Lichen diversity in serpentine habitats of the North Coast Range, California

. Macrolichen diversity and community composition were determined for an area of high (HMBA) in Six Rivers National Forest. The Coast Ranges have been suggested to have high lichen diversity, yet detailed site-specific macrolichen surveys are lacking for the area. The HMBA is characterized by the presence of ultramafic (serpentine) soils, contributing to its diverse assemblage of conifers. Here we present comprehensive data on macrolichens of the HMBA integrated with environmental variables at the landscape level. Twenty 0.4 ha sampling plots were positioned across the varying habitats of the HMBA and macrolichens were intensively sampled from all substrata. Out of 888 total collections, 119 macrolichen species in 52 genera were identified, 63 species were sequenced for the mycobiont internal transcribed spacer (ITS) region, and all species were vouchered. Microenvironmental influences on lichen community composition were ordinated with nonmetric multidimensional scaling (NMS). Within-plot measured environmental variables with strongest correlations to ordination Axis 1 were 1) total tree basal area, 2) proportion of conifer basal area relative to hardwoods, and 3) distance between plot center and nearest stream. Distinct macrolichen communities were found in plots containing primarily conifers versus mixed hardwood-conifer plots. All plots contained both nitrogen-fixing and pendulous forage macrolichens; in each of the three hardwood-dominated plots, nitrogen-fixing lichens composed nearly a third of the species total. When epiphytic macrolichen species richness and dominance within the HMBA were compared to data from other regional forests, the HMBA showed comparable community composition but averaged 39% higher species richness. Results from this study can help inform management of the HMBA as well as future taxonomic and ecological research on regional macrolichens.