Association between severity of prescribed burns and subsequent activity of conifer-infesting beetles in stands of longleaf pine

Abstract

A randomized complete block experiment was performed to measure the effect of prescribed, dormant-season burns of three different levels of severity (measured as fuel consumption and soil surface heating) on subsequent insect infestation and mortality of mature longleaf pine (Pinus palustris Mill.). Multiple-funnel traps baited with a low release rate of turpentine and ethanol were used to monitor activity of certain coniferophagous beetles. Non-aggressive species, including the root beetles Hylastes salebrosus Eichhoff and H. tenuis Eichhoff, the ambrosia beetle Xyleborus pubescens Zimmermann, the reproduction weevil Pachylobius picivorus (Germar), and buprestid borers, were attracted to burned plots in numbers that correlated positively with burn severity. Beetle attraction to burned sites was greatest in the first weeks post-burn and disappeared by the second year. Two potential tree-killing bark beetles, Dendroctonus terebrans (Olivier) and Ips grandicollis (Eichhoff), were trapped in significant numbers but exhibited no attraction to burned plots. Tree mortality correlated significantly with the severity of the burns and amounted to 5% of stems in the hottest burn treatment after 3 years. The majority of the mortality was observed in the second and third years post-burn. Attacks of Ips and Dendroctonus bark beetles were apparent on nearly all dead or dying trees, and evidence suggested that root pathogens may have contributed to tree susceptibility to beetle attack and mortality. Our data indicate that selection of burn regimes that reduce or eliminate consumption of duff (e.g., favoring heading fires over backing fires) could significantly reduce mortality of longleaf pine managed for long rotations. Published by Elsevier B.V.

Comparison of postfire mortality in endemic Corsican black pine (Pinus nigra ssp. laricio) and its direct competitor (Pinus pinaster)

“…Because of the rarity, beauty, and ecological importance of old pines, forest managers go to great lengths to conserve damaged stands. But the presence of many dead trees increases the risk of healthy trees being attacked by bark beetles (Jenkins 1990;Ryan and Amman 1994;Sullivan et al 2003), and foresters are also looking to mitigate the visual impact of damaged forest. Thus, the conservation of laricio pine in its competition with maritime pine requires tools that can be used to assess the likelihood of mortality in damaged trees, coupled with pertinent forest management prescriptions.…”

“…Model variables consist of dendrometric parameters (height, diameter at breast height) and several indicators of fire severity (crown scorch volume, bole length charred, bark char). Mortality generally occurs 2 or 3 years after the fire, but may be observed in old pines 13 years later (Rigolot 1992;McHugh and Kolb 2003;Sullivan et al 2003).…”

Snag characteristics and dynamics following natural and artificially induced mortality in a managed loblolly pine forest

“…We observed a fairly stable snag population with offsetting recruitment and loss rates during the pretreatment period. Annual tree mortality rates in the region are known to be low for this age class of pines, with primary causes being lightning strikes, root disease, beetle kill, and, occasionally, prescribed fire (Barnard 1999;Sullivan et al 2003;Outcalt 2008). Moorman et al (1999) documented similarly low annual recruitment rates and a slight net loss over the measurement interval.…”

“…Snag size is influenced by forest age (Ohmann et al 1994), and the number of snags can be affected by thinning (Hagar et al 1996). Although management is typically believed to limit snag resources, it can also increase them through actions such as prescribed fire (Sullivan et al 2003), establishment of high stem densities that leads to density-dependent tree mortality (Garber et al 2005), and thinning that induces root disease mortality (Barnard 1999).…”

Short-term effects of low-intensity prescribed fire on ground-dwelling invertebrates in a Canarian pine forest

“…Some groups of invertebrates, such as beetles and some spiders, have been shown to increase after fire treatment (Sullivan et al, 2003). This is likely because their activity can increase due to changes in the microclimate at the litter surface (Andersen and Yen, 1988;Neumann and Tolhurst, 1991), resulting in an increase of catches.…”