Ericoid mycorrhizal fungi mediate the response of ombrotrophic peatlands to fertilization: a modeling study

Abstract

Summary Ericaceous shrubs adapt to the nutrient‐poor conditions in ombrotrophic peatlands by forming symbiotic associations with ericoid mycorrhizal (ERM) fungi. Increased nutrient availability may diminish the role of ERM pathways in shrub nutrient uptake, consequently altering the biogeochemical cycling within bogs. To explore the significance of ERM fungi in ombrotrophic peatlands, we developed the model MWMmic (a peat cohort‐based biogeochemical model) into MWMmic‐NP by explicitly incorporating plant‐soil nitrogen (N) and phosphorus (P) cycling and ERM fungi processes. The new model was applied to simulate the biogeochemical cycles in the Mer Bleue (MB) bog in Ontario, Canada, and their responses to fertilization. MWMmic_NP reproduced the carbon(C)–N–P cycles and vegetation dynamics observed in the MB bog, and their responses to fertilization. Our simulations showed that fertilization increased shrub biomass by reducing the C allocation to ERM fungi, subsequently suppressing the growth of underlying Sphagnum mosses, and decreasing the peatland C sequestration. Our species removal simulation further demonstrated that ERM fungi were key to maintaining the shrub–moss coexistence and C sink function of bogs. Our results suggest that ERM fungi play a significant role in the biogeochemical cycles in ombrotrophic peatlands and should be considered in future modeling efforts.

Protecting nature's most effective carbon sink: an important role for fungi in peatlands

“…The study by Shao et al . (2023) provides some of the first support that in peat bogs the confirmed role of peat mosses as ecosystem engineers (van Breemen, 1995) needs to be shared with ErM fungi.…”

“…In this issue of New Phytologist , Shao et al . (2023, pp. 80–95) remind us that the influence of enviro‐climatic change on peatland ecosystem functioning should not only be studied for the plant and soil components in isolation, but that their interactions should also be considered.…”

“…Modeling of removal is essentially the computational equivalent of the empirical species removal or exclusion approaches in which the role of the removed species in the ecosystem is inferred by comparison with an intact control. Ongoing plant-removal field experiments (Ward et al, 2013;Robroek et al, 2015) could offer an exciting opportunity to verify the hypotheses proposed by Shao et al (2023) in situ.…”

“…Peat mosses ultimately get ousted due to shading (Limpens et al, 2011), impeding the net carbon uptake of the ecosystem. But Shao et al (2023) suggest that the mechanisms for shrub encroachment following nutrient enrichment are more complex. Shao et al (2023) reveal a stabilising role for ErM fungi in maintaining the competitive equilibrium between the moss and the ericaceous shrub communities under nutrient-limiting conditions.…”

“…But Shao et al (2023) suggest that the mechanisms for shrub encroachment following nutrient enrichment are more complex. Shao et al (2023) reveal a stabilising role for ErM fungi in maintaining the competitive equilibrium between the moss and the ericaceous shrub communities under nutrient-limiting conditions. The authors extended an existing process-based model (MWMmic, Shao et al, 2022) Canada).…”