Seeps, Stairs, and Obi-wan conobea

I have long noticed that on the east side of UT Tower, there is a spot on the granite stairs leading up towards the xeriscape area that seems continually to leak water, running across the pavement and down the stairs.

At first I thought it was some leak from pipes underneath the building, but eventually I've come to believe that it is in fact a natural seep.
Seeps are places where water naturally oozes out of the ground. The City of Austin has a handout on seeps, which I'll quote:

Seeps may conjure images of dripping, moss-laden rocks along cliffs in a forest. But seeps can be a common occurrence in urban areas as well. Water moves through natural and urban landscapes below the surface, unseen until it is forced out of the ground by things like bedrock or impervious clay. When this happens, it creates a seep.

This is what I assume is happening here. Water takes the path of least resistance. My interpretation is that the water was flowing underground through some porous material—maybe loose construction gravel or sand, maybe something else—when it hit something impenetrable underneath, causing the water to leap to the surface. It seems that around Austin, the underlying geology (limestone, karstic features, clay and river alluvium/deposits) makes the area a prime place for seeps to occur. The handout previously mentioned lists a few geologic formations in the Austin area which create ripe conditions for seeps.

At the crook of the stairs where the water comes out, Obi-wan conobea (Leucospora multifida) has taken a spot. It's an annual forb that naturally occurs in seasonallly moist gravelly or sandy areas, areas with loose alluvium and a fair bit of moisture. It must be a prime spot for this species, since the plants seems to reliably return even after dying away from heat or frost.

However, Obi-wan seems to be a bit of an explorer... as beyond those natural areas, he seems equally happy to thrive in more urban environments. Stairs and any sort of "step" area are a favorite.

In other words, anywhere there's a rocky "step" at a right angle—a flat step, and a vertical face, be it the next step, the curb or the wall—and sufficient moisture... General Conobea will be there. He also has been seen up in more ludicrous spots, e.g. up of the rooftop of Patterson Hall.

I would be remiss not to mention the origin of this plant's common name—if the reader is not already acquainted with the tale as viewable in the previous link. The plant was named by a well-known Chicago-area botanist, Floyd Swink, who evidently had a sense of humor:

The derivation of the strange common name comes from a publication of Floyd Swink, who named this plant after a character in the movie Star Wars, although the publisher did not discover this until after his book was already published (John White, personal communication). Another common name for this plant is Narrow-Leaved Paleseed, which was undoubtedly invented by a botanist. A scientific synonym for this species is Conobea multifida.

All that aside, natural seeps are interesting microhabitats to search for plants. Often, unusual finds—plants which thrive in higher moisture soils—will occur in seep areas, an island of moisture surrounded by otherwise dry and exposed uplands. An excellent example are the easternmost populations of Primula meadia, the Eastern Shooting Star, which grow in the Canyonlands east of the Balcones Escarpment. Something to keep in mind.

由使用者 arnanthescout arnanthescout2023年11月15日 14:53 所貼文


This makes a lot of sense. Didn't we see this before in the "Return of the Jedi"?

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