Impacts of contrasting land-use history on composition, soils, and development of mixed-oak, coastal plain forests on Shelter Island, New York

摘要

The Mashomack Preserve on Shelter Island, New York contains one of the premier oak-dominated coastal plain forests in the northeastern U.S. It represents a unique opportunity to study woody species in juxtaposed forests that differ primarily in past land-use (logging versus agriculture). We researched how contrasting land-use history affected: 1) tree species composition, size, and age structure; 2) soil chemistry and morphology; 3) the dominance of Smilax, a native invasive shrub; and 4) the historical ecology and successional pathways. Randomly located plots were sampled for vegetation and soils in the unplowed interior forest versus the maritime forest that was cleared and/or plowed for agriculture and grazing in the 18th and 19th centuries and then abandoned after 1870. The upper soil profile was examined for soil nutrients and pH, the presence/absence of a plow layer (Ap) and for soil charcoal. Tree cores (N = 130) were taken across both forest types to include the full range of species and diameter size classes to assess temporal and spatial variation in recruitment. Maritime forests are closer to the ocean shore and are dominated by Quercus velutina, Sassafras albidum, Carya glabra, and Q. alba, whereas the interior forests are dominated byQ. velutina, Acer rubrum, C. glabra, and Q. prinus. The interior forest plots appear to have continually supported forests, have soils that are somewhat doughtier and less fertile, and lack a plowed horizon, but have frequent soil charcoal as compared with the maritime forest. Formerly plowed and grazed maritime soils are more fertile and Q. alba has greater importance, while Q. velutina has lower importance. Following agricultural abandonment, the maritime forest understory became dominated by thickets of Smilax and presently has lower tree diversity than interior forests. Tree regeneration is sparse in both forest types due, at least in part, to intense browsing by white-tailed deer (Odocoileus virginianus). The interior forest exhibits a predictable successional pathway from mixed-oak to A. rubrum and Fagus grandifolia, which is not apparent in the maritime black oak forests. We believe that differences in overstory and understory composition, species diversity, and successional pathways between the two forest types can be mainly attributed to contrasting land-use history. Smilax is a super-dominant species that has profoundly influenced many ecological processes on the preserve and if left unchecked will continue to do so long into the future.