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RELATIONSHIPS OF NITROGEN LOADINGS, RESIDENTIAL DEVELOPMENT, AND PHYSICAL CHARACTERISTICS WITH PLANT STRUCTURE IN NEW ENGLAND SALT MARSHES
Citation:
Wigand, C, R A. McKinney, M Charpentier, M Chintala, AND G B. Thursby. RELATIONSHIPS OF NITROGEN LOADINGS, RESIDENTIAL DEVELOPMENT, AND PHYSICAL CHARACTERISTICS WITH PLANT STRUCTURE IN NEW ENGLAND SALT MARSHES. ESTUARIES 26(6):1494-1504, (2003).
Description:
We examined the vascular plant species richness and the extent, density, and height of Spartina species of ten Narragansett Bay, Rhode Island (United States) fringe salt marshes which had a wide range of residential land development N-loadings associated with their watersheds. Significant inverse relationships of tall S. alterniflora with species richness and with the extent and density of S. patens and short S. alterniflora were observed. Extent and density of S. patens and extent of short S. alterniflora were positively and significantly related with plant species richness. Marsh elevation and area did not significantly correlate with plant structure. Flood tide height significantly and inversely correlated with S. patens, but did not significantly relate to S. alterniflora or plant species richness. Marsh width significantly and positively correlated with plant species richness and S. patens and inversely correlated with tall S. alterniflora. Significant inverse relationships were observed for N-load, % residential development, and slope with S. patens, short S. alterniflora, and species richness, and significant positive relationships with tall S. alterniflora. The marsh slope and width were significantly correlated with N-load and residential development that made it difficult to determine to what extent anthropogenic stressors were contributing to the variation in the plant structure among the marshes. At five marshes with similar slopes, there were significant inverse relationships of N-load with S. patens (density and extent) and a positive relationship with tall S. alterniflora (extent). Although there were no significant relationships of slope with the plant metrics among the five sites, other physical factors, such as the flood tide height and marsh width, significantly correlated with the extent and density of Spartina species. Significant relationships of N-load with plant structure (albeit confounded by the effect of the physical characteristics) support the hypothesis of competitive displacement of dominant marsh plants under elevated nitrogen. It is likely that the varying plant structure in New England marshes is a response to a combination of natural factors and multiple anthropogenic stressors (e.g., eutrophication and sea level rise).