Gordon D Alex R, Burke David J, Carrino-Kyker Sarah R, Bashian-Victoroff Claudia, Mabrouk Adam I, Van Stan John T
Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, OH, 44115, USA.
The Holden Arboretum, Kirtland, OH, 44094, USA.
Microb Ecol. 2025 Sep 2;88(1):93. doi: 10.1007/s00248-025-02593-2.
Stemflow, the concentrated fraction of rainfall that drains down tree trunks, can translocate canopy biota to the forest floor, but its eukaryotic composition remains uncharacterized via eDNA methods. We collected stemflow from 18 Fagus grandifolia (American beech) trees during ten storms in northeastern Ohio (USA) and analyzed 18S rRNA eDNA to resolve transported microbial-eukaryote communities. Over 12 million reads (83 samples) revealed 920 zero-radius OTUs spanning fungi, algae, protists, and metazoans. Community composition differed significantly among storm events (PERMANOVA F = 3.6, r = 0.31, p < 0.001) and among NOAA HYSPLIT modeled air-mass back-trajectories (F = 8.9, r = 0.36, p < 0.001). Summer storms were dominated by fungal taxa (Entomophthoromycota, Basidiomycota, and Ascomycota comprised up to 90% of reads), whereas late-autumn and winter storms carried mainly algal stramenopiles (Ochrophyta). Large storms (> 60 mm event) mobilized conspicuously higher relative abundances of larger metazoans (tardigrades and arthropods). We infer from stemflow eDNA that (i) seasonal resource shifts in tree canopies favor parasitic fungi in summer and saprotrophic fungi in autumn; (ii) northerly winter storms entrain Great Lakes aerosol algae that deposit onto canopies; (iii) rainfall intensity and duration jointly control the detachment of well-attached canopy eukaryotes. Together, our results establish stemflow eDNA as a non-invasive window into storm-mediated linkages between above- and below-ground biodiversity, offering new scope for monitoring canopy microbiomes under intensifying hydro-climatic regimes.
茎流是沿树干流下的降雨浓缩部分，它能将冠层生物群转移到森林地面，但其真核生物组成通过环境DNA方法仍未得到表征。我们在美国俄亥俄州东北部的十次暴风雨期间，从18棵北美山毛榉树上收集了茎流，并分析了18S rRNA环境DNA，以解析被运输的微生物真核生物群落。超过1200万个读数（83个样本）揭示了920个零半径操作分类单元，涵盖真菌、藻类、原生生物和后生动物。群落组成在暴风雨事件之间（PERMANOVA检验：F = 3.6，r = 0.31，p < 0.001）以及美国国家海洋和大气管理局（NOAA）的HYSPLIT模型模拟的气团后向轨迹之间（F = 8.9，r = 0.36，p < 0.001）存在显著差异。夏季暴风雨以真菌类群为主（虫霉门、担子菌门和子囊菌门占读数的比例高达90%），而晚秋和冬季暴风雨主要携带藻类硅藻（褐藻门）。大型暴风雨（> 60毫米降雨事件）显著调动了相对丰度更高的大型后生动物（缓步动物和节肢动物）。我们从茎流环境DNA推断出：（i）树冠层季节性资源转移有利于夏季的寄生真菌和秋季的腐生真菌；（ii）冬季北风暴风雨夹带五大湖的气溶胶藻类，这些藻类沉积在树冠上；（iii）降雨强度和持续时间共同控制附着良好的树冠真核生物的脱离。总之，我们的研究结果将茎流环境DNA确立为一个非侵入性窗口，用于了解暴风雨介导的地上和地下生物多样性之间的联系，为在日益强化的水文气候条件下监测树冠微生物群落提供了新的视角。
