Document Type

Conference Paper

Publication Date

1991

Publication Title

Proceedings of the Back Bay Ecological Symposium

Pages

222-248

Conference Name

Back Bay Ecological Symposium

Abstract

An inventory was undertaken to determine the type and extent of the emergent tidal wetlands in Back Bay, which, historically, has ranged from a lunar tidal brackish estuary to a wind tidal freshwater system. The inventory was conducted primarily by boat with visual observations made for each marsh. The configuration and areal extent of each marsh was determined from USGS topographic maps and confirmed with aerial photography where necessary. Approximately 9925 acres of wetlands as defined by the Commonwealth of Virginia were identified within the watershed. These wetlands supported a very diverse flora consisting of over 109 species.

The five dominant species accounted for almost 75% of the wetland acreage. They included: cattails, Typha spp., (4004 acres), needlerush, ]uncus roemerianus, (2371 acres), big cordgrass, Spartina cynosuroides, (605 acres), saltmeadow hay, Sp.artina patens, (449 acres) and switchgrass Panicum virgatum, (427 acres). The remainder of the species represented a diverse mixture of brackish plants with a significant component of freshwater species.

The emergent tidal wetlands are dominated by plants typically indicative of brackish conditions even though the system now tends toward freshwater conditions under normal circumstances. These brackish species are probably relicts from when Back Bay was directly influenced by the salinity and tides afforded by inlets to the ocean. The brackish communities because of their continued dominance appear to be more adaptable to the periods of freshwater than the freshwater species are to periods of brackish conditions. These historical oscillations between brackish and fresh conditions are probably responsible for much of the plant diversity found. These plant communities are not static either, as evidenced by changes in the coverage of common reed, Phragmites australis, which has increased substantially between this inventory done in 1977 and recent (1990) observations.

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