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European oaks: cultural history
and ecology
Presented by Oliver Rackham, Corpus Christi College, Cambridge, England.
Or10001@cam.ac.uk
Europe has nearly thirty different species of oak. It invaded the continent 10 000 years ago and thereafter became common in most parts of the continent. When the gla-cier of the last ice age withdrew northward, mixed deciduous forest migrated up from refuges in the south parts of Europe. One reason for its successful colonisation is that it is highly adaptive to different kinds of
environments. It can grow in almost any soil, in various climates and on dif-ferent altitudes. It regenerates through cloning or seeds and it can grow very large or stay really small, like some Greek species that are more bush-like than tree-like. They invade abandoned fi elds; grow on grazed land and along the railways in England. They grow in forests, in oak coppices, scattered among other trees, in wood pastures and on farmland. There are evergreen oaks with really deep root system, and deciduous species with more shallow roots.
Different species benefi t to different degrees from various human activi-ties, like woodcutting, pasturing, abandonment of land and burning. Some oaks can resist fi re, since they have a barque that protects the trunk against the fl ames. Others yet have underground tubules for regeneration after fi re.
Benefi ts of the oak tree for human use
The oak tree also has a unique range of uses for humans. Some of these uses are determined by the properties of the different oak, but they also vary from one human culture to another. In Japan, the oak tree is a low status tree, in Spain it is not at all used as a timber tree. In France, the timber is used as railway sleepers, whilst in Sweden it was used for the grounds in the houses during the earlier centuries. In England, the majority of the buildings from the middle ages were made of oak. One building consisted of 300 small oaks. At that time, they more often used the young oaks for timber production and the trees rarely grew as big as they are today. They used the size that was suitable for the purpose. The whole oak tree was sometimes used for making dug-out boats, which should have been quite a hard work to do, since the tree is really hard and can easily split.
Lit-huania. It is the perfect timber for furniture, since its structure is really hard and it hardly ever rots. The leaves were used as food for the cattle, the acorns for both animal- and human food. The barrels in which whisky and wine was aged was made out of oak wood. And it was, and is, a symbol of majesty.
The oak change
The oak is also a victim of the tree globalization. Since the beginning of the century the oak has gone through a drastic change. During the early 20th
century, there was a fungi – Phytophthora quercina – that was spread from North America and reached Europe. It invaded the oak trees’ root system and made it weaker and less tolerant to shade. The result of this infection is that the oak now is less competitive against other tree species. While the oak struggles against the shade and competes for light, the fungus is an extra bur-den for the tree. Also, the fungus probably makes it harder for the oak tree to carry out the photosynthesis. This is probably one reason why there is such a lack of younger oak trees in England – the regeneration is prohibited by the fungi infection.
Picture 3:
A fi eld with old pollarded oak trees – a method that has been used to prevent the tree from casting shade, and also to protect valuable timber from grazers. Picture 4:
Coppicing is the practice of cutting trees to ground level, in order for the tree to produce more timber. Picture 1 and 2:
Through history, oak timber has been used by mankind for the construction of i.e. houses, churches and ships.
Oak behaviour in relation to large
herbivores
Presented by Frans Vera, Driebergen,
Netherland.
Fvera49@xs4all.nl
The present is the key to the past. That is the basic rule in paleoecology, for recons-tructing the past. In other words – species behave today as they did in the past. The present is that oak is a light demanding species that do not regenerate well in forest reserves in the company of more shade tolerant species. In fact, they are
ousted within two centuries by these species. Oak is obviously not a closed canopy forest tree.
However, pollen analysis show that in the past, oak was present together with these shade tolerant species for thousands of years. Also at present day, oak regenerates very well in the presence of shade tolerant species – in wood pastures and on wooded meadows. These habitats are park-like landscapes, grazed by livestock like cattle and horses, and also by species of wild ungu-lates like deer and moose. And since they prevent the landscape from turning into a closed canopy forest, they facilitate the regeneration of oaks.
Present forests are former wood pastures
Many of the forest reserves today were actually wood pastures in the past. When these forest reserves were established, cattle and horse were removed, since those were considered to be alien species introduced by man. Without these grazing animals, wood pastures soon turned into close canopy forests – where oak regeneration is poor or absent as a result of oak disappears, to-gether with other light demanding plant species.
In the primeval vegetation, there were indigenous species of large grazing ungulates
in the past, for example the aurochs that became extinct in the 1600s, and the tarpan that became extinct in 1887. These ungulates, together with other grazing and browsing wild ungulates like European bison, red deer, roe deer, elk and wild boar kept the landscape open. These grazing and browsing species that still exist today, like bison, red deer and elk, are everywhere kept artifi cially in very low densities, since they prevent the regeneration of trees in the forests and therefore possess a threat to the traditional forestry. They are also kept in low densities in forest reserves, because of the classic theory about the primeval vegetation. This theory states that the primeval vegetation
was a closed canopy forest. Forest reserves are considered to be modern ana-logues of the primeval vegetation. Because in high densities existing grazing and browsing animals can prevent the regeneration of trees in forests, these animals are also artifi cially kept in low densities in these forest reserves. Wit-hout a suffi cient amount of wild ungulates, and the domestic animals remo-ved from the landscape, the wood pastures soon turned into closed canopy forests, where oak and other light-demanding species disappear.
Shrubs as a protection from overgrazing
The process of regeneration of trees in wood pastures is that young trees – among them oaks - are nursed by thorny shrub species like blackthorn and hawthorn or by other plant species that are not or less palatable for large ungulates. These species are also light demanding and establish themselves in open grassland, grazed by cattle and horse. Within these, oak and other tree seedlings and saplings can grow up. Oak is very common in wood-pas-tures, because there the jay hoards acorns in the fringes of the thorny shrubs. Thereby the jay plants acorns where seedlings and saplings of oak meet al-most optimum conditions to grow up, that is in full daylight and protected by a nurse species. If the nurse species concern small scrubs, seedlings and saplings of tree species grow up as solitary, so-called open grown trees. If the nurse species spreads clonally, like the blackthorn does, groves are formed . Inside the groves the regeneration of trees is prevented at fi rst by the shade and secondly by the large ungulates themselves, a phenomenon that is known from the practice of forestry and grazing forests by livestock. It is a non-li-near, cyclic succession where thorny shrubs invade an open grazed grassland. The shrubs remain solitary or scrubs are formed, which allows seedlings of trees to grow up, protected by the shrubs and solitary open grown trees, or groves, are formed. The trees die and the groves change into open grassland, where the thorny shrubs establish again.
In many forest reserves today, which are mainly closed canopy forests, there are still large oaks However, their presence is not a proof of positive oak regeneration in closed canopy forests. It is a memory from the past, when the forest was a parklike wood pasture,
with grazing livestock and other large indigenous ungulates. Former wood pastures now being closes canopy forests are representatives of a mixture of two different histories. Because of the presence of oak in combination with shade tolerant tree spe-cies, it is not the closed forest that is the closest modern analogue of primeval vegetation – it is the park like wood pastures together with cattle and horse and other wild living ungulates who facilitate the establishment of trees in open grassland, and at the same time prevent the regeneration of trees in the groves (forests), and by doing so, inducing a non-linear, cyclic succession .
Picture 1: Oak is not a closed canopy forest tree species.
The history of oak in the
Scandinavian landscape since the
last ice age
Presented by Richard Bradshaw, University of Liverpool, England.
Richard.bradshaw@liverpool.ac.uk
Genetic and paleoecological studies reveal the patterns of oak colonisation through Europe and into Scandinavia after the last ice age. The historical distribution of oak was fi rst estimated through studies of pol-len; and this was confi rmed by the genetic and molecular biology studies that were done later. There are two lines of oaks, one emerging from Italy and one from Spain. (Picture 2)
The primary driving force for the dist-ribution of oak has been climatic changes. Populations were largest and reached their northernmost extent about 6 000 years ago and has slowly retreated southwards ever since. This is seen in the actual distri-bution of trees, but also in the paleoecolo-gical studies of pollen.
Foresights about climatic change that will result in warmer temperatures predict that the oak will have a larger distribution in the upco-ming years. It will spread up to more northern parts of Sweden and will also have a larger population throughout Europe.
Human activities infl uence oak distribution
It is, however, not only the climate that ef-fects the oak distribution. It is a species that is highly affected by human activities and dis-turbance changes. Fire, for instance, is one factor that strongly infl uences the oak distribution. It
is of great ecological importance in broad-leaved forests, but has the latest centuries been more or less abandoned from northern European forests. Oak gain on fi re, compared to several of its competitors. They can withstand fi re to a certain extent, and its pollen can better survive a fi re than the pollen of,
Picture 1: The oak distribution today (above) and under future climate (below)
Another factor is grazing and browsing by animals – the importance of large ungulates on past forest structures. One unknown and still uncertain variable is the size and the number of the past ungulate populations. Several observations, however, show that it is probably not only the ungulate pres-sure that has formed the historic landscape. It is highly probable that there were several different factors that infl uenced the historic forest structures.
The effect of fi re and grazing
Studies in two different forests in Halland show how present forest structure has developed. During the 20th century there were an extensive planting of
spruce, and the forests are today dense with a closed canopy. Plant macrofos-sils show that more open conditions prevailed earlier. There are signifi cant amounts of large charcoal fragments recorded at these sites from the middle ages, and smaller amounts until 1650. The following years, until the early 1800s, it is just sporadic occurrence of charcoal. Fire as the mean for keep-ing the forest open was replaced by grazkeep-ing animals from 1700s to the mid 1900s when the forest canopy closed.
Fire, together with grazing and browsing, maintained the forest open during earlier centuries, and was probably an important factor in the process of oak regeneration. Historical forest structure was probably more open and varied than found in present day reference forests.
The conclusions drawn from these studies are: • Oak history is driven by climatic change
• There is a strong relationship with moderate fi re regime • Herbivores are one of several controls
• The future for oaks in Sweden looks good, because of the upcoming warmer climate.
The political history of the oaks
in Sweden from the 16
th
to 20
th
century
Presented by Per Eliasson, University of Lund. Sweden.
per.eliasson@lut.mah.se
The confl ict in Sweden between the state power and the peasants over oak trees was one about many different values – culture, economy, politics and ecology. It was not only about ownership and timber, but also about the oaks role in damaging the crops and about the oak as a symbol of the crown.
In 1558, the Swedish King Gustav Vasa declared that all oaks belonged to the crown, at least all oaks on taxed- and crown land. Nobility owned the trees on noble land. The main purpose was to save the oaks to the navy, for the production of ships. Farmers could ask for permission to fell oaks on their land, but it was very diffi cult to obtain. The felling also had to be done with a saw instead of the usual axe, and it had to be followed by compulsory planting of oaks – two new oaks for each one felled. The planting was done in small plantations, usually with bad results.
Historic oak decline
So, felling an oak was not an easy thing to do Because oaks have quite a big impact on the vegetation and crops on the farmers’ lands by casting a sha-dow below it, farmers started an extensive branch cutting, partly to reduce the leaf mass, but also driven by a sheer oak-hatred, hence, more or less a deliberate destruction of royal oaks. The result was a rapid decline in the number of trees fi t for the navy’s use.
It was not only the farmers’ branch cutting that resulted in oak decline. Naval offi cers in Kalmar and in Kronoberg made a fi rst oak inventory in 1729–1732. In Kalmar the navy had used a lot of the good oaks, to build ships for the war. The inventory showed a huge difference between the two areas. In Kronoberg there were a lot more healthy oaks than in Kalmar and the portion of bad quality oaks was substantially higher in Kalmar than in Kronoberg
Nation wide oak inventory
The fi rst nation wide inventory was made in 1791–1795. The oaks were counted, the position of the oaks were recorded as well as the quality of the
trees. Finally, they marked the trees that were supposed to be saved with a sign.
In the second nationwide inventory, in 1819-1825, the navy offi cers that performed it discovered that the number of good oaks had been reduced by 82 percent. The parliament came up with a solution in 1828, to try and save the oaks. New trees, useful for the crown, were to be planted. At the same time they decided that the peasants could buy the oaks on their land after a new inventory. In 1832, a new inventory was made; this time not only the good oaks were counted. This time, they marked the oaks that were going to be felled – in the fi rst inventories they marked the oaks they wanted to save.
The farmers oak-hatred, manifested in branch cutting, and the navy’s own stamps ruined the timber trees. These scars were an easy way in for fungus that started the decay process. In addition, the navy’s selective felling of good trees and the farmers legal felling for clearance contributed to a landscape dotted with large numbers of dead, decaying and hollow trees. The resulting landscape changes were initially good for biodiversity, since the decaying trees maintained habitats for many species. However, since many of the good oaks at the same time were cut down, there were few trees left to grow old and to constitute new habitats for the insects and fungi.
The consequence of the oak-hatred and the battle between peasants and the crown, as well as the massive felling of good oaks to build ships for the war – was a rapid deterioration of oaks. Remaining oaks grew mostly on noble land and crown estates and even today the best oak habitats are on these land areas – as a memory of our history.
Picture 1: An old map over Lake Vättern and a request from the crown to plant new oaks.
Plant
The Oak Tree, from Peasant
Torment to a Unifying Concept of
Landscape Management
Written by Jerker Moström, National Heritage Board of Sweden, Sweden.
jerker.mostrom@raa.se
The expression “Tender oak trees and young noblemen should be hated” is an ironic peasant saying originating from the 18th century. It expresses the hatred within the peasant community towards the nobility and the oak trees, caused by what they perceived as injustices in the contemporary Swedish fo-restry acts.
In the Middle Ages the oak tree, regardless of its place of growth, was more or less considered state property. During the 16th and 17th century this
policy was reinforced as a result of the consolidation of the state interests and the expansion of its military power. The production of oak tree timber was dedicated to the Royal Navy. Therefore the felling of oak trees was an exclu-sive state affair on both crown land and on allodial land.
What caused the strong dislike for the oak among the peasants were obvi-ously the restrictions on their land use but also the fact that the oak trees had a negative impact on the arable land. The dense tree crowns shaded the fi elds and stunted the crop growth. Due to the slow decomposition of the acidic oak leaves, fi elds, meadows and grazing lands covered with oaks were also generally less productive.
Picture 2: Today the oak tree is seen as a versatile asset which enriches the landscape in many ways. However, only a few centuries ago it was a source of confl icts bet-ween the state and the peasants. Photo: Kristina Ask. Picture 1: The appearance of the grand oak tree of
Rumskulla is an obvious reminder of the great time depth of the landscape. Photo: Nicklas Jansson.
A symbol of power and opression
During the 17th century the oak became not only an important source of
income for the nobility but also a physical symbol of the wealth and power of the aristocracy. Ideally manors should be surrounded by oak tree forests and the roads within the estate should be designed as oak tree-lined avenues. While the peasants did what they could to limit the damage on their land by secretly eradicating the plants and damaging the old trees by pruning, bur-ning and removal of the bark, the nobility took active measures to encourage the growth of oak trees.
During the 19 th century the forestry policies changed and the restrictions
on oak trees on crown- and allodial land expired. Initially peasants were only allowed to exploit old and bad oaks, but later on the restrictions were completely removed, resulting in a rapid decrease of the number of oak trees since the peasants were eager to get rid of their hated enemies.
A new symbolic value
From the mid-19th century and onwards, the associations projected onto the oak tree gradually changed. Land owners now gained equal property rights and the overall inequalities of the pre-industrial society subsided. As a result of this, the oak tree was no longer perceived by common people as the phy-sical manifestation of oppression and injustice. Today the oak is attributed positive characteristics.
The oak tree of Rumskulla (Kvilleken), in the county of Kalmar, offers mind-staggering perspectives on the time depth of the landscape considering it is literally still a living prehistoric organism. By the time the Rumskulla oak was a sprouting plant a thousand years ago the people of Scandinavia were busy carving runic stones and exploring Europe with their Viking ships.
At the moment we are facing the great challenge of implementing the European landscape convention into Swedish management practice. The landscape convention stresses the importance of local participation as well as a multidisciplinary approach to the landscape. It also conveys a multipurpose perspective on the use of the landscape. The oak tree is no longer a signal of social injustice causing disagreement and division, but rather a symbol of diversity and richness in the landscape. Perhaps it is also the kind of unifying concept that the landscape convention asks for. Yet, one might also wonder whether the oak tree landscapes even would have arisen, if the European landscape convention had been implemented in the past, giving the nobility, freeholders and tenants equal rights in defi ning the values and use of the landscape.
Changes in the biodiversity of oak
habitats in Sweden through the
last centuries
Presented by Sven G. Nilsson, Lund University, Sweden
sveng.nilsson@telia.com
The typical oak habitat in Sweden today is probably the cultural landscape with wood pastures. The disturbances from human activities in the landscape have changed during the last centuries. Fire and grazing is more or less gone, which probably is one reason why the regeneration of oaks has
declined. Since the mid 1800s the meadows in Sweden are more or less gone. Also, the fl ooded areas along rivers were in earlier days an ideal habitat for oaks, since they are more resistant to fl ooding than most broad-leaved tree species. When these areas were turned into haymaking areas or farming land, the oaks disappeared.
The drastic changes in the distribution, number and ecological quality of old oaks in Sweden has also had effects on the biodiversity. There is direct evidence from historical records of birds, lichens and some insects that used to be widespread in the Swedish landscape, but now are very rare or have even gone extinct.
Oak as a habitat for many species
The oak is associated with a number of species – the biodiversity in the tree is very high. It is a complex web of factors that contribute to the oak as a habi-tat for many species. The long life cycle, the different stages of decay etc are probably important reasons for the high biodiversity.
The oak is a very stable habitat. A dying or decaying oak does not disappear or undergo dramatic changes for a couple of hundred years. That makes an old oak favourable compared to a more temporary substrate such as a wind-felt tree.
When the oak disappears, many beetle, fungi and lichens go with it. One example is the bird Dendrocopos medius. It went extinct in 1982 in Sweden, although it still exists in some sites with old oaks around Europe. In the 18th
century it was a common bird in the south of Sweden. When the protec-tion of oaks disappeared 1832, the oak habitats started to fragment. Recent studies have shown that one pair needs an area of at least ten hectares with many old oaks. A viable population can establish when there are many such sites not too far from each other, which is hardly so in Sweden today.
Because the birds do not move more than ten kilometres, the fragmentation and the loss of habitat eventually led to the bird’s extinction.
Habitat changes that affect the fauna
Among the beetles that are associated with the oak, the Lucanus cervus is one of the most characteristics. It used to be very common in the south of Sweden, especially when the oaks were very abundant on the pastures and meadows, up until the beginning of the 19th century.
But as the amount of oak trees has decreased, so has the habitats for the
L. cervus, which is why the beetle is not as common today as it used to be.
Another beetle, highly associated with oak, is the Osmoderma eremita. It is not often seen, since it can live its entire life in the same tree. Only fi fteen percent of the adult beetles leave their original tree and those who do, do not move very far. The beetle is sort of an indicator of high biodiversity. In the presence of the O. eremita, there are a lot of other, often vulnerable, species. Although there are more than 200 sites in Sweden where the O. eremita is observed, very few of these are appraised to be viable in the long run, mainly because these sites are too far from each other, but also because most of them inhabit less than 500 individuals.
The future for many of these species depend on how the oak landscape is managed in the future and the regeneration of oaks has to be substantially larger than it is today. It is now a lack of the 100–200 years old oak genera-tions in the Swedish landscape. For biodiversity conservation in the south of Sweden, the oak tree is the most important tree.
Photo: Aivars Petrins
Picture 1 and 2: Two species, highly associated with the oak. The
Lucanus cervus, which is still seen in the Swedish oak
landscape, and the Dendrocopos medius which has now gone extinct in Sweden.
The fauna and fl ora on oaks – how
important are the Swedish oak
ha-bitats in a European perspective?
Presented by Anders Dahlberg, Swedish species information centre, SLU, Sweden.
Anders.dahlberg@artdata.slu.se
Oaks, especially old and coarse ones, har-bour a remarkable interesting and diverse fl ora and fauna. In Sweden, it is the tree species that are associated with the highest number of species, probably for several reasons. One is that the tree can get really old, at this coarse state it can provide many different niches. The associated species
have evolved when the oaks were more frequent and are often dependent on an oak habitat with many oaks where distances between them are short.
Dramatic landscape changes
With changed land use practices, the oak landscape has gone through a dra-matic transformation in Sweden as well as in the rest of Europe. Old growth deciduous forests, meadows and wood pastures have been reduced to a small part of their original coverage. As a consequence of the decline in oak ha-bitats, several of the species associated with the oak tree are also becoming more and more threatened.
It is necessary to make priorities in conservation and management of species diversity. The oak associated biological values must be defi ned and analysed. Either from a species perspective by studying what species are found, how they are distributed and what their possible future may look like. Or, from a habitat perspective by looking at the occurrence of the habitat and its quality. Unfortunately has no such analysis has been conducted at the European level. It require a substantial amount of information. A pragmatic option is thus to use national analyses complemented with all avaliable infor-mation.
Red Lists as a tool for conservation
Using the Red Lists can be one basis for setting priorities in management and conservation of nature. It consist of a compilation of species ecology, distri-bution and status and evaluates the species risk of becoming extinct. A red listed species can be:
• Common but declining • Uncommon and declining • Very unusual
Nearly 700 oak associated species are on the Swedish Red List from 2005, mainly beetles, but also fungi and lichens. Several of these species appear to have a noteworthy share of their European population in Sweden. 140 of the red-listed
species are estimated to have more than ten percent of their European population in Sweden, and 30 more are estimated to have at least 20 percent.
Of the oak associated species on the Red List, the major part consists of different kinds of beetles. Natura 2000, a EU network with the aim to con-serve species diversity, will follow up the status of three oak associated beet-les species. Their status and development will be thoroughly analysed. One of these is Osmoderma eremita, or the Hermit beetle. It now lives in 1 000 known localities in Europe, with the highest concentration in Sweden.
Lichen communities of Swedish giant old oaks are of high international value. Especially in south-eastern Sweden, there is an abundant and rich fl ora, due to the concentrations and continuity of giant oaks in combination with good air quality. Swedish oaks comprise eleven species on the Red List, which have more than 25 percent of the European populations. There are also 170 red listed oak fungi of which several have a large part of their European population in Sweden. Hapalopilus croceus is one of these. It is extremly rare and threatened throughout Europe. It has only 130 European sites and a large share of the European occurrence are in Sweden.
All of these species are more or less dependent on old giant oaks. The Swedish concentration of giant oaks in pasture woodlands is exceptional, de-spite only a small faction of its earlier occurence, although especially Britain has high numbers of giant oaks. Also Spain, Greece and Russia has a substan-tial amount of old oaks. However, due to the severe decline in oak habitats in Sweden as well as in other European countries during the last 200 years, the future of the
biologi-cal diversity depends on management. The oak-habitats in Sweden are signifi cant from an Euro-pean perspective and Swe-den has an international responsibility to manage these habitats to secure its biodiversity values for the future.
Picture 1: Map over European distribution of giant oaks.
Picture 2: Nearly 700 oak associated Swedish species were red-lis-ted in 2005.
What about the regeneration of
oaks in the Swedish forests?
Presented by Frank Götmark, University of Göteborg, Sweden.
Frank.gotmark@zool.gu.se
In planning for future forests and in the commitment to favour oaks, there has to be deep knowledge about the occurrence and development of seedlings and saplings. The regeneration of oak has recently been studied in two different surveys. The fi rst one was in non-protected forests, mostly coniferous. The other was in woodland key habitats; with
plots both in conservation cutting areas and in areas with free development. The purpose of the studies was to understand the oak regeneration in relation to dif-ferent forest types, the oak ecology, forest management and forest policy.
The defi nitions used in the studies are:
• Coniferous forest: at least 60 percent conifers
• Broadleaved forest: at least 70 percent broadleaved trees • Seedling: small oak, less than 25 cm tall
• Sapling: small oak, ≥ 1,3 m tall to 5 cm in diameter at 1,3 meter • “Large” oak tree, or oak tree: ≥ 15 cm in diameter at 1,3 meter • Young forest: average height of trees less than 7 meter
• High forest: average height of trees more than 7 meter
Regeneration in broad leaved- and coniferous forests
In the fi rst survey, the regeneration of oaks in deciduous and broad-leaved forests was compared. The results showed that there is considerable more regeneration of oak in broad-leaved forests, but since there are so many more coniferous forests in Sweden, the overall result is that there are substantially more young oaks growing in coniferous forests than in broad-leaved forests. YOUNG FORESTS
Coniferous: 32–43 oak saplings per hectare Broad-leaved: > 300 oak saplings per hectare HIGH FOREST
Coniferous: 32–60 oak saplings per hectare Broad-leaved: 56–146 oak saplings per hectare
Overall: 63–74 percent of all saplings in the study area (Southern third of
Sweden), grew in coniferous young and high forest. These saplings may be favoured rather than removed and it is potentially easy to increase the density
The effect of conservation cutting
In the other study, in woodland key habitats and nature reserves, the focus was on differences in oak regeneration due to cutting or thinning versus free development. The survey started in 2000, and during the winter 2002/2003 half of the one-hectare study plots were thinned by the removal of 25–30 percent of the tree biomass. In 2005 the oak saplings and seedlings was coun-ted again and the results showed that thinning increases seedling density. More light favours survival and growth of oak seedlings. Partial cutting is hence one way to favour oak regeneration.
In a comparison between a national forest inventory during the years 1983 to 1987 and a similar inventory during 1998-2002, the differences in oak regeneration is striking - the oak saplings have decreased substantially, mainly due to browsing by deer and moose. The conclusions from this study is that the forest practices and conservation policies that dominate the Swe-dish forestry does obviously not favour oak saplings or seedlings. However, the same inventory shows that the number of large oak trees has increased during the same period, so the management of today favours big oaks before young oaks. Since the results from several surveys show that good survival and growth in oak seedlings requires canopy opening, it can be stated that the practice of conservation cutting is necessary to strengthen the regenera-tion of oak.
Picture 3 and 4: The practice of conserva-tion cutting allows the sunlight to reach the ground, which favours the regeneration of oak. Picture 1 and 2:
Before and after conserva-tion cutting in one of the study areas.
Fluid relationships: The inclusional
neighbourhood of oak trees and
fungi
Presented by Alan Rayner, University of Bath, England.
a.d.m.rayner@bath.ac.uk
What is an oak? A tree? Or a perfect habi-tat for fungi and beetle? Simple questions like that can sometimes be really hard to answer, as the answers may very well be diverse. However – they all contribute to an overall understanding of the subject.
In ecology, the problem is that we tend to defi ne natural forms, like oaks, as
discre-te objects in a fi xed perspective. For millennia, our attitudes have been biased through believing that nature can be defi ned into discrete material bodies that are separated rather than pooled dynamically together. This way of looking at nature, natural form, tends to create a dualism – is it this way? Or is it that way? With or against? It is a sort of logic that in the end probably underlies many kinds of mismanagement, since it excludes a lot of possibilities.
Present way of looking at nature
Another problem, when we are trying to answer simple questions, is that we tend to separate ourselves from nature, as well as isolate the object (in this case the oak tree). It leads to the alienation from our natural human neigh-bourhood, and leads to environmentally unsustainable practices. There is no such thing as an isolated natural form or object; there are no complete, fi xed boundaries or dividing lines in nature. So, the next question that follows is: what is neighbourhood? It often tends to be perceived either as the surroun-ding of an individual entity or as a group of entities within a defi ned space. But – as mentioned earlier – there are no such thing as boundaries or dividing lines in nature. And as for the oak tree – all the confi nes of an oak tree are to some degree impermanent and permeable. Full of holes. Indeed a holey place!
And what is a fungus? Fungi could be thought of as dynamic relational fl ow-forms that can inhabit the living space of the equally dynamic relational neighbourhood that we call an oak tree. And as a river is infl uenced by, and infl uences the landscape it fl ows through, so do the fungi and oak tree infl u-ence one another reciprocally. Because there is no object that acts in a va-cuum, an object cannot be isolated from its surroundings. The fungi and the oak shape and reshape one another’s lives.
Including instead of excluding
There is a need for transformation in our view of the world and ourselves. We need a view that does not exclude, but that rather includes. A shift in the way we frame reality, from fi xed to dynamic. A radically different perspective emerges from “inclusionality” – the awareness of space as an inclusion of natural dynamic geometry. We need to think about how our perceptions of reality affect our appreciation and management of natural form and beauty, like the oak tree and the fungi. Perhaps the most important role of ecology is to understand complex fl uid dynamic relationships rather than take sides in what objectivity might lead us to perceive as the War of One against Other.
Picture 2: Painting made by Alan Rayner – Fountains of the forest. Picture 1:
Co-creative sculpting by fungi and oak.
Habitat requirements and
distribu-tion of wood- and bark inhabiting
fungi on oak
Presented by Stellan Sunhede, Skövde University, Sweden. Stellan.
sunhede@his.se
One of the main characteristics of oak is the high biodiversity associated with the tree. There are many beetles, several lichens and a large amount of fungi that lives in or on the oak tree. In order to assess the amount of oak associated fungi, the non-lichenized wood- and bark inhabiting fungi on oak trees are being mapped and calcu-lated in an ongoing project. So far, 95 000
oaks in Denmark, Estonia, Finland, Latvia, Lithuania, Norway and Sweden, have been surveyed with respect to population structure, spatial distribution, habitat and substrate requirement. The fungus fl ora on individual oaks has been inventoried with a little extra focus on rare and endangered species.
Brown rot and white rot
The oak trees are inhabited by a lot of different fungi, and these can – rough-ly – be divided into two groups: brown rot and white rot fungi, respectiverough-ly. The brown rot species decompose cellulose and leave the lignin as a brownish rest. The white rot fungi fi rst remove the lignin and then decompose a lot of the cellulose, but they leave some behind as a whitish remnant.
The most common brown rot species associated with oak, are
Laetipo-rus sulphureus and Daedalea quercina. A rare species causing brown rot is Piptoporus quercinus. The different fungi contribute to make the oak hollow
and create varying habitats for other organisms, in particular insects. There are a lot more white rot fungi than brown rot fungi on oak trees. Phellinus
robustus is one of the most common species, while Inonotus dryadeus is a
rare fungus, which only occurs in habitats with a rich herbal fl ora. Even more rare is Ganoderma resinaceum, which is only found in three sites in Sweden – in Skåne,Halland and Blekinge.
Rare fungi in Sweden
One of the most beautiful oak habitats in Sweden is seen in Halltorps hage
on Öland. Here grow several old and thick oaks, and on some of these the very rare Hapalopilus croceus is found. It is one of the fungi that are on the red-list for endangered species, and it will probably become even more rare
Picture 3:
One of the inventoried sites – a wood pasture.
Picture 4:
Inonotus dryadeus
Picture 1:
One of the inventoried sites – a fjord slope.
Picture 2:
Fistulina hepatica
since it lives solely on old oaks. There are not enough middle-aged oaks to replace the old ones as they die.
The most famous Swedish oak is probably Rumskullaeken in Småland. It is a fairly low tree, but with a substantial girth - more than 14 meters in circumference. It has been hollow for a long time; even Carl von Linné wrote in his stories about the oak – and it was then used as a tool shed. It is the fungus Fistulina hepatica that has contributed to the hole in the tree. The activity of this fungus has precluded the possibility to decide the age of the oak, but by omparing the tree to other oak trees the age is estimated to about 1 000 years. Many times, the individual oak is colonized by several different fungi, both brown and white rot species. It is quite common that the fungi specialize on different parts of the oak. Some species are for example almost always found on thick branches, while others are mostly seen near the base of the tree. One way to protect and preserve threatened species of fungi is to leave dead branches and dead, standing or fallen trees. These will make up a perfect substrate for several fungi. Most fungi do not infect undamaged oaks, but a small scar on the trunk or a broken branch may be enough for a fungus to colonize the wood. One way to preserve these fungi is to inoculate an oak with mycelia. This will speed up the decay in fresh trees in order to create habitats for rare insects, as well as to transfer rare and endangered wood fungi.
The interaction of oak-fungi and
beetles and the use of a saproxylic
index in Britain
Presented by Keith Alexander, Ecological consultant, England.
Keith.alexander@waitrose.com
The invertebrate fauna which is directly dependent on decaying wood comprises over 1 800 species in Britain, of which 700 are beetles. That equals six percent of the total invertebrate fauna and 20 percent of the beetles in Britain. Oak trees support an important part of this fauna.
It is not only old, hollow and dying
trees that are substrate for this fauna. Also young trees have dead branches, even though they are small. As they grow and mature, more branches die, bigger and often particularly lower parts of the tree. Early heartwood decay begins when the tree is mature, even though it still has a full crown and good lateral branching. As it grows older, the crown starts to get thinner, and the the heartwood on the oak gets more and more hollow, the crown eventually starts to sink andthe oak tends to “grow downwards”.
Factors that infl uence the fauna
During these stages there are several different fungi associated with the tree, fungi that many beetles depend on. The beetle species have very particular requirements, both in terms of type of fungal decay and the tree’s stage of decay process. Also the situation of the decay and the host tree is important for the beetles. Other factors which affect the fauna is:
• Total number of trees
• Density of trees – open grown vs. high forest • Age structure of trees
• Management history – continuity • Each site is unique
In order to succeed with a good conservation, there is, among others, need for a species list and a comparison of different sites. There also need to be a recording of tree factors as numbers, age and size, as well as informa-tion about the different beetles rarity. The types of sites that are typically rich in species are the ones with a long history of tree cover, often on relatively uncultivated land and former hunting preserves.
Measuring rarity
There are several reasons why a species is rare. It can have a low mobility, the niche can be rare, it can be under-recorded, unknown or a recent colonist. It can even be a newly established non-native species. Traditional inventories are therefore not always enough. A new tool, Index of Ecological Continuity (IEC) is one way to reduce the uncertainty.
The Index of Ecological Continuity is a scoring system, used in order to assist in the site assessment. It consists of a list where the different selected beetles have scores according to their rarity and occurrence in old habitats – the more restricted to habitats. The sum of all the scores of the species found on a particular tree then signals the conservation value of that habitat.
The IEC saproxylic beetle list contains 180 species, which are graded ac-cording to:
1. Only known from sites with old trees and long history (3 scores) 2. Mainly in the above (2 scores)
3. More widespread but collectively characteristic (1 score)
An IEC total score of 25 or more is assessed as a site having national importance. The Index of Ecological Continuity, and the saproxylic beetle list have to be revised over time and continuously developed. But, it provides a working tool and a robust scheme for the nature conservation work. It is now adopted by nature conservation agency in England, but there is also need for a European IEC listing.
Figure 1:
Diagram showing Index of Ecological Continuity (IEC) for a number of sites in dif-ferent age classes.
What can we learn from the
ecology of Osmoderma eremita?
Presented by Thomas Ranius, Swedish University of Agricultural Sciences, Sweden
thomas.ranius@entom.slu.se
In Europe, old growth broad-leaved forests have declined to only a small fraction of their original extent. Until the 19th cen-tury, old oaks were fairly widespread in pasture woodlands and wooded meadows. Abandoned management and changed land use practices have severely reduced these habitats. When the old trees became scarce,
the species associated with them became confi ned to small remnants of their original habitats.
Habitat requirements for Hermit beetle
Osmoderma eremita, or the Hermit beetle, is dependent on hollow trees. The
larvae develop in wood mould inside the tree during three-four years, and the adult beetle is seen only for a few weeks in July and August. It has a high priority in EU’s Habitat Directive, and is used as a model species in research. There are records from 2 100 localities, but in only 900 of these localities there are records since 1990. As these 900 are the ones where people have been searching for O. eremita, they may very well exist on even more sites, for instance, in south-eastern Europe. In Sweden, the species mainly occurs in old hollow oaks in pasture woodlands.
Surveing spatial distribution
For conservation efforts to be effective, it is important to understand how the spatial structure of the oak habitat infl uences O. eremita. For that reason, a number of sites were surveyed, differing in size and density of suitable sites in the surrounding. Eight litres of mould was taken from each tree, and sear-ched for remains of adult beetle body parts. The frequency of presence per tree increased with stand size; single trees always lacked parts of O. eremita completely.
With further studies – telemetry and capture-recapture – it was shown that there were on average eleven beetles per tree and year, with a variation between zero and 85 beetles per tree and year. These surveys also confi rmed that the beetles are rather prone to stay in the same tree their entire life, with only 15 percent moving to another tree.
Fragmentation – a threat to the Hermit beetle
One conclusion drawn from these results is that fragmentation is negative to the beetle. Trees in small stands are used to a lower extent by the beetle, and are consequently less valuable, in comparison to trees in larger stands. A simple population viability analysis based on the present knowledge, suggest that many of the O. eremita populations will go extinct even if the habitat quality remains constant. However, the extinctions may very well take deca-des, or even centuries.
Some consequences for nature conservation are:
• Maintain or improve localities where the species is present. It is rarely useful to create stepping-stones or corridors.
• It is important to avoid bottle necks in the number of suitable trees over time.
• It is necessary to increase the number of suitable trees in many loca-lities. Do not try to save every single locality, but give priority to larger ones, or localities with a potential for restoration.
Picture 1:
Adult beetle of O. eremita. Photo: Niklas Jönsson
Picture 2:
Distribution of O. eremita. Blue dot: last record before 1950, or the time unknown; black dot: last record 1950-1990; red dot: last record in 1990 or later.
What have we learnt from massive
inventories of the oak beetle fauna
and how can we use the results for
their long term conservation?
By Nicklas Jansson and Karl-Olof Bergman, Linköping university, Sweden.
Nicklas.jansson@e.lst.se karbe@ifm.liu.se
The oak trees are the trees that inhabit most saproxylic species in Sweden. There has been several projects that has described the saproxylic beetle fauna on old oaks in Östergötland, during the years 1992-2003. One of these was a recent inventory of 74 sites. Different kinds of traps were placed
in and around old oaks, suitable for saproxylic beetles. Window traps were placed on brances in interesting habitats, and pit-fall traps in the mould in old trees.
Each tree has a unique fauna – and with traps on fi ve trees, 50 percent of the fauna were caught, with 20 trees, 90 percent of the fauna was caught. All in all, 198 oak associated saproxylic beetle was found, of which 47 is on the red list.
Various characteristics are important for species diversity
One conclusion drawn from the inventory is that the sunlight is important to some of the oak living species, and that forest regrowth therefore are negative both for the old oaks and for some of its inhabitants. It was also clear that a large girth is positive for species richness as well as the age of the tree. Most species was found in oak trees in stage fi ve and six. A comparison between were there are most species rich sites in Östergötland coincides with the sites were there are most old oaks. The most common beetles are spread all over the county.
For conservation purposes of species richness, there has to be and active conservation and proper management of old oaks. Beetles dependent on hol-low oaks with wood mould is the dominant group of red-listed species asso-ciated with oak habitats. One hollow oak may be enough for some
individu-als – for a while. But how much is enough to ensure the long term survival of beetles associated with old, hollow oaks? Some questions need to be answe-red in order to work out a long term management plan for the conservation of oak living beetles:
• How many hollow oaks do the organisms need for a functional meta-population?
• How many hollow oaks are suitable for a certain species? • What is the fraction of hollow oaks in a stable population with
regard to age distribution?
• How large area do a stable oak population need?
A large oak habitat is vital for stable beetle populations
A mix of data from two of the sensitive species, Elater ferrugineus and
Osmoderma eremita was used as models for calculations of long term
survi-val. Several studies, both empirical and theoretical, indicate that at least 20 hollow trees (patches) are needed to maintain a stable meta-population of beetles associated with old, hollow oaks. But all hollow oaks are not suitable, and it is the oaks in stages fi ve and six with a lot of wood mould that har-bour a large proportion of the beetle individuals. Around 25 percent of the oaks in those stages are suitable as a substrate for E. ferrugineus according to empirical data.
For a population of oaks to have a stable age distribution without gaps, only 15 percent of the area should consist of hollow oaks. After following a scheme where information about age distribution of oak together with information about area requirements of single oaks is added, the conclusion was that a minimum of 57 ha:s is needed for maintaining a stable popula-tion of beetles. However, up to 954 ha:s may be needed for the most habitat specifi c individual species. It can also be stated that,
unfortunately, this is not what reality looks like. The oak habitats today are distributed in small patches over the county. The fragmentation is a big problem for the beetles, since they move very short distances. So, the overall conclusion is that there is need for a landscape approach for the long term conservation of organisms dependent on hollow oaks in Östergötland. Overgrown areas have to be restored, young oaks should be planted in strategic fi elds, the oaks need to be actively favoured during forest practises and the oak timber production must be encouraged to create larger continous oak areas.
Picture 1: The different stages of hollowness in oaktrees.
Oak regeneration challenges in
na-ture based forest management
Presented by Palle Madsen, Forest and Landscape, KVL, Denmark.
pam@kvl.dk
Nature based forest management has gre-atly gained popularity in Denmark over the last 15 years. It is emerging from a more traditional forestry, which goes back 200 years. At that time forest clearance had reach almost an ecological catastrophe. Large parts of the country was covered by heath land and the few remaining forests
were heavily grazed. This led to a shortage in wood supplies for the society, and plantations of fast growing non-native conifers was thought to be a solu-tion to the problem.
Today’s nature based forest management system is a movement away from plantation forestry towards a system more nature like. It is part of a general trend in forest and landscape management on both public and privat-ely owned land. It rose from increased focus on multi-functional forestry and from the problems associated with traditional forestry, caused by insuffi cient stand stability, reduced timber prices and high regeneration costs.
Various aims and interests
The Danish landscape is mainly characterized by farmland. 61 percent of the area is farmland, while only eleven percent are forests, of which, 37 per-cent are broadleaved forests (25 000 hectares in Denmark are oak stands). Additionally, the government decided 15 years ago that the Danish forest land area should double within the next century.
Management plans have a wide variety of aims and interests depending on ownership, site etc. Recreation, biodiversity, nature conservation, wood production, bio-energy, landscape aesthetics, cultural heritage and ground water protection are among the most common. Private landowners may in their goal setting particularly focus on issues like property value, investments, hunting and the mere pleasure of ownership.
Ultimately the challenge for management is how to recognize all these aims and how to handle shifting aims over time. It seems vital to try and keep as many doors open for the future as possible in this process, since nobody knows what the future will bring – a strategy that calls for both economical and ecological sustainability.
Nature based forestry – working methods
The toolbox for a nature based forest management consist of several different parts. Continous cover forestry is one of the common characteristics, alt-hough clear-cuts of e.g. unstable stands may become relevant. Mixed species and uneven aged forest structures are also some of the typical characteristics. However, the species and structural diversity may not be found at the small scale in each part of a forest. The heterogeneity is more to be found within a scale of hectares rather than parts of a hectare. Nature based forestry is also about growing site adapted species and therefore primarily native species. Natural regeneration is the dominating regeneration form and pesticides or fertilization is hardly used.
Oak regeneration is a major challenge in the nature based forest manage-ment due to widespread use of the continuous cover approach. Canopy shade and competition from more shade tolerant or fast growing species are known to create diffi culties for oak regeneration. Additionally, small oak are attrac-tive for deer and it is often stated that “oaks have no future in nature based silviculture”.
However, various theories of the historic landscape can serve as a valuable source of inspiration for new methods in forest and landscape management.
Several studies have shown that the oak regenerates well over time in a grazed forest. Shade and competitors are removed which allow the oak to establish, often sheltered by species like wild apple, sloe, hawthorn and roses, to protect the seedlings and saplings from grazers.
An important challenge seems to develop oak regeneration methods for nature based forest management. The approach is largely to mimic the na-tural ecosystem processes and dynamics. Oaks seem to call for new ways of combining grazing by domestic stock, wildlife management, and regeneration measures like direct seeding and planting of various species mixtures.
Picture 1:
Average establishment rate for oak seeding at 20 Danish ex-periments at clearcuts. Some were monitored only one year and some up to four years.
Geographical analysis of oak
environments in Sweden and
Östergötland
Presented by Jens Johannesson, Kenneth Claesson and Tommy Ek, County Administrative Board of Östergötland, Sweden.
Jens.johannesson@e.lst.se Kenneth.claesson@e.lst.se Tommy.ek@e.lst.se
During 1990-2004, the County Administrative Board of Östergötland sur-veyed the landscape for valuable oak habitats. The result of that study is a map of 18 000 hectares of oak and other broad-leaved high-value cores and data about its biodiversity. It covers most of the broad-leaved habitats with high natural value, but it is still only 1,7 percent of the total land area of Östergötland and probably only 30-50 percent of the historical broad-leaved environments.
High value cores in Östergötland
Of the surveyed high-value cores, 1 500 hectares – or nine percent – are in nature reserves. 94 percent of the high-value cores are dependent on grazing, but only 30 percent are actually grazed today. The distribution of red listed and rare species are well known after this survey. Some of these species have a large proportion of their European distribution in Östergötland.
The oak landscape was classifi ed into four different groups, with regard to the age of the oaks and the size of the area. The high-value cores are found in oak-wood pastures, on steep slopes, in grazed oak-pine forest, oak forests or in urban environments.
Ancient trees in Östergötland
In another survey, also performed by the County Administrative Board, Östergötland was surveyed for ancient trees during 1997-2006. Every old
or ancient tree was mapped and described and positioned on a GIS sheet, by unemployed but trained people. More than 110 000 trees have been recor-ded. Of these, 25 000 are oaks and 15 000 of these are more than one meter in diameter. An additional 200 000 younger oaks have been counted, but not described.
By a newly developed system for describing the hollowness in oaks, the shortages of hollow and/or old oaks in certain areas was recorded. The sys-tem consists of seven stages of which the fi rst was not used in this study. The possibilities for regeneration and the amount of replacement trees are now quite well known. In this project there are also plans for restoration of over-grown pastures and oaks, with fi nancial support to the landowners.
Preservation by the use of a new tool
With a new tool – high value tract – there are new possibilities to preserve species in the long run. A high value tract is an area characterised by a con-centration of high value cores and/or a high concon-centration of red listed spe-cies.
With a more geographically concentrated nature conservation, there are better chances to get a higher degree of ecological functionality. Nation (or county) wide full-scale surveys of valuable nature in Sweden will give new possibilities for conservation. However, it should be used with care. One risk is that areas not fully surveyed will not be classifi ed as high-value tracts, even though they should. In a normal landscape, around one half to two percent of the forest is (identifi ed as) high value core, very rarely above ten percent. Combined digital data of the distribution of red data book species and high value cores, as well as experience-based information was used to deli-neate high value tracts in the County of Östergötland. For example, in the tract of S:t Anna and Gryt archipelago, the total area is 44 200 hectares, of which 1 502 hectares are classifi ed as high value core, equalling almost seven percent of the land area. Within this area there are 136 red data book species.
To conclude – 30-50 percent of the oak habitats in the 18th and 19th
century remain today in the best high value tracts. 70 percent of these areas are not grazed today, resulting in 46 percent of the ancient oaks being over-grown.
With these new tools and the detailed knowledge about oak habitats in Östergötland, the next step will be to make a landscape strategy for restoring these areas.
Veteran oak tree surveys and
ma-nagement at United Kingdom sites
Presented by Neville Fay
Treework Environmental Practice (TEP) & the Ancient Tree Forum (ATF), England
nevfay@treeworks.co.uk
The quality and the condition of Britain’s old tree heritage are refl ected in the great number of ancient tree sites found in the British Isles. The majority of large sites are in the southern part of England. To protect and better manage these sites, the Ancient Tree Forum was established. It works to
increase awareness, promote better protection, and to avoid loss of ancient trees by improving knowledge and science on the subject.
The ATF does not only work within Britain, but also cooperates with groups in other countries, like Spain and Sweden. However, there are some differences between the perspectives in these countries. In Britain, the focus is more on the ecosystem, whereas in Sweden the main interest lies in the species associated with ancient trees.
Veteran and ancient oaks
The defi nitions of veteran versus ancient trees are not always obvious. A simple rule states that “All ancient trees are veteran, but not all veterans are ancient”. The arboricultural classifi cation relates to tree age, so that an ancient tree is one that is beyond full maturity and in the fi nal stage of life, which is often the longest stage.
To monitor veteran trees and their habitat features in Britain, a Specialist Survey Method (SSM), operating at three survey levels, was developed in 19971. A signifi cant number of ancient tree sites in England have now been
surveyed by this method. It has proven to be a useful tool to understand the habitats and to compare habitat quality and characteristics between key sites.
Using the SSM it is possible to obtain detailed information about tree data, form, habitat and associated species. TEP have further designed an arboricultural enhancement to the SSM (called the SSM+). This is used to provide an understanding of the tree’s viability and structural condition, and forecasts the probability of future decline, estimating the risk of failure for each individual tree. The information is used to formulate Individual Tree Management Plans (ITMP) and to minimise future ancient or veteran tree loss – which is an essential strategy as old trees are obviously hard to replace. This methodology has also been used at important Swedish veteran tree sites, such as Särö Västerskog, Hördalen andHallstad Äng.
Replacement trees
Veteran tree management need to enhance the viability of the existing popu-lation while incorporating an effective replacement strategy for young trees. The loss of ancient trees is slow and hard to recover from - with 40 percent fewer saplings you get 40 percent fewer trees 250 years later. ITMPs are used to guide the restoration program for individual veteran trees, using arbori-cultural techniques such as retrenchment pruning. The plan runs for over 30 years with a number of return periods during those years.
New arboricultural techniques have been developed that mimic the natral processes in the way trees age, fracture and decline. This approach is infl u-enced by the many different disciplines that contribute to the ATF and this now forms the basis of British “environmental arboriculture”. Some typical methods in this approach include:
• Mimicking storm breakage • Natural fracture techniques • Crown restoration
• Retrenchment pruning • Coronet cutting • Rip cuts
• Haloing; the slow release from competition • Enhancement of the rhyzosphere
The interactions between the tree and its surrounding are important if the arboricultural program should succeed in supporting a functioning tree-eco-system. Therefore the whole root-space and soil ecosystem, with associated fungi and insects has to be taken into account.
The assessment of tree population dynamics at veteran oak sites shows loss-rates of between one to two percent per annum, indicates that there is a need to prevent man-made infl uences that lead to tree failure while develo-ping strategic management programs to reduce such losses since all ancient trees are important.
1 Obtainable at www.treeworks.co.uk/downloads/SSM_HandBook.pdf
Ancient Tree UK Distribution
(KA)
