Fungal OTUs during dead wood succession of aspen

During decomposition of organic matter, microbial communities may follow
different successional trajectories depending on the initial environment
and colonizers. The timing and order of the assembly history can lead to
divergent communities through priority effects. We explored how assembly
history and substrate quality affected fungal dead wood communities and
decomposition, 1.5 and 4.5 years after tree felling. In addition, we
investigated the effect of invertebrate exclusion during the first two
summers. For aspen (Populus tremula) logs, we measured initial bark and
wood resource quality, and surveyed the fungal communities by DNA
metabarcoding at different time points during succession. We found that a
gradient in fungal community composition was related to resource quality
and we discuss how this may reflect tolerance-dominance trade-offs in
fungal life history strategies. As with previous studies, the initial
amount of bark tannins was negatively correlated with wood decomposition
rate over 4.5 years. The latent fungal community explained variation in
community composition after 1.5, but not after 4.5 years, of succession.
Although the assembly history of latent fungi may cause alternate
trajectories in successional communities, our results indicate that the
communities may easily converge with the arrival of secondary colonizers.
We also identified a strong invertebrate-induced priority effect of fungal
communities, even after 4.5 years of succession, thereby adding crucial
knowledge to the importance of invertebrates in affecting fungal community
development. By measuring and manipulating aspects of assembly history and
resource quality that have rarely been studied, we expand our
understanding of the complexity of fungal community dynamics.

在有机质分解过程中，微生物群落可能遵循不同的演替轨迹，其差异取决于初始环境与初始定植类群。群落组装历史的时序与顺序可通过优先效应（priority effects）导致群落产生分化。本研究探究了树木砍伐后1.5年与4.5年时，群落组装历史与基质质量对枯木真菌群落及分解过程的影响。此外，我们还考察了前两个夏季中排除无脊椎动物的处理效应。针对欧洲山杨（Populus tremula）的伐桩原木，我们测定了其初始树皮与木材的资源质量，并通过DNA宏条形码（DNA metabarcoding）技术在演替过程的多个时间点对真菌群落进行了调查。研究发现，真菌群落组成的梯度变化与资源质量相关，我们就此讨论了这一现象可能反映的真菌生活史策略中的耐受-优势权衡（tolerance-dominance trade-offs）。与既往研究一致，4.5年观测周期内，树皮单宁的初始含量与木材分解速率呈负相关。潜在真菌群落可解释演替1.5年后的群落组成变异，但无法解释演替4.5年后的群落组成变异。尽管潜在真菌的组装历史可能导致演替群落出现替代轨迹，但本研究结果显示，随着次级定植类群的迁入，群落可快速趋于趋同。我们还发现，即使在演替4.5年后，无脊椎动物仍可诱导产生显著的真菌群落优先效应，这为无脊椎动物在调控真菌群落发育过程中的重要性补充了关键认知。本研究通过测定与操控此前鲜有研究的群落组装历史与资源质量维度，拓展了我们对真菌群落动态复杂性的认知。