Age group forest

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Comparison of the ideally almost constant dimensional distribution in the plenter forest to the dimensional distribution of an age group forest that changes depending on the age.

The age group forest (in the prevailing type of operation of the single high forest ) is still the predominant type of operation for forestry wood production in Germany and Europe . In Germany it covers around 90% of the forest area. One speaks of age group forest when silviculture takes place in a cycle of planting, care, harvest (clear cutting) and replanting.

In natural forests, forest regeneration takes place irregularly both in terms of time and space, so that - depending on the succession phase - more or fewer trees of all ages grow next to each other. However, if - as is often the case in the evergreen coniferous forests of the earth's boreal forest belt - large-scale destruction of the vegetation (so-called " calamities "; in particular due to fire, storm and insect infestation), the entire area is rejuvenated and rejuvenated instead of. However, this comparison must not lead to the misconception that an age group forest is like a near-natural, northern coniferous forest after a calamity: The natural forest has a larger number of species despite the species-poor tree inventory in the boreal zone, the dead wood that occurs remains on the area and natural regeneration is unplanned . In the context of natural succession and selection , a completely different forest appearance quickly emerges than in the dense, evenly planted and regularly thinned commercial forest.

Silvicultural system

In a very similar way, work is carried out in the age group forest on the basis of homogeneous units of area of trees of the same age with a very small number of tree species. The management takes place accordingly in terms of area and stock within the framework of cultivation , clearing , thinning with or without prior use of the wood that is not ready for cutting and the end use of the stock that is ready for cutting after reaching the turnover period (= capital turnover). The resulting large amounts of wood at one fell location meet the needs of data acquisition and mechanized wood harvesting as well as logistics . The age group forest is particularly machine- and rationalization-friendly and therefore very popular in forestry practice despite its sufficiently recognized problems. Age group forest management also tends to monoculture with precisely those tree species that can be planted on the bare land without any problems and thus artificially rejuvenated (especially with conifers). The native deciduous tree species (e.g. beech and oak) tend to be disadvantaged in the age group economy or, as experience shows, lead to significantly higher costs and young forest risks (hoofed game bites, damage caused by drought, frost damage, etc.). In addition to the prevailing type of operation of the high forest, also the very rare, historical middle and coppice forest - thus also two-shift and two-layer stands as well as the maintenance operation, which are of no forestry importance due to their unfavorable use and cost structure, belong to the operating class of the age-group forest.

Historical meaning

Historically, the age class model is related to the development of the concept of mass sustainability , compliance with which is one of the central goals of the forest management inventory and planning process, forest management . In this respect, despite all the weaknesses of this approach from today's point of view, the first theoretically based implementation of sustainable forest management followed from the age-class forest , which until recently has been primarily oriented towards the sustainability of wood mass production. At the same time, the age group forest is the nucleus of sustainable forest management, even if it cannot meet more modern, in particular ecological and biological requirements.

Ecological assessment

The major calamities that regularly occur in the age group forest (e.g. due to snow breakage , storms, insect damage, fungus infestation, dryness, major fires, etc.) lead to its extensive rejection in the forest policy and ecological discussion today. This has led to state forest operations in Germany transferring parts of the homogeneous age-class forests into structurally rich permanent mixed forests . The age group forest tends to lead to structural poverty in the forest over a large area (see Gaussian normal distribution above) and thus to biological niche poverty. As a result, it lacks “biological” sustainability , which leads to a fundamental rejection of the age class economy by nature conservation. The forestry source of the extinction of typical forest species is seen in it, as well as the extreme lack of dead wood structures in the commercial forest (especially in larger dimensions ), since the “clean economy” inevitably prompts the age class manager to remove all sick and dying trees to counter biological risks in monoculture forests. The now generally prevailing criticism of age-group forests is intensified from the point of view of the threat of climate change, which will lead to both increased calamities and the ecological failure of important conifer species in age-group forests (especially spruce). Above all, calamities in the age-group forest due to the lack of structure and tree species usually lead to bare land - with almost complete release of the biogenic CO 2 storage - and subsequent, cost-intensive new plantings. Age-class forests therefore lack the necessary resilience to face climate change, which is a considerable economic and ecological disadvantage compared to permanent forests . The accelerated conversion of the age-class forests is therefore now seen in forest policy as having no alternative.

Individual evidence

  1. a b cf. in detail: Wilhelm Bode / Martin von Hohnhorst: Waldwende. From forest forest to natural forest , Munich 1994 (4th edition Munich 2000, ISBN 3-406-45984-6 )
  2. cf. z. B .: The eco-forest. Recipe against forest dieback. , Spiegel No. 48/1994
  3. cf. u. a .: National strategy on biological diversity , adopted by the Federal Cabinet on November 7, 2007