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1. What are mycorrhizal traits?

   https://doi.org/10.1016/j.tree.2022.04.003  

   Chaudhary, V. Bala ; Holland, E. Penelope ; Charman-Anderson, Suw ; Guzman, Aidee ; Bell-Dereske, Lukas ; Cheeke, Tanya E. ; Corrales, Adriana ; Duchicela, Jessica ; Egan, Cameron ; Gupta, Manju M. ; et al ( May 2022 , Trends in Ecology & Evolution)
2. Mycorrhizal types influence island biogeography of plants

   https://doi.org/10.1038/s42003-021-02649-2  

   Delavaux, Camille S. ; Weigelt, Patrick ; Dawson, Wayne ; Essl, Franz ; van Kleunen, Mark ; König, Christian ; Pergl, Jan ; Pyšek, Petr ; Stein, Anke ; Winter, Marten ; et al ( December 2021 , Communications Biology)

   Abstract Plant colonization of islands may be limited by the availability of symbionts, particularly arbuscular mycorrhizal (AM) fungi, which have limited dispersal ability compared to ectomycorrhizal and ericoid (EEM) as well as orchid mycorrhizal (ORC) fungi. We tested for such differential island colonization within contemporary angiosperm floras worldwide. We found evidence that AM plants experience a stronger mycorrhizal filter than other mycorrhizal or non-mycorrhizal (NM) plant species, with decreased proportions of native AM plant species on islands relative to mainlands. This effect intensified with island isolation, particularly for non-endemic plant species. The proportion of endemic AM plant species increased with island isolation, consistent with diversification filling niches left open by the mycorrhizal filter. We further found evidence of humans overcoming the initial mycorrhizal filter. Naturalized floras showed higher proportions of AM plant species than native floras, a pattern that increased with increasing isolation and land-use intensity. This work provides evidence that mycorrhizal fungal symbionts shape plant colonization of islands and subsequent diversification. 

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3. Tree Canopies Reflect Mycorrhizal Composition

   https://doi.org/10.1029/2021GL092764  

   Sousa, Daniel ; Fisher, Joshua B. ; Galvan, Fernando Romero ; Pavlick, Ryan P. ; Cordell, Susan ; Giambelluca, Thomas W. ; Giardina, Christian P. ; Gilbert, Gregory S. ; Imran‐Narahari, Faith ; Litton, Creighton M. ; et al ( May 2021 , Geophysical Research Letters)

   Mycorrhizae alter global patterns of CO₂fertilization, carbon storage, and elemental cycling, yet knowledge of their global distributions is currently limited by the availability of forest inventory data. Here, we show that maps of tree‐mycorrhizal associations (hereafter “mycorrhizal maps”) can be improved by the novel technology of imaging spectroscopy because mycorrhizal signatures propagate up from plant roots to impact forest canopy chemistry. We analyzed measurements from 143 airborne imaging spectroscopy surveys over 112,975 individual trees collected across 13 years. Results show remarkable accuracy in capturing ground truth observations of mycorrhizal associations from canopy signals across disparate landscapes (R² = 0.92,p < 0.01). Upcoming imaging spectroscopy satellite missions can reveal new insights into landscape‐scale variations in water, nitrogen, phosphorus, carotenoid/anthocyanin, and cellulose/lignin composition. Applied globally, this approach could improve the spatial precision of mycorrhizal distributions by a factor of roughly 10⁴and facilitate the incorporation of dynamic shifts in forest composition into Earth system models.

    

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4. The impact of ice storms on mycorrhizal fungi varies by season and mycorrhizal type in a hardwood forest

   https://doi.org/10.1002/ecs2.4526  

   Yancey, C. E. ; Juice, S. M. ; Classen, A. T. ; Rustad, L. ; Adair, E. Carol ( May 2023 , Ecosphere)

   Extreme weather events, such as ice storms, are increasing and have potentially large impacts on forests, including belowground structures such as fine roots and mycorrhizal fungi. Many forest trees rely on the mutualistic relationship between mycorrhizal fungi and plants; a relationship that, when disrupted, can negatively impact tree net primary productivity. We took advantage of a large‐scale ice storm manipulation in the northeastern United States to test the hypothesis that increasing ice storm intensity and frequency would reduce ectomycorrhizal fungal root tips per unit root length and arbuscular mycorrhizal fungal structures per unit root length, hereafter colonization. We found that ice storm intensity reduced spring ectomycorrhizal fungal and arbuscular mycorrhizal fungal colonization. However, these patterns changed in the fall, where ice storm intensity still reduced ectomycorrhizal fungal root tips, but arbuscular mycorrhizal fungal colonization was higher in ice storm treatments than controls. The amount of ectomycorrhizal fungal root tips and arbuscular mycorrhizal fungal colonization differed seasonally: ectomycorrhizal fungal root tips were 1.7× higher in the spring than in the fall, while arbuscular mycorrhizal fungal colonization was 3× higher in the fall than in the spring. Our results indicate that mycorrhizal fungal colonization responses to ice storm severity vary temporally and by mycorrhizal fungal type. Further, arbuscular mycorrhizal fungi may recover from ice storms relatively quickly, potentially aiding forests in their recovery, whereas ice storms may have a long lasting impact on ectomycorrhizal fungi.

    

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5. Ericoid mycorrhizal shrubs alter the relationship between tree mycorrhizal dominance and soil carbon and nitrogen

   https://doi.org/10.1111/1365-2745.13734  

   Ward, Elisabeth B. ; Duguid, Marlyse C. ; Kuebbing, Sara E. ; Lendemer, James C. ; Warren, II, Robert J. ; Bradford, Mark A. ( July 2021 , Journal of Ecology)

   Plant–fungal associations strongly influence forest carbon and nitrogen cycling. The prevailing framework for understanding these relationships is through the relative abundance of arbuscular (AM) versus ectomycorrhizal (EcM) trees. Ericoid mycorrhizal (ErM) shrubs are also common in forests and interactions between co‐occurring ErM shrubs and AM and EcM trees could shift soil biogeochemical responses. Here we test hypotheses that the effects of ErM shrubs on soil carbon and nitrogen either extend or are redundant with those of EcM trees.

   Using regional vegetation inventory data (>3,500 plot observations) we evaluated the frequency, richness and relative abundance of ErM plants in temperate forests in the eastern United States and examined their relationship with EcM plant cover. We then used surface soil (7 cm) data from 414 plots within a single forest to analyse relationships between ErM plant cover, relative EcM tree basal area and soil carbon and nitrogen concentrations while accounting for other biogeochemical controls, such as soil moisture.

   At both scales, we found a positive relationship between ErM and EcM plants, and the majority of ErM plants were in the shrub layer. Within the forest site, ErM plants strongly modulated tree mycorrhizal dominance effects. We found negative relationships between EcM relative basal area and soil carbon and nitrogen concentrations, but these relationships were weak to negligible in the absence of ErM plants. Both EcM relative basal area and ErM plant cover were positively associated with the soil carbon‐to‐nitrogen ratio. However, this relationship was driven by relatively lower nitrogen for EcM trees and higher carbon for ErM plants. As such, the functional effects of ErM plants on soil biogeochemistry neither extended nor were redundant with those of EcM trees.

   Synthesis. We found that ErM shrubs strongly influenced the relationship between tree mycorrhizal associations and soil biogeochemistry, and the effects of ErM shrubs and EcM trees on carbon and nitrogen were functionally distinct. Our findings suggest that ErM shrubs could confound interpretation of AM versus EcM tree effects in ecosystems where they co‐occur but also bolster growing calls to consider mycorrhizal functional types as variables that strongly influence forest biogeochemistry.

    

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