Vowles Tage, Lindwall Frida, Ekblad Alf, Bahram Mohammad, Furneaux Brendan R, Ryberg Martin, Björk Robert G
Department of Earth Sciences University of Gothenburg Gothenburg Sweden.
Department of Biological and Environmental Sciences University of Gothenburg Gothenburg Sweden.
Ecol Evol. 2017 Dec 14;8(2):1019-1030. doi: 10.1002/ece3.3657. eCollection 2018 Jan.
Mycorrhizal associations are widespread in high-latitude ecosystems and are potentially of great importance for global carbon dynamics. Although large herbivores play a key part in shaping subarctic plant communities, their impact on mycorrhizal dynamics is largely unknown. We measured extramatrical mycelial (EMM) biomass during one growing season in 16-year-old herbivore exclosures and unenclosed control plots (ambient), at three mountain birch forests and two shrub heath sites, in the Scandes forest-tundra ecotone. We also used high-throughput amplicon sequencing for taxonomic identification to investigate differences in fungal species composition. At the birch forest sites, EMM biomass was significantly higher in exclosures (1.36 ± 0.43 g C/m) than in ambient conditions (0.66 ± 0.17 g C/m) and was positively influenced by soil thawing degree-days. At the shrub heath sites, there was no significant effect on EMM biomass (exclosures: 0.72 ± 0.09 g C/m; ambient plots: 1.43 ± 0.94). However, EMM biomass was negatively related to abundance, which was greater in exclosures, suggesting that grazing affected EMM biomass positively. We found no significant treatment effects on fungal diversity but the most abundant ectomycorrhizal lineage/cortinarius, showed a near-significant positive effect of herbivore exclusion ( = .08), indicating that herbivory also affects fungal community composition. These results suggest that herbivory can influence fungal biomass in highly context-dependent ways in subarctic ecosystems. Considering the importance of root-associated fungi for ecosystem carbon balance, these findings could have far-reaching implications.
菌根共生在高纬度生态系统中广泛存在，对全球碳动态可能具有重要意义。尽管大型食草动物在塑造亚北极植物群落方面起着关键作用，但其对菌根动态的影响在很大程度上尚不清楚。我们在斯堪的纳维亚森林 - 苔原交错带的三个山地桦木林和两个灌丛石南荒地的16年食草动物围栏和未围栏对照地块（环境对照）的一个生长季节内，测量了根外菌丝（EMM）生物量。我们还使用高通量扩增子测序进行分类鉴定，以研究真菌物种组成的差异。在桦木林地块，围栏内的EMM生物量（1.36±0.43 g C/m）显著高于环境对照条件下（0.66±0.17 g C/m），并且受到土壤解冻度日的正向影响。在灌丛石南荒地，对EMM生物量没有显著影响（围栏内：0.72±0.09 g C/m；环境对照地块：1.43±0.94）。然而，EMM生物量与多度呈负相关，围栏内的多度更大，这表明放牧对EMM生物量有正向影响。我们没有发现对真菌多样性有显著的处理效应，但最丰富的外生菌根谱系/丝膜菌属，显示出食草动物排除的接近显著的正向效应（P = 0.08），表明食草作用也影响真菌群落组成。这些结果表明，在亚北极生态系统中，食草作用可以以高度依赖环境的方式影响真菌生物量。考虑到与根相关真菌对生态系统碳平衡的重要性，这些发现可能具有深远的意义。
