Atmospheric nitrogen enrichment changes nutrient stoichiometry and reduces fungal N supply to peatland ericoid mycorrhizal shrubs

Does Shift in Vegetation Abundance After Nitrogen and Phosphorus Additions Play a Key Role in Regulating Fungal Community Structure in a Northern Peatland?

“…The effect of accumulative N and/or P additions over a long period seems to override the effect of addition rate on peatland ecosystem functioning (e.g., Larmola et al, 2013 ). As excepted, the long-term addition of N or P exerted a strong impact on the fungal community ( Figure 1 ), and similar results were demonstrated in other studies (e.g., Carrara et al, 2018 ; Kiheri et al, 2020 ; Vesala et al, 2021 ). A clear shift in community composition appears from being shared by copiotrophic Ascomycota, and oligotrophic Basidiomycota, and Glomeromycota ( Yao et al, 2017 ) after short-term N and/or P additions, to being overwhelmingly dominated by copiotrophic Ascomycota after N and/or P additions over 10 years.…”

“…Besides, plant competition between PFT for nutrients will likely reshape the community of ericoid mycorrhizal (ErMF), arbuscular mycorrhizal (AMF), and ectomycorrhizal fungi (EcMF), which in turn regulates plant–plant interactions and ecosystem processes ( Smith and Read, 2008 ; Tedersoo et al, 2020 ). Furthermore, cumulative N deposition may eventually weaken the symbiotic association of mycorrhizal fungi with their host plants, and increase C loss by facilitating the activity of saprotrophic fungi ( Fernandez and Kennedy, 2016 ; Verbruggen et al, 2017 ; Vesala et al, 2021 ). In addition, we know little of what effects P addition and its interaction with N have on peatlands, which hinders our perception of important changes in the community structure of fungal functional guilds and implications on C storage in the face of uncertain N and P deposition regimes.…”

“…Therefore, we hypothesized that, (H2) the cascading effect of altered PFT abundance on fungal community structure would be intense after long-term N and/or P additions. Furthermore, as nutrient enrichment will reduce plant dependence on mycorrhizal fungi to access limiting nutrients ( Smith and Read, 2008 ; Leff et al, 2015 ; Vesala et al, 2021 ), we specifically hypothesized that, (H3) nutrient addition would decrease the relative abundance of mycorrhizal fungi and increase that of saprotrophs in general, and lignocellulose-degrading fungi (i.e., white-rot fungi) in particular. Given that Sphagnum are vulnerable to excess N addition, P addition may ameliorate this negative effect ( Limpens et al, 2004 ; Carfrae et al, 2007 ).…”

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“…Besides, plant competition between PFT for nutrients will likely reshape the community of ericoid mycorrhizal (ErMF), arbuscular mycorrhizal (AMF), and ectomycorrhizal fungi (EcMF), which in turn regulates plant-plant interactions and ecosystem processes (Smith and Read, 2008;Tedersoo et al, 2020). Furthermore, cumulative N deposition may eventually weaken the symbiotic association of mycorrhizal fungi with their host plants, and increase C loss by facilitating the activity of saprotrophic fungi (Fernandez and Kennedy, 2016;Verbruggen et al, 2017;Vesala et al, 2021). In addition, we know little of what effects P addition and its interaction with N have on peatlands, which hinders our perception of important changes in the community structure of fungal functional guilds and implications on C storage in the face of uncertain N and P deposition regimes.…”

“…Therefore, we hypothesized that, (H2) the cascading effect of altered PFT abundance on fungal community structure would be intense after long-term N and/or P additions. Furthermore, as nutrient enrichment will reduce plant dependence on mycorrhizal fungi to access limiting nutrients (Smith and Read, 2008;Leff et al, 2015;Vesala et al, 2021), we specifically hypothesized that, (H3) nutrient addition would decrease the relative abundance of mycorrhizal fungi and increase that of saprotrophs in general, and lignocellulosedegrading fungi (i.e., white-rot fungi) in particular. Given that Sphagnum are vulnerable to excess N addition, P addition may ameliorate this negative effect (Limpens et al, 2004;Carfrae et al, 2007).…”