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Michaud, Talia [1], Cline, Lauren [2], Hobbie, Erik [3], Gutknecht, Jessica [4], Kennedy, Peter [5].

Century-long herbarium collections reveal novel mycorrhizal responses to global change.

Mycorrhizal mediation of carbon (C) and nitrogen (N) cycling through forest systems renders mycorrhizal responses to anthropogenic environmental change globally consequential. Experimental studies detailing the effects of individual drivers, like atmospheric N deposition and elevated atmospheric carbon dioxide (CO2) concentrations, however, have generated conflicting predictions of mycorrhizal feedbacks. A historical analysis of mycorrhizal responses to global change enables us to evaluate these conflicting predictions with the potential of uncovering novel effects of global change. Through analysis of nutrient and stable isotope concentrations in fungal and plant herbarium specimens collected in Minnesota over the last century, we assessed changes in plant and fungal nutrition and C/N trade between ectomycorrhizal (EM) plants and fungi. Linear mixed-effects models indicate that foliar and sporocarp N concentrations declined by 0.41% on average from 1900 to 2010. These results reflect broadscale declines in plant N nutrition in temperate North America and Europe and represent the first report of declining fungal N nutrition. d15N, closely linked to soil microbial activity and EM C/N transfer, also declined significantly across all groups by 5‰ on average. Over time, d15N was significantly elevated in EM trees and fungi compared to arbuscular mycorrhizal trees and saprophytic fungi, indicating that EM fungi are immobilizing relatively less N for biomass production than in the past, instead transferring relatively more N to their plant partners. This might be indicative of declining C availability for EM fungi. While mirroring reports of EM sensitivity to shifting environmental conditions, this finding is not consistent with predictions that EM fungi will respond to elevated atmospheric CO2 and N limitation by immobilizing more N in biomass. Finally, trends in sporocarp N concentrations among EM fungi indicate that those with greater soil exploration capacities have been uniquely insulated from N limitation over the last century, echoing reports of diverse responses to environmental change hinging on life history strategy. This diverse response within the EM fungal group supports a nuanced approach to predictive modeling of mycorrhizal feedbacks. Ultimately, these unexpected findings highlight the importance of considering the interactive and cumulative effects of global change and the value of a historical approach to mycorrhizal ecology enabled by herbaria collections.

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1 - University of Minnesota, Plant and Microbial Biology, Biological Sciences 804, 1445 Gortner Ave, St Paul, MN, 55108, USA
2 - Bayer Crop Sciences, USA
3 - University of New Hampshire, Earth Sciences, Earth Systems Research Center, Morse Hall 451, Durham, NH, 03824, USA
4 - University of Minnesota, Soil, Water, and Climate, S-431 Soils Bldg, 1529 Gortner Ave, St Paul, MN, 55108, USA
5 - University of Minnesota, Plant and Microbial Biology, Biological Sciences 806, 1445 Gortner Ave, St Paul, MN, 55108, USA

mycorrhizal fungi
climate change
temperate forests

Presentation Type: Oral Paper
Session: MY7, Mycology: Fungus-Plant Interactions: Arbuscular Mycorrhizae, Climate Change, and Microbiome
Location: /
Date: Friday, July 23rd, 2021
Time: 11:15 AM(EDT)
Number: MY7006
Abstract ID:896
Candidate for Awards:None

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