Jean Mélanie, Holland-Moritz Hannah, Melvin April M, Johnstone Jill F, Mack Michelle C
Center for Ecosystem Science and Society, Northern Arizona University, Flagstaff, AZ, 86011, USA.
Department of Biology, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada.
New Phytol. 2020 Sep;227(5):1335-1349. doi: 10.1111/nph.16611. Epub 2020 May 28.
Nitrogen (N )-fixing moss microbial communities play key roles in nitrogen cycling of boreal forests. Forest type and leaf litter inputs regulate moss abundance, but how they control moss microbiomes and N -fixation remains understudied. We examined the impacts of forest type and broadleaf litter on microbial community composition and N -fixation rates of Hylocomium splendens and Pleurozium schreberi. We conducted a moss transplant and leaf litter manipulation experiment at three sites with paired paper birch (Betula neoalaskana) and black spruce (Picea mariana) stands in Alaska. We characterized bacterial communities using marker gene sequencing, determined N -fixation rates using stable isotopes ( N ) and measured environmental covariates. Mosses native to and transplanted into spruce stands supported generally higher N -fixation and distinct microbial communities compared to similar treatments in birch stands. High leaf litter inputs shifted microbial community composition for both moss species and reduced N -fixation rates for H. splendens, which had the highest rates. N -fixation was positively associated with several bacterial taxa, including cyanobacteria. The moss microbiome and environmental conditions controlled N -fixation at the stand and transplant scales. Predicted shifts from spruce- to deciduous-dominated stands will interact with the relative abundances of mosses supporting different microbiomes and N -fixation rates, which could affect stand-level N inputs.
固氮苔藓微生物群落对北方森林的氮循环起着关键作用。森林类型和落叶输入量会调节苔藓的丰度，但它们如何控制苔藓微生物群落和固氮作用仍有待深入研究。我们研究了森林类型和阔叶落叶对华丽塔藓（Hylocomium splendens）和高山拟垂枝藓（Pleurozium schreberi）微生物群落组成和固氮率的影响。我们在阿拉斯加三个有配对的纸皮桦（Betula neoalaskana）林分和黑云杉（Picea mariana）林分的地点进行了苔藓移植和落叶处理实验。我们使用标记基因测序来表征细菌群落，使用稳定同位素（N）测定固氮率，并测量环境协变量。与桦树林分中的类似处理相比，云杉林分中本地生长和移植的苔藓通常具有更高的固氮率和独特的微生物群落。高落叶输入量改变了两种苔藓的微生物群落组成，并降低了固氮率最高的华丽塔藓的固氮率。固氮作用与包括蓝细菌在内的几种细菌类群呈正相关。苔藓微生物群落和环境条件在林分和移植尺度上控制着固氮作用。预计从云杉为主的林分到落叶为主的林分的转变将与支持不同微生物群落和固氮率的苔藓相对丰度相互作用，这可能会影响林分水平的氮输入。
