Forest conversion

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The forest conversion is a forestry measure which has a massive change in the forest scenes, especially of tree species composition and age class relations result. As a rule, the goal is to create forest stands with natural structures and life cycles. Usually single-layer, non-site coniferous forests are to be developed through silvicultural measures to structured, site-appropriate deciduous and mixed forests .

The reasons for the forest conversion are diverse: The greatest interest is the functional justice of the forests. These concern economic aspects as well as social and ecological ones. Therefore, forest conversion is always seen in the context of sustainability .

The forest conversion is fraught with economic upheaval. The conversion itself costs money (through necessary interventions, losses due to premature end use , planting costs if there are no seed trees in the vicinity), on the other hand, the yields in the deciduous forest can usually only be reaped later after the conversion than in the coniferous forest. The liquidity flow therefore occurs later, but is then constant and usually higher. Therefore, a conversion should always be preceded by a business analysis. In extreme cases, there is a risk of major liquidity losses, especially shortly after the conversion phase.

Terms

Unsatisfactory stands (tree species, structure) are changed during forest conversion. A distinction must be made between two technical terms.

Overpass

Overpass has several meanings and describes in the forestry sense:

conversion

Conversion in the silvicultural context means the conversion of an unsatisfactory stand while changing the tree species composition.

Forest conversion in Germany

Windthrow in a pure spruce stand

The forest in Germany covers around 11.4 million hectares. The most common tree species are currently the Norway spruce ( Picea abies ) with 26.0 percent and the Scots pine ( Pinus sylvestris ) with 22.9 percent. By nature, however, the German forests would be strongly characterized by deciduous trees, especially the common beech ( Fagus sylvatica ). Today's tree species composition with high proportions of conifers reflects the forest use of the past centuries. From the Middle Ages to the early 19th century, many forests in Germany were overexploited or cleared. In order to avert an imminent wood shortage , these devastated forests and bare areas were reforested with spruce on the better soils with a good water supply and with Scots pine on the more nutrient-poor and drier locations as part of sustainable forestry . These two robust tree species cope better with the difficult ecological conditions on clear-cut areas than frost-sensitive tree species such as red beech and silver fir ( Abies alba ) and also deliver high timber yields. During and after the two world wars, the war destruction, the reparation blows and the need for wood for the reconstruction resulted in large bare areas, on which pure stands of spruce and pine were often established again. With the reconstruction of the German forests, the forest owners and forest people at the time - in view of the large areas and only limited funds available - made a great cultural contribution.

It soon became clear, however, that the large-scale and age-matched conifer stands also cause major problems, such as mass reproduction of bark beetles and other insects, soil acidification and an increased risk of forest fires and wind throws . Since the forest dying debate at the beginning of the 1980s and at the latest since the major windthrow damage caused by the Vivian and Wiebke hurricanes in 1990, the foresters and many forest owners have therefore been gradually converting the pure conifer stands into species-rich and stable mixed forests as a precautionary measure . This preventive forest conversion is also gaining in importance in view of climate change , as the tree species spruce and Scots pine , which were originally adapted to the climatic conditions of the mountains and the boreal zone , are likely to become even more susceptible to damage with the higher temperatures and longer dry periods. The progress made in forest conversion in Germany over the past few decades is also reflected in the results of the federal forest inventories :

  • In the period between the First Federal Forest Inventory (BWI I) 1987 and the Second Federal Forest Inventory (BWI II) 2002, the area of ​​the spruce decreased by 219,000 hectares in the old federal states , while the area of ​​the beech trees increased by 151,000 hectares. In addition to the planned forest conversion, larger areas of calamity from wind throws (hurricanes Vivian , Wiebke and Lothar ) and bark beetle infestation played an important role in this development.
  • In the period between the Second National Forest Inventory (BWI II) in 2002 and the Third National Forest Inventory in 2012, the spruce area in the entire federal territory decreased by a further 242,000 hectares and the pine area also decreased by 85,000 hectares. The damage caused by bark beetles after the drought summer 2003 and the windthrow damage caused by Hurricane Kyrill in 2007 contributed to this. In contrast, the beech area expanded by a further 102,000 hectares and the area of ​​the other deciduous trees by 213,000 hectares. The conifer species Douglas fir and silver fir , which are important for forest conversion, have also increased their area slightly by 35,000 hectares and 19,000 hectares, respectively. The total area of ​​deciduous trees rose by 2.8 percentage points to 44.5 percent between 2002 and 2012, while the proportion of conifers decreased accordingly to 55.5 percent.

The need for forest conversion in Germany is still high. According to the Third National Forest Inventory (2012), 24 percent of the German forest area has no mixed tree species or a mixed tree share of less than 10 percent. In the pine forests in particular, there are still 43 percent pure stands. But 29 percent of the spruce forests, which are particularly susceptible to damage, are not mixed either.

literature

  • Peter Fritz (Ed.): Ecological forest conversion in Germany - questions, answers, perspectives . Munich
  • Konstantin von Teuffel (ed.): Forest conversion. For future-oriented forest management . Springer, Berlin, Heidelberg and New York 2005, 422 (XVI) S., ISBN 3-540-23980-4
  • Federal Ministry of Food and Agriculture (BMEL, Ed.): The Forest in Germany - Selected Results of the Third National Forest Inventory , Berlin 2014. Online version (PDF; 5 MB)

Web links

Individual evidence

  1. ↑ a b Results database of the Third National Forest Inventory (2012) . Retrieved September 1, 2015.
  2. ↑ BMEL (Ed.): The Forest in Germany - Selected Results of the Third National Forest Inventory , p. 5.
  3. ↑ BMEL (Ed.): The Forest in Germany - Selected Results of the Third National Forest Inventory , p. 19.
  4. ↑ BMEL (Ed.): The Forest in Germany - Selected Results of the Third National Forest Inventory , p. 19.