Ground Beetles as Indicators of Land Type Diversity in the Green Mountains of Vermont

Abstract

Ground beetles (Coleoptera: Carabidae) captured in pitfall traps were compared within and among three Ecological Land Types in the Green Mountain National Forest, Vermont, to determine if beetle distributions can be linked to an ecological classification system designed to reflect biological diversity. Beetles were sampled in a nested‐scale design comprising three ecological land types, three polygons representing each ecological land type, five sites within each polygon, and six individual traps at each site. A nested analysis of variance showed only 2 of 35 species to vary significantly in relative abundance across ecological land types; most of the significant effects were at the site scale. To determine whether sites might sort into groups based on their beetle assemblages, sites were ordinated by detrended correspondence analysis and classified by two‐way indicator species analysis. Ordinations suggested that the distribution of ground beetles was somewhat influenced by site moisture; classification separated groups of hygrophilous species and wet sites from other ecologically uninterpretable species assemblages and site‐groups. Several of the site‐groups contained sites affiliated primarily with one ecological land type. However, a nested analysis of variance using the relative abundance of each of the species assemblages again showed most significant effects to be at the site scale. Results indicated that ground beetle distributions were not significantly linked with ecological land types and that the ground beetle fauna of the mid‐elevation forests of the western Green Mountains is comprised mainly of forest generalists, with some specialist species responding to a moisture gradient at the site scale. Because the ecological land type units did not explain distributions of carabids, these organisms should next be related to higher and lower scales within the classification system. Distributions of other invertebrate and vertebrate species should also be studied to test the utility of this ecological classification system for monitoring forest biodiversity.