Monday, May 29, 2023

Psammophyte Beach Bum in a Barren Land: Sporobolus virginicus in Paracas, Peru

The area around the beach town of Paracas in Peru is pure desert, a desolate land with nary a plant beyond those weedy and cultivated critters that settled into the few human settlements in the region.

But close to the sea, various native plants clung to life against the all encompassing dryness. Precipitation is under 1 cm per year in the region (!), and the few areas with water are an oasis that attracts life.

One of the few plants that was not deliberately planted was Sporobolus virginicus, which thrived in large clusters next to the beach in town. It is called Seashore Dropseed in the USA.

This species is found all over the Caribbean and American coastal mainland, and is an extreme halophyte. That is, it is able to tolerate high salt concentrations, something that is advantageous in the saltwater drenched beaches where it loves to bum around. Some populations of this species can tolerate up to 1.5 M NaCl, which is 3 times the salt concentration of sea water!

In addition, the species is a psammophyte, which simply means that it can thrive in areas that are sandy and often unstable. This again makes it suitable for the changeable landscape of coastal beaches.

The grass itself is a short but tough looking critter, with stiff pointy leaves and a seemingly aggressive manner. Even its flowerheads are no nonsense structures bereft of any extraneous adornments. If this is a beach bum, then it's one that you don't want to tangle with. In fact, I saw one Paracas cluster sending ramets deep into  the midst of a neighboring plant, an act that seemed quite hostile. But appearances can be deceiving, and I have not seen any references that indicate the species has become invasive, or that it is even a particularly aggressive species in all the many places that you can find it.

It is also relatively easy to identify in beach settings, although one needs to see the flowerheads to differentiate it quickly from something like Paspalum vaginatum (which has the more typical Paspalum inflorescence). So the next time you are walking along a beach and see clusters of S. virginicus, think about its adaptability to both salt and sand, and marvel about the tenaciousness of this cosmopolitan beach bum.

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