SPATIAL VARIABILITY IN SOIL PHYSICAL CHARACTERISTICS IN BOCA RATON, FL. REVEALED BY GROUND PENETRATING RADAR (GPR)

More than half of the Earth’s terrestrial surface has been transformed by anthropogenic activity. Yet the impacts of global transformation on the critical zone, especially near the sunlit subsurface, are not well quantified. An ecological preserve located in Boca Raton, FL. currently hosts three distinct vegetation communities (managed grasslands, oak hammock, and upland scrub) and is susceptible to the negative impacts caused by surrounding urban expansion. Little is known about how soil characteristics of the subsurface may influence hydrological processes across the preserve. This study presents preliminary results of a survey to better understand the influence of soil characteristics across the ecological preserve. A set of non-invasive geophysical surveys using ground-penetrating radar (GPR) combined with direct coring was conducted within each habitat to define subsurface characteristics. GPR surveys were conducted using an array of 50, 100, 200, 250 and 500 MHz antenna frequencies in each habitat. A combination of common midpoint and common offset surveys were used to estimate lateral changes in travel time to the water table. Lateral changes in porosity at each site were then estimated using the complex refractive index model (CRIM). These results will be compared with soil moisture content measurements to determine for lateral changes in soil moisture at each site. The outcomes from this study have implications for better understanding the impacts to hydrological processes as land use surrounding the preserve continues to change, and therefore assist in establishing a baseline for the detection of temporal changes.