San Felasco Sweetgum Seed Rain

A couple of cavers came down from Tennessee last weekend to relax in Florida’s warmer weather, so Bruce, JJ and I took them out to San Felasco Hammock State Park for some biking and hiking on Saturday. We took the Cellon Creek Loop (south) bike trail to the Tung Nut Loop bike trail through an overgrown field to Sanchez Prairie. At that point, the Tennesseans had to turn back due to one of them just not quite being over his recent head cold. Bruce, JJ and I abandoned the bikes at the edge of the prairie and continued on foot from there. We hiked first along the toe of the prairie’s western slope to the third tributary, then wandered westward along the edge of that little karst valley to its head, from which we hiked back to the bikes along the “highland rim” of the prairie and then biked back to the vehicles. My GPS recorded 7.5 miles of biking and another 3.0 miles of hiking – an easy day, for once! Well, it‘s easy if you’re not sick.

The layout of the karst valleys is interesting to me. Imagine three lines of sinkholes developing in impermeable sediments atop soft limestone, trending in fairly straight lines (lineaments) oriented roughly east to west. Give those lineaments a little geological time and a couple of things happen. First, the sinks expand until they coalesce, and second, new sinks form westward of the last ones. By this process, the valleys undergo headward erosion and extend into the uplands. Unfortunately, very little rock is exposed and no caves are apparent.

Seepage springs occur at the head of each valley and occasionally along the lower slopes of the valleys. These lateral seeps are heavily damaged by feral pigs, which root up anything edible to a pig and then wallow in the clayey spring run bottoms. Whatever ferneries might once have existed in these places are now reduced to a few sprigs here and there. I saw a group of feral pigs a few weeks ago in the third valley, and we saw a group there again on Saturday. Based on the number of pigs, their sizes and coloration, I suspect this is the same (family?) group I saw before. A predictable nuisance is a manageable nuisance. Is anyone from park management reading this?

We did not see any feral pigs in the prairie bottom, but then I didn’t see any feral pigs in that part of the bottom last time, either. Perhaps that area is part of the territory of the pigs in the third valley.

Upon returning to the bikes, Bruce and JJ noticed they were being “rained” upon by tiny objects. From my more sheltered location it sounded like they were being pelted by aphid honeydew, but when I went over to them it became immediately obvious what it was. Back in 1971, I was walking across the University of Florida campus at, well, probably exactly this same time of the year through a monocultural stand of small but mature sweetgum trees. As I stopped to look at something I have since forgotten, the faint sound of a light rain could be heard, but instead of tiny droplets on my sleeve there were tiny seeds from the sweetgums. Evidently, sweetgum seeds dehisce simultaneously and then fall in one or more episodes over a short period of time. That is what Bruce and JJ had noticed – a sweetgum seed rain! When looking at darker backdrops like a downed tree trunk we could readily see the seeds falling abundantly. What a pity that our cameras were unable to video the event. It was only the second time in my life that I have experienced a sweetgum seed rain, and was a first for Bruce and JJ.

Incidentally, sweetgum seeds contain shikimic acid, the starting ingredient for making antiviral drugs to combat bird flu.