Tom Wessels, MA
Department of Environmental Studies
This thesis explores the relationship between the abundance of alpine plants known to be nested over a set of summits and the order of their disappearance from the nestedness matrix of Atmar and Patterson (1995). Nestedness means that the species on smaller/species-poor summits are successive subsets of the species on larger/species-richer summits. Plants abundance (percent cover) was measured using two-level stratified sampling on 6 summits in the White Mountains of New Hampshire ranging in elevation from 1235 m to 1603 m. Species that were less abundant overall tended to disappear first as species richness decreased on the summits. This relationship allows one to infer relative abundance from nestedness data, which is much easier to obtain that abundance data. If found to be generally applicable, then nestedness data can be used to identify species at risk and help focus conservation efforts. Data obtained from the 43 primary sampling units (PSUs) were also analyzed using TWINSPAN for classification and canonical correspondence analysis (CCA) for ordination. The distribution of the communities identified by TWINSPAN was strongly influenced by environmental factors, especially slope and elevation. Abundance data also sheds light on the causes of nestedness which are discussed briefly.