Long-term site responses to season and interval of underburns on the Georgia Piedmont

Between 1987 and 1988, twenty-four approximately 2-acre plots were established in Jones County, Georgia on the Hitchiti Experimental Forest which is also known as the Brender Demonstration Forest. These plots have not burned since prior to 1939. Treatments were applied to track site changes over time from five short return interval underburn treatments. These treatments, replicated 4 times, were comprised of: biennial dormant season headfires, triennial dormant season headfires, triennial dormant season backfires, triennial growing season headfires, growing season headfires every 6 years, and unburned controls. Triennial dormant season treatments were eventually combined. Variables tracked over time include the impact of fire on overstory pine growth, midstory (in this study midstory includes understory plants > 4.5 feet high) structure and composition, seedling (in this study including all woody plants < 4.5 feet high and all other plants regardless of height) species dominance, percent cover, pine seedling establishment and mortality, and forest floor consumption. Several thousand overstory and midstory trees were tagged, GPS coordinates recorded and their survival and growth followed over time. Vegetation was measured in nested circular plots and on line transects. Live and dead overstory trees on two 0.2 acre (1/5 ac) subplots per treatment plot were tallied annually by species with diameter at breast height and height, measured and pest damage/mortality by pathogen, lightning and wind damage recorded. Basal area was calculated periodically. Some overstory pines were bored to determine age (typically after death). Midstory live and dead trees were tallied annually on six 0.02 acre subplots per treatment plot. Seedlings were tallied on eighteen 0.001 acre (MA = milacre) subplots per treatment plot by species/species group, and percent of the subplot area in vines, herbs, moss, live woody material, dead plant material, and void of plant material (exposed mineral soil). Six 33 feet line transects per treatment plot were divided into 6 inch segments and dominant seedling species/species group tallied annually. Over 150 species/species groups were identified and tracked over time. Weights of likely available live fuel were determined by species/species group prior to each burn, as were weights of likely available dead fuel for various categories/size classes. Paired postburn samples were collected to determine consumption of various fuel categories. Overstory and midstory pine crown scorch, foliage consumption, and hardwood mortality were tallied within two weeks following each burn. Other vegetation datasets include pine seedling establishment and survival over time on the 18 MA subplots per treatment plot. Red cockaded woodpecker (RCW) related information was collected annually by Region 8 (Southern Region) of the USFS and is available from them. Live and dead fuel moisture data were sampled prior to every burn and can include preburn moisture content grab samples, 10-hour fuel stick readings, and random lumber probe readings. Fire behavior records of headfires and backfires can include rate of spread, flame length, flame angle, flame zone depth, short distance spotting, slopovers, burnout time, and percent of plot burned. The study plan called for observations of fire residence time as well, but such observations were rarely recorded. Weather data include on-plot hand-held instrument observations of surface wind velocity, ambient temperature and relative humidity (RH). On-site data collected can include precipitation, ambient temperature, RH and wind traces from recording gauges. Keetch Byram Drought Index (KBDI) calculation and National Fire danger Rating System NFDRS predictions and other weather observations taken at two nearby Georgia Forestry Commission weather stations were also included.
The purpose of this study was to quantify long-term site response to various short return interval dormant and growing season underburns on the lower Piedmont of Georgia. Objectives include: 1) establish a preburn data base from which the magnitude of any treatment-induced changes can be judged; 2) measure overstory pine growth response; 3) document pine seedling establishment and subsequent survival; and, 4) quantify changes in hardwood stature and composition, and 5) track changes in the forest floor.
Original metadata date was 11/10/2016. Minor metadata updates on 12/16/2016.