BREEDING CUTTING

“Forestry is not everything, but without it everything is nothing”

 

BREEDING CUTTING – OPPORTUNITY FOR NATURAL PRODUCTION OF QUALITY WOOD
MARTIN BORISOV*, TSENKO TSENOV **, GRUD POPOV ***,
JOACHIM SCHELZER ****, WALTER MATAYS **** 1

Crop cuttings are silvicultural activities for the application of scientifically based methods for timely and rational guidance of the natural development of forests in a desired direction (Leibundgut. 1987).

In Bulgaria, plantations, that need cultivation cuttings have an area close to 825000 huh, which is 22% of the total area of ​​forests. From an economic point of view, this activity is unattractive, because a significant part of the breeding activities are without material yield or with low profitability. This necessitates the search for approaches, which preserve and improve the ecological functions of plantations, their resistance to biotic and abiotic factors, the assortment structure of the stands and the quality of the harvested wood, while at the same time the time and costs of their implementation are minimal.

The purpose of the publication is to present a modern concept , in which the biological characteristics of tree species are used (“biological automation”) and natural successional processes to ensure environmentally friendly production of high-quality wood. For the first time in a comprehensive form, this concept was more widely applied before ca 20 years in the province of Saarland - Germany.

The applied concept is based on the following more important principles:
– Excellent knowledge of the biology of tree species, habitat conditions and forest dynamics,
– A combination of environmentally friendly, economic and social goals,
– Freedom of action of the forester regarding the period, the type and intensity of silvicultural intervention,
– Compliance with the current market reality,
– Continuous training and improvement of the qualifications of the participants.
With the application of this concept, the production of high quality is achieved, valuable, coreless wood for a shorter period, while preserving all the ecological functions of the forest.

1. Content of the concept.

1.1 General notes

Various cycles take place in forest communities, which are affected by periodic fluctuations. When human impacts do not exceed these fluctuations for the relevant community, can be accepted, that this is environmental management.
* LTU
** DOG
*** IG at BAN
**** SAARFORST, Germany

Biological diversity should be taken as a key parameter for environmentally friendly forest management. It can be viewed at different levels:
– A variety of living spaces
– Species diversity (compared to undisturbed forests)
– Genetic diversity
The term «species diversity» should always be associated with the potential natural forest community. When this is considered, only in exceptional cases will it make sense to artificially import rare and endangered tree species, which are embedded in the long-term goal of forest development.

Succession areas are released after windy and/or calamity areas, which are not accepted as catastrophes, but much more like violations. They initiate natural processes, which should proceed as independently as possible. Events, which affect or hinder these processes – e.g. tillage, eradication, Remove the “competitive” vegetation, intensive afforestation – are counterproductive from an environmental point of view. The undisturbed development of pioneer phases with their typical tree species such as birch, aspen, Rowan etc., have a positive influence on the development of the ecosystem. Allowing self-regulation mechanisms in the most important phases of forest development ensure the preservation of the genetic potential of all tree species involved in the succession. The foothills is the bottom of the opportunities to restore the forest on areas, occurred after natural disturbances, and also for afforestation of areas, which until now have not been occupied by forest. The task of the pre-forest is to provide the following advantages for the tree species lying in the long-term goal of forest development:
– Frost protection,
– Protection from direct sunlight,
– Suppression of competition from other vegetation.
The forest floor primarily supports the development of shade-tolerant tree species. Even with afforestation with shade-tolerant species, they should only be imported under the pre-forest assembly.

If, due to the impossibility of timely development of a forest and/or because its species must remain as companions in the future forest, it has to be artificially created from species suitable for the purpose (alder, Rowan, cherry etc.). These species do not adversely affect desirable later successional tree species.

In farming, it must be given advantage of native tree species. In the sense of biological automation, natural regeneration takes precedence, when it consists predominantly of native or at least locally suitable tree species, according to the long-term goal of forest development. “Resuming a move” not wanted. To a much greater extent, natural regeneration in different size groups and windows is desired in the process of stock formation. (maturity stage) and during the main use.

The economic goal of the concept is the production of high-quality wood. It is known from previous experience, that the wood is of good quality and valuable when it is of large size, without plugs, without disabilities, it has symmetrically formed annual rings and is without internal tension. It should be considered, that not every large tree produces quality wood. It is known from theory and practice, that in the production of large-sized timber, the crown is the engine of growth. The larger the crown area, the more powerful is its photosynthetic activity, which is the basis of wood production.

It has been found, that in the lower ones 25% from the height to maturity of tree species is concentrated almost 50% of the total biomass, and with good quality and approx 80% of the net worth of the tree. This is valid, then, when the others 70 – 75% from the height of the tree of the future is occupied by a powerful, strong and symmetrical crown (fig.1). that's why, in this concept, efforts are directed towards growing a certain number of trees, in which the lower section (25% from the potential height) to be of a sufficiently large diameter (targeted) and without plugs.

This silvicultural concept does not use the classic terminology for breeding activities, i.e. lighting, purges, thinning and test tubes. That is right, because these terms are appropriate in plantation management, and in the present conception all interventions are targeted at the individual tree!

1.2 Stages in application of the concept

1.2.1 First stage – Intervention in the emergence phase:

These are breeding events in youngsters with a maximum height of up to approx 3 m. They are different depending on whether a young plant is grown in an open area or under the structure of the old plantation.

Economic goal at this stage is undisturbed development of tree species underlying the long-term goal of forest development, which will allow the fastest possible assembly of the young plantation.

Past experience shows, that measures to support shade-tolerant versus pioneer species are very rarely required. The positive impact of pioneer tree species goes far beyond their impact as competitors to commercial tree species.

The undergrowth must not be endangered or damaged as a result of breeding activities. Thus, it is generally not desirable to remove them during the first half of the growing season, because the young shoots are not sufficiently woody. The use of machine brush cutters and chainsaws is not desirable, because when a competitor's stem is cut from the stump, multiple stump shoots develop - the "hydra effect" (fig.2).

Recommended refraction of competitive saplings of pioneer species at half the height of economic tree species. This eliminates strong competition from pioneer species, while preserving their protective functions. When breaking, not all the connections between the root and the crown are broken and the sapling lives for some time.

It is recommended that this event be carried out in the period of advanced vegetation - the end of July, beginning of August. Such events should never be held over the entire area, but only pointwise!

1.2.2 Second stage – Intervention in the qualification phase (differentiation):
This is silvicultural intervention, which takes place in young plantations, whose height is between 3 m and 12 m, by exception to 15 m.
By applying targeted, point breeding activities, the aim is to have as little impact as possible on this stage of development.

No activities should take place at the same time, which disrupt or even hinder natural processes, which increase the quality (especially the self-sharpening and drying of the branches along the stem).

An important condition from a technological point of view is to have access to the individual trees and the possibility of their observation, which is achieved by making clearcuts (access lines) in the young forest.
Targeted silvicultural intervention is applied only there, where prevention of negative development is necessary.
The distance between the clearings is 20 m and they bet when the self-sharpening has reached human height, because otherwise they will make a lot of noise.
Their width should ensure good passability and is 1 – 1.5 m.

At this stage, the so-called are determined on the area “option trees”. These are super-vigorous or vigorous trees with good stem quality.
For such options, representatives of all available tree species can be chosen.

Threats to the development of option trees are assessed and their competitors are determined. These are trees, which currently or in forecast until next entry (5-6 years) will limit the development of trees height options.

– All interventions are carried out in the upper part of the assembly. Interventions in the middle and lower part lead to unwanted homogenization of areas and disruption of structural diversity.
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– Lively, but with poor quality trees are usually ringed. They remain as a corset for several more years, with which they also support the self-sharpening process. Trees, which three stems/branches in quality trees are removed.
– In mixed young forests, the fast developing ones (light-loving) tree species such as. the cherry, ash tree, oak, reach the time to grow the tree of the future, while at the same time for the other species (shade tolerant) differentiation processes are still taking place, which must not be interrupted. The transition between the differentiation phase and the dimensioning phase should be smooth.
Rare tree species (“rarities)” and rare tree forms (“pieties)” must be preserved, regardless of their quality.
The rarer a given tree species is than the long-term goal of forest development, the lower the quality requirements for it.
During work, measures must be taken to shape the periphery of the forest.
In the differentiation phase, they are sufficient 2 afternoon events, in which are separated by 3 – 7 hours per hectare (in experienced workers).
An important element of this method is the ringing of the stems of individual trees. Ringing the bark of the tree interferes with the advanced phase of differentiation and the ringed tree dies slowly, this enables selected trees (options) to slowly occupy the vacated space. Technically, the bark and cambium are removed with a knife and an iron brush at chest height (this is the ergonomic height). Brushing the cut plays a very important role during juicing, it prevents healing and ensures success. Ideally, the ringed tree decays in a standing position.
The interim conducted so far “classic” thinning in most cases results in a disruption of differentiation in the stand. This promotes the formation of thicker branches of the crown and the self-sharpening of the crowns is delayed. There is a danger of missing the optimal time to enter the accumulation phase and the best trees can lose their vitality. It is known, that undisturbed differentiation accelerates the self-sharpening of branches to the desired height.
An important condition for the application of the method is the knowledge of the differences in the growth process of different tree species, to use the differentiation phase and choose an appropriate time for the accumulation phase. In some tree species, the accumulation phase begins at the following age: for the aspen of 9-12 years, for the birch of 12 – 15 years, snot on 25 – 30 years, for the oak of 25 – 30 years, for the beech of 30 – 40 years.
In the previous practice, criteria for evaluating trees during cultivation were mainly related to the quality of the stem and crown, as well as the uniform spatial distribution, as often stem quality was the main criteria and too many trees of the future were selected. For foresters in the past, vitality was often considered a disadvantage. In modern times
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forestry, new concepts such as super-vibrant are imposed, minimum distance and quality.
When applying this method of management, the task is to determine:
? Which tree has differentiated optimally and has the best starting crown? -it is observed whether the crowns are alive and whether the self-truncation is 25 % from the final height of the tree.
? Which defects do not allow a given tree to be selected for the future? – forked trees are not selected, with thick dry branches, branches, with a sharp angle of growth, /the forks, thick dry branches can lead to further stem rot and false core in beech/, with a thickening at the base of the branch, which forms under dying branches / branches in the shade of the green crown do not contribute to growth, because they need more energy than they produce, these branches should be removed at the beginning of the accumulation phase/
? What should be the distance between the trees of the future? – 10 – 15 m. distance is the critical value for most tree species. Before long, the tree crowns of the future begin to interfere if this distance is less.
ІІ. Processes in carrying out the method
When applying the method, two silvicultural interventions are distinguished - interventions in the differentiation phase and intervention in the dimensioning phase (accumulation).
General
In most cases it is necessary “introductory” intervention, since not all species tolerate in the beginning phase of accumulation the successive, release of the crown. Species such as sycamore and especially oaks, they often react to the successive defeat of competitors by forming water shoots. Therefore, a moderate removal of a is recommended 3, 4 competitors. They are removed there, where is the direction of active development of the main branches of the crown. When the tree of the future acclimatizes to the new environment, competitors are completely eliminated. After that, the crown can be developed symmetrically.
Growing the tree of the future involves removing all competitors, that touch the crown. In successive cultivation, a weaker development of aquatic shoots is observed on the crown of the super-vibrant trees. Competitors of the following species can be removed from deciduous tree species with one intervention: clear, birch, beech, cherry. In the case of oaks and sycamores, it is necessary “introductory” intervention, to prevent the formation of water shoots.
To achieve “illuminated” crown after removing competitors (in the accumulation phase) the main branches of the tree of the future should be light “showered” with light. This is achieved by removing competitors around the selected tree. Because competing crowns are often smaller, then the access of light around the crown of the tree of the future is slightly dosed.
When conducting the method, competition for water is observed. As the crown of the tree of the future struggles for light, so there is a struggle for water and nutrients between the roots. Water means growth and life, survival. Everyone
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competitor around the tree of the future uses its own water tank and no “want” to share it with other trees.
Successive release of the tree of the future creates an opportunity for more light to reach the crown (vacated space), it also means more area for the root system of the tree of the future. If it has previously fought with competitors for water, after their removal there is calm. This also helps the other trees on the periphery of the tree of the future. The root system becomes more powerful and increases stability.
When determining the trees of the future, an assessment of the shape of the crown is carried out. Trees with horizontal branches are accepted as a form meeting the requirements. Vitality and great growth are expected from these crowns. Branches use increased shoot growth to occupy space. Thin branches, rising at an acute angle to the sky, are not able to occupy the free spaces. Their crowns cannot respond properly to the removal of competitors.
Check whether the branches are V- and U- figurative. In principle, a tree of the future with a V-branch is not selected, regardless of the tree species.
When evaluating crowns, preference is given to high branching, since with him the architecture of the crown is more- favorable and the branches are protected by the lower bearing branches of the crown.
It is possible for super-living trees to have one-sided crowns. Differentiation rarely works that way, that the super-life trees have a crown developed in all directions, when the accumulation phase occurs. This does not play a special role at a young age, since the more important part of the crown will be formed only in case, that the elimination of competitors in the build-up phase began at the most appropriate time. The diameter and height of the crown develop with each passing year.
Of essential importance is the question of which side we should first help a tree. We have to help the crown from there, where she can absorb the help quickly. If the branches of the crown on the right, for example, are weak and small, quick intervention is not necessary. This would even lead to the death of branches from the left. With an introductory intervention, competitors must be eliminated. However, this does not mean, that other trees will not be removed during subsequent interventions.
When the trees are on a slope, looking up the slope, each tree is taller than its immediate neighbor below. In the struggle for light, the upper neighbor grows more easily above the crown of the tree below. Thus, that this phenomenon is valid for any tree, therefore the crowns of all are developed from the country, where the light falls from. That's why, when starting cultivation in the accumulation phase, competitors must be removed from the top of the slope.
Too many trees of the future should not be selected, because the distance between them is too small. There are very few competitors in the fields between them and in growing the trees of the future, the interstices disappear very quickly. Then trees of the future become competitors for each other, the withering of living branches continues and self-tearing continues upward. It's getting to the cutting of trees of the future, as they become competitors and the removed trees leave large spaces in the assembly, which can no longer be occupied by the crowns of the remaining trees.
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For crown molding success (growing in the accumulation phase) must be observed, that the tree of the future can only form an optimal crown when it is young enough (biological causes). If cultivation has started late, then no large one can form, productive crown. In that case it is accepted, that it is “too late” for such intervention. Then traditional cultivation is applied, as the crown cannot develop much.
There are several important differences when growing in the build-up phase (dimensioning) and classical thinning. In growing for dimensioning, the individual super-vibrant value tree plays a central role. It should produce high-quality assortments. It works only with the trees of the future and the spaces between them have “serving” character and is not grown in them. The trees in these spaces remain with relatively small crowns and subsequently when they are cut down they provide dosed light to the tree of the future.
In classical thinning, the intervention is carried out over the entire area of ​​the plantation and almost all good trees are cared for, and the laggards or the trees “wolves” are removed. This is how a uniform and homogeneous forest is obtained
There is a difference between homogenized trees and the overall stability of a forest grown using this method. When the trees have the same mostly small crowns, uniform height and diameter homogenized trees appear when working on the entire plantation area. In a storm, the homogenized forest vibrates in unison. This noise can lead to tree resonance or a massive windbreak or windstorm.
Overall stability depends on individual and collective stability. In a forest managed by this method, the trees of the future are grown earlier and have a high individual stability against wind. Over time, they take up more and more space in the plantation.
An essential point in this method is, that nothing takes place in the intervening spaces. When working in the intermediate areas, the collective stability of the forest is weakened, as all trees are cared for, and for the trees of the future they are insufficient. The crowns of the trees in the intermediate areas also become large. Thus, careful care for the tree of the future becomes impossible. After all, many of the trees are undergrown. In the maturity phase, when trees are not capable of quick reaction they will have low individual stability, which cannot be raised and is in danger of falling down in a storm.
The following requirements are placed on the crowns of the trees of the future and those in the intermediate areas: the crown of the tree of the future must begin after 25 % self-pruned stem from the expected final height of the tree. Thus, a large and powerful crown develops and conditions are created for obtaining high-quality wood from the thick self-pruned stem under the crown. The crowns of the trees in the intervening areas are drawn upwards over time and remain small. If it is necessary to grow the tree of the future, they must be removed. Trees from the intermediate areas are used for mass timber production.
If the distance between the trees of the future is sufficient, then the intermediate areas decrease gradually. With each growing of the tree of the future, the intermediate area becomes smaller and smaller, and sections, in which no tree of the future is selected remain as reserve areas. When working in the intermediate areas, the collective stability of the forest is weakened. In such a case, care is taken of all the trees, and for the trees of the future they are insufficient. The crowns of the trees
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in the intermediate areas they also become large and careful care of the tree of the future becomes impossible.
Towards the end of growing for sizing, where the tree of the future is not threatened by competitors, the trees in the intermediate areas initially remain, and during the maturity phase, timber can be harvested here.
When in the phase of differentiation the trees do not self-prune, pruning is necessary. Many trees of the future may have dry unfallen branches. Such branches are removed quickly and easily, as this procedure should not be considered gardening
A distinction must be made between light shoots and shade shoots. The light branches appear when the stem is exposed to direct sunlight and the light branches protect the stem from the sun and heat. Trees with large crowns do not often form light shoots (own shading from the crown). In these cases, the described is recommended “introductory” cultivation, which slowly prepares the tree of the future for the new light conditions. Shade shoots appear in depressed trees. They often have large leaves, which help the tree absorb even the smallest quantum of light.
Care must be taken when felling trees for primary use. For example, if crowns of felled trees lie on the undergrowth for one growing season, after a while the pressed and injured saplings develop crookedly towards the light. The crooked stem becomes woody and acquires a permanent curvature. Only years later does the old crown of the fallen tree rot. Trees with curved stems cannot subsequently be selected as trees of the future.
The method of individual cultivation of the trees of the future is entirely based on scientifically established dependencies in the field of biology, the physiology and dynamics of physical processes affecting the life of forest ecosystems
Conclusions and recommendations
1. This concept allows for self-regulation mechanisms in the most important phases of forest development, which ensure the preservation of the genetic potential of all tree species involved in the succession.
2. The application of this concept is linked to the potential natural forest community and only in exceptional cases will it make sense to artificially import rare and endangered tree species, which are embedded in the long-term goal of forest development.
3. The sustainable application of the concept allows to achieve a significant increase in the participation of biotope wood in the medium and long term.
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4. The concept makes it possible to realize the task of producing high-quality wood and a greater possibility of its root accumulation for a long period of time while preserving the main technical parameters of the wood.
5. When applying this concept, the intensity of interventions/management is as small as possible, which has the least lasting negative impact on forest dynamics.
6. With the implementation of the concept, costs - time have been significantly reduced, labor and funds, when carrying out breeding activities.
7. The implementation of this concept requires continuous review and improvement of the qualifications of the forestry and technical personnel involved.
8. At the 1st stage in the young, we should refrain from reducing the number of stems and adjusting the composition, with the exception of interventions imposed on pioneer tree species!
9. In the 2nd stage, in the young plantations, cultivation measures are directed only to viable ones (vital) poor quality trees (negative selection) until then, until the goal of differentiation is achieved,
10. In the III-th stage, the death of living branches from the base of the crowns of the trees of the future should not be allowed
11. For trees of the future, priority should be given to local species, and only as a second choice suitable for the conditions of the habitat species that are present no less than 15-25 m from each other.
12. An even distribution of the trees of the future is not a primary goal.
13. Rare tree species (companions), which meet the long-term goal of forest development, are selected, regardless of their quality, for the so-called “ecological trees of the future” and are managed in a manner, which guarantees their preservation
14. It is not advisable to choose trees of the future along the technological paths!
15. The sustainable application of the principles of interventions to the tree of the future represents a timely rejection of large-scale schematic interventions on the entire plantation and a transition to management of the individual tree.
16. Into the plantings, in which few are found “trees of the future” attention is paid only to them and they are not chosen “trees of the future with lowered criteria”. 17. In the sections, where no tree of the future is found, nothing is done and they remain as reserve areas. Uses can be made here entering the maturity phase
18. The only criterion for the intensity of the interventions in relation to the tree of the future is their need to obtain space for the development of the crown, in order to obtain a uniform width of the annual rings. 19. The removal or suppression of alien species is recommended only then, when they interfere/compete strongly with native and habitat-appropriate species in the long term.
20. Interventions in the spaces between the trees of the future should not take place
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21. In plantations where some cuttings have already been carried out using other/classical methods, the interventions are tailored to this – use of introductory interventions, at small distances of “the trees of the future” – on the lower limit of 15 m, etc..
22. With the main use of the root, some of the trees of the future are left as biotopes. These may be predetermined already in the dimensioning phase, or they may be determined during the main use.
23. All branches and waste wood up to 10 cm is not taken out of the forest.
24. Interventions with the tree of the future require highly skilled workers, knowing the biological and ecological characteristics of tree species. They know the felling techniques that remove and reduce the threats to the trees of the future when felling takes place.
25. Cultivation activities are not carried out during the first half of the growing season.