Responses of Florida Scrub Vegetation to Water Additions from a Groundwater Treatment Project and to Hurricane Disturbance

Abstract

Florida scrub is a fire-maintained shrub vegetation of well-drained, sandy soils; dominant species include several species of Quercus and Serenoa repens. In a remediation project, treated groundwater was distributed through an exfiltration gallery into intact scrub. We established eight permanent line-intercept transects (15 m length) in the site in April 2002, four close to the exfiltration gallery and four more distant from it. We sampled vegetation, <0.5 m and ≥0.5 m, along each transect and measured vegetation height at four points (0, 5, 10, 15 m) annually through 2019. The initial phase of the project operated from October 2002 to early March 2004 (494 days) and distributed 1.74 × 108 L of water. The final phase of the project occurred from March 2005 through August 2008 (1,251 days) and distributed 1.90 × 108 L of water. Pumping raised the water table near the exfiltration gallery. Vegetation height did not differ between the near and far transects initially. Vegetation height increased in the near transects by 2004 with the greatest percent change in 2003 and 2004 as did total cover ≥0.5 m. Total cover <0.5 m and bare ground were similar initially in the near and far transects and declined in the near transects by 2004. Scrub species, particularly the dominant scrub oaks, increased height and cover in response to water additions with no loss of dominant scrub species and no establishment of mesophytes. Hurricane Frances (September 2004) reduced cover ≥0.5 m the following year. Hurricane Matthew (October 2016) and Hurricane Irma (September 2017) caused greater damage including breaking limbs as reflected in reduced height and total cover ≥0.5 m probably because the older, taller scrub was more vulnerable to wind damage.