Data from: Prescribed fire does not promote outbreaks of a primary bark beetle at low-density populations

The causes of bark beetle outbreaks – particularly the role of
disturbances – are poorly understood. Stand-scale disturbances, like
fires, can suddenly improve local host susceptibility and may attract
beetles; however, whether such increases can lead to outbreaks in
post-disturbance stands is unclear. Using low-density Dendroctonus
ponderosae mountain pine beetle populations in Pinus contorta lodgepole
pine forests in western Canada, we investigated whether prescribed fires
promote outbreaks or provide only short-term resources. Proportionally
more burned than non-burned trees were attacked. At one site, beetle
attacks increased in response to a resource pulse, but the proportions of
attacked trees and numbers of attacks per tree declined over four years
after fire. Elsewhere, beetle attacks remained very low. As the resource
(phloem) quality of burned trees remained high three years after fire, we
propose that post-fire mortality, resulting in fewer available host trees,
can at least partially explain why D. ponderosae did not build up
populations in burned stands. Synthesis and applications. Our study
emphasizes the importance of examining long-term trends in fire–bark
beetle interactions, and of understanding low-density beetle populations.
Because fire does not seem to promote mountain pine beetle outbreaks, we
recommend the continued use of prescribed fire for the general management
of P. contorta forests with low-density beetle populations.

树皮甲虫暴发的成因——尤其是干扰所扮演的角色——目前仍未得到充分阐明。林分尺度的干扰（如火灾）可骤然提升本地寄主林木的易感性，并可能吸引甲虫；然而此类易感性的提升是否会引发干扰后林分的甲虫暴发，目前尚无定论。
本研究以加拿大西部扭叶松（Pinus contorta）林内的低密度山松甲虫（Dendroctonus ponderosae）种群为研究对象，探究计划火烧是否会推动甲虫暴发，抑或仅能提供短期的寄主资源。
研究结果显示，遭火烧的林木受甲虫侵袭的比例显著高于未火烧林木。在其中一处样地，甲虫侵袭数量随寄主资源脉冲出现上升，但火烧后四年间，受侵袭林木占比与单株林木的侵袭虫数均呈下降趋势。在其余样地，甲虫侵袭始终维持在极低水平。
尽管火烧后三年，火烧林木的韧皮部（寄主资源）品质仍维持较高水平，但我们推测，火烧后林木死亡导致可用寄主林木数量减少，至少可部分解释山松甲虫为何未在火烧林分内形成种群暴发。
研究总结与应用启示：本研究强调了探究火灾与树皮甲虫互作长期趋势，以及关注低密度甲虫种群的重要性。鉴于计划火烧似乎并未推动山松甲虫暴发，我们建议在低密度甲虫种群的扭叶松林分通用经营中，继续采用计划火烧手段。