Florida scrub is a fire-maintained shrub vegetation of well-drained, sandy soils; dominant species include several species of Quercus and Serenoa repens. Many Florida scrub species are xeromorphic with adaptations to periodic drought. In a remediation project on Kennedy Space Center, treated groundwater was distributed through an exfiltration gallery into intact scrub. This scrub site had been cut and burned for habitat restoration in 1996. In April 2002 we established 8 permanent line-intercept vegetation transects (15 m length) in the scrub site, four located close to the water exfiltration gallery and four more distant from it. We sampled vegetation in two height strata, < 0.5 m and ≥ 0.5 m, along each transect and measured vegetation height at four points (0, 5, 10, 15 m). This sampling has been repeated annually through 2019. The initial phase of the project operated from October 2002 to early March 2004 (494 days) and distributed 1.74 x 108 L of treated water. The final phase of the project occurred from March 2005 through August 2008 (1251 days) and distributed 1.9 x 108 L of water. These data allow us to examine if scrub height growth, cover, and species composition responds to a raised water table.
Results/Conclusions
Groundwater monitoring wells indicated that pumping raised the water table near the exfiltration gallery. Vegetation height did not differ between transects near the gallery and those farther from it before water additions. Vegetation height increased substantially in the near transects by 2004 and remained higher through 2019. The greatest year-to-year percent change in vegetation height in the near transects occurred in 2003 and 2004. Total cover ≥ 0.5 m increased substantially in the near transects by 2004 and showed the greatest percent increases in 2003 and 2004. Total cover < 0.5 m and bare ground were initially similar in the near and far transects and declined in the near transects by 2004. Non-metric multidimensional scaling (NMS) ordination suggests that the near transects occupied somewhat more xeric conditions initially. Successional vectors from NMS ordination showed similar but not overlapping patterns of change in the near and far transects over time. Scrub species, particularly the dominant scrub oaks (Quercus chapmanii, Q. geminata, Q. myrtifolia) increased height and cover in response to water additions, but no loss of dominant scrub species occurred, and there was no establishment of mesophytic species in the intact scrub.