CUTTHROAT GRASS ON URBAN NATURAL AREAS, PALM BEACH COUNTY, FL: ENVIRONMENTAL CONTROLS ON DISTRIBUTION AND PROPAGATION

Panicum abscissum,(cutthroat grass), is an endemic perennial species of endangered grass found in association with hill slopes of the central Florida Ridges from Orange to Palm Beach Counties. Three locations of extant cutthroat grass communities have been identified in Palm Beach County, two of which are Pondhawk Natural Area (PNA) and Yamato Natural Area (YNA) which are in close proximity to densely populated urban areas. Historically wetlands, both PNA and YNA are small, highly disturbed natural areas that no longer sustain natural wetland conditions due to the building of canals and the subsequent lowering of the water table.

This paper presents the results of a preliminary investigation into how soil properties, water table elevation, and overstory canopy cover influence the occurrence and vigor of cutthroat grass at PNA and YNA. Seven sites containing cutthroat grass were included in this study, four at PNA and three at YNA. While there were several clumps of cutthroat growing within each site, there were also other plant species and areas of bare ground. Three square monitoring plots with cutthroat grass present on them (CP) were randomly selected, and three additional plots where cutthroat grass was absent (CA) were similarly selected at each site. We compared the soil properties and canopy cover of CP and CA sites and related soil properties, water table depth, and canopy cover to indicators of cutthroat vigor at the CP sites.

Our results indicate that none of the environmental variables we considered have a significant influence on where cutthroat grass occurs; however, cutthroat vigor improves with increasing soil EC, decreasing soil pH, and higher proportions of silt and clay. Additionally, the depth to water data suggest that cutthroat grass growth is more robust where the water table is relatively shallow.