Specific tree surveys
Examples of tree surveys are investigation of site conditions, tree stability or tree pulling test, sonic tomography (SoT), electrical resistance tomography (EIT) and transplanting possibilities of trees. A brief description is given below.
In the urban environment many trees are faced with an inadequate habitat. This becomes evident when a tree displays disappointing growth and premature failure. Trees often do not achieve the desired final image. Examples of inadequate habitat or growth site include insufficient space for rootgrowth, soil compaction, an increase in ground level, altered soil-water balance or recent construction work. An important component in the growth site survey is fieldwork, here trenches are dug or drilled to make abnormalities below groundlevel visible. Often this can be translated to the problems the tree has, since almost 70% of the tree problems is related to soil conditions. If necessary or desired, soil samples are taken for specific analysis.
Tree pulling test
Trees derive their stability from the root system and rooting space. A damaged root system or degeneration by fungi results in a decreased stability. To measure tree stability, the behavior of the stem base and root system under controlled tension is registered by inclinometers. Elastometers measure the bending capacity of the tree, here reduced breaking resistance due to cavities or decay by fungal activities can be detected.
The tree pulling test is based on scientific research by Lothar Wessolly. Processing of raw data is done by software where the specific wood properties and wind load analysis are taken into account. Different scenario’s can be calculated showing effects of pruning on the stability of the tree.
Wood rot in the stem of a tree can develop after damage due to an accident, unfavourable timing of pruning or other causes. The breaking resistance of a tree decreases when a cavity due to wood decay enlarges or when the area of affected wood rot is increased. Sonic tomography (SoT) with the Picus together with electrical resistance tomography (EIT) can very accurately locate the wood rot, measure the size of the cavity and the speed of the wood rotting process, which can give a prognosis for the tree. Depending on the situation, a Picus measurement can be combined with elastometry, part of a tree-pulling test, to determine the breaking resistance.
Over time or during the planning process for redevelopment it may become clear that the tree cannot remain at their current location. Cutting down the tree is usually not the best option, since time and money has been invested to maintain the trees. Possibly, the tree can be moved to a different location. Transplantation of a tree is often cheaper than removal and investment in a new tree. Research looking into the possibility to transplant a tree take into account factors from above and below the ground, at the tree site and in the vicinity. For example, the necessary space for the tree and the presence of underground infrastructure. Tree technically, species characteristics and transplantation experience with the species are taken into consideration. Evaluation of the condition and current quality of the tree are important factors in this process. Due to the fact that the necessary preparation time, transplanting method, working method and a new tree site is unique for every tree, efforts to make the transplantation a success will be addressed in a written report as accurate as possible.
Often research questions or problems concerning trees are not standard and request a specific designed research method to solve the issue at hand. Examples are:
- Excluding or confirmation of (new) affected tissue
- Management plan for monumental trees
- Tree- or crown-anchoring
- Participation in review committees
- Expert opininion during conflicts
- Development of possible growth sites at groundlevel or roofs
- Writing an approach of implementation
- Monitoring of construction or other situations concerning trees
- Age determination by annual ring analysis