Published online by Cambridge University Press: 10 March 2017
Field survey by a taxonomist or specialist biologist (‘taxonomic survey’) provides a comprehensive inventory of species in a habitat. Common and conspicuous species are rapidly recorded and search effort can be targeted to inconspicuous or rare species. However, the subjective nature of taxonomic survey limits its usefulness in ecological monitoring and analysis. In contrast, ‘ecological sampling’, focused on the standardized use of repeated sub-units such as quadrats, is designed to quantify the observational error of results, allowing for more robust statistical treatment. Nevertheless, the spatial extent of recording will be lower during ecological sampling, and rarities might be missed. Despite their differences, these two approaches are often assumed to be congruent for decision making. Taxonomic survey is commonly used to identify priority sites for conservation (including species-rich sites, or those with many rare/threatened species) while ecological sampling is used to design conservation strategy by relating species richness or composition to habitat dynamics. If these contrasting approaches are indeed congruent, then trends in species richness and community composition, detected by ecological sampling, will mirror the results of taxonomic survey so that management confidently protects the attributes for which a site was prioritized. This study performed both taxonomic survey and ecological sampling for lichen epiphytes in 13 woodland study sites in Scotland. To understand the procedure of taxonomic survey, fieldwork by a professional taxonomist was structured by effort into 15-minute time intervals. As expected, taxonomic survey discovered more species per site, while ecological sampling (allowing a measure of species frequency) resolved greater variation in community composition. However, the patterns of richness and species composition obtained from the different methods were correlated, suggesting an overall high degree of congruence in identifying and then managing priority sites. Furthermore, when exploring the taxonomic survey in detail, we found that a minimum effort of 45 minutes was required to accurately determine species richness differences among contrasting woodland sites.