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Natural communities dominated by longleaf pine (Pinus palustris Mill.) once covered an estimated two thirds of the forested area in the southeastern United States. Today, less than 1.2 million ha remain. However, over the past 10–15 years, public land managers have begun to restore many longleaf pine forests. More recently incentive programs have prompted reforestation and afforestation programs on nonindustrial private lands. These activities have been facilitated by improved longleaf regeneration technology and by expanded educational and outreach efforts. In the South, there is also a growing trend towards longer rotations due to changes in wood/fiber markets and prices. These trends suggest a new strategy to increase terrestrial carbon storage in the southeastern United States in a way that provides many simultaneous ecological and economic benefits. For example, longleaf pine is a long-lived species with a low mortality rate. Among the southern pine species, it has a high specific gravity and can tolerate a very wide variety of habitats. Longleaf pine is better able to sustain growth at older ages (over 150 years) and is tolerant to fire and many insects and diseases. Recent research also indicates that longleaf pine managed for longer rotations outperforms other commercial southern pine species on most sites and might better adapt to future climate scenarios with higher temperatures and higher atmospheric CO2 levels. Moreover, the higher-value, longer-lasting wood products derived from longleaf pine forests will continue to store carbon over long time periods.

Occupational safety and health concerns have been raised in a number of southern states by workers conducting prescribed burns on forest lands treated with herbicides. Modeling assessments coupled with laboratory experiments have shown that the risk of airborne herbicide residues to workers is insignificant, even if the fire occurs immediately after herbicide application. However, no field studies had been conducted to confirm these findings. To bridge that gap, a field validation study was conducted in Georgia to measure breathing zone concentrations of smoke suspended particulate matter (SPM), herbicide residues, and carbon monoxide (CO) on 14 operational prescribed fires. Smoke was monitored on sites treated with labeled rates of forestry herbicides containing the active ingredients imazapyr, triclopyr, hexazinone, and picloram. The sites were burned within 30-169 days after herbicide application. Tract size ranged from 2.4 to 154 hectares. Personal monitors and area monitors employing glass fiber filters and polyurethane foam collection media were used. No herbicide residues were detected in the 140 smoke samples from the 14 fires conducted in this study. The sensitivity of the monitoring methods was in the 0.1 to 4.0 micrograms/m3 range, which is several hundred to several thousand times less than any established occupational exposure limit for herbicides. The SPM and CO monitored on these fires is the first time breathing zone concentrations of these smoke constituents have been measured in the South. As expected, concentrations were highly variable depending on fire conditions and the location of personnel. Worker respirable (2.3-microns particle cut point) SPM concentrations ranged between 0.2 and 3.7 mg/m3.(ABSTRACT TRUNCATED AT 250 WORDS)

Pine bark beetle insecticide treatment plots were established on the Ocala National Forest, in central Florida. Each plot consisted of five sand pine, Pinus clausa (Chapm. Ex. Engelm) Vassey ex. Sarg., trees treated with either 0.5% lindane (benzene hexachloride) or 2% chlorpyrifos (0,0-diethyl 0-(3,5,6-trichloro-2-pgridyl) phosphorothioate). After 4 months, mean residue levels ranged from 0.32 to 35.8 mg/kg for lindane and < 0.1 to 76.1 mg/kg for chlorpyrifos. Chlorpyrifos was more persistent in wood than lindane. In a separate laboratory study, lindane or chlorpyrifos were applied to powdered wood and then burned under controlled conditions to determine carryover in combustion products. With slow heating to 500°C (20°C/min.), 42.7% of the lindane and 28.3% of the chlorpyrifos were recovered in the smoke stream. With rapid combustion at 600°C, all lindane and chlorpyrifos residues were thermally degraded. These findings were related to the risk of burning insecticide treated wood as firewood inside houses. Even under the worst case slow burning conditions, human exposure to airborne residues would be well under “safe-sided” threshold limit values and less than 0.2% of the acceptable daily intake established by the World Health Organization.

Twelve forest fuels that varied widely in nitrogen content were burned in a thermogravimetric system, and nitrogen oxide production was analyzed by chemiluminescence. The effects of fuel nitrogen concentration, available oxygen, flow rate, and heating rate on nitrogen oxide production were examined. Results show that fuel nitrogen is an important source of nitrogen oxides from the low-temperature (

Data on the optical absorption properties (expressed as a specific absorption, Ba) of the smoke emissions from fires with forest fuels have been determined for a series of low-intensity field fires and a series of laboratory scale fires. The Ba data have been used to estimate the emission factors for graphitic carbon [EF(Ce)] for these test fires to provide data needed for regional visibility studies, tropospheric air chemistry studies, and studies evaluating nuclear winter scenarios.

Potential exposure to pesticide residues resulting from burning wood treated with phenoxy and pyridine herbicides was assessed. Wood samples from trees treated with 2,4-D [2,4-dichlorophenoxy acetic acid], dicamba [3,6-dichloro-o-anisic acid], dichlorprop [2-(2,4-dichlorphenoxy) propionic acid], picloram [4-amino-3,5,6-trichloropicolinic acid], and triclopyr (3,5,6-trichloro-2-pyri dinyl)oxy acetic acid contained variable amounts of parent compound residues at 4, 8, and 12 months after application. At the time of the latter sampling, residues of 2,4-D, dicamba, and picloram were

Absorption properties of smokes from laboratory fires that represent prescription burns in the Southern states have been quantified to relate variations in measured absorption parameters to variation in fire conditions and to estimate emission factors for elemental carbon. Results showed significant differences in absorption of the smoke emissions between flaming and smoldering combustion with specific absorption coefficient Ba values ranging from 0.04 m2 g−1 for smoldering combustion to 1 m2 g−1 at 632.8 nm for flaming combustion. These measured optical properties and previously measured size data were used in Mie calculations to determine the overall radiative properties for the smokes from these fires. Mie calculations for λ = 550 nm indicate that somewhat less than 50% of the extinction will be due to particulate matter absorption in flaming combustion, whereas only about 5% of the extinction will be due to absorption under purely smoldering conditions. Calculated mass concentration/scattering (Cm/σs) ratios for λ = 500 nm show only a slight variation with nIM, decreasing from 3.3 × 105 μg m−2 at an imaginary refractive index (nIM) = 0.07 to a value of 2.7 × 105 μgm−2 at nIM = 0.007. The ratios calculated for the low absorption cases are generally consistent with previous experimental observations, although these calculations suggest that some of the variations seen in this ratio are consistent with variation due to differences in the optical properties of the particulates.