Multi-Aged Forest Fragments in Atlantic France that are Surrounded by Meadows Retain a Richer Epiphyte Lichen Flora

ABSTRACT This project was focused on identifying the effect of environmental factors on epiphytic lichen species by using a multiscale design applied within multi-aged forest fragments. The field investigations were performed within 20 forest fragments, of which 14 were surrounded by crops and six were surrounded by meadows. Sampling units of 10 by 10 m were selected from the exterior to the interior of each forest fragment following the perimeter line; other sampling units were selected following the same perimeter line to the centre of the forests. The spatial gradient represented by the exterior and interior parts of the forest fragments, surrounding matrix and forest structure (i.e., the presence of larger trees) significantly supported patterns of lichen abundance and diversity. Lichen abundance and diversity were significantly influenced by microhabitat and macrohabitat drivers on the relatively large trees in the forest fragments surrounded by both crops and meadows. Lichen species replacement was significantly described by both larger and thinner trees situated in the interior and at the exterior of the forest fragments surrounded by meadows. The lichen richness was significantly higher on larger trees situated in the interior of the forest fragments surrounded by meadows. The mature structure of forests and the surrounding matrix significantly determined the pattern of epiphytic lichen species. Furthermore, larger and thinner trees harbour very rare lichen species within forest fragments surrounded by both crops and meadows. Forest management practices based on selective cutting on a short rotation cycle did not exert a negative impact on epiphytic lichen.