Effects of log length on Polygraphus proximus attack

Polygraphus proximus Blandford (Coleoptera: Curculionidae: Scolytinae), a
non-aggressive bark beetle, has caused mortality of Abies spp. in Western
Siberia, Central Asia, European Russia as well as Japan. Removing dead
trees (i.e. salvage logging) and thinning stands are considered one of the
best practices to reduce the risk of bark beetle outbreaks. However,
salvaging or removing dead and thinned trees requires significant effort.
Thus, to determine whether cutting trees shorter would reduce P. proximus
infestation, we exposed A. sachalinensis logs of various lengths on the
ground in a forest stand. The attack density of P. proximus significantly
decreased with shorter log lengths. It can be concluded that cutting into
short logs and leaving them on the ground are effective practices to
reduce the chance of P. proximus outbreaks after natural disturbances and
thinning.

近缘多毛小蠹（Polygraphus proximus Blandford）隶属于鞘翅目（Coleoptera）象甲科（Curculionidae）小蠹亚科（Scolytinae），是一类弱攻击性树皮甲虫。该虫已在西西伯利亚、中亚、俄罗斯欧洲区域及日本引发冷杉属（Abies）植物死亡事件。清理枯立木（即灾后采伐（salvage logging））与林分疏伐，被视作降低树皮甲虫种群暴发风险的最优实践方案之一。但此类灾后采伐或疏伐作业需投入大量人力与物力成本。为此，为明确缩短木段长度能否减轻近缘多毛小蠹的侵染危害，研究团队在林分内将不同长度的萨哈林冷杉（Abies sachalinensis）原木裸露放置于地面开展试验。结果表明，近缘多毛小蠹的攻击密度随原木长度缩短呈现显著下降趋势。综上可得出结论：将原木截短并留存于林地地面，可有效降低自然扰动及林分疏伐后近缘多毛小蠹的种群暴发概率。