- Wetwood is a term used for both a disease of wood and for the wood, altered
as a result of the disease.
Wetwood is wood infected by anaerobic bacteria mostly. The infected wood is altered in ways that disrupt membranes, high pH, and low amounts of free oxygen as micro spaces are filled with water and leakage of substances leads to high concentrations of elements. These alterations create a niche. Wetwood is a type of protection wood similar to discolored wood in early stages, except that the infecting microorganisms are usually anaerobic bacteria. They also infect wounds, branch stubs and root stubs. The bacteria so alter the wood -high pH, high moisture, low oxygen -that infection by decay-causing fungi is stalled. Spider heart is a common feature in forest trees, especially white oaks. As the first crack forms, other cracks form that equalize the loading. Rarely will there be only one major crack or seam in a forest tree. Wetwood lubricates the cracks. Trees in the genera Ulmus, and Populus seemed to have evolved with wetwood as a form of protection wood. When wetwood begins to decrease, rot begins to increase.
Another story on wetwood: WETWOOD -Wood altered to a higher state of protection against mechanical disruption or decay by pathogens that make the wood so high in moisture pH and microelements that decay-causing pathogens are not able to infect. A disease of wood caused mostly by bacteria that are facultative for free oxygen. The wetwood- causing pathogens alter in some way the permeability of the wood cell walls. The moisture content of the wood may increase. Yet in some trees the moisture content of infected wood is no higher than healthy sapwood. But the wood that is infected should normally be much lower in moisture content than healthy sapwood. For example, if healthy sapwood has a normal moisture content of 90% -weight of water to weight of dried wood- and normal aged wood has a moisture content of 30% then infected aged wood that has a moisture content of 90% is the same as healthy sapwood, but three fold higher than normal aged wood. The infected wood would also have a high pH and a high concentration of microelements. Which means the wood would have a very low resistance to an electric current. Wetwood is easily detected by the Shigometer because the wood does have a very low electrical resistance. It is very important to understand that wetwood is a protection "trade off" for the tree. In a sense, it is better for the tree to have an infection that causes a small amount of injury than to have the wood cells attacked by pathogens that could rapidly cause decay and mechanical disruption and death by breakage. When wetwood dries, decay-causing fungi attack rapidly. Some trees such as species in the genera Ulmus, Populus, and Betula, have developed along with the wetwood organisms to the mutual survival benefit of both tree and organisms. The wetwood organisms can exist as anaerobics-live with little or no free oxygen. They often produce methane, which is a colorless, odorless gas. The gas may force wetwood-formed liquids out of the tree trunk, and the fluids may flow down the trunk killing many surface bark-inhabiting organisms such as algae, mosses, and lichens. The wetwood liquids may stain the bark white. The liquids may also kill turf. The wetwood organisms commonly infect dying branches. The bacteria spread through the branch protection zones most of the time. The columns of wetwood follow the CODIT patterns. Wetwood may also form in roots, and the organisms may spread upward as roots die. The only way to understand patterns of wetwood formation is to study longitudinal sections of trunks, branches, and roots. The wetwood organisms stay within the tissues at the time a branch or root died. Wetwood organisms do not spread radially beyond the limits of the wood present at the time a branch or root died, or at the time a root was inflicted. There is no mystery to wetwood. The organisms follow the same CODIT patterns as other organisms. Wetwood organisms may also form in heartwood or false heartwood. In some trees, such as American Elms and species of Populus the wetwood organisms infect the wood long before normal aging processes would occur. The wetwood-altered wood never can become normal heartwood in such a case. And, finally, it is better for the tree to have a little wetwood than a great amount of decayed wood. Do not drain wetwood columns, unless you want decayed columns instead. (See "Water And Decay") (See "Wetwood / Branches")
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