Windthrow

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In forestry, windthrow refers to trees uprooted by wind, or to the phenomenon that causes such uprooting to occur. Windthrow is called windsnap when tree bole breakage occurs instead of uprooting. Windthrow, as a form of ecological disturbance, generates a variety of unique resources on which certain forest processes are highly dependent. Severe uprooting opens bare patches of mineral soil that can act as seed sinks. These patches have been shown, in the Pacific Northwest of the United States, to have higher biodiversity than the surrounding forest floor. Additionally, the gap created in the forest canopy when windthrow occurs yields an increase in light, moisture, and nutrient availability in near proximity to the disturbance. Windthrow is commonly the end result of tree senescence, where multiple factors contributing to the declining health of a tree increase its susceptibility to windthrow. Thus, windthrow can act as a rejuvenating process whereby regeneration is made possible with new resource availability.

Windthrow can result from logging, especially in young forests managed specifically for timber. This occurs when the removal of certain trees at a forest's edge increases the exposure of the remaining trees to the wind. The resulting damage can be a significant factor in the evolution of a forest. Forest stands adjacent to lakes or other natural edge-creating features have structural characteristics similar to those of a clearcut, but do not necessarily have a higher susceptibility to windthrow than interior stands. This is because a tree's rooting strength is developed through growth feedback with wind movement. If a tree does not experience much wind movement during the stem exclusion phase of stand succession, it is not likely to develop a resistance to wind. Thus, when a fully or partially developed stand is bisected by a clearcut, the seed trees and forest edges adjacent to the clearcut may not be capable of withstanding forces in which they didn't develop.

Trees with heavy growths of ivy, wisteria, or kudzu are already stressed and may be more susceptible to windthrow.

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