Edge effects on an epiphytic lichen in fragmented forests

Increased amount of edge habitat is one of several important consequences of forest fragmentation. Consequently, we must understand the responses of plants and animals to edges to formulate adequate recommendations for conservation of biodiversity Epiphytic lichens are a well-suited subject for a study of abiotic edge effects because they gain nutrients and water directly from the atmosphere. We present a temporal model of edge effects on lichens based on empirical data for the pendulous fruticose species Alectoria sarmentosa Ten high-contrast edges of different age between mature Picea abies forest and large clearcuts (10-260 ha) were studied in northwestern Sweden. Abundance of A. sarmentosa (mass on I-m branch sections and maximum thallus length per tree) was estimated in the lower canopy in four 10 x 50-m(2) plots located 5-100 nz into the forest. The abundance of A. sarmentosa was markedly lower at the edge compared to the interior at 9 of 10 study sites. Lichen mass constituted 22% of that in the interior at young edges (0.5-2.5 years) and 55% at old edges (8-16 years). The length of A. sarmentosa was significantly affected by both distance from the edge and site location. Maximum edge effects extended 25-50 m into the forest at moderately exposed sites. The major factor reducing lichen abundance was physical damage by strong wind. Large, pendulous lichens such as A. sarmentosa are prone to thallus fragmentation. At older edges lichen abundance had recovered inside the edge (20-30 m), probably due to increased growth in response to increased irradiance. Our analysis supports the view that edge effects may be strongly dynamic over time and caused by the inter action of several factors. We conclude that epiphytic lichens have large potential as indicators of forest edge effects.