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1. Frankia diversity in sympatrically occurring red alder (Alnus rubra) and Sitka alder (Alnus viridis) trees in an early successional environment

   https://doi.org/10.1007/s00468-022-02317-w  

   Wolfe, Emily R. ; Singleton, Sebastian ; Stewart, Nathan U. ; Balkan, Mehmet A. ; Ballhorn, Daniel J. ( October 2022 , Trees)
2. Phosphorus Mobilizing Enzymes of Alnus-Associated Ectomycorrhizal Fungi in an Alaskan Boreal Floodplain

   https://doi.org/10.3390/f10070554  

   Ruess, Roger W. ; Swanson, Michaela M. ; Kielland, Knut ; McFarland, Jack W. ; Olson, Karl D. ; Taylor, D. Lee ( July 2019 , Forests)

   Because of its high phosphorus (P) demands, it is likely that the abundance, distribution, and N-fixing capacity of Alnus in boreal forests are tightly coupled with P availability and the mobilization and uptake of soil P via ectomycorrhizal fungi (EMF). We examined whether Alnus shifts EMF communities in coordination with increasingly more complex organic P forms across a 200-year-old successional sequence along the Tanana River in interior Alaska. Root-tip activities of acid phosphatase, phosphodiesterase, and phytase of A. tenuifolia-associated EMF were positively intercorrelated but did not change in a predictable manner across the shrub, to hardwood to coniferous forest successional sequence. Approximately half of all Alnus roots were colonized by Alnicola and Tomentella taxa, and ordination analysis indicated that the EMF community on Alnus is a relatively distinct, host-specific group. Despite differences in the activities of the two Alnus dominants to mobilize acid phosphatase and phosphodiesterase, the root-tip activities of P-mobilizing enzymes of the Alnus-EMF community were not dramatically different from other co-occurring boreal plant hosts. This suggests that if Alnus has a greater influence on P cycling than other plant functional types, additional factors influencing P mobilization and uptake at the root and/or whole-plant level must be involved. 

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3. Colonization by nitrogen-fixing Frankia bacteria causes short-term increases in herbivore susceptibility in red alder (Alnus rubra) seedlings

   https://doi.org/10.1007/s00442-017-3888-2  

   Ballhorn, Daniel J. ; Elias, Jacob D. ; Balkan, M. A. ; Fordyce, Rachel F. ; Kennedy, Peter G. ( June 2017 , Oecologia)
4. Tall shrub (Alnus, Betula, Juniperus, Salix, and Shepherdia) densities at Brooks Range treelines, Alaska (2019-2022)

   https://doi.org/10.18739/A2TX3579M  

   Roman Dial, Russell Wong ( January 2023 , NSF Arctic Data Center)

   Stem counts of tall shrubs (height from 0.3 to greater than 2 meters) during 2019, 2020, 2021 and 2022 as sampled within n = 594 5-meter radius plots (area = 78.5 square meters), each centered on a selected white spruce adult called "Focal Tree". The purpose of this dataset was to examine spatial variation in tall shrub densities of the most important genera across the Brooks Range and in relation to local microclimates. It also provides a baseline for future shrub stem counts to determine changes in abundance. 

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5. Differences in foliar endophyte communities of red alder (Alnus rubra) exposed to varying air pollutant levels

   Wolfe, E.R ; Kautz, S. ; Singleton, S.L. ; Ballhorn, D.J. ( January 2018 , Botany)

   In the Pacific Northwest, Alnus rubra Bong. (red alder) is a common deciduous tree species especially prevalent in riparian corridors and disturbed sites, including metropolitan areas undergoing land use changes and development. Importantly, red alder is also considered a bioindicator for ozone pollution and, like all plants, harbors a diverse endophyte community that may interact with aerial pollutants. In this study, we surveyed foliar fungal endophyte communities (microfungi) in red alder leaves from the metropolitan area of Portland, Oregon, USA, using culture-based techniques, and found that communities differed significantly by site. Our results suggest that the fungal endophyte community composition in red alder leaves may be influenced in part by local air pollution sources, likely in conjunction with other site characteristics. As urban areas expand, more studies should focus on how the urban environment affects plant–microbe community ecology and endophyte–host interactions, as well as on the long-term consequences for other ecosystem processes such as leaf litter decomposition. 

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