Interactions among prescribed fire, herbivore pressure and shortleaf pine ( Pinus echinata) regeneration following southern pine beetle ( Dendroctonus frontalis) mortality

Abstract

We monitored natural and artificially regenerating shortleaf pine ( Pinus echinata) seedlings and their associated herbivores in forests stands that suffered extensive overstory mortality due to the southern pine beetle ( Dendroctonus frontalis). Seedling performance was evaluated based on survival and absolute and relative growth rates. Trapping stations were established to monitor the abundance and seasonal activity of pine regeneration insects. Seedlings were regularly inspected for the frequency and severity of herbivore pressure. Seedling performance, insect abundance and activity, and herbivore pressure were compared between stands treated with prescribed fire and untreated controls. Survival and absolute growth rates were greatest for naturally regenerating seedlings. Naturally regenerating seedlings grew more vigorously in the burned areas, but prescribed fire did not influence the growth of planted seedlings. Relative height growth comparisons indicated the growth potential of planted seedlings was not significantly different from that of the natural seedlings. Herbivore pressure was greater on natural regeneration, possibly due to superior seedling health and vigor. Pine weevil ( Hylobius pales and Pissodes nemorensis) and Nantucket pine tip moth ( Rhyacionia frustrana) abundance and herbivore pressure did not differ between the burned and unburned stands, but there was a significant interaction between sampling date and prescribed fire on their seasonal activity. Conifer sawfly (Hymenoptera: Diprionidae) abundance and activity was effectively suppressed by prescribed fire treatments. Pine webworm ( Tetralopha robustella) infestations occurred with greater frequency and severity on seedlings growing in burned areas. Mammalian herbivory was minimal. Herbivore-induced seedling mortality was low, and herbivory did not reduce seedling growth. Growth of naturally regenerating shortleaf pine seedlings was greater in burned plots.