 year old oak with 20-30 year old beech underneath. The oak was considered to be no longer growing vigorously as shown by the lack of lifelines, or orange strips in the bark fissures. It is possible that the vigour of the young beech is robbing them of soil water and the answer appears to be to thin the oak and favour the better beech stems, which will in turn shade the stems of oak and prevent epicormics.
| Close to Nature Forestry (Continuous Cover) |
We were then shown an area of woodland, which had been left to develop with no intervention for many years. The subject of close to nature forestry and continuous cover forestry was raised as a result. Based around the German/Swiss system where felling is concentrated mainly on the largest trees the aim is to produce a mixed age and species stand with natural regeneration the main form of restocking. It was felt that conversion to continuous cover would take at least 50-100 years to achieve at Petersgaard. Mikal is not keen on this system as he feels the quality is poor in comparison to planting with a known provenance. In addition, members of the group wondered about the need to convert such high quality, high value stands as are found here. Others felt that in coming years the increasing emphasis on close to nature forestry and sustainable forestry may make it essential to adopt these methods.
This led on to a discussion on Certification for which there was very little enthusiasm. However should the market require it, 5 ha of purely natural woodland has been retained to allow potential certification.
| Monuments in the Forest |
Mikal showed us two of his prized trees, an oak and a beech, which he refers to as the “monuments in the forest”. Both had been left growing for 2-3 rotations making them around 200 years old. They were trees the like of which few of us had ever witnessed. Almost 150cm dbh and 18 metres to the first branch they towered above us with breathtaking grandeur. Twenty years ago the oak tree, with a volume of around 20m3, had received an offer of £3000/m3 which was declined. Tantalisingly he also told us of an ash tree of similar proportions in the wood, but time had run out….
| Estates and Gardens |
As well as the woodlands we were given the opportunity to tour the estate houses and gardens that were in many ways just as impressive as the woodlands. The houses were large and built in traditional Danish style. The gardens were mature and studded with large spreading specimen trees. Hospitality was offered and at Petersgaard I had the unique experience of asking the Queen’s Chamberlain for more tea (Peter Iuel has recently taken this honoured post) !
All in all the trip proved to be a truly memorable, enjoyable and enlightening one. The local contacts of the organiser Edward Brun gave us access to people and places that would have been impossible alone. We cannot speak too highly of the hospitality and insight given to us by the hosts and their incomparable woodlands. The trip has given us a great indication of what it takes to grow top quality broadleaves and our thanks go once again to Woodland Heritage.
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