The salt marsh environment is interesting because it is composed of several layered environments, each of which have their corresponding population of species. The low marsh is closer to the sea, and is inundated daily by the rising tide, whereas the high marsh is only flooded during times of exceptionally high tides.
I have noted the ubiquity of Phragmites australis in Cheesequake State Park in earlier posts, but two other grass species are present in force, especially around the crabbing bridge that is one of the main attractions of the park.
|S. patens in front of P. australis. Individuals of the latter shoot up in the midst of S. patens.|
|S. alterniflora along the water edges|
|P. australis lines the edges of lakes and ponds in the park|
P. australis of course has been deemed the villain in this tale. It is the invasive, and it supplants the native salt marsh plants in its relentless march towards dominance, forming extensive monocultures of 4 meter tall grasses. Its dominance then causes changes in both the biotic and abiotic environment around it.
For example, because of its faster growth rate and investment in below ground structures, the dense mats of decaying organic matter that accumulate in tidal marches dominated by P. australis actually elevate the wetland surface. The very dense stands of this species also slow the movement of tidal water, such that flooding is less deep and less prolonged.
|P. australis blocks view of a pond|
|P. australis looms behind a wading egret|
So the next time you see dense stands of P. australis hogging a shoreline, don't immediately despair over the fate of that environment. Things may be more complicated than a simple black and white perspective on such invasives.