Bark decomposition is an underexamined component of soil carbon cycling and soil community assembly. Numerous studies have shown faster decomposition of leaf litter in “home” environments (i.e. within soil adjacent to the plant that produced the leaves), suggesting potential legacy effects from previous deposition of similar litter. This is expected to occur through, in part, accumulation of microorganisms that metabolize substrates the litter provides. Whether a similar “home-field advantage” (HFA) exists for bark decomposition is unknown, but this dynamic may differ because annual bark deposits to soil are minimal relative to leaf deposits. We hypothesized that (1) as with leaf litter, bark will be better decomposed near to the tree from which it was collected, and (2) that decomposing bark can initiate change in soil microbial composition. To test these hypotheses, we used a full factorial design that included two bark types (collected from eastern hemlock, Tsuga canadensis, and white oak, Quercus alba) and two soil types (‘home’ and ‘away’) within a temperate mixed hardwood forest at the Shale Hills Catchment in central Pennsylvania, USA. Bark was excised from 25 replicates of each tree type, buried in either home or away soil, and incubated belowground from July 2017 to June 2018. Decomposition was assessed through proportionate mass loss over time, while microbial composition in the bark and adjacent soil was assessed through high-throughput sequencing of 16S rRNA gene and fungal ITS fragments. Overall, bark degraded faster in white oak soils, and there was also an effect of bark type on decomposition. Although white oak bark decomposed more quickly in its home environment, this could be due to either soil conditioning or inherent differences in the soils in which each species grows. Soil microbial assemblages also sorted according to bark type rather than soil type, suggesting that bark strongly influences the composition of nearby microorganisms during decomposition. Our results suggest that both bark type and soil type are important factors during bark decomposition, but our findings suggest no clear evidence for HFA.

中文翻译：

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白橡木土壤中的树皮分解优于东部铁杉土壤，而树皮类型导致土壤微生物组成的一致变化

树皮分解是土壤碳循环和土壤群落组装的一个未被充分研究的组成部分。大量研究表明，在“家庭”环境中（即在与产生叶子的植物相邻的土壤中）凋落物分解速度更快，这表明先前类似凋落物沉积的潜在遗留影响。预计这部分是通过代谢垃圾提供的底物的微生物的积累而发生的。树皮分解是否存在类似的“主场优势”（HFA）尚不得而知，但这种动态可能有所不同，因为每年树皮对土壤的沉积量相对于叶沉积量而言是最小的。我们假设 (1) 与落叶一样，树皮在收集树皮附近会更好地分解，并且 (2) 分解树皮可以引发土壤微生物组成的变化。为了测试这些假设，我们使用了一个完整的析因设计，其中包括两种树皮类型（从东部铁杉、Tsuga canadensis 和白橡树、Quercus alba 中收集）和两种土壤类型（“家”和“外”）在温带混合硬木中美国宾夕法尼亚州中部页岩山集水区的森林。从每种树种的 25 个重复中切下树皮，埋在家里或外地土壤中，并于 2017 年 7 月至 2018 年 6 月在地下培养。通过随时间的质量损失成比例来评估分解，同时评估树皮和相邻土壤中的微生物组成通过对 16S rRNA 基因和真菌 ITS 片段进行高通量测序。总体而言，白橡木土壤中的树皮降解速度更快，而且树皮类型对分解也有影响。虽然白橡树树皮在它的家庭环境中分解得更快，这可能是由于土壤调节或每个物种生长的土壤的内在差异。土壤微生物组合也根据树皮类型而不是土壤类型进行分类，这表明树皮在分解过程中强烈影响附近微生物的组成。我们的研究结果表明，树皮类型和土壤类型都是树皮分解过程中的重要因素，但我们的研究结果表明没有明确的 HFA 证据。