WHEN YOU DON’T HAVE ROCKS: MAPPING VEGETATION TO DETERMINE SOILS AND USING SOILWEB TO “GROUND TRUTH”

One of the inherent challenges in teaching physical geology at a 2-year college in Orlando, FL is the absence of traditional field examples that can be reached during the time frame of a single class session. Valencia College is situated on relict dunes of quartz sand and the nearest (very small) outcrop of rock is over an hour away. One way to introduce students to geologic mapping is to have them map vegetation as a proxy for the soils that form in the quartz sands.

Tibet Butler Nature Preserve is a natural area in western Orlando that has experienced little to no human alteration or development and is well-suited for this mapping exercise. The area contains several natural communities including scrub, pine flatwoods, bay and cypress swamps, a cypress dome, and freshwater marshes. Using a data-logging app with Ipads and GPS sensors, students work in teams of 2 or 3 to record changes in vegetation type along trails at the preserve. They note changes with a waypoint and photo document the different species at each location. When possible, they sample the soil and note soil color and composition (percent quartz and percent organic material). The results of their vegetation surveys are saved as KML files (Google Earth) and used to produce annotated maps of changes in natural communities along the trails. Finally, students suggest possible soil types for each area and results are compared with USDA SoilWeb (Google Earth) maps.