Department of Environmental Science, Aarhus University, 4000 Roskilde, Denmark.
Department of Plant and Environmental Science, University of Copenhagen, 1871 Copenhagen, Denmark.
Sci Total Environ. 2022 Jun 25;827:153877. doi: 10.1016/j.scitotenv.2022.153877. Epub 2022 Feb 23.
Grazing herbivores may affect soil microbial communities indirectly by impacting soil structure and vegetation composition. In high arctic environments, this impact is poorly elucidated, while having potentially wide-reaching effects on the ecosystem. This study examines how a key arctic herbivore, the muskox Ovibos moschatus, affects the soil microbial community in a high arctic fen. Environmental DNA was extracted from soil samples taken from grazed control plots and from muskox exclosures established 5 years prior. We sequenced amplicons of the 16S rRNA gene to provide insight into the microbial communities. We found that in the grazed control plots, microbial communities exhibited high evenness and displayed highly similar overall diversity. In plots where muskoxen had been excluded, microbial diversity was significantly reduced, and had more uneven intra-sample populations and overall lower ecological richness and evenness. We observed that the composition of microbial communities in grazed soils were significantly affected by the presence of muskoxen, as seen by elevated relative abundances of Bacteroides and Firmicutes, two major phyla found in muskox faeces. Furthermore, an increase in relative abundance of bacteria involved in degradation of recalcitrant carbohydrates and cycling of nitrogen was observed in grazed soil. Ungrazed soils displayed increased abundances of bacteria potentially involved in anaerobic oxidation of methane, whereas some methanogens were more abundant in grazed soils. This corroborates a previous finding that methane emissions are higher in arctic fens under muskox grazing. Our results show that the presence of large herbivores stimulates soil microbial diversity and has a homogenizing influence on the inter-species dynamics in soil microbial communities. The findings of this study, thus, improve our understanding of the effect of herbivore grazing on arctic ecosystems and the derived methane cycling.
食草动物可能会通过影响土壤结构和植被组成来间接影响土壤微生物群落。在高北极环境中，这种影响还没有被很好地阐明，但它可能对生态系统产生广泛的影响。本研究探讨了关键的北极食草动物麝香牛 Ovibos moschatus 如何影响高北极湿地的土壤微生物群落。从放牧对照样地和 5 年前建立的麝香牛围栏内采集土壤样本，提取环境 DNA。我们对 16S rRNA 基因的扩增子进行测序，以深入了解微生物群落。我们发现，在放牧对照样地中，微生物群落表现出较高的均匀度，整体多样性非常相似。在麝香牛被隔离的样地中，微生物多样性显著降低，样本内种群更加不均匀，整体生态丰富度和均匀度也较低。我们观察到，放牧土壤中微生物群落的组成受到麝香牛的存在显著影响，这表现在 Bacteroides 和 Firmicutes 等两个在麝香牛粪便中发现的主要门的相对丰度升高。此外，在放牧土壤中还观察到参与难降解碳水化合物降解和氮循环的细菌相对丰度增加。未放牧土壤中可能参与甲烷厌氧氧化的细菌丰度增加，而一些产甲烷菌在放牧土壤中更为丰富。这证实了先前的发现，即在麝香牛放牧的北极湿地中，甲烷排放量更高。我们的研究结果表明，大型食草动物的存在刺激了土壤微生物多样性，并对土壤微生物群落中的种间动态产生了同质化影响。因此，本研究的结果提高了我们对食草动物放牧对北极生态系统和衍生甲烷循环的影响的理解。
