Multi-taxon and forest structure sampling for identification of indicators and monitoring of old-growth forest

The most commonly used old-growth forest indicators are structural attributes; nevertheless, they do not necessarily represent the biodiversity value of old-growth forests. The aim of this study is to analyse the relationships between species richness data of different taxa and structural indicators of old-growth and to identify taxonomic/functional groups, species and structural attributes that may be used as indicators of old growth. To achieve this goal we sampled forest structure, vascular plants, lichens, bryophytes, fungi, saproxylic beetles and birds in mature and old-growth stands in southern Italy. We calculated Spearman's correlation coefficients between species richness data and structural attributes. Analyses of indicator species, co-occurrences and two-way clusters were performed on the multi-taxonomic list. The group of vascular plants most significantly correlated with other groups in terms of species richness; furthermore, it displays the highest proportion of between-group co-occurrences. The resulting multi-taxonomic list of potential indicators may serve as an effective means of detecting and monitoring forest ecosystems; however, for this goal, structure-based indicators, such as forest structural attributes and vascular plant species composition, are of primary importance. © 2010 Società Botanica Italiana.