The revered image of a tree is the stand alone; the individual, an icon of strength and durability. But these characteristics are not a given thing, each tree adapts to its environment and changes over time to alter its physical disposition in respect of necessity. In relation to wind, wounding, and environmental change. As such a tree is an example of what patience for change can bring.
To succeed Tree Inspection cannot just provide an understanding of the tree as an isolated entity; consideration must be given to the situation and environment in which the tree has developed. Trees adapt to their surroundings.
Before a tree inspection commences, a site history should be established. Reviewing the types and levels of change within the trees local environment will guide observations.
Changes may include; the removal of individual trees within a stand. Changes in drainage, or wind exposure, will dramatically effect remaining members of the group. By altering drainage and irrigation relationships and changing the dynamics of wind resistance, newly exposed trees face different physical and physiological stresses.
An individual tree inspection begins at ground level. Here; tree species, soil quality,rooting conditions, soil level, irrigation and drainage characteristics can be determined. The level of soil compaction may be tested to evaluate the aeration capacity of the soil. Compact soils can cause problems by restricting the trees ability to discharge the gasses produced as part of the growth cycle. Continual heavy foot traffic and the heavy equipment used in construction can cause compacted soils.
A soil test may be made to assess the fertility of the soil. Testing establishes the presence and degree of vital nutrients and the acid balance of the soil. An imbalance of nutrients, overly acidic, or alkaline soil can cause poor vitality and expose the tree to disease. In certain situations a soil moisture may also be necessary to assess the availability of water to the root system.The presence of fungal fruiting bodies, mushrooms, can indicate decay. Certain decay fungi may destroy support tissues and leave conductive tissues unharmed. The tree appears healthy and continues to grow until the decay outpaces the new growth, or the trees ability to compartmentalize or 'wall off' decay. Other species of fungus act quickly and destroy the flexibility of wood leaving the tree prone to wind snap. The type of decay and its effect on the stability of the wood depends on the species of fungus involved. The strength loss due to decay may be measured. A root crown examination may be necessary if root decay is suspected. By removing the soil at the base of the tree the location, health and condition of the absorbing and support roots can be evaluated.In the primary examination of the root crown and trunk a mallet is used to test for loose bark. Bark lifting can indicate dead or hollow areas and give signs of the presence of decay in the root crown zone and at the base of the trunk. The mallet may be used to "sound" for decay but this has limited reliability in some species. If decay is suspected the tree will be tested using the Resistograph Further testing devices are described in Decay and Defect Detection.
The inspection continues with above ground observation of the tree if necessary, climbing into the canopy of the tree. An assessment is made of leaf color and size. Trunk, branch, and twig color, size and condition, are also assessed. Crown density, past and current growth are combined with an evaluation of the growth habit. Changes in growth rate may indicate prior disease or injury. Previous treatments such as pruning, or cabling are observed. Any growth defects are noted, along with: weak limbs, discolored or missing bark, cavities in branches or trunks and the presence of disease, insects and other stress indications. Trees produce adaptive growth to compensate for the stress related to growth and injury. The shape and formation of limbs and trunks can show the ability of the tree to compensate for weakness or indicate internal problems that may lead to failure. The interpretation of these changes in form is part of a growing body of knowledge pioneered in Europe. The knowledge is not new but the application is: Dr. Claus Mattheck of the Karlsruhe Institute and colleagues, have developed a system of structural evaluation based on the bio-engineering principals. The examination of trees using these principals is incorporated in V.T.A. Visual Tree Assessement.
The V.T.A. method and the background information can be found in the Body Language of Trees Claus Mattheck.
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