The inclusion of overlooked lichen microhabitats in standardized forest biodiversity monitoring

Epiphytic lichens are increasingly included in forest biodiversity monitoring schemes, but most of the standardized guidelines consider only lichens colonizing a small part of tree trunks (1.0-1.5 m) and overlook other important microhabitats, such as fallen branches and stumps. In this paper, we present results of a small-scale pilot study to evaluate the possible advantage of including four distinct microhabitats in standardized procedures for assessing epiphytic lichen diversity. Trunk bases, trunks between 100 and 150 cm above the ground, stumps, and fallen branches were each sampled with a different standardized sampling method along a forest age gradient in temperate deciduous forests of the Caucasian region. Plot-level species richness was contrasted between the standardized sampling procedures of different substrata and a non-probabilistic floristic sampling. The interactions between sampling procedure and stand age were analysed using linear mixed models, and non-metric multidimensional scaling (NMDS) and multi-response permutation procedures (MRPP) were used for comparing species composition. Overall, 97 species were recorded, their richness increasing with increasing stand age. Results were consistent across the gradient of stand age and demonstrated that the adoption of standardized sampling procedures which include stumps and fallen branches in addition to tree trunks would increase the capability of maximizing species capture. This approach would allow researchers to evaluate lichen patterns by simultaneously considering the response of different communities sensitive to different stand-related factors. Despite the likelihood that a non-probabilistic floristic survey would give a more exhaustive picture of the plot-level lichen diversity, standardized sampling procedures that include tree trunks, fallen branches and stumps are likely to represent a reasonable trade-off between exhaustiveness and cost-effectiveness