THE RELATIONSHIP BETWEEN COASTAL PLAIN POND VEGETATION AND ENVIRONMENT AT LOCAL AND BROAD SPATIAL SCALES

摘要

Coastal plain ponds support many plant species that have been designated as threatened due to human alteration of the hydrology and nutrient availability. Understanding how these species respond to environmental gradients at multiple spatial scales can support conservation efforts. I examined the relationship between plant species composition and environmental variables that operate at two spatial scales: within (local-scale) and among (broad-scale) 18 coastal plain ponds on the island of Martha's Vineyard, Massachusetts. Patterns in species composition occurred at both local and broad scales. Elevation along the water-depth gradient was the only local factor strongly correlated with species composition. Significant broad-scale environmental factors included surficial geology, hydrology, and specific conductance of pond water. Overall patterns in vegetation species composition and abundance were more closely related to broad-scale environmental variables than to local environmental variables, suggesting that pondshore vegetation is largely determined by variables that are expressed at the broad scale. Conservation organizations concerned with protecting the coastal plain pond ecosystem should, therefore, protect a network of ponds that captures the full range of environmental variability, because ponds that vary in hydrologic regime, surficial geology, and water salinity exhibit significantly different patterns in species composition