USGS Open-file Report 04-1302
Version 1.0
Figure 3. Tidal zonation of marsh vegetation for Blackwater NWR (not to scale).
Blackwater NWR marshes are brackish marshes supporting a high diversity of vegetation. Depending on salt and flood tolerance different plant species occupy different elevation ranges in saltmarsh habitat. Marsh zone between MLW and MHW is low or intertidal marsh. Marsh surface in this zone is inundated by water during tidal cycle for 2/3 of a day. Saltmeadow cordgrass, occupies low marsh zone. Closer to the MHW limit, saltmarsh cordgrass, and shorter form of saltmeadow cordgrass coexist. Above MHW limit, marsh surface is inundated by tides only for very short periods of time, during spring tides. This is the high marsh habitat occupied by salt grass, three-square bulrush and black needlerush. Common reed often grows on the outer edge of the marsh surface. Three-square bulrush is the dominant marsh vegetation in Blackwater NWR.
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