Tree health
[1] Biotic sources include insects (e.g. that bore into the tree), mammals (e.g. deer that rub bark off), fungi, birds, nematodes, bacteria and viroids.
[3] 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).
[4] Without arboricultural advice, lay people and construction professionals may not be aware how easily or indirectly a tree can be killed.
[citation needed] Fallen logs of white spruce and trembling aspen at various stages of decomposition 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.
[5] 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, 29 zygomycetes, and 222 mitosporic fungi.
[citation needed] 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.
[6] 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.
Techniques have emerged based on Matheny & Clark's [7] 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).
Extent is related to a percentage of a factor such as canopy, roots or bark,[clarification needed] and duration is based on the length of time that the activity interferes with the tree's normal functions.
[citation needed] In the US, protocols for tree management prior to, during and after construction activities are well established, tested and refined.
