(Galactia refers to milky stems on one species. Botanist Stephen Elliott lived in Beaufort, SC, where he was first to collect this species.)
Today’s visit to the Kiplinger Nature Preserve in Stuart, Florida, saw the first big blooming loblolly bay flowers of the season, a relative of tea and camellias featured some time ago in this blog.
Today is Wednesday, not the usual Friday trip, due to travel plans. Crabs were crab-walking all about, and a black racer popped up for a peep at us.
This was white-flower day, with the loblolly bays, tarflower, pineland asters, and the plant of the day, Elliott’s Milkpea.
It seems to be designed perfectly for where it lives: largely in pine flatwoods and scrub. In short, it has to live conditions ranging from sunny to shady, where fires pass by, where water is intermittent, and where the world’s poorest soils strive to stifle growth. The plants possess extremely log underground runners, a rapidly growing twining stem able to sprawl, spread and climb over the ground and over shrubby companions, tolerance for shade or sun alike, and leaves with adjustable positions. The most noteworthy and most-studied adaptation is its nitrogen-fixing root nodules.
Although most legume roots “fix” nitrogen, that is, extract it with bacterial help from the air and transform it into fertilizer, this skill seems to matter especially in the sterile world where Elliott’s Milkpea holds forth. Nitrogen is scanty in the sterile leached white sand of scrub, where much nitrogen fixation is the work of microbes in the surface crust. Pine flatwoods soil is sterile too…sandy, often poorly drained, and with a dark layer that presumably blocks nutrient exchange.
For reasons such as these, Elliott’s Milkpea has become a guinea pig for ecologists asking questions concerning the effects of rising carbon dioxide concentrations. Closely related is the relationship of rising carbon dioxide to nitrogen fixation, and what better test subject than a vigorous pea living in a natural sand box?
Nitrogen fixation and carbon (dioxide) have a direct link. The symbiotic nitrogen-fixing bacteria are paid in carbon for their ammonia fertilizer a swap. So then, a plant using carbon to buy nitrogen might enjoy a boost if given more carbon to trade. Biologist B.A. Hungate at Northern Arizona University and collaborators studied today’s species exposed to artificially high carbon dioxide over several years. At first, elevated carbon dioxide boosted nitrogen fixation, presumably an advantage to the pea plants and thus potentially capable of messing with species balance. After approximately a year, however, the boost disappeared, probably because, especially in awful soil, resources other than carbon and nitrogen became limiting. I might make my car go faster by putting the pedal to the metal, until an empty gas tank (or a state trooper) become limiting. What runs low, according to researchers, might be the element molybdenum.