CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China.
Department of Biology, Terrestrial Ecology Section, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark.
Ann Bot. 2022 Jan 28;129(2):147-160. doi: 10.1093/aob/mcab127.
Cyanobacteria associated with mosses represent a main nitrogen (N) source in pristine, high-latitude and -altitude ecosystems due to their ability to fix N2. However, despite progress made regarding moss-cyanobacteria associations, the factors driving the large interspecific variation in N2 fixation activity between moss species remain elusive. The aim of the study was to identify the traits of mosses that determine cyanobacterial colonization and thus N2 fixation activity.
Four moss species varying in N2 fixation activity were used to assess cyanobacterial abundance and activity to correlate it with moss traits (morphological, chemical, water-balance traits) for each species.
Moss hydration rate was one of the pivotal traits, explaining 56 and 38 % of the variation in N2 fixation and cyanobacterial colonization, respectively, and was linked to morphological traits of the moss species. Higher abundance of cyanobacteria was found on shoots with smaller leaves, and with a high frequency of leaves. High phenol concentration inhibited N2 fixation but not colonization. These traits driving interspecific variation in cyanobacterial colonization, however, are also affected by the environment, and lead to intraspecific variation. Approximately 24 % of paraphyllia, filamentous appendages on Hylocomium splendens stems, were colonized by cyanobacteria.
Our findings show that interspecific variations in moss traits drive differences in cyanobacterial colonization and thus, N2 fixation activity among moss species. The key traits identified here that control moss-associated N2 fixation and cyanobacterial colonization could lead to improved predictions of N2 fixation in different moss species as a function of their morphology.
由于蓝藻能够固定 N2，因此与苔藓共生的蓝藻是原始高纬度和高海拔生态系统中主要的氮（N）来源。然而，尽管在苔藓-蓝藻共生方面取得了进展，但驱动不同苔藓物种之间固氮活性的巨大种间差异的因素仍难以捉摸。本研究旨在确定决定蓝藻定殖进而决定固氮活性的苔藓特征。
我们使用了四种固氮活性不同的苔藓物种，评估了蓝藻的丰度和活性，并将其与每种苔藓的特征（形态、化学、水分平衡特征）相关联。
苔藓的水合速率是关键特征之一，分别解释了 56%和 38%的固氮和蓝藻定殖的变异，并且与苔藓物种的形态特征有关。在叶片较小且叶片出现频率较高的枝条上发现了更多的蓝藻。较高的酚浓度抑制了固氮，但不抑制定殖。这些驱动蓝藻定殖种间差异的特征也受到环境的影响，导致种内变异。在 Hylocomium splendens 茎上的丝状附属物拟叶中，约有 24%被蓝藻定殖。
我们的研究结果表明，苔藓特征的种间差异驱动了不同苔藓物种之间的蓝藻定殖差异，进而影响了固氮活性。这里确定的控制苔藓相关固氮和蓝藻定殖的关键特征，可能会提高对不同苔藓物种固氮能力的预测，这取决于它们的形态。
