Environmental predictors of forest expansion on open coastal barrens |
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Authors: | Scott T Burley Jeremy T Lundholm |
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Institution: | (1) Biology Department/Environmental Studies Program, Saint Mary’s University, Halifax, NS, B3H 3C3, Canada; |
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Abstract: | Rock barrens support rare plant species but may be threatened by forest expansion. We determined the extent of forest expansion
onto open coastal barrens and identified environmental correlates of dynamic versus persistent barrens in Nova Scotia, Canada.
We used aerial photos to quantify the amount of forest expansion over the last 70 years at five coastal barrens sites and
GIS to derive topographic and other environmental predictors to differentiate persistent coastal barrens compared with persistent
forests or barrens that succeed to forests. Linear discriminant and classification tree analyses identified the variables
associated with each class of habitat. Coastal barrens decreased by an average of 7.9% (from 4.2 to 24.6% depending on the
site) in the last 70 years due to forest expansion. The best predictors of persistent barrens were elevation and distance
to coast. Environmental factors such as topographical heterogeneity and evidence of fire varied among sites. Climatic and
edaphic conditions near the coast and in exposed inland areas may protect coastal barrens vegetation from forest expansion.
Evidence of fire was not found at all barrens sites, thus at least some of the persistent open barrens are likely maintained
by shallow soils, salt spray, and wind exposure. All three classes of habitat had distinct vegetation, and the only rare species
was found in a persistent barren. Management of human activities in such landscapes should take into account the dynamic nature
of barrens vegetation, while prioritizing conservation efforts in persistent barrens. |
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