ResourcesIdentification of Important Habitats in Coastal New HampshireChapter 10. Cordgrass and Salt HaySmooth cordgrass (Spartina alterniflora) and salt hay, (S.
patens) occur in estuarine areas along the New Hampshire coast. These
vascular plants often grow in adjacent stands, or grade from one into
the other, based on soil elevation, permeability, and salinity. Both species
are of major ecological importance as habitat for fishes, birds, mammals,
and invertebrates, and as primary producers of organic matter for coastal
food chains. In the current context their habitats are appraised in terms
of their suitability for growth of these plants; other aspects are considered
in the analyses for fish and wildlife species which rely on the plant
communities. DATA SOURCES: Cordgrass habitat was identified from
the actual persistent occurrence of the plants. Marsh vegetation of coastal
New Hampshire has been mapped from aerial photography by National Wetlands
Inventory (NWI). The Great Bay Aerial Salt Marsh Mapping Project (Ward
et al. 1991) mapped marsh and algae vegetation of Great Bay and the Piscataqua
River. Digital coverages were obtained of both data sets from NWI and
from New Hampshire GRANIT, respectively. MAPPING OF HABITATS: Polygons designated by NWI as estuarine
intertidal emergent were selected, then attributed to S. alterniflora
or S. patens according to the NWI modifiers. Those areas NWI
characterized as 'regularly flooded' were regarded as S. alterniflora;
those designated 'irregularly flooded' were labeled S. patens.
We selected the more detailed Salt Marsh Mapping Project polygons and
used these to supplement or replace the corresponding NWI polygons. Vegetation
was designated as alterniflora or patens according to
configuration and location. Polygons that were long and narrow (area /
perimeter < 40) were mostly fringing or linear features, dominated
by the low marsh species S. alterniflora. The wider polygons
in saline portions of the estuary were identified as high marsh, predominantly
S. patens. The combined polygon coverage was converted to a grid-cell format. For
each species, all cells were assigned a habitat quality score of 10, or
optimal habitat, since the actual presence of the species demonstrated
the suitability of conditions (Figures
of Cordgrass Habitat and
Salt Meadow Hay Habitat). |
