ABSTRACT
Physical forces, such as geomorphology and hydrology, are the primary factors controlling pattern and process in a salt marsh. This study was designed to examine how these controlling factors operate during the natural development of a barrier island salt marsh ecosystem. A particular emphasis was placed on the creekbank zone because of the increased topographic relief associated with the morphology of the creek. A chronosequence of marshes was employed to define the changes that take place within the marsh on a successional time scale. There are predictable changes that take place in the physico-chemical variables associated with the substrate, and in the productivity, growth form, and tissue element composition of Spartina alterniflora. The processes associated with the interaction between biotic and abiotic factors appears to be driving the observed changes. In all of the young marshes, the zone closest to the creekbank exhibited values of physico-chemistry and productivity representative of an older marsh, such that the marsh near the creek appears more mature. This implies that the physical forces associated with the regional morphology are driving the process of succession at a faster rate in this zone.

This chronosequence contained two young creeks of similar age which exhibited significantly different rates of primary production. While these two young creeks were similar in their local morphology, they differed in their regional morphology. One creek received drainage from a large upland catchment area, and the other received drainage from a small catchment which contains a salt flat. The inflow of large quantities of fresh groundwater from the upland catchment produced lower salinities, and led to greater S. alterniflora production. The other creek had no significant upland drainage, and therefore had high salinities and low macrophyte production. When there is lower production, the processes linked to the interaction between biotic and abiotic factors is diminished, and the maturation process is slowed. Thus, the regional geomorphology, which determines the local hydrology, controls the patterns and processes associated with the ecological development of the marsh. This study suggests that the geomorphology, on both a local and a regional scale, is important in controlling the developmental processes which result in the observed patterns of physico-chemistry and productivity in a salt marsh.


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