Dynamics of arbuscular mycorrhizal fungal community structure and functioning along a nitrogen enrichment gradient in an alpine meadow ecosystem

Abstract

Nitrogen (N) availability is increasing dramatically in many ecosystems, but the influence of elevated N on the functioning of arbuscular mycorrhizal (AM) fungi in natural ecosystems is not well understood. We measured AM fungal community structure and mycorrhizal function simultaneously across an experimental N addition gradient in an alpine meadow that is limited by N but not by phosphorus (P). AM fungal communities at both whole-plant-community (mixed roots) and single-plant-species (Elymus nutans roots) scales were described using pyro-sequencing, and the mycorrhizal functioning was quantified using a mycorrhizal-suppression treatment in the field (whole-plant-community scale) and a glasshouse inoculation experiment (single-plant-species scale). Nitrogen enrichment progressively reduced AM fungal abundance, changed AM fungal community composition, and shifted mycorrhizal functioning towards parasitism at both whole-plant-community and E. nutans scales. N-induced shifts in AM fungal community composition were tightly linked to soil N availability and/or plant species richness, whereas the shifts in mycorrhizal function were associated with the communities of specific AM fungal lineages. The observed changes in both AM fungal community structure and functioning across an N enrichment gradient highlight that N enrichment of ecosystems that are not P-limited can induce parasitic mycorrhizal functioning and influence plant community structure and ecosystem sustainability.

Arbuscular mycorrhizal fungi in European grasslands under nutrient pollution

“…For instance, diversity of ectomycorrhizal fungi from forest ecosystems has been shown to be adversely affected by nitrogen pollution (Cox, Barsoum, Lilleskov, & Bidartondo, ; Lilleskov, Kuyper, Bidartondo, & Hobbie, ; van der Linde et al, ). Likewise, the diversity and abundance of arbuscular mycorrhizal fungi from grassland and, particularly, agricultural ecosystems have been shown to be negatively affected by nutrient enrichment (De Beenhouwer et al, ; Jiang et al, ; Leff et al, ; Van Geel et al, ). Changes in arbuscular mycorrhizal fungal communities can be expected to alter host plant fitness and ecosystem functioning, shifting mycorrhizal symbiosis phenotypes from mainly mutualistic forms in nutrient‐poor ecosystems to commensalism and parasitism in increasingly nutrient‐rich ecosystems (Johnson, Wilson, Wilson, Miller, & Bowker, ; Wei et al, ).…”

Cross‐scale integration of mycorrhizal function

“…The fire that new methods ignited in fungal ecology (Hibbett et al ., ) has, undoubtedly, attracted a broad field of researchers to a rather narrow set of similar questions. With this special collection, understanding of the biodiversity of AM fungi gains a range of new insights with an interesting focus on grasslands (in this issue of New Phytologist , Jiang et al ., , pp. 1222–1235; Neuenkamp et al ., , pp.…”

“…1262–1272), across different spatial scales in Åland archipelago of Finland (Rasmussen et al ., , pp. 1248–1261) and in Tibetan alpine grasslands in China (Jiang et al ., , pp. 1222–1235).…”

“…Causal effects of mycorrhizal fungi, either on the host (Jiang et al ., , pp. 1222–1235; Köhler et al ., , pp.…”

“…The study by Jiang et al . (, pp. 1222–1235) provides a good example by manipulating AM fungal communities in the field and testing the response of fungi to nutrient addition.…”