Wednesday, December 9, 2015

Mangroves!

  Residents and longtime visitors to Cedar Key are aware that much of the land- and seascape in the area has changed in recent years. With the help of global warming, black mangrove (Avicenna germinans) trees have invaded salt marsh, become established along shorelines, and have grown up on low islands and oyster bars. Sensitive to cold, these mostly tropical trees are "pruned" when upper branches suffer from frostbite, or are even killed outright by freezing temperatures. Lacking serious freezes for a number of years the trees have grown both in size and coverage locally.

 
Black mangroves dominate scenes in Cedar Key's backwater areas.


Mangroves reproduce prodigiously, and over time tend to form dense canopies that shade out salt marsh plants and other shoreline vegetation.

Reproduction of black mangroves under the Cemetery Point boardwalk. Young plants with leaves, interspersed in this image with the leafless pneumatophorees extending from the roots of larger trees.
Red mangroves (Riphora mangle) are even less tolerant of cold than the unrelated black mangroves, and in the past they have been relatively rare in the Cedar Key area. They seem to be increasing, however, and can be seen at a number of places around the islands. Several small plants can be seen from the boardwalk and observation deck in Cemetery Point Park.

Red mangrove seen from the observation deck at Cemetery Point.


Small red mangrove seen from the Cemetery Point boardwalk.

Red mangroves can be distinguished from black mangroves by four different characteristics. The most striking difference is in their distinctive prop roots, which grow out from their trunks and curve down into the moist soil. Their leaves are broader than black mangrove leaves, and they are a more vibrant green than the grayish green leaves of black mangroves. Finally, they tend to have trunks that grow straight upward, rather than branching near the base, as do many black mangroves.

A single hard freeze could kill most of our red mangroves, but even then a few are likely to persist. And, if our climate continues to warm as is predicted, our wetlands are in for continued change.

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