Sorting plots not taxa for studying vegetation structure and plant species richness

Abstract

Most sampling methodologies do not stratify the vegetation and thus provide no information on the herb layer, where the species richness of whole vegetation stands may be largely controlled. Braun-Blanquet relevés do provide such data, and a large relevé database for eastern North America was used to try to identify factors related to species richness. Statistical analysis showed little relationship between plot-scale species richness and measurable environmental factors, including climate, but herb layer richness did seem to be related to site physical properties. Geographically extensive vegetation inventories can thus perhaps be used to study plot-scale species richness, if the fieldwork includes adequate description of site topography and substrate properties. Relevés can then be sorted, based on these physical properties, in order to identify habitat situations that may be related to species richness more closely than are more general environmental conditions. The extent to which the resulting plot groupings show relatively consistent vegetation structure and species richness may provide insight into their controls.

Keywords:

• Plant species richness
• plot scale, substrate properties
• verbal habitat descriptors
• plot sorting
• Eastern North American Vegetation Survey