Givnish, TJ , Volin, JC , Glaser, PH .
Self-assembly of patterned landscapes in the central Everglades: a model for the integration of hydrological, biogeochemical, and ecological processes.
We propose that spatially coupled, positive and negative feedbacks among vegetation, hydrology, nutrient levels, peat accumulation, and landforms have driven the self-assembly of the slough-sawgrass ridge-tree island patterning of Shark River Slough in Everglades National Park and adjacent Water Conservation Areas. A detailed understanding of these feedbacks is fundamental to any attempt to predict the ecological effects of the multi-billion $ “replumbing” of the Everglades: shifts in water levels and flows will not simply move vegetation zones up and down existing microtopographic gradients, but alter those gradients as well, possibly quite rapidly. Random “bumps” above the general level of the wet, sloping peatland should be amplified, as a result of better soil aeration allowing more rapid plant growth and peat deposition, with only slight increases in peat decomposition. Egrets and other top carnivores should be attracted to these rises as woody plants invade, funneling nutrients (especially P) and further accelerating plant and peat growth. As the resulting tree islands grow in size and number, sheet flow of surface drainage must lie longer and deeper in the intervening areas, preventing additional ridges or islands from forming. Streamlining of tree islands arises not from erosion or deposition, but simply as a self-organizing pattern that minimizes mixing of nutrient-poor and nutrient-rich waters. We are testing this model using stratigraphy and measurements of present-day production and decomposition along gradients of microtopography, soil depth, and flow speeds in different portions of the central Everglades that have had radically different flow regimes as a consequence of water-control policies over the past several decades. Our aim is to integrate our findings with data on the present-day distributions of various vegetation bands and a model for landscape-scale sheetflow to ask how proposed changes in water-control policy might affect the result mosaic of vegetation, landforms, and hydroregimes.
1 - University of Wisconsin-Madison, Botany, 430 Lincoln Drive, Madison, Wisconsin, 53706-1381, USA
2 - Florida Atlantic University, Biology, 2912 College Avenue, Davie, Florida, 33314, USA
3 - University of Minnesota, Limnological Research Center, 310 Pillsbury Drive SE, St. Paul, Minnesota, 55455, USA
Presentation Type: Paper
Location: Wasatch (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 8:00 AM