Tree health
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Tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
s can live for a long time but eventually die, either from natural causes or killed by man. Ill-health of trees can be diagnosed, and early treatment, pruning or felling to prevent the spread may result in
timber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, wi ...
stocks and amenity trees being saved. Tree owners and
Arborist An arborist, tree surgeon, or (less commonly) arboriculturist, is a professional in the practice of arboriculture, which is the cultivation, management, and study of individual trees, shrubs, vines, and other perennial woody plants in dend ...
s/arboriculturists need to be aware of the risk posed by hazardous trees. Construction projects sometimes avoidably damage trees.


Sources of tree damage

The causes of tree damage and abnormalities can conveniently be divided into either biotic (from living sources) or abiotic (from non-living sources). Biotic sources include insects (e.g. that bore into the tree), mammals (e.g. deer that rub bark off),
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
, birds,
nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant-Parasitism, parasitic nematodes also known as eelworms. They are a diverse animal phylum inhab ...
s, bacteria and
viroid Viroids are small single-stranded, circular RNAs that are infectious pathogens. Unlike viruses, they have no protein coating. All known viroids are inhabitants of angiosperms (flowering plants), and most cause diseases, whose respective economi ...
s. Abiotic sources include
lightning Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...
, vehicles impacts,
construction Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and com ...
activities,
drought A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D.  Jiang, A.  Khan, W.  Pokam Mba, D.  Rosenfeld, J. Tierney, an ...
, waterlogging,
frost Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a gas) ...
, winds, chemicals in the soil and air and
soil nutrient Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former t ...
deficiencies. Construction activities can involve any of a number of damage types, including grade changes or compaction that prevent aeration to roots, spills involving toxic chemicals such as cement or
petroleum product Petroleum products are materials derived from crude oil (petroleum) as it is processed in oil refineries. Unlike petrochemicals, which are a collection of well-defined usually pure organic compounds, petroleum products are complex mixtures. The m ...
s, or severing of branches or roots. Trees with thinner bark such as
birch A birch is a thin-leaved deciduous hardwood tree of the genus ''Betula'' (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus ''Betula'' contains 30 ...
and
American sycamore ''Platanus occidentalis'', also known as American sycamore, American planetree, western plane, occidental plane, buttonwood, and water beech, is a species of ''Platanus'' native to the eastern and central United States, the mountains of northeas ...
are more sensitive to such damage. One of the most common naturally occurring hazards in large trees is weakness in the union between trunk and branch (or between co-dominant substems). 'V'-shaped unions may create weakness and increase failure risk; in some situations this can be reduced by tree cabling, which limits how far the union can flex in strong winds or other loads.. Any of these damage sources and the natural ageing of trees may result in trees or parts of them failing prematurely. The term "hazard trees" is commonly used by arborists/arboriculturists, and industry groups such as power line operators, for trees that, due to disease or other factors, are more susceptible to falling in windstorms, or having parts of the tree fall. Damage may also disfigure amenity trees, create unacceptable risks to people, reduce the safe useful life of trees or reduce the value of commercial timber. Trees can withstand large amounts of some types of damage and survive, but even small amounts of other traumas can result in death, disfiguration or hazards. Established trees will normally not tolerate any appreciable disturbance of the root system. Without arboricultural advice, lay people and construction professionals may not be aware how easily or indirectly a tree can be killed.


Decay studies

Fallen logs of white spruce and trembling aspen at various stages of
decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...
were sampled from undisturbed and 1, 14, and 28-year-old post-fire and post-harvest sites in northern Alberta, and studied for differences in the associated microfungus communities (Lumley et al. 2001).Lumley, T.C.; Gignac, L.D.; Currah, R.S. 2001. Microfungus communities of white spruce and trembling aspen logs at different stages of decay in disturbed and undisturbed sites in the boreal mixedwood region of Alberta. Can. J. Bot. 79:76–92. Wood samples were plated directly onto each of 6 different media and from these fungal species were identified and enumerated over a 24-month period. Approximately 10 000 isolates were obtained, representing 292 species of filamentous microfungi, including 41
ascomycetes Ascomycota is a phylum of the kingdom Fungi that, together with the Basidiomycota, forms the subkingdom Dikarya. Its members are commonly known as the sac fungi or ascomycetes. It is the largest phylum of Fungi, with over 64,000 species. The defi ...
, 29
zygomycetes Zygomycota, or zygote fungi, is a former phylum, division or phylum of the kingdom Fungi. The members are now part of two Phylum, phyla: the Mucoromycota and Zoopagomycotina, Zoopagomycota. Approximately 1060 species are known. They are mostly t ...
, and 222 mitosporic fungi. The most commonly isolated species were ''
Trichoderma viride ''Trichoderma viride'' is a fungus and a biofungicide. It is used for seed- and soil treatment for suppression of various diseases caused by fungal pathogens. Biology ''T. viride'' is a mold which produces spores asexually, by mitosis. I ...
, Rhinocladiella atrovirens, Penicillium pinophilum'' and ''Mortierella ramanniana''. Cluster analysis and ordination of microfungus communities in logs showed that the tree species of the log had the greatest influence on the species composition of communities. Fungus community composition was also correlated with the stage of decomposition.
Species richness Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative a ...
was highest in logs from undisturbed sites, and lowest in logs from the most recently disturbed sites. Species diversity (Shannon-Weaver) was only slightly higher at undisturbed sites than at disturbed sites. The most significant environmental factor was log moisture, which increased proportionately with stage of decomposition and was significantly correlated with climatic factors. Wounds inflicted on residual trees during partial cutting often provide portals for decay fungi. Affected trees are prone to blowdown and breakage at the wound site, and even if they survive to rotation age their value is reduced by staining and decay in the wood. The influence of temperature on microbial diversity in wounds in white and black spruces was investigated by Dumas and McLaughlin (2003).Dumas, M.T.; McLaughlin, J.A. 2003. Microbes inhabiting ''Picea'' wounds and their antagonism to ''Haematostereum sanguinolentum'' p. 181–193 ''in'' Laflamme, G.; Bérubé, J.A.; Bussières, G. (Eds.). Root and Butt Rots of Forest Trees. Proc. 10th Internat. Conf. on Root and Butt Rots, IUFRO Working Party 7.02.01, Quebec QC, Sept. 2001. Nat. Resour. Can., Can. For. Serv., Inf. Rep. LAU-X-126. 450 p. Samples were taken from trees wounded during manual or feller-buncher partial cutting and skidding operations in the Black Sturgeon Forest, 120 km northeast of Thunder Bay, Ontario. The samples were taken from 76 trees in early October when the mean aerial temperature exceeded 0 °C and 23 trees in late October/early November when the mean aerial temperature was below 0 °C, to serve as the pre-freeze-up and post-freeze-up groups, respectively. The wounds were sampled and cultured. The number and ratio of bacteria, actinomycetes, and fungi on one-week-old wounds varied between pre- and post- freeze-up wounds, wound locations, and media. However, random samples of the different classes of microbes isolated from the 2 spruce species did not differ significantly, indicating no relationship between tree species and microbe. Wounds were more common on stems (94) than on roots (64) or butts (33). Wounds on roots averaged 2 and 3 times the area of those on stems and butts, respectively. More
bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
than
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...
were isolated from the pre-freeze-up wounds than from the post-freeze-up wounds, while fungi were more plentiful than bacteria on the post freeze-up wounds.


Tree risk assessment

Evaluating the danger a tree presents, whether by its state of health or by its situation, to people and/or property is called Tree Risk Assessment. Techniques have emerged based on Matheny & Clark's matrix of three factors which contribute to the degree of risk namely (i) failure potential (ii) size of defective part and (iii) target rating (how often something or someone is present to be harmed or damaged). Subsequently, a Quantified Tree Risk Assessment ("QTRA") system has been developed by others that calculates the risk numerically with reference to cost implications of tree damage and published societal norms of acceptable, tolerable and unacceptable risk. The International Society of Abroriculture updated its approach in 2012 with a qualitative (words based) matrix known as Qualitative Tree Risk Assessment ("TRAQ") To comply with the tree owner's legal duty of care to occupiers, visitors, passers-by or neighbours, where regular observation or monitoring of the tree's condition is not possible, tree inspections should be carried out at appropriate intervals by a competent person and their risk reduction recommendations should be implemented.


Construction and tree protection

Assessment of the damaging effect of construction activities on a tree can be based on three factors: severity, extent and duration. Fundamentally activity should avoid the crown of the tree and the volume of rooting required by the tree for ongoing vitality. Severity is related to the degree of intrusion into the rooting area and resultant root loss. Extent is related to a percentage of a factor such as canopy, roots or bark, and duration is based on the length of time that the activity interferes with the tree's normal functions. Various organisations, such as the International Society of Arboriculture, the British Standards Institute and the Tree Industry Association (formerly the National Arborist Association), have long recognised the sensitivity of tree health to construction activities. The effects are important because they can result in monetary and/or amenity value losses due to tree damage and resultant remediation or replacement costs, and/or prosecution for violation of government ordinances (in the UK, planning laws, regulations and policies) or community- or subdivision restrictions. In the US, protocols for tree management prior to, during and after construction activities are well established, tested and refined. These basic steps are involved: * Review of the construction plans * Development of the related tree inventory * Application of standard construction tree management protocols * Assessment of potential for tree damage * Development of a tree protection plan (providing for pre-, concurrent, and post construction damage prevention and remediation steps) * Development of a remediation plan * Implementation of tree protection zones (TPZ) * Assessment of construction tree damage, post-construction * Implementation of the remediation plan In the UK, a similar protocol exists.BS5837 (2012): Trees in relation to design, demolition and construction - Recommendations, British Standards Institute, 2012


References

{{Portal, Trees


External links


Tree protection zone calculator


Trees