SALT MARSH BIOLOGICAL MAPPING |
Emergent wetland vegetation is a critical component GIS PROJECTS MAL and SAV Surveys
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of estuarine ecosystems, providing productivity, nutrient cycling, and important habitat for a range of species. This habitat is affected by a variety of natural and human induced stressors, including climate change, sea level rise, invasive species, and urbanization. Emergent wetland vegetation makes up about 13 percent of the Reserve.
In an effort to track estuarine change over time, we are developing and testing methodologies for monitoring emergent wetland habitat cover within the reserve boundary. The objectives of this study were to create a “baseline” GIS database of the current spatial extent and distribution of emergent marsh habitats within the Reserve’s, and to establish a set of protocols for assessing future change. To map existing conditions of emergent wetland habitat cover, aerial digital imagery (true color and infrared) was obtained in the fall of 2004 and used to digitize polygons of dominant species assemblages within high marsh, low marsh, fresh wetland and transition zones. Mapped units were verified in the field to determine the limits of aerial imagery interpretation. Optimum mapping scale for distinction of most dominant vegetation communities was determined to be at 1:1000 feet. This yielded mapping products of existing distributions of dominant vegetation assemblages. However, stands of the invasive Phragmites australis were often difficult to differentiate from other peripheral high marsh vegetation in aerial digital imagery, and thus were delineated using GPS on the ground. These mapping products combined with the developed protocols will enable comparisons with future monitoring events to detect changes in habitat cover.