| Heavy fuel loads were created by multiple southern pine beetle (Dendroctonus frontalis Ehrh.) outbreaks throughout the southern Piedmont between 1999 and 2002. Prescribed burning and mechanical mastication are proposed to reduce fuel loading in beetle-killed pine (Pinus L. spp.) stands in the upper South Carolina Piedmont, but their ecological impacts are unknown. Prescribed burning reduced fuelbed continuity by consuming litter (Oi) and fine (1- and 10-hr timelag size classes) woody fuels immediately after the treatment. Duff (Oe + Oa) layer thickness also decreased and mineral soil was exposed in some areas. Mastication resulted in a thick, continuous layer of shredded and ground live and dead standing vegetation and dead and down woody debris being deposited on the forest floor.;Burning caused immediate reductions in exchangeable Ca, P, and Al, but significant differences did not persist into Yr 2. Mastication reduced P and Al and increased K, but again significant differences were transient. Neither VAM nor ECM soil inoculum potential (SIP) observed from soil bioassays in Yr 1 were significantly different among treatments, but both were highly variable within treated stands. ECM SIP was positively associated with NH 4+-N concentration, peak burning temperature, and duration of heating above 50°C when measured at the soil-duff (Oe + Oa) interface. Conversely, VAM SIP was negatively associated with NH4 +-N concentration, peak burning temperature, and heating duration. Best-subset regression additionally revealed that post-treatment SIP was associated with pre-treatment vegetation assemblages.;Oak ((Quercus L. spp.) sprouts grew slower than other hardwoods competitors, but comprised a substantial portion of the advance regeneration pool in burned stands. The mastication treatment apparently damaged basal buds of advance regeneration and sprouting was inhibited. Overall, large advance hardwood regeneration was less abundant and there were proportionately fewer oak than other hardwood stems after mastication when compared to prescribed burning. By Yr 2 post-treatment, large advance oak regeneration was sufficient to reasonably ensure that oak would be a significant component of burned stands at crown closure but insufficient in masticated stands. First-year survival of planted loblolly pine ((P. taeda L.) seedlings was highest in masticated stands when compared to the other treatments and likely related to reduced growth of woody and herbaceous competition. Non-metric multidimensional scaling ordination revealed that the understory plant communities in burned and masticated stands were similar to one another, but distinct from the control. Plants associated with dry, open conditions were encouraged by the active treatments whereas there was a higher incidence of plants associated with shaded and moist conditions in the control. Results of this study will assist forest managers in evaluating treatment options for different silvicultural objectives in beetle-killed southern pine stands. |
