Evaluation - Demonstration Sites
The Corkscrew Swamp Sanctuary is a natural system managed by the National Audubon Society to maintain native plants and animals found in the area and preserve the unique ecological processes of the region. The sanctuary is located northeast of Naples and includes a 2.25-mile raised boardwalk that takes visitors through several distinct habitats found within the 11,000-acre refuge, including the largest remaining virgin bald cypress forest in North America. Other habitats along the sanctuary's boardwalk include: pine flatwood, wet prairie, pond cypress, marsh, and lettuce lakes. You can view a virtual tour of the sanctuary.
Even with all the effort made by the sanctuary staff to remove and control invasive plants, a significant threat still remains from neighboring properties that conceal the pests within their midst. Seeds from invasive plants on private lands, spread by air currents, flowing water, and animal life, regularly find their way into sensitive ecosystems where they sprout and carry on the invasion process.
Named after its environmentally sensitive neighbor, the Corkscrew Swamp Sanctuary demonstration site rests on four privately-owned contiguous properties adjacent to the sanctuary. The site is characterized as a pine flatwood with scattered wet prairies and primarily sandy soils. Table 1 contains additional information on soil qualities and chemistry. Following vegetation removal efforts and several wildfires, melaleuca aggressively invaded the site and now occurs on 13 acres at a remarkably high density of 14,012 trees per acre. Current tree sizes, when measured at breast height (dbh = 1.3 m), range from 0.1 to 15.3 cm (0.04 to 6 inches), with an average diameter of 2.2 cm (0.9 inches). Table 2 presents the size distribution of these trees.
Although melaleuca is by far the most dominant plant species at the site, 43 other species also coexist within the demonstration area. Native species, including slash pine, saw palmetto, and spike rush, comprise the majority of identified plants occurring within the demonstration site, as compared to six invasive exotics. The remaining 17 have yet to be identified or are of uncertain origin. Table 3 contains a complete list of plant species.
Three conventional melaleuca control approaches are featured at the Corkscrew Sanctuary Demonstration site:
- felling trees and treating the stumps
- hack and squirt
- broadcasting of herbicides
The integration of biological control with each of the other conventional control approaches is also exhibited. In addition, a smaller demonstration is available on the effectiveness of "off the shelf" herbicides that homeowners can purchase from local hardware and garden stores. You can find a detailed description of these approaches on the Corkscrew Swamp Sanctuary Demonstration Site web page.
We monitor the efficacy of these control approaches by delineating multiple study plots in each treatment area and measuring over time the melaleuca mortality, recruitment and changes in plant species composition. With these measures of efficacy, coupled with the cost of each treatment, we compare the different approaches as to their suitability for small land owners and landscape managers.