Pec Gregory J, Karst Justine, Taylor D Lee, Cigan Paul W, Erbilgin Nadir, Cooke Janice E K, Simard Suzanne W, Cahill James F
Department of Biological Sciences, University of Alberta, B717a Biological Sciences Building, Edmonton, Alberta, T6G 2E9, Canada.
Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, Alberta, T6G 2E3, Canada.
New Phytol. 2017 Jan;213(2):864-873. doi: 10.1111/nph.14195. Epub 2016 Sep 23.
Western North American landscapes are rapidly being transformed by forest die-off caused by mountain pine beetle (Dendroctonus ponderosae), with implications for plant and soil communities. The mechanisms that drive changes in soil community structure, particularly for the highly prevalent ectomycorrhizal fungi in pine forests, are complex and intertwined. Critical to enhancing understanding will be disentangling the relative importance of host tree mortality from changes in soil chemistry following tree death. Here, we used a recent bark beetle outbreak in lodgepole pine (Pinus contorta) forests of western Canada to test whether the effects of tree mortality altered the richness and composition of belowground fungal communities, including ectomycorrhizal and saprotrophic fungi. We also determined the effects of environmental factors (i.e. soil nutrients, moisture, and phenolics) and geographical distance, both of which can influence the richness and composition of soil fungi. The richness of both groups of soil fungi declined and the overall composition was altered by beetle-induced tree mortality. Soil nutrients, soil phenolics and geographical distance influenced the community structure of soil fungi; however, the relative importance of these factors differed between ectomycorrhizal and saprotrophic fungi. The independent effects of tree mortality, soil phenolics and geographical distance influenced the community composition of ectomycorrhizal fungi, while the community composition of saprotrophic fungi was weakly but significantly correlated with the geographical distance of plots. Taken together, our results indicate that both deterministic and stochastic processes structure soil fungal communities following landscape-scale insect outbreaks and reflect the independent roles tree mortality, soil chemistry and geographical distance play in regulating the community composition of soil fungi.
北美西部的景观正迅速因山松甲虫（Dendroctonus ponderosae）导致的森林死亡而发生改变，这对植物和土壤群落产生了影响。驱动土壤群落结构变化的机制很复杂且相互交织，尤其是对于松林中普遍存在的外生菌根真菌而言。增强理解的关键在于厘清寄主树死亡的相对重要性与树木死亡后土壤化学变化之间的关系。在此，我们利用加拿大西部黑松林近期爆发的树皮甲虫疫情，来测试树木死亡的影响是否改变了地下真菌群落的丰富度和组成，包括外生菌根真菌和腐生真菌。我们还确定了环境因素（即土壤养分、湿度和酚类物质）以及地理距离的影响，这两者都可能影响土壤真菌的丰富度和组成。甲虫导致的树木死亡使两组土壤真菌的丰富度均下降，且整体组成发生了改变。土壤养分、土壤酚类物质和地理距离影响了土壤真菌的群落结构；然而，这些因素在外生菌根真菌和腐生真菌之间的相对重要性有所不同。树木死亡、土壤酚类物质和地理距离的独立影响对外生菌根真菌的群落组成产生了作用，而腐生真菌的群落组成与样地的地理距离呈弱但显著的相关性。综合来看，我们的结果表明，在景观尺度的昆虫爆发后，确定性和随机性过程共同构建了土壤真菌群落，并反映了树木死亡、土壤化学和地理距离在调节土壤真菌群落组成中所起的独立作用。
