Umbrella strike

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Shelterwood in the clear cutting loose book industry with well developed natural regeneration .

As screen flip , or on harvested in which is forestry a type of harvesting referred to, wherein the canopy of a stock will be thinned by removal of individual trees.

history

The basic concept of the umbrella strike was first set up in the 18th century in the Hanau-Munzenberg Forestry Regulations of 1736 and later further specified by Georg Ludwig Hartig (1791). On the basis of the methods described by Hartig, umbrella chopping developed into the dominant form of timber harvesting in the 19th century. It was primarily used in beech stands, but also in mixed stands of fir, spruce and beech and achieved satisfactory results, whereas in pure pine and spruce stands, the umbrella strike was not successful due to insufficient yields. At the end of the 19th century, the umbrella slap developed into the Femelschlag .

Action

Regardless of the type of tree, the course of an umbrella stroke is divided into six phases that extend over a period of 10 to 30 years.

  1. Closed old wood: The stand consists almost exclusively of old wood, all trees are roughly the same size and form a closed canopy.
  2. Preparatory cut: By removing approx. 15% of the additional wood supply, the canopy is carefully opened and the implementation processes on the ground are improved. This step can be skipped for crops with favorable soil conditions.
  3. Insemination cut: In this phase, known as the fattening year, 30–40% of the additional volume is removed. This creates a light canopy that allows the entire area of ​​the stand to be tapered . Before the seeds are dropped by the tree, the soil is prepared for rejuvenation, as far as necessary, using various processing methods.
  4. Clearing cut: In this phase, most of the old wood screen is cleared. The proportion here depends on the development of the taper. In order to maintain an ecological protective effect, a loose, very light umbrella remains.
  5. Clearance blow: The remnants of the old wood, which are mainly on the edge of the stand, are removed. Individual trees that do not restrict the progress of regeneration can remain.
  6. Conclusion: The old structure was completely replaced by a rejuvenation that was evenly spread across the entire area. In this phase there are no more trees from the old stand.

This classic type of umbrella strike is sometimes heavily modified for various reasons. Due to improved soil conditions in the past, the preparatory cut is often dispensed with. The improvement in soil conditions also results in an improvement in the growing conditions for soil plants. This creates the risk of weed growth in the young growth. To counteract this, before opening the canopy, make sure that the young plants have a head start over the ground plants in their development. Otherwise it may be necessary to take expensive countermeasures to protect the young growth. Fattening years, in which high yields are achieved by removing large amounts of waste wood, lose their importance and are often made dependent on the progress of regeneration. Furthermore, the remaining individual umbrella trees are used today to further develop the individual trunks through the higher exposure of the tree and thus to achieve a higher-quality yield when harvesting.

Forms of umbrella strike

The following are the most important forms of umbrella strike:

  • Large umbrella cut: Uniform umbrella position on large areas, e.g. B. whole departments or sub-departments.
  • Zone umbrella cut: Uniform umbrella position at a depth of one to three old tree lengths, usually beginning in the part of the stand that is to be rejuvenated away from the storm.
  • Stripe umbrella strike: Uniform umbrella position at a depth of up to the length of an old tree, starting in the part of the stand to be rejuvenated that is facing away from the storm.

Ecological importance

The umbrella strike is of particular importance for the development of shade and half shade tree species. These tree species need an environment that is poor in competition and protected from excessive weather influences in order to be able to develop optimally. Due to the slowly progressing thinning of the umbrella, the young growth can grow without too great an influence of these disturbing factors and is strong enough at the end of the umbrella stroke to assert itself against these external influences.

Advantages and disadvantages

Umbrella cutting represents the most important form of forest regeneration alongside clear cutting . If a stand is to be renewed through natural regeneration alone, umbrella cutting is the predominant method.

The following advantages and disadvantages arise with silvicultural regeneration by means of an umbrella blow:

advantages

  • Shade and semi-shade tree species can, according to their ecological requirements, naturally rejuvenate under umbrella protection and develop there until they can cope with the environmental conditions of the wilderness - temperature extremes, competing ground vegetation.
  • By appropriate cutting guidance, light tree species can also be introduced in groups or clusters into the group population of shadow-bearing species.
  • If mixed stands are sought, they can be achieved through natural regeneration if mother trees of the corresponding tree species are present or through artificial introduction if there are no such trees.
  • If natural regeneration fails or is impossible, the entire regeneration process can also be carried out artificially through planting or sowing.
  • If, at the latest at the beginning of the regeneration, a spatial arrangement appropriate to the terrain is created for each stand, then the harvest of the old trees above the regeneration that has arrived causes only minor technical difficulties.
  • If longer roofing periods are observed, there may be considerable increases in clearing on the exempted old trees. If the logs are of high quality, this is associated with a significant increase in value.

disadvantage

  • In the fattening years of the seldom fructifying tree species, non-market-oriented amounts of wood can occur if more wood is harvested to promote the arrival of rejuvenation.
  • The harvest costs for clearing and clearing cuts are increased because surcharges have to be paid for special care when cutting and backing.
  • The risk of storm throwns in waste wood increases considerably in the first few years after the umbrella is in place.

literature

Individual evidence

  1. ↑ Peter Burschel / Jürgen Huss: Ground plan of silviculture: A guide for study and practice 3rd edition Freising / Freiburg. 2003, p. 123. ISBN 3-8001-4570-7
  2. ↑ Peter Burschel / Jürgen Huss: Ground plan of silviculture: A guide for study and practice 3rd edition Freising / Freiburg. 2003, p. 125. ISBN 3-8001-4570-7
  3. ↑ Peter Burschel / Jürgen Huss: Ground plan of silviculture: A guide for study and practice 3rd edition Freising / Freiburg. 2003, p. 141. ISBN 3-8001-4570-7