Effects of life-history traits on responses of plant species to forest fragmentation

Knowing the general principles of plant-environment relationships is required to be able to predict changes in species occurrence and abundance in changing landscapes. Because habitat fragmentation may affect the dispersal, establishment, and persistence of species in various ways, we expected associations between species life-history traits related to these processes and their responses to fragmentation. We tested (1) whether groups of plant species with specific biological attributes are especially affected by forest fragmentation and (2) whether regionally rare species are more negatively affected than more common species. We surveyed 145 deciduous forest patches in northwestern Germany for the presence of a large set of forest plant species. For each of 82 species, we collected data on eight life-history traits and estimated species' responses to decreased patch size and increased distance to other occupied forest patches. We classified species into two emergent groups that differed strongly with respect to most considered life-history traits. The group of species that was more negatively affected by isolation mostly consisted of clonal forest specialist species characterized by few and heavy diaspores, lack of dispersal structures, small size, short-lived seeds, and insect pollination. There was no effect of patch area. Univariate analyses revealed (marginally) significant relationships between species' responses to isolation and diaspore number and mass, plant height, and habitat preference and between responses to patch area and seed-bank longevity plant height, and habitat preference. Regional frequency of occurrence was not correlated to species' responses to fragmentation and did not differ between the two emergent groups. Rare species, however, were smaller and produced fewer and shorter-lived diaspores than common species. Forest fragmentation may thus threaten species differently, depending on their specific biological characteristics. Approaches based on life-history traits potentially allow prediction of species' responses to habitat fragmentation and may therefore aid in the assessment of the endangerment of plant species and ultimately in the conservation of biological diversity.