Invasion of Matrix Species in Small Habitat Patches
Stefan Ås, Department of Animal Ecology,NULL, Uppsala University, Sweden
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The diversity, expressed as species richness in equal-sized samples, of wood-living beetles in successional stages of deciduous forest after forest fires approximately 100 years ago did not differ between patch sizes in this study. Thus, the crucial question for conservation is whether the lack of reduction in diversity in small patches means that a number of small patches can elevate the regional diversity as efficiently as can one larger area. In the present study, the smaller patches did not differ from larger patches in substrate availability, quality, or heterogeneity. The frequency of a group of species was measured as the number of occurrences, viz. the number of trees on which a species was found, summed over all species in the group. The number of occurrences of species unique to the specific patch-size group did not differ between large and small patches. The number of occurrences of species that preferred matrix areas (managed coniferous forest and clearcuts) was, however, larger than expected in small patches. The results indicate that small patches, although having high local (alpha
) diversity, are more similar in species composition to neighboring matrix areas (reduced beta
diversity). Thus, small areas contribute less to the regional (gamma
) diversity than do larger areas.
alpha (local) diversity, beta (between-habitats) diversity, deciduous forest, disturbance, diversity, fire, gamma (regional) diversity, invasion, matrix habitat, patch size, species-richness.