Long-term Study of Fire Season and Frequency in Pine Forest and Associated Cypress Wetlands, Big Cypress National Preserve: Project Description and Preliminary Data

Snyder, James; Belles, Holly

South Florida slash pine forests represent one of the region's most fire-dependent and imperiled ecosystems. While lightning-ignited fires during the May to July period surely burned substantial areas before the arrival of Europeans, indigenous people had most likely been burning at other seasons for thousands of years. Even in large natural areas like Everglades National Park, a lightning-driven fire regime cannot be allowed to operate because of human health and safety concerns. Prescribed fire will be required to restore and maintain South Florida pinelands. This long-term study will document the ecological effects of a wide range of potential fire management strategies on South Florida pinelands. The main objective of the project is to establish the baseline conditions and begin the experimental treatments for a long-term study of season and frequency of burning. The research will provide detailed data on vegetation response to different burning regimes that will be used to refine prescribed burning programs on Department of lnterior lands in South Florida. Because many of the effects of fire regime will not become evident until after several repetitions of the experimental treatments, this study must be treated as a long-term ecological study. The experimental study has been set up in the Raccoon Point area of eastern Big Cypress National Preserve, where the most extensive unlogged stands of South Florida slash pine (Pinus elliottii var. densa) remain. The pinelands exist as a mosaic of slightly elevated "islands" within a matrix of cypress domes and dwarf cypress prairies. The study site surrounds the Raccoon Point oil field and is divided into 18 experimental burn units. Each burn unit includes at least 50 ha of pine forest. Within each unit, three permanent 1.0 ha tree plots were established. Smaller 0.1 ha vegetation plots are located in the center of each tree plot and at two additional locations to sample herbaceous and shrubby vegetation. There are a total of 54 tree plots and 90 vegetation plots. The experimental treatments consist of burning at three seasons (spring, or early wet season, when the largest human-caused or lightning-caused wildfires occur; summer, or mid wet season when there are frequent, but generally small, lightning-ignited fires; and winter, or mid dry season when conditions are frequently favorable for prescribed burning) and two frequencies (every 3 years and every 6 years) for a total of six treatment combinations. Each treatment is replicated three times, with one replicate being burned per year for three years. All the experimental prescribed burns are conducted by the Big Cypress National Preserve Fire Management Division. Beginning in 1996, two units have been burned at each season, representing both short- and long frequency treatments. Some treatment burns were postponed to subsequent years because of abnormally wet conditions or because of state-wide burning bans brought on by drought conditions. By spring 2000, all 18 of the initial experimental prescribed burns were completed and the second cycle of burns of the 3-year treatments was begun. Some preliminary data from the tree plots are included in this report.