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1. 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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2. 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)
3. A nearly century long (1920-2017) Siberian alder (Alnus viridis ssp. fruticosa) secondary growth record near Sagwon Bluffs Alaska, USA

   https://doi.org/10.18739/A27M0421K  

   Drew, Jackson; Bret-Harte, Marion; Buchwal, Agata; Heslop, Calvin (January 2023, NSF Arctic Data Center)

   This data set contains measures of growth ring widths of Siberian alder (Alnus viridis ssp. fruticosa) from along the Sagwon Bluffs, Alaska, USA that was used to address how alder respond to temperature overtime and how plant age impacts their climate sensitivity. There are six individual files. One, the growth ring width data from each cross-section or part taken from an individual Siberian alder. Two, a data set of the detrended chronology with climate data over the period of 1920-2017. Three, a data set of individual detrended secondary growth with temperature and age data over the period of 1977-2016. Four, a data set relating individual alder's first 30 years of growth to temperature and the time period it started growth in. Five, a data set of detrended growth from cross-sections taken from each Siberian alder, age class information, and temperature. Finally, a data set containing the number of ramets, nodule biomass per area, and nitrogen fixation rate. 

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4. Genotypic Diversity and Host-Specificity of Frankia Bacteria Associated with Sympatric Populations of Alnus rubra and Alnus rhombifolia in Oregon

   https://doi.org/10.3955/046.093.0307  

   Balkan, Mehmet A.; Stewart, Nathan U.; Kauffman, Emily S.; Wolfe, Emily R.; Ballhorn, Daniel J. (September 2019, Northwest Science)
5. 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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