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Severe low-pressure storm systems frequently generate windthrow gaps, or openings in the canopy created by the death of a large branch or one or more trees. Frequent windthrow events generate a forest mosaic of different age classes and species. These small-scale disturbance events are the primary source of forest turnover.
The creation of canopy gaps results in temporary increases in the availability of light, water and nutrients and decreases in root competition, which allow canopy recruitment of saplings. Tree species respond differently to variation in gap size, origin, orientation and age. For example, sugar maple and beech thrive in the shady small canopy gaps (20-100m2), while white ash and tulip tree require sunny larger canopy gaps (>400m2), which occur less frequently. As gap size increases, woody species diversity and the size and number of stems increase. Gaps formed by wind-uprooted trees are typically larger with more exposed bare soil than gaps formed by stem breakage. Stem-breakage gaps may favor root sprouted saplings, while uprooted tree gaps can allow less shade tolerant species such as oak or tuliptree to establish.
For more information, see: Coastal Habitat Assessment, Section V (PDF)