|title||VOB procurement and contract regulations for construction work - Part C: General technical contract conditions for construction work (ATV) - landscaping work|
|Brief description:||If the rootstock is cleared, the rootstock and at least 20 cm of the roots and roots over 10 cm in diameter are removed.|
Clearing is the removal of woody plants , trees and shrubs including their roots . A distinction is made between area clearing and rootstock clearing . The latter means the removal of the rootstock of a single felled tree from the ground . The two approaches differ fundamentally, both in terms of the vegetative situation and the technical procedures, requirements and applicable regulations. The following shows the rootstock clearing.
Individual trees are usually cleared in private gardens and on cultivated or communal areas such as parks , gardens, greenery along the road , pedestrian zones , and cemeteries .
Difference between partial and complete clearing
If a tree is felled, the stump - also called stump - and the underground part of the tree - the roots - are left over. When clearing the rootstock of a single tree, a distinction is made between partial and complete clearing. In the case of partial clearing, parts of the root wood remain in the ground. With a complete clearing, the tree stump and all the root wood (root stock and roots as well as most of the far-reaching strong and lateral roots) are removed from the ground.
The principles of landscaping apply to clearing work . All main and ancillary services in the area of the topsoil are regulated in the DIN 18320 : VOB procurement and contract regulations for construction works, part C: General technical contract conditions for construction works (ATV) - "Landscaping", which was revised in September 2012, August 2015 and September 2016 . The clearing procedure itself is not prescribed in it.
As of 2015, the width and depth of the roots to be removed when clearing was stipulated: The central rootstock is to be removed up to 20 cm outside the root approach. The strong roots with diameters over 10 cm to a depth of 30 cm must also be removed. In addition to precise removal, DIN 18320 also stipulates the storage of the root wood. From all these requirements, it follows that complete clearing is the technically correct procedure, which makes demands on the clearing process.
Root wood risks
The DIN specifies complete clearing in order to prepare the tree site for replanting on the one hand and to protect it in the long term on the other. Because fungal infestation on remaining root wood in the ground can affect the stability and break resistance of a tree by being transferred to existing trees. Trees in urban areas in particular suffer from stress from waterlogging, prolonged drought , injuries, exhaust fumes or road salt ; this weakens their vitality and defense mechanisms, making them more susceptible to tree fungus infestation and more likely to pose a threat to people, buildings and other objects. In addition, rot can damage newly planted or remaining trees.
Putrefaction refers to the oxygen-free, i.e. anaerobic decomposition of organic material (here root stock or root remains) by microorganisms . From a certain depth in the ground, there is usually a lack of oxygen . Putrefaction can also occur in the upper soil layers, for example in loamy soils or in urban soils, which are often compacted . The bacterial decomposition produces gases such as methane , ammonia or hydrogen sulfide . These inhibit the growth of new plantings or remaining trees and can even lead to the death of all vegetation . Most of the time, putrefaction damages a site permanently.
Root wood remaining in the soil forms the breeding ground for many types of fungus. Honey fungus species, common root sponges , burn crust fungus or lacquer spores are parasitic fungi that attack and decompose dead wood as well as living trees. This process often takes place with a long delay, so that an incomplete clearing (partial clearing, area clearing) can damage a site decades later.
The spread of fungi takes place very differently, for example through spore distribution or root welds. The latter means that root-borne fungi spread between trees of the same species. Hallimasch species can also form fungal threads, so-called rhizomorphs , with which they expand from the infested substrate over distances of 50 meters and more to a new host.
A complete clearing carried out in accordance with the standards minimizes the risk of rot and fungal attack and helps to maintain the health of a tree location.
Common deforestation processes include milling and dredging with standard equipment. Another, meanwhile established alternative is removing the roots with the clearing knife .
Clearing with the tiller
During milling, the rotating cutting unit cuts the root stock. For felling of tree stumps often root or stump grinders used small and medium size. Their depth is limited, however, so that it is not possible to completely remove the root stock as prescribed in the DIN. Larger cutters can reach a depth of 80 cm, but are comparatively expensive and rarely available. In populated areas in particular, it is often difficult to mill a rhizome underground, as curbs , borders, underground cables and pipes are often in the way. Since it cannot be foreseen where the strong and lateral roots located further out and how far they reach down, the milling process is not suitable for searching the entire tree bed for roots. The risk of damaging cables and lines lying underground with the milling machine would be too great.
Clearing with an excavator and standard equipment
Often clearing is also carried out with the excavator including standard equipment, mostly backhoe buckets , grabs and possibly ripper teeth . In order to be able to carry out a complete clearing according to DIN specifications, the complete clearing area including the root wood must first be exposed. For such large-scale work, sufficient space is required around the root stock, which is often lacking in urban areas. The alternative of tearing up the stump requires enormous forces; For example, a root with a diameter of 10 cm has a holding force of more than 40 t. In the event of uncontrolled tearing, there is also the risk of damaging edging or the road surface .
Clearing with an excavator and special tools
A clearing knife is an excavator attachment tool that was specially developed for complete clearing . The working depth and radius are only limited by the excavator arm. The clearing of the central rhizome as prescribed in DIN 18320 can be carried out with the clearing knife, as can the strong and lateral roots that are further out.
When clearing, the clearing knife scrapes off the stump piece by piece. The strong and side roots can then be removed from the entire root space of the felled tree. At the same time, the soil is loosened. A new planting is therefore possible immediately after the clearing.
The topsoil is preserved in this process. The pieces of wood and roots brought to light are largely free of soil and large in volume, in contrast to the procedure with the classic stump grinder, which creates a mixture of wood chips, soil, stones, etc. The pieces of wood can be easily collected and stored - as required by the directive - or used as firewood, for example.
Another advantage in urban areas compared to milling is that the excavator driver has a good overview of the clearing area. This minimizes the risk of damaging cables, lines or other obstacles. In addition, no stones or earth are thrown up when clearing with a clearing knife, which significantly reduces the need for barriers.
- ↑ H. Neidlein: Roots have to be completely removed . In: campos . Edition 2. Verlag Eugen Ulmer, Stuttgart 2011, p. 12-13 .
- ↑ J. Hädicke: With bite: clearing stumps with the root rat . In: Agricultural engineering . Edition 5. Deutscher Landwirtschaftsverlag GmbH, Hanover 2011, p. 8-9 .
- ^ J. Zeitner: cutting, drilling, milling. Powerfully remove tree stumps. DEGA GALABau, edition 11. Verlag Eugen Ulmer, Stuttgart 2015, p. 32-35 .
- ↑ Ekkehard Musche: Compact stump milling . In: green + space . Edition Speciale, edition 1. Verlag dergartenbau, Zuchwil 2015.
- ↑ Ekkehard Musche: Handbook care devices. Purchasing, operation, maintenance . Verlag Eugen Ulmer, Stuttgart 2015, ISBN 978-3-8001-3381-9 , pp. 155 .