The national fire and fire surrogate study: early results and future challenges

but age was used as a blocking factor to reduce variability. Each of three blocks contained four sites dominated either by pulpwood-sized trees [diameter at breast height (d.b.h.) 6 to 10 inches, block 1], by sawtimber-sized trees (d.b.h. > 10 inches, block 3), or by a mixture of pulpwood- and sawtimbersized trees (block 2). All sites were dominated by either loblolly (P. taeda L.) or shortleaf (P. echinata Mill.) pines with mixtures of oaks and other hardwoods in the understory and midstory. Treatments included thinning, prescribed burning, thinning followed by prescribed burning, and an untreated control. Levels of thinning and prescribed burning are defined by NFFS protocols to reduce fuels sufficiently so that most overstory trees will survive a subsequent wildfire. At the Piedmont site, thinning was from below and left a residual basal area of 80 square feet per acre. The burn-only treatment was conducted in spring 2001 with a prescription designed to open the canopy. A combination of strip head fires and flanking fires was used. Flame heights varied from 1 foot to > 10 feet. Burning on the thin and burn treatment was delayed until the spring of 2002 to allow heavy fuel loads to partially decompose. The prescription for these fires was for intensity to be high enough to remove fuels but not high enough to damage overstory trees. Strip head fires were used with flame heights that ranged from 1 to 4 feet. Over 400 variables were measured for individual studies on the Piedmont site. Detailed methods for all measurements cannot be described here but can be found in the study proposal located at http://www.fs.fed.us/ffs/execsumm-4-17-00.htm. Measurements were made 1 year prior to treatment and 1, 3, and 5 years after treatments. Study results for selected variables for the first year following treatment are presented here.