Department of Geology and Geological Engineering
Van Tuyl Lecture Series- Fall 2015
4:00-5:00 p.m. in Berthoud Hall Room 241
Thursday, September 10, 2015
Pamela L. Sullivan
Department of Geography
University of Kansas
“Hydrogeochemical and Geomorphological Evolution of Tree Islands in the
Everglades”
Abstract: Recent evidence suggests the interaction between biological and
physical feedback mechanisms supports the spatial heterogeneity of wetlands,
and thus helps maintain the biodiversity and function of the ecosystem. In the
Everglades, one feedback mechanism that has been hypothesized to maintain
landscape heterogeneity by promoting tree island stability is the transpirationdriven ion accumulation mechanism. Here, transpiration by overlying trees draws
groundwater into the islands, creating a hydrologic sink that traps and stores
solutes and nutrients. Here, we seek to: 1) test if the transpiration-driven ion
accumulation mechanism persists in the Everglades; 2) quantify the conditions in
which it is initiated; and, 3) determine the effects of underlying geology and tree
growth in governing the evolution of the tree island groundwater geochemistry.
We observed that tree transpiration led to the advective movement of water and
associated ions toward the center of the tree islands, supporting CaCO3
precipitation and thus mineral soil development. Interestingly, these processes
were more pronounced on islands underlain by peat than limestone, suggesting
a feedback mechanism that protects peat tree islands from oxidation during
extreme droughts. The depletion in groundwater nutrient concentrations as tree
biomass accumulated was observed on all islands and signified the development
of tight nutrient cycling. We conclude tree growth and geologic materials
mediated the transpiration-driven ion accumulation mechanism, that this
mechanism can establish within three years of planting and helps to govern both
the hydrologeochemical and geomorphological evolution of the Everglades.
Contact Information: Pamela L. Sullivan, Department of Geography, University of
Kansas, 1475 Jayhawk Blvd., Lawrence, KS 66045 USA, Phone: (785)-864-6561,
Email: plsullivan@ku.edu