Contrasting responses of epiphytic and dead wood-dwelling lichen diversity to forest management abandonment in silver fir mature woodlands

In the Alps, many forests are under abandonment because of direct protection or the unprofitability of timber production. The objective of this study was to analyse the effect of silviculture abandonment on the species richness and composition of epiphytic and dead wood-dwelling lichens in silver fir woodlands. An abandoned and a currently non-intensively managed forest watershed of the eastern Italian Alps that were matched for topography, stand structure, plant community and history of use were selected and randomly sampled for the lichen diversity of their silver fir mature stands. Generalised linear mixed models were used for the analyses of the species richness, whereas the species composition patterns were explored by redundancy analysis. The diversity of both of the lichen guilds were explained by the microhabitat conditions related to the contrasting management regimes, but they had opposite responses to the abandonment of the silvicultural activities. The epiphytic lichen communities were richer in species in the managed than in the abandoned silver fir woodlands. However, the effect of a 50 year management cessation on the epiphytic lichens may change in the long term when natural disturbances create gaps and increase the attributes of old-growth forests. The dead wood-dwelling lichen species richness was higher in the abandoned forest because an increased availability of types of dead wood is usually rare in managed forests. The dead wood-dwelling lichen communities of the managed forests were a subset of a more diverse community that was developing in the abandoned forest. Our results indicated that, in non-intensively managed silver fir mature stands, lichen diversity may benefit from the retention of logs and snags, which provide habitat features typical of old-growth forests.