Forest damage
Forest damage describes the damage to and endangerment of tree stocks through changes in site conditions or damaging events that overstrain the resistance and adaptability of the trees. They increase the susceptibility to diseases and can lead to the death of trees and even large-scale deforestation .
These processes, which also predominantly take place in the forest ecosystem, are called damage from an economic point of view if they reduce the timber yield , impair the management of the forest, the functions of the forest or other primarily anthropocentric assessments such as the appearance of the landscape and natural aesthetics. The last consequence of forest damage is large bald areas.
The term forest diseases refers to tree diseases in the narrower sense. Often it is also used as a synonym for forest damage. In his standard work on forest diseases, Fritz Schwerdtfeger justifies the equation with the fact that this would be the case “if we understand the concept of disease ecologically and relate it to the community. The threat to existence then consists in a disruption of the relationship structure. ”One damage to the ecology is the elimination of a species from an ecosystem, such as that of the elm in the course of the“ Dutch elm disease ”. The economic assessment of such damage can only be derived indirectly and with great uncertainty.
Manifestations
Forest damage is differentiated according to whether it is of natural origin (forest damage in the traditional sense) or whether it is caused directly or indirectly by humans . There is also new type of forest damage that has appeared since the late 1970s and which - presumably - can be traced back to various causes as a complex disease (" forest dieback ").
- See also: Broken tree - view of the individual tree, not the forest structure
Natural forest damage
A distinction is made between abiotic and biotic forest damage. The most important abiotic stress factors for forests are the physically effective causes of storms, snow and fire. Drought (lack of water), mechanical injuries, landslides and avalanches , electricity and radioactivity act in the same way . Soil acidification and heavy metals, substance inputs, lack of oxygen (excess water) and lack of nutrients have a chemical effect .
Abiotic causes
The starting point for abiotic forest damage is usually a weather or weather anomaly, which in turn often creates the conditions for the large-scale occurrence of biotic damage. Hurricanes break trees from ( windfall ) or uproot this (windfall) - as a result it can lead to proliferation of insects. Drought weakens vegetation and increases the risk of fire in forests , which can also cause significant damage. In rarer cases there is flooding in forests whose trees are not adapted to such environmental stress .
frost
Frost endangers some tree species especially after the beginning of the vegetation period : These "late frosts" destroy the cell tissue of leaves on young trees or of newly formed needles of evergreen conifers, which is why needles and shoots wither and often die. Needle losses caused by late frost are referred to as “frost chutes”. Low-lying locations without any drainage options for cold air are at risk, so we speak of “frost holes” or “ cold air lakes ”. The risk is particularly high (in the northern hemisphere) on slopes facing south and south-west due to the increased solar radiation: the trees there sprout earlier after winter. Among the tree species that are particularly endangered by late frost are the European beech and silver fir , which for this reason are usually only rejuvenated under umbrella. In analogy to this, "early frosts" can occur at the end of the growing season, which are generally considered to be less dangerous.
Winter frost can also have a negative impact on the health of trees. However, since most tree species are adapted to their respective locations, damage from winter frosts rarely occurs. Tree species of foreign origin, such as the Douglas fir, are more susceptible if they sprout earlier. A lack of potassium increases the susceptibility to damage, as this element is important for the frost hardening of the conifers in winter. On clear, i.e. sunny winter days, frost dryness can appear, which causes needle discoloration and loss (in the course of summer). Frost drought is triggered by the fact that winter sunlight stimulates assimilation processes in the conifer needles. The water required for successful photosynthesis is not available to the trees, however, because it is frozen and therefore cannot be mobilized in the soil. The water shortage stress is exacerbated by wind, which increases transpiration . Frosttrocknis due, among other things, the height of the tree line , so the height above sea level, from the growth of trees is no longer possible.
Typical frost damage is also "frost plates". Solar radiation heats the bark of beech, spruce and other thin bark tree species, which is heavily stressed by the cold inside the trunk and tears open lengthways. Later, the bark lifts up on both sides of a crack. The damage is strongly reminiscent of sunburn or bark fire.
Frost cracks are longitudinal cracks in the trunk that arise in free-standing deciduous trees when there is a sudden drop in temperature due to tensions caused by the shrinkage of the cellulose in the wood associated with freeze-drying . The previously common term "ice gap" is wrong because, contrary to initial assumptions, the formation of the gap is not caused by the transition from liquid water to ice, which is associated with an increase in volume. Ring-pored hardwoods such as oaks and elms are particularly at risk from this type of abiotic damage. Similar cracks are caused by lightning strikes.
heat
In addition to the general water shortage stress, which weakens the defenses of trees against biotic causes of damage (formation of resin and inhibiting substances), physical tensions can arise in the wood. Heat cracks can occur during drought stress , especially on younger conifers. In the case of deciduous trees (beeches), too, in addition to premature leaf fall, branches can fall off due to sudden branch breakage (summer break). A lack of water and the associated tree water deficit trigger strong tensions in the wood. The trunk rips open about a meter above the ground; this can continue to the crown and is used by other pathogens, especially fungal pathogens, such as the bleeding coniferous layer fungus as an entry point into the wood body.
If thin-bark trees like the European beech are suddenly exposed and the trunk of the summer sun is shining directly on them, this can lead to "sunburn": the bark bursts on the most sunny side and flakes off. Subsequent wound rot infections are not uncommon.
snow and ice
Snow, especially wet snow, can have a negative impact due to the pressure it exerts on trees. Coniferous trees that are not appropriate to the location (such as bristle spruce) and the branches of leafy deciduous trees are very susceptible to snow breakage (i.e. broken branches). Snow shovel occurs on slopes due to the downward flow of the snow cover, which pushes young trees out of the vertical and causes saber growth , or lever saplings out of the ground. Because of their evergreen nature, conifers are more endangered than deciduous trees.
Icicles ("ice" and "scent appendages") can form on trees. Like wet snow, they can overload the load-bearing capacity of branches and twigs. Hailstones break the branches through their kinetic energy.
Storm
Storms either lead to windbreak (tree tops or branches break off) or windthrow (the tree is uprooted). Damage arises from the unplanned and premature use of the tree in question, from damage to other trees when they topple over, the high costs of processing the damage (fatal accidents are not uncommon) and the damage to other trees that occur during processing. If processing is not carried out, in the case of coniferous wood the danger of a mass reproduction of bark and wood-breeding insects increases. Far-reaching preparatory measures are often necessary for the subsequent establishment of a culture.
Fire
Forest stands are destroyed by crown fires; other types of forest fire are less harmful. Ground fires only burn the organic layer of the forest floor. However, peat fires are devastating, as they are difficult to extinguish, smolder for a long time underground and kill the roots of trees. However, forest fires are also part of the natural dynamics of some forest types in the boreal zone.
Nutritional disorders
Nutritional disorders are also possible as abiotic causes of damage. These manifest themselves as discoloration on leaves or needles in the event of a lack of certain nutritional elements such as iron and manganese ("calcium chlorosis"), phosphorus, potassium, copper or magnesium. Nitrogen deficiency leads to stunted growth, and oversaturation with nitrogen also weakens trees (magnesium deficiency symptoms are common). Substance inputs can have a toxic effect, such as road salt. Chloride ions lower the osmotic potential.
A lack of oxygen can be brought about by flooding. Many trees in the temperate zone can survive for around 15 to 25 days without consequences, depending on the species and vitality. However, a lack of oxygen can also be caused by soil compaction.
Other abiotic causes
Electricity can damage trees in the form of lightning strikes. The trunk then tears open along its length. These cracks are covered by the tree. However, decades later, they can still be clearly recognized by strip-shaped thickenings along the course of the crack, which are called "lightning strips" according to their cause. Outwardly, they hardly differ from the overburden of cracks caused by frost or heat.
Metal splinters can be found in trees when acts of war have taken place in the corresponding forest area. These are fragments of bombs and grenades that do not, or only marginally, influence the vitality of a tree; however, they represent a significant reduction in the value of the wood because they can seriously damage saws and other machines and increase the risk of accidents for workers. As a rule, log processing companies are now equipped with metal detectors; However, discounts are to be expected.
A special type of environmental pollution is the contamination of forests by radioactive material. Wood contaminated in this way can no longer be used if limit values are exceeded.
Biotic causes
Biotic forest damage is caused by " forest pests ", ie animals such as game , mice , insects and by fungi , bacteria or viruses . They are only triggered by populations of certain organisms. Classifying a species in a “pest” category is ecologically incorrect, but is often done in practice for reasons of simpler handling. Apart from vertebrates, there are a large number of pathogenic organisms.
Damage thresholds are often calculated for assessing socio-economic damage (point in time from which the cost of countermeasures is lower than the damage to be expected). In the case of insect populations, critical numbers are used as indicators for these damage thresholds. Damage thresholds are not calculated for damage caused by hunted animal species in Germany, since the regulation of population density is the responsibility of game management.
Artifacts
In Germany, the browsing of shoots and buds by deer with the preference for certain tree species is a frequent problem, which by far accounts for the largest part of the effort to ward off damage from game in regeneration stands. The ecological damage caused by deer is also significant, as they are very selective in their diet. There is a segregation of species and the regional extinction of certain herbs such as the Turkish lily , the hare lettuce and the narrow-leaved willowherb . At the same grasses are promoted so indirectly, the rejuvenation of forests difficult ( quaking grass sedge , known as "seaweed", Calamagrostis , honey grass , wire and Blütenschmiele , moor grass , White and Green Rushes ). Roebucks form new antlers every year, which are initially covered by a bast, which is swept away by the animals on resin-rich young conifers after the growth phase is complete. The goats also beat trees in exuberance.
Under certain circumstances, red deer peel the bark from the trunk of younger trees in order to eat it. As a result, these trees are severely damaged. In forestry, wild boars only cause significant damage by eating seeds. Every now and then, individual trees are damaged by the animals' rubbing against the bark ("painting trees"). Like goats, chamois can damage trees considerably by eating bark and leaves.
Small mammals
Mice, especially bank vole and earth vole , gnaw the roots and / or bark of trees, preferably deciduous trees, and can thus cause the total loss of young stands. Other species of mice, including the wood mouse , do only minor damage by eating seeds. Even gray squirrel peeling bark, but always older in the crown of trees. This creates a feeding pattern of a ring around the width of a hand. The damaged branches die off, rot penetrates the trunk.
Insects and arachnids
Many species of beetles feed on different parts of the plant body. They breed in wood (wood borer, longhorn beetle) or between wood and bark (bark beetle). While the former devalues the wood, the latter can fatally damage a tree by breaking lines. Some wasps are also wood breeders. These Sirex species, such as the blue spruce wasp ( S. noctilio ), are so important as pests in wood in many countries in the southern hemisphere that so-called Sirex certificates are required for international trade, which prove that the wood is resistant to infestation by the Wasp was treated. Among the numerous weevils that mainly attack leaf organs, the great brown weevil is of great importance in Central Europe . Butterflies mainly appear as leaf eaters. Heavily infested trees are sometimes completely devoured by caterpillars . They die if such baldness occurs in successive years. The nun , various tensioners and curlers appear in particular . Lice suck sap on bark, leaves or needles. If the buds are eaten by insects, the shoots become distorted.
Among the arachnids , mites play a role as pathogens on trees. Gall mites produce their characteristic plant gall , which only slightly affects the health of trees, while spider mites suck on leaf cells and then quickly dry them up. The consequences are a reduction in assimilation and premature leaf fall.
Mushrooms
As (obligatory or optional) parasites , fungi can attack different parts of the plant body. Saprophytic fungi feed on the dead wood of a tree. Depending on whether lignin or cellulose is broken down, one speaks of white or brown rot . Infected trees appear healthy on the outside for a very long time, as the decomposition processes take place inside the trunk and do not impair vitality. Only in very advanced stages do the fruiting bodies show up on the bark. Discoloration in the wood caused by fungi also represents a technical devaluation. As a rule, rot fungi penetrate the organism through damage to the trunk or via the roots. In particular honey mushrooms and root sponges are important "harmful organisms". Other fungi are found on the leaf organs. This group includes rust fungi , oak powdery mildew , or black and white snow mold . New types of infections are, for example, ash dieback and soot bark disease in maples
Insects and fungi sometimes appear as complex diseases, for example in Dutch elm disease .
Bacteria, viruses and others
Bacterial diseases such as those caused by Pseudomonas syringae can be recognized by characteristic wood deformations that are known as "cancer". The diseases take a long time. Viruses show up by certain pattern-shaped, light discolorations on leaves. These chloroses appear like a mosaic, as spots, rings or bands. Some viruses also cause leaf deformation. They often belong to the Poty or Porex group. An exact determination is often only possible under laboratory conditions. Viruses are usually not fatal to trees.
Protozoal diseases are also possible .
Historical forest damage
A distinction is made between “classic smoke damage”, which was already described by the forest scientist Karl Gayer in 1866 and which has occurred more frequently since the beginning of the industrial revolution . Smoke damage always occurs in the area of the emitters, while new types of forest damage occur far away from the emitters.
Novel forest damage
From the beginning of the 1970s in Central Europe, the extensive death of the silver fir was observed , which spread increasingly in Germany and a little later also spread to the spruce. One began to speak of "forest dieback".
The causes of new types of forest damage have not yet been fully clarified. A connection with human environmental pollution , possibly in interaction with other stress factors, is certain . Three basic hypotheses were examined:
- the smoke damage hypothesis (direct action of gaseous substances such as ozone and sulfur dioxide on needles and leaves);
- The acid rain hypothesis (the effect of gaseous substances on the soil leads to its acidification and thus to a change in site properties: release of toxic aluminum ions ; chlorides , heavy metals and organic pollutants damage the fine roots of trees, thus reducing the uptake of water and nutrients and thus reducing them the resistance of trees to drought , frost and disease)
- the stress hypothesis (many other stress factors impaired the vitality of the forests and increased susceptibility to other causes of damage).
Risk factors
General risk factors and prevention
Much damage can be prevented through silvicultural expertise - other effects than external effects cannot be influenced by forest management alone.
Abiotic factors
The extent to which forests are damaged by storms depends on various factors. Tall trees are always more at risk than low ones. A single tree is more stable, the larger the diameter of a trunk at chest height is in relation to the total height ( h / d ratio ).
The risk of forest fires can be reduced by minimizing combustible material in the stock; however, the removal of dead wood creates conflicts with nature conservation goals. Whole populations are mostly destroyed by flames or insect damage when it comes to single-layer monocultures . Conifers are generally more endangered than deciduous trees . Dense young stands burn more easily than old stands with only a few large trees.
Biotic factors
Possibilities for prevention exist in the attraction (distraction) or the deterrence of the organisms by chemical or physical stimuli. Methods of attraction by means of fragrances (those of one's own species or those of trees), light or acoustic signals represent a smooth transition to therapeutic measures (baiting), but are common for estimating population developments. The dynamics of some potentially harmful insect species are monitored in order to be able to react quickly to gradations if necessary. Pheromone traps are used to monitor insect populations. Conclusions about the development of the population can be drawn from the number of animals caught.
It is also possible to regulate reproduction through contraception in rodents, or by sterilization or genetic defects (non-viable embryos develop from eggs). The development inhibition, however, takes effect at a later stage in the development of an organism.
To prevent the mass reproduction of insects, it is advisable to remove endangered wood from the forest in good time. Catch trees are stronger conifers that provide a habitat for bark and wood-breeding insects. The removal of such trees, which are often specially felled for this purpose, before the flight of the second generation helps to slow down population development. It is also important to promote antagonists of potential “pest species”. Parasitic wasps act as parasitoids on many of these species in the juvenile stage. As adult animals, however, they are dependent on the presence of flowering plants. By promoting such plants, the risk of phytophagous insects gradation is reduced. Fire and insect gradations are, however, an integral part of the ecosystem in some forests, such as the boreal coniferous forest . Countermeasures are not always useful or desirable in such cases.
Damage to forests by rodents can also be avoided through silvicultural measures. Tall grasses represent a habitat for mice. Their emergence can be prevented by taking into account the initial situation when the stand is established, in the context of young stand maintenance, or, if necessary, by short manual maintenance; here there is also a link to the population regulation of deer. Predators such as the fox and the wild cat can naturally help prevent mice from eating. This can largely be ensured through habitat maintenance and careful game management. At particularly endangered young stands of deciduous trees, about 2 to 3 meter high poles for birds of prey are sometimes set up.
Human factors
In the climax stage of natural succession, the composition of the species and individuals in a primeval forest corresponds to the optimum in terms of biotic and abiotic environmental factors and therefore the greatest possible resistance to forest damage. Forestry silviculture will not achieve this perfection because not all location factors can be determined and taken into account. Anthropogenic factors that lead to forest damage therefore not only include pollutant emissions in the form of acid rain , heavy metals and nitrogenous fertilizers , but also begin with the “artificially” selected tillering. The following measures can favor the occurrence of forest damage:
- The cultivation of non- autochthonous (alien) tree species - such as the spruce outside the mountains in the deciduous forest level
- The constant removal of the biomass without replacement by removing wood
- The tillering of large areas with the same or a few species, although different microclimatic, hydrological and soil chemical conditions would naturally lead to very different forest types
- Plants modified by breeding can cause a change in stability - the trees, for example, are not able to withstand storms unscathed or are more susceptible to diseases (however, opposing effects, so-called resistance breeding, are also possible)
- Monocultures or too dense forest cover increase the risk of abiotic forest damage, especially windthrow. This includes both stand and single tree training.
Forestry techniques also lead to direct human damage. These can be collisions of trees with the remaining trees during the timber harvest , or later when the timber is transported from the stand onto a forest path ("back damage"). The wounds on the bark allow pathogens to enter the plant organism , especially fungi. In addition, the use of heavy machinery leads to considerable soil compaction, which has a negative impact on the herbaceous layer and the root area of the trees.
Ultimately, biotic damage such as massive browsing by deer or the peeling of trees by deer is indirectly human. Excessive game populations in regions without large predators such as the lynx or the wolf can be attributed to poor hunting management . Preventive measures against browsing and peeling are not only possible by reducing the density of game, but also by passive protective measures against rejuvenation. Rejuvenation areas that are susceptible to browsing are often fenced in until the sapling has grown “over the roe” of the deer, ie has reached a height of around 130 to 150 cm. During this time, fence maintenance measures are often necessary. Deer fences have to meet higher requirements and are more expensive. The problem with fencing off areas is the relocation and thus the increase in browsing pressure on neighboring forest areas. As an alternative, individual trees can be protected against browsing mechanically (using "wire pants") or chemically (by coating with denaturant).
Risks from climate change
Complex reactions and an increase in forest damage are to be expected as a result of the emerging climatic changes in the course of global warming . The exact consequences are difficult to estimate due to the uncertain prognoses regarding the quality and extent of the change in the climate . Silvicultural countermeasures are often not possible, apart from the gradual conversion of susceptible pure coniferous stands into more climate-tolerant mixed forests.
Provided that there is no change in the amount of precipitation with an increased mean temperature in the vegetation period and thus the rate of evapotranspiration increases, water shortages can occur. This means that production downtimes, susceptibility to disease and the loss of one or more tree species are likely. The risk of forest fires increases. The increase in the CO 2 content of the air could partially counteract a water shortage, as photosynthesis would become more water- efficient.
If, however, an increase in temperature during the vegetation period is also associated with an increase in precipitation, then - in addition to conceivable positive effects on the net increase - other instabilities are caused: Changes in the competitive conditions between tree species are possible, which would require an adaptation of the regeneration and thinning concepts to avoid economic damage to avoid. Biotic damage becomes more likely because the resistance of trees to pathogens , whose living conditions are expected to be improved, could change. Mild winters and a longer vegetation period have a strong influence on the growth behavior of harmful populations such as that of certain butterflies or beetles.
However, not only the amount of precipitation, but also the frequency of rainfall is a relevant factor. Should longer dry periods occur during the vegetation period, this can lead to serious damage to the vegetation . Species with oceanic climates would be particularly affected.
There are many indications that the frequency and severity of storm events is increasing, which will repeatedly overwhelm the stability of many forests (especially those of coniferous crops that are not suitable for their location). The same applies to the risk of snow breakage, which would increase with an increase in snowfall at air temperatures around freezing point.
In Germany, the rise in temperature since the 2010s has resulted in extensive forest damage, particularly in spruce forests, with several overly dry years. In 2019, as a countermeasure, federal and state politicians called for reforestation with less sensitive mixed forests.
Losses can also be seen in a number of other main tree species, such as oak, beech, pine, fir, ash or maple. In the context of climate stress, there is also talk of “new tree deaths”, since an overall increased mortality, with a tendency for older and larger specimens, can be observed in Central Europe.
Therapies
Only preventive measures can be taken against abiotic damage to forests, which reduce the risk of forest damage or disease. Forward-looking measures can also be taken against biotic damage, but there is also the option of curbing existing mass reproductions of animals within the framework of forest protection , or actively decimating the population.
On the one hand, technical measures can be taken: in addition to removing brood substrate, manual collection of the animals from trees can also be considered. This is very time-consuming and is generally not carried out on forest plants in Central Europe . The massive introduction of “beneficial insects” such as parasitic wasps is possible. Biotechnological measures also include fungi, bacteria and viruses. The use of such pathogens, however, not only presents technical difficulties (especially in cultivation), but also involves risks due to the possible adaptation of the pathogen to other hosts, including humans.
Another option is the use of pesticides . These should have the properties of being highly selective (only poison the animal species whose population causes damage), it should act quickly, be highly toxic (kill almost the entire population in order not to generate resistance ), have no side effects and minimal persistence (rapid degradation , all degradation products are non-toxic). The use of pesticides is viewed critically due to the substances entering the ecosystem, but is a standard practice in plantations .
Extent and importance
Forest condition report and damage levels
Forced by concerns about the health of the forest at the end of the 1970s, the federal states in Germany have been carrying out regular forest condition inventories since 1983 using a statistically uniform sampling procedure, the results of which are summarized by the responsible Federal Ministry (currently the Federal Ministry of Food, Agriculture and Consumer Protection ). The first forest condition report was published the following year. Before 2003, this happened annually, since then "once per legislative period", ie every four years. However, individual federal states have retained the practice of annual forest status surveys, for example Baden-Württemberg .
Although the method is sometimes questioned, the process has now been harmonized across Europe in the ICP Forests program, in which a total of 41 countries are participating. It is therefore part of the forest environmental monitoring . A total of 24 trees per sampling point are estimated along a permanent network of 16 × 16 km (the network is usually denser at the state level). The state of the crown serves as a guide for the vitality of the forests. Deviations from a fully leafy crown are estimated as needle or leaf loss in 5% increments. The 5% levels are combined into so-called "damage levels". The damage levels 2 - 4 can be summarized in the category "clear crown deflations".
| Damage level | feature | Crown defoliation |
|---|---|---|
| 0 | healthy (without damage features) | 0-10% |
| 1 | ailing (weakly damaged) | 10-25% |
| 2 | ill (moderately damaged) | 25-60% |
| 3 | dying (badly damaged) | > 60% |
| 4th | dead | largely without needles (without leaves) |
Yellowing of leaves and needles is taken into account if the characteristic applies to more than 25% of the crown. The damage level is raised to a maximum of level 3.
Have a major impact on the condition of the crowns
- the presence of "harmful organisms",
- the age of the trees (the older the trees, the sooner crown defoliation is observed),
- the weather (drought, cold),
- Fructification (fructifying trees are more likely to have crown defoliation),
- inputs of substances into the forest caused by humans through air pollution.
In addition, further characteristics are included that are relevant for the evaluation of the data or that are of interest in the context of forest environmental monitoring in the assessment of climate changes and the development of possible adaptation strategies of forestry. One takes into account
- Environmental damage
- Peeling damage
- other game damage
- Fungal damage
- Wind, snow and ice break
- sunburn
- Insect damage
- Metal splinter damage
State of health of forests in Eurasia and North America
Assessment based on the condition of the crown
Using the European harmonized procedure for assessing the vitality of forests by assessing the condition of the crown, around 130,000 trees were assessed at 6,045 sample points in Europe (including Russia), of which 21.9% had needle or leaf losses of more than 25%. These values can be much higher locally. Between 1997 and 2006, improvements were found on a quarter of the areas, deterioration to around 10%. The absolute highest level of crown defoliation was observed (in Germany) in 2004, which, due to the weather, can be attributed to the exceptional drought in 2003 .
Assessment and extent of individual causes of damage
Data on the development of damage caused by all kinds of factors are only available for European countries from around 1950. The amount of wood affected can be estimated. The economic damage is very difficult to quantify. Even more complicated is an assessment of all the damage that has occurred to the total value of the forest, taking into account values that are difficult to monetize, for example cultural aspects.
Overall, less data are available across Europe for assessing individual causes of forest diseases than for assessing the condition of the crown.
If Russia is not included, there are around 193 million hectares of forest in Europe , from which , according to FAO data , around 500 million cubic meters of wood are harvested each year, including damaged wood. As a result of natural causes alone, an average of 35 million cubic meters of wood was produced every year between 1950 and 2000 (0.15% of the wood supply in European forests). Storms caused over half of this volume (53%), fire 16%, snow 3% and other abiotic causes were responsible for a further 5%. Biotic causes were found in 16% of the cases, with bark beetle populations again being named as the cause for half of this volume. The rest of the wood could not be clearly assigned to any of these categories.
Abiotic causes
Due to the storms of the 1990s in Central Europe ( "Vivian" , "Wiebke" and "Lothar" ) alone, around 340 million cubic meters of wood had to be removed from the forest. The financial damage caused by “Lothar” was estimated by the German Forestry Council (DFWR) at around 1 billion euros. In 2005 hurricane Gudrun caused 75 million cubic meters of damaged wood in 1.64 million hectares of forest in Sweden. The last severe hurricane in Central Europe was "Kyrill" on January 18, 2007.
Forest fires in Europe are a phenomenon in the Mediterranean region (93.6% of all fire-burned areas are located there). Portugal and Spain are primarily affected, with almost half of all fire areas. On average, around 178,000 hectares of forest go up in flames in Europe every year. In 2007, particularly devastating forest fires occurred in Greece . Most forest fires are not caused by lightning strikes, as in natural systems, but by humans (carelessness, arson). In North America, around 2 million hectares of forest burn every year, in Russia up to 6 million hectares.
Biotic causes
In Europe around 2.7% of all forests are currently damaged by forest diseases of a biotic nature. With just over a million hectares, Italy has the largest forest area of all countries that has been damaged in this way. Biotic damage from insect gradations (from the bark beetles, especially the printer, also populations of Lymantria monacha) was first observed in Europe on a large scale between 1845 and 1867 (Lymantria), when an epidemic spread across the continent, which resulted in a total of 135 million cubic meters of damaged wood caused. In 1868 the first bark beetle calamity occurred in the Czech Republic. There were other notable gradations in Germany in 1890, in 1920 (again in Czechoslovakia), after the Second World War (when there was a lack of workers to clear storm surfaces), and in various Central European countries at the end of the 1960s. The last major epidemic in Europe occurred between 1990 and 1997. Damage from game is found in 3.1% of all forest areas in Europe. The trend points to further increases.
In North America , about 0.6 million hectares of forest are destroyed by insect damage every year, for Russia state estimates amount at least 0.2 million hectares of destroyed forest and almost 0.9 million hectares of stands damaged by biotic causes.
Immediate human causes
New types of forest damage caused by humans occurred in Central Europe in particular in the 1980s and aroused fears about the future of the forest in industrialized countries. The term “forest dieback” became well known in the German-speaking world. On larger areas one saw devastated forests in exposed low mountain ranges. However, the mass death of all forests, which was forecast at times, did not materialize. The causes have not yet been fully clarified, but it is believed that pollutant inputs were one of the main reasons for the phenomenon.
The immissions of air pollutants, especially sulfur, have now been greatly reduced in Europe. All forests in Central Europe are polluted with high levels of nitrogen pollution, including from motor vehicle traffic. This leads to rapid growth with a simultaneous lack of other important elements such as magnesium , which reduces the resistance of trees to pathogens.
In Germany, too, according to the forest status report from 2007, with reference to the Federal Environment Agency , between 1990 and 2005:
- Sulfur dioxide (SO 2 ): −90%
- Nitrogen oxides (NO x ): −50%
- Volatile hydrocarbons (without methane): −65%
- Ammonia (NH 3 ): −16%
The exposure of the forests to ozone (O 3 ) was exceeded at over half of the measuring stations.
"Smoke damage" was known to a limited extent as early as the 19th century and has been observed in many places in Europe. The Katowice region was affected in Poland ; even today, south and south-west Poland are heavily influenced by the input of substances. Of the Baltic States, Latvia has the most damaged forests. In Russia there is serious damage on the Kola Peninsula , near Kemerovo and in central Siberia, as well as near Bratsk .
Also in Russia, damage to the forest due to radioactivity in the catchment area of nuclear facilities, as well as in the Kaluga , Bryansk and 13 other administrative units as a result of the Chernobyl reactor disaster was reported. According to government reports, around one million hectares are contaminated.
In the 1970s, nickel ore smelting in Sudbury , Ontaria, Canada caused acid rain and acidification of the soil in the region through the release of SO 2 , which caused forest and other vegetation to die off. From 1978 onwards, the regional administration began to whitewash, fertilize and replant the soil.
literature
- Peter Burschel , Jürgen Huss : Outline of the silviculture. A guide for study and practice . 2nd, revised and expanded edition. Parey, Berlin 1997, ISBN 3-8263-3045-5 .
- Fritz Schwerdtfeger : The forest diseases. Textbook of forest pathology and forest protection . 4th, revised edition. Parey, Hamburg / Berlin 1981, ISBN 3-490-09116-7 .
- Mart-Jan Schelhaas: Impacts of natural disturbances on the development of European forest resources. Application of model approaches from tree and stand levels to large-scale scenarios . (Alterra Scientific contributions 23). Alterra, Wageningen 2008, ISBN 978-90-327-0356-1 .
- Rudi Holzberger: The so-called forest dieback: on the career of a cliché: the topic of the forest in journalistic discourse. Eppe, Bergatreute 2002, ISBN 3-89089-750-9 .
Web links
- Forest Damage Database in Europe (DFDE), European Forest Institute, Joensuu, Finland. Available online at http://efi.int/publications-bank/database-forest-disturbances-europe-dfde-technical-description
swell
- ↑ a b The Kosmos Forest and Forest Lexicon. Stuttgart 2002, ISBN 3-440-09316-6 , pp. 793f.
- ↑ Peter Burschel , Jürgen Huss : Ground plan of the silviculture. A guide for study and practice. 2nd, revised and expanded edition. Parey, Berlin 1999, ISBN 3-8263-3045-5 , p. 92. (overview)
- ^ Fritz Schwerdtfeger : The forest diseases. Textbook of forest pathology and forest protection . 4th, revised edition. Parey, Hamburg / Berlin 1981, ISBN 3-490-09116-7 .
- ↑ How the forest suffers from drought , Neue Zürcher Zeitung, August 2, 2018.
- ↑ NM Nabatoff: Lesowodstwo. Uchebnoe posobia. Isdatelstwo Moskowskogo Gosudarstvennogo Universiteta Lesa, Moscow 2002, p. 171 ff.
- ↑ Burschel, Huss: Ground plan of silviculture. 1999, p. 300.
- ↑ Burschel, Huss: Ground plan of silviculture. 1999, p. 303.
- ↑ Stefan Ebner, Andreas Scherer: The most important forest pests. Insects, mushrooms, small mammals. Leopold Stocker Verlag , Graz / Stuttgart 2001, ISBN 3-7020-0914-0 .
- ^ Karl Gayer: The mixed forest . Berlin 1866.
- ↑ Carl Reuss , Julius von Schröder : The damage to the vegetation by smoke and the Upper Harz hut smoke damage. Berlin 1883. (New edition: 1987, ISBN 3-487-08279-9 )
- ^ A. Bemmann: Eastern Europe with Russia. In: Josef Herkendell, Jürgen Pretzsch (Hrsg.): The forests of the earth. Inventory and perspectives. Beck, Munich 1995, ISBN 3-406-39227-X , p. 86.
- ^ Heinrich Hofmeister: Habitat forest. Plant communities and their ecology. 4th, revised edition. Parey, Berlin 1997, ISBN 3-8263-8446-6 .
- ↑ Fritz Scheffer: Textbook of soil science. 14th, revised and expanded edition. Enke, Stuttgart 1998, ISBN 3-432-84774-2 , pp. 326-330.
- ↑ Burschel, Huss: Ground plan of silviculture. 1999, p. 131.
- ↑ a b c Wolfgang Schwenke: Guide to forest zoology and forest protection against animals. Parey, Hamburg / Berlin 1981, ISBN 3-490-06816-5 , pp. 156-164.
- ↑ a b c P. Burschel, J. Huss: Ground plan of silviculture. A guide for study and practice. 2nd revised and expanded edition. Parey, Berlin 1997, ISBN 3-8263-3045-5 , p. 87.
- ↑ a b c d e P. Burschel, J. Huss: Ground plan of the silviculture. A guide for study and practice. 2nd revised and expanded edition. Parey, Berlin 1997, ISBN 3-8263-3045-5 , p. 26 f.
- ↑ Discussion about measures to combat large-scale forest damage is picking up speed , www.arte.tv, August 1, 2019
- ^ Forest ministers want to help German forests with the "Moritzburg Declaration" www.mdr.de, August 1, 2019
-
↑ Cornelius Senf, et al .: Canopy mortality has doubled in Europe's temperate forests over the last three decades. In: Nature Communications Vol. 9 (2018), Article number 4978 ( online , nature.com); also:
After the forest dieback comes the tree die. science.ORF.at, November 26, 2018;
New tree deaths in Central Europe? scinexx.de, November 27, 2018. - ↑ see ICP Forests
- ↑ a b c d e Federal Ministry of Food, Agriculture and Consumer Protection: Results of the 2007 Forest Condition Survey.
- ↑ a b Horst Kramer, Alparslan Akça: Guide to forest measurement. 3rd expanded edition. JD Sauerländer, Frankfurt am Main 1995, ISBN 3-7939-0830-5 , pp. 207f.
- ^ Ministerial Conference on the Protection of Forests in Europe: State of Europe's Forests 2007. The MCPFE Report on Sustainable Forest Management in Europe. MCPFE Liaison Unit, Warsaw 2007, ISBN 978-83-922396-8-0 , p. 23f.
- ↑ a b c MJ Schelhaas: Impacts of natural disturbances on the development of European forest resources: application of model approaches from tree and stand levels to large-scale scenarios. (Alterra Scientific contributions 23). Alterra, Wageningen 2008, ISBN 978-90-327-0356-1 , pp. 10-17.
- ^ FAO: State of the World's Forests 2007. FAO, Rome 2007.
- ↑ a b c Ministerial Conference on the Protection of Forests in Europe: State of Europe's Forests 2007. The MCPFE Report on Sustainable Forest Management in Europe. MCPFE Liaison Unit, Warsaw 2007, ISBN 978-83-922396-8-0 , p. 26.
- ↑ The area around Olympia no longer exists. on: tagesspiegel.de , accessed on April 26, 2008.
- ↑ a b U. Treter: Canada and USA. In: Josef Herkendell, Jürgen Pretzsch (Hrsg.): The forests of the earth. Inventory and perspectives. Beck, Munich 1995, ISBN 3-406-39227-X , p. 118.
- ↑ a b A. Bemmann: Eastern Europe with Russia. In: Herkendell, Pretzsch (ed.): The forests of the earth. Inventory and perspectives. Beck, Munich 1995, ISBN 3-406-39227-X , p. 93 f.
- ↑ MJ Schelhaas: Impacts of natural disturbances on the development of European forest resources: application of model approaches from tree and stand levels to large-scale scenarios. (Alterra Scientific contributions 23). Alterra, Wageningen 2008, ISBN 978-90-327-0356-1 , p. 43.
- ^ Ministry of Natural Resources of the Russian Federation: Russian Forests 2005. Forest Industry Publishing House, Moscow, ISBN 5-94737-014-X , pp. 26f.
- ^ Ministerial Conference on the Protection of Forests in Europe : State of Europe's Forests 2007. The MCPFE Report on Sustainable Forest Management in Europe. MCPFE Liaison Unit, Warsaw 2007, ISBN 978-83-922396-8-0 , p. 21.
- ^ Ministry of Natural Resources of the Russian Federation: Russian Forests 2005. Forest Industry Publishing House, Moscow, ISBN 5-94737-014-X , p. 28.
- ↑ HC Martin (ed.): Acidic Precipitation: Proceedings of the International Symposium on Acidic Precipitation Symposium in Muskoka, Ontario, September 15-20, 1985; Springer Science & Business Media, publication November 11, 2013, accessed July 14, 2019. - 200 of 400 papers presented, pp. 543–545 of the reading sample.