Tree diversity reduces the risk of bark beetle infestation for preferred conifer species, but increases the risk for less preferred hosts
Tree diversity reduces the risk of bark beetle infestation for preferred conifer species, but increases the risk for less preferred hosts
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DOI：
10.1111/1365-2745.13672
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发表时间：
2021-05-16
影响因子：
5.5
通讯作者：
Fruend, Jochen
中科院分区：
文献类型：
--
作者：
Berthelot, Sylvie;Fruehbrodt, Tobias;Fruend, Jochen
近几十年来，欧洲温带森林一再遭受严重干旱。干旱削弱的森林往往更容易受到树皮甲虫等虫害的影响。树种多样性，预计将增加抗旱和害虫的抵抗力，但一个积极的树木多样性对减少虫害的影响的证据在很大程度上是circumstantial.Here，我们测试了树木的多样性和树木的地理起源对树皮甲虫侵扰的影响在一个大的，年轻的树木多样性实验，从欧洲和北美的6个阔叶树和6个针叶树物种。较低的虫害风险，预计外来树种在每一个同类对（云杉，落叶松和松树）和混合物具有较高的物种丰富度和较高的阔叶比例。在2018年夏季的严重干旱之后，针叶树受到六齿云杉树皮甲虫Pityogenes chalcographus的袭击。2018/2019年冬季，所有针叶树物种上都记录到了小蠹钻孔。挪威云杉和欧洲落叶松是受影响最大的物种，因此被认为是小蠹的主要宿主。对于这两个物种，虫害的概率随着树木多样性的增加而降低（尽管这只对落叶松有意义）。相比之下，松树，这是较少的整体，更有可能被侵扰的地块与高树木多样性。外来树木往往是较少的侵扰，最明确的支持敌人释放时，考虑到纯针叶林的侵扰强度的水平。总体而言，树的多样性和树种起源的影响是不强的实验场地内，在边缘比在中心观察到更高的感染率的位置的效果。合成。增加树木的多样性可能会降低树皮甲虫侵扰的风险，属容易高侵扰率（云杉和落叶松），但风险较低的首选属（松，并在一定程度上的外来树种）可能会增加与树木的多样性，由于溢出首选主机。在混交林中，即使是相对专门的虫害，也可能在树种之间重新分配，而不是减少所有树种的虫害风险。
In recent decades, European temperate forests have repeatedly suffered from severe droughts. Drought-weakened forests have often become more susceptible to pest outbreaks such as bark beetle infestations. Tree species diversity is expected to increase resistance to drought and pests, but evidence for a positive tree diversity effect on insect pest reduction is largely circumstantial.Here we tested the effects of tree diversity and biogeographic origin of tree species on bark beetle infestation in a large, young tree diversity experiment, with six broadleaved and six conifer species from Europe and North America. Lower infestation risk was expected for the exotic tree species in each congeneric pair (spruce, larch and pine) and for mixtures with higher species richness and higher broadleaf proportion. Following a severe drought in summer 2018, the conifer trees were attacked by the six-toothed spruce bark beetle Pityogenes chalcographus. Bark beetle boreholes were recorded in winter 2018/2019 on all conifer species.Norway spruce Picea abies and European larch Larix decidua were the most infested species and thus considered main hosts of the bark beetle. For these two species, probability of infestation decreased with increasing tree diversity (although this was only significant for Larix). In contrast, Pinus, which were less infested overall, were more likely to be infested in plots with high tree diversity. Exotic trees tended to be less infested, with clearest support for enemy release found at the level of infestation intensity when considering pure conifer stands. Overall, the effects of tree diversity and tree species origin were not as strong as the effect of position within the experimental site, where higher rates of infestation were observed at the edge than in the centre.Synthesis. Increasing tree diversity may reduce the risk of bark beetle infestation for genera prone to high infestation rates (Picea and Larix), but risk for less preferred genera (Pinus, and to some extent the exotic tree species) may increase with tree diversity due to spillover from preferred hosts. In mixed forests, the risk of infestation, even by relatively specialized insect pests, may be redistributed among tree species rather than reduced for all.