Fire Frequency and the Pine Barrens of New Jersey

Abstract

FORMAN, R. T. T. and R. E. BOERNER (Dept. Bot., Rutgers Univ., New Brunswick, NJ 08903). Fire frequency and the Pine Barrens of New Jersey. Bull. Torrey Bot. Club 108: 34-50. 1981.-State fire r ecords and literature citatioiis wvere examined to estimate both regional fire frequency and point fire frequency. The number of annual wildfires in the 550,000 hectare Pine Barrens has remained at approximately 1100 since 1940 when fire control became effective. The total area burned annually dropped sharply from about 22,000 ha during 1906-1939 to 8,000 ha in the past four decades. Extensive wildfires of 8,000-16,000 ha each are common. Since 1838, about every two decades on the average, 10% or more of the predominant pine and oak forest burns in a single year (50,000 ha). An average point in the piine and oak forest burns currently at about 65 year intervals, compared with 20 year intervals earlier this century. The number of wildfires in the region correlates linearly with the number of dry months in a year. However, the area burned annually is constant with up to four dry months during the January-toSeptember period; both average and variability of area burned increases with five or more dry months. The results suggest the upland Pine Barrens are a mosaic of fire-caused patches at two levels of scale: a fine-grained scale of small (averaging 6 ha) young patches imprinted on a coarse-grained scale of large (several tens of ha), variable-sized patches more than four decades old. The drop in point fire frequency favors (a) non fire-adapted populations, (b) hardwoods swamp replacing cedar swamp, and (c) loss of the coarsegrained landscape mosaic.