Since 1967, a total of 210 fires have been documented at Archbold, ranging in size from <0.1 to 248.9 ha. For each fire, we record spatial extent (ARCGIS coverage, now using Trimble GPS to map borders) and intensity (4 intensity levels). Overall, 115 of the fires were prescribed burns, 64 were started by lightning, 25 were accidental, and 6 were escapes from prescribed burns. Prior to 1990, the majority of the fires (87.8%) at Archbold were lightning-ignited or accidental fires, with a few key prescribed burns. From 1990 to the present, prescribed fires have accounted for 78.6% of all fires at the Station. Since 1984, escapes (n=6) from prescribed burns have accounted for 446.1 ha being burned. Lightning ignited fires are still common but have generally been suppressed usually because of location, extreme conditions or lack of suitable staff and equipment for control, thus seldom burning > 1 ha. Accidental fires have ranged between 0-4 per year and typically burned < 1 ha.
For prescribed burns, Archbold is divided into 176 burn units of varying size, and the status of each burn unit is updated annually based on the fire-return interval. The fire management plan is built around six modal fire-return intervals (2-5 years for sandhill, swales, and cutthroat flatwoods; 6-9 years for most flatwoods and for seasonal ponds; 6-9 and 10-19 years for scrubby flatwoods; 10-19 years for hickory scrub; 20-59 years for rosemary scrub; 20-59 and 60-100 years for sand pine scrub; and 60-100 years for bayhead swamp). The plurality of land area for each vegetation type is targeted for the modal fire return interval, although wide variation is included because of a complex landscape mosaic and specific fire experiments.
We have conducted a GIS analysis showing the current fire status of each burn unit and vegetation type and evaluate whether we have met fire return intervals targets. Some vegetation types remain behind in burning, and we discuss plans to gradually bring these areas into compliance with our plan. A large (260 ha), intense 2001 accidental fire is also causing us to adjust burning plans, postponing burning in adjacent areas of the landscape for conservation and research purposes. Archbold’s fire management has been successful in providing habitat for endangered species, providing research and educational opportunities, providing heterogeneity in fire regimes over our landscape, and providing conditions where lightning-ignited and accidental fires can be more easily absorbed.