From freshwater to salt marsh

Figure 13. Downstream, salt water flooding pushes back the mature forest. (Photograph by the author. More about the photograph)

Our boat drifts slowly downstream past swamp forests and freshwater marshes. (My boat of choice for this part of the trip has no motor because I am in no hurry to get past the wildflowers, birds, and abundant wildlife that decorate the lower extremities of coastal river.) But even slow boats eventually reach the point where salt water extends inland. At that point a rapid change in the plant community takes place. This change is dramatic proof that relatively few species of higher plants can tolerate immersion in salt water. The most salt-tolerant tree in North Carolina is the red cedar, so as we approach the ocean we will expect to see more and more cedars. Eventually, though, we see the true salt marsh species replace the cat tails, saw grass, and cedars as we get to water with measurable salt in it.

Figure 13 shows such a transition zone. The mature forest can no longer live on the river bank; it is kept some distance back by frequent salt water floods. Between the forest and the river, we see scattered red cedars on higher elevations and freshwater marsh plants like sawgrass and cattails on lower ones. Note, however, the different colored plant at the river’s edge. This is a black needle rush, a plant typical of coastal salt marshes where it grows on surfaces only irregularly flooded with salt water. It finds the same irregular immersion in salty water here.

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