Song Zewei, Vail Andrew, Sadowsky Michael J, Schilling Jonathan S
Department of Bioproducts and Biosystems Engineering, University of Minnesota, 2004 Folwell Avenue, St. Paul, MN, 55108, USA.
Microb Ecol. 2015 May;69(4):758-67. doi: 10.1007/s00248-015-0588-5. Epub 2015 Mar 8.
The relative amounts of hyphal inoculum in forest soils may determine the capacity for fungi to compete with and replace early colonizers of wood in ground contact. Our aim in this study was to test the flexibility of priority effects (colonization timing) by varying the timing of inoculum introduction (i.e., precolonization) and amount of inoculum (i.e., inoculum potential). We controlled these variables in soil-block microcosms using fungi with known competitive outcomes in similar conditions, tracking isolate-specific fungal biomass, and residue physiochemistry over time. In the precolonization trial (experiment I), a brown rot fungus Gloeophyllum trabeum was given 1, 3, or 5 weeks to precolonize wood blocks (oak, birch, pine, and spruce) prior the introduction of a white rot fungus, Irpex lacteus, a more aggressive colonizer in this set-up. In the inoculum potential trial (experiment II), the fungi were inoculated simultaneously, but with eightfold higher brown rot inoculum than that of experiment I. As expected, longer precolonization duration increased the chance for the less-competitive brown rot fungus to outcompete its white rot opponent. Higher brown rot fungal inoculum outside of the wood matrix also resulted in competitive success for the brown rot isolate in most cases. These temporal shifts in fungal dominance were detectable in a 'community snapshot' as isolate-specific quantitative PCR, but also as functionally-relevant consequences of wood rot type, including carbohydrate depolymerization and pH. These results from a controlled system reinforce fungal-fungal interaction and suggest that relative inoculum availability beyond the wood matrix (i.e., soils) might regulate the duration of priority effects and shift the functional trajectory of wood decomposition.
森林土壤中菌丝接种体的相对数量可能决定真菌与地面接触木材的早期定殖者竞争并取而代之的能力。我们在本研究中的目标是通过改变接种体引入时间（即预定殖）和接种体量（即接种体潜力）来测试优先效应（定殖时间）的灵活性。我们在土壤块微宇宙中控制这些变量，使用在类似条件下具有已知竞争结果的真菌，随时间追踪特定分离株的真菌生物量和残留物物理化学性质。在预定殖试验（实验I）中，在引入白腐真菌乳白耙齿菌（Irpex lacteus，在本实验设置中是更具侵略性的定殖者）之前，给予褐腐真菌密粘褶菌（Gloeophyllum trabeum）1、3或5周时间预定殖木块（橡木、桦木、松木和云杉）。在接种体潜力试验（实验II）中，两种真菌同时接种，但褐腐接种体的量是实验I的八倍。正如预期的那样，预定殖持续时间越长，竞争力较弱的褐腐真菌战胜其白腐对手的机会就越大。木材基质外更高的褐腐真菌接种量在大多数情况下也导致褐腐分离株竞争成功。这些真菌优势的时间变化在“群落快照”中可通过特定分离株的定量PCR检测到，也可作为木材腐朽类型的功能相关后果检测到，包括碳水化合物解聚和pH值。来自受控系统的这些结果强化了真菌与真菌之间的相互作用，并表明木材基质（即土壤）之外的相对接种体可用性可能调节优先效应的持续时间，并改变木材分解的功能轨迹。
