Sep 19, 2011

Tree islands next door

Slash pine marks the high ground of Big Cypress Swamp.

What’s the equivalent next door in the Everglades?


Water-animated diagram of major habitats of the Everglades

That would be the tree islands.

As shown in the diagram below, the tree islands of The Glades and the slash pine of The Big Cypress are perched at approximately the same height relative to the natural rise and fall of the water table. Neither sees water within their realm, if at all, until the very peak of the summer-fall wet season.


The glades isn't so much deeper ...
as in total percentage it has more deep area

Tree islands are different in other ways:

For one, they comprise a much smaller percentage of the total landscape (less than five percent) in comparison to the approximate twenty percent of the Big Cypress Swamp which is comprised of pinelands.


Two, tree islands are also surrounded by deeper water.

The vast majority of the Everglades is slough and ridge. Stepping off a tree island will land you in a knee deep slough whereas as similar step from the slash pines islands of The Big Cypress will put you in shin deep (or even dry) marl prairie instead.

September stage in Shark Slough is down compared to last year


Caveat:

At least that’s usually the case.


Water levels are running low this summer in Everglades Nat’l Park. This is usually the time of year when waters are encroaching at the perimeters of the tree islands. Instead – thanks to a deficit of rain and the closed gates upstream, water stage is a good half foot below that level.

Compare that to the Big Cypress Swamp where the wetting front rose into the pines a good month ago.

Here's the full hydrologic history going back to the 1950s.

Do you see how this fall's peak is down
relative to the period from 1995 to 2005?
Why?

For one, it’s been rainier … plus we don’t rely on gates.


Big Cypress Nat’l Preserve is largely a rain-driven watershed.

4 comments:

Robert V. Sobczak said...

Here's a comment I received by email:

I enjoy your watershed journal-it is very useful and informative. I think you need to check your elevations in the Everglades. Tree Islands are not the highest elevations embedded in the ecosystem. The pine keys of ENP and Taylor Slough, are relative "nose bleed" country. And, yes, as much as our local hydro folks try to erase them from the ecosystem-they are clearly part of the Everglades.

Rick, Everglades Nat'l Park.

Robert V. Sobczak said...

Here's another comment by email:

Mesic slash pine marks the high ground of the Big Cypress National Preserve. Tree Islands often with a tropical hardwood hammock component are the high ground of the Everglades proper and on the eastern border the pine rocklands are considered the high ground.

Jim

Janie said...

Interesting to learn the difference between these high ground areas in two different preserves.

Robert V. Sobczak said...

Good points. By next door I was thinking more along the lines of the other side of the L28 Levee, which is mostly ridge and slough. On the east side of the Everglades, farther south, the comparison erodes.