Tuesday, September 13, 2005

Geog 316 journal - Coastal salt marsh gradients

When you study geography in California you inevitably come across the Sierra Nevada transect. The typical graphic will show the elevation gradient from west to east and the associated tree species often delimited by elevation. It's a great driving reference as the changes in tree types occur at a scale that may be otherwise imperceptible on foot.

So when Liam drew the example of a salinity gradient in a salt marsh I was captivated. Apparently plant communities in a salt marsh will vary depending upon how much salt is in the soil. From salty to fresh, plant communities will create a continuum of mud flat to salt marsh to sedges to cattails. I take the ferry to Larkspur whose landing is flanked on the north by some pretty good examples at Corte Madera Marsh. The great thing about a salt marsh is that the gradients happen at a smaller ecological scale and you can actually see to whole mosaic with advantage of some elevation.

I biked over and I have to say the patterns were not readily apparent. I was still in that Sierra Nevada mindset - I was thinking elevationally. The plant communities were not falling out that way though, the mosaic was more a complicated patchwork. I moved on. On my ride home I pass another little piece of salt marsh along Corte Madera creek. This one is far smaller but the gradient was immediately recognizable. The salinity barriers were being driven by the drainage network in the marsh. The meandering streams had banks of taller sedges, while the interior areas furthest from the streams (more dessication, more salt) had the salt marsh community (pickleweed and chordgrass).

I've stopped at this marsh to breathe in the relief that nature brings hundreds of times, but this time I saw it differently. Now I like it even more.