Early responses of biodiversity indicators to various thinning treatments in mountain beech forests

In recent decades, the conservation of biodiversity has become one of the main functions to be considered in managing forests in an ecologically sustainable way. Forest management practices are primary drivers of diversity and may enhance or decrease forest biodiversity, according to the applied measures (thinning options). We focused on three beech (Fagus sylvatica L.) forests across a latitudinal gradient in Italy, characterized by different structures resulting from dissimilar management histories. We tested the short-term effects of differently-based silvicultural interventions vs. stands where no silvicultural practices were applied on biodiversity indicators and related proxies: deadwood amounts, microhabitats density, floristic richness and life forms abundance. In each study area, the occurrence of the cited indicators and proxies was evaluated before and after the implementation of crop tree thinning (CTT) and thinning from below (LT) methods, comparing them with control areas where no interventions were realized. After two years, the management options resulted in different responses of the investigated parameters. The CTT increased deadwood amounts in comparison with the LT ones, while stumps increased significantly after the LT thinning. Microhabitats increased significantly where the interventions were not realized. On the contrary, they remained unvaried after the LT treatments. CTT thinning created favorable conditions for the development of microhabitats and their proliferation in the long term. Two years after application of the CTT thinning treatment, all forest stands demonstrated a significant increase in the floristic richness and herb layer cover. Significant differences were also found in the frequency and cover of life forms in relation to both silvicultural treatments. These findings provide a better understanding of short-term effects of silvicultural treatments useful for maintaining biodiversity in mountain beech forests.