Du Baoguo, Frühbrodt Tobias, Delb Horst, Burzlaff Tim, Biedermann Peter H W, Kreuzwieser Jürgen
Chair of Ecosystem Physiology, University of Freiburg, Georges-Köhler-Allee 53, 79110 Freiburg, Germany.
Department of Forest Protection, Forest Research Institute of Baden-Württemberg, Wonnhaldestraße 4, 79100 Freiburg, Germany.
Tree Physiol. 2025 Jan 25;45(1). doi: 10.1093/treephys/tpae152.
Norway spruce (Picea abies L.) is economically one of the most important conifer species in Europe. Spruce forests are threatened by outbreaks of the bark beetle Ips typographus L., and this will worsen with a projected warmer and drier climate and increased outbreak dynamic following storms. Volatile terpenes and aromatics play pivotal roles in defence of trees, however little is known about the emission dynamics of these compounds from trees colonized with I. typographus, particularly in dependence on the beetle's developmental stages and colonization densities. Here, we analysed the emission profiles of volatile organic compounds (VOCs) from spruce logs colonized with low (LDT) and high (HDT) densities of I. typographus from the initial colonization until the emergence of the next beetle generation. A first VOCs emission peak appeared directly after colonization and lasted for 1 week. It mainly consisted of monoterpenoids and most likely reflected the trees' constitutive defence against herbivory. Under HDT, a second emission maximum occurred during the larval stage, whereas under LDT a second peak appeared later during maturation feeding of callow beetles. In contrast to the first peak, sesquiterpenoids, aromatics and oxygenated monoterpenoids dominated the second peak, possibly reflecting the trees' induced defence. Developing beetles seem to face a variety of defence compounds even if the tree has been overwhelmed and colonization by parental beetles was already successful. The specific release patterns under LDT and HDT might be due to different availability of precursor compounds, depletion of constitutively stored compounds and differences in microbial activities associated with the bark beetles. The present study highlights constitutive defence of spruce trees upon herbivore attack, and the effect of infestation density on the temporal dynamics of induced defence. Particularly the oxygenated monoterpenoid terpinen-4-ol may be used as cue to assess habitat quality and competition by newly arriving beetles.
挪威云杉（Picea abies L.）是欧洲经济上最重要的针叶树种之一。云杉林受到树皮甲虫 Ips typographus L. 爆发的威胁，并且随着预计气候变暖变干以及风暴后爆发动态增加，这种情况将恶化。挥发性萜类和芳香族化合物在树木防御中起关键作用，然而对于被 Ips typographus 侵染的树木中这些化合物的排放动态，尤其是依赖于甲虫发育阶段和侵染密度的情况，人们了解甚少。在此，我们分析了从初始侵染到下一代甲虫出现期间，被低密度（LDT）和高密度（HDT）Ips typographus 侵染的云杉原木中挥发性有机化合物（VOCs）的排放概况。首次VOCs排放峰值在侵染后立即出现并持续1周。它主要由单萜类化合物组成，很可能反映了树木对食草动物的组成性防御。在HDT条件下，第二次排放最大值出现在幼虫阶段，而在LDT条件下，第二个峰值出现在新羽化甲虫的成熟取食阶段后期。与第一个峰值不同，倍半萜类、芳香族化合物和氧化单萜类化合物在第二个峰值中占主导，可能反映了树木的诱导防御。即使树木已被亲代甲虫压倒并成功侵染，发育中的甲虫似乎仍面临多种防御化合物。LDT和HDT条件下的特定释放模式可能是由于前体化合物的可用性不同、组成性储存化合物的消耗以及与树皮甲虫相关的微生物活动差异。本研究突出了云杉树在食草动物攻击时的组成性防御，以及侵染密度对诱导防御时间动态的影响。特别是氧化单萜类化合物萜品-4-醇可作为新到达甲虫评估栖息地质量和竞争的线索。
