While driving north in spring (in this case to our VA farm in mid March) I like to stop occasionally to judge the progress of the seasons. One such regular stop is at a bridge on A1A just north of Callahan, FL. This is a channelized creek/canal which allows driving into a swamp forest a short distance. From the photo of the canal you may judge that despite the dredging this is a pretty spot which allows a peek into some of the myriad wonders of a southern swamp. It is a “blackwater” area just east of the Okefenokee Swamp which is characterized by solute-poor, clear, but darkly stained water; the color is caused by dissolution of tannins from decaying leaves. This situation is derived from the poor nutrients of the sandy soils, the heightened necessity plants thus have of protecting their leaves from herbivores, and the ability of tannins to bind with proteins and block digestion by insects. Humans have figured out how to detoxify such phenols by adding milk to tea and coffee, which allows milk proteins to bind to the tannins. The soils and waters are quite low in pH and this leads to the occurrence of animals that have special adaptations to survive in such stringent conditions. One such fish is the blue-spotted sunfish (see photo) which is also extremely beautiful despite, or perhaps because of, living in such dark surroundings.
One of the most startling colors of spring in southern swamps is the bright green of the new leaves of cypress, in this case bald cypress. In bald cypress the leaves are flat and in pond cypress folded. There has been much debate as to whether these two cypresses are distinct species or just ecotypes; bald cypress are predominantly found in the center of swamps and pond cypress on the margins. The slow growth of cypress has hindered experiments to test these theories since transplantation of young cypresses to a variety of wetland depths could provide useful information. At the moment it seems that there may be a combination of fixed genetic and plastic effects involved.
Although there were very few spring warblers in evidence (just a few parulas singing), there were some exciting spring wildflowers putting on quite a show. I was most impressed by a small tree, the red buckeye, which I do not associate with this type of habitat. Its flowers are quite unusual and seem designed for pollination by hummingbirds. A very different flower was the bluish pine hyacinth (see photo) which was found here in a very different habitat than the usual pine flatwoods. Finally I noticed a flower that reminded me of Oxalis from the VA mountains, but in this case was a violet wood sorrel in a southern swamp. The lines in the flower that radiate from the center are interesting and possibly represent clues provided to insect pollinators for finding the nectar.
Driving north with the spring is a fascinating experience and I highly recommend it. It is the closest you can come to time travel, since you definitely have the feeling that you are going backwards in time as you go further north.
Bill Dunson, Englewood, FL & Galax, VA