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Title: Roots Mediate the Effects of Snowpack Decline on Soil Bacteria, Fungi, and Nitrogen Cycling in a Northern Hardwood Forest
Authors: Sorensen, Patrick O
Bhatnagar, Jennifer M
Christenson, Lynn
Durán, Jorge 
Fahey, Timothy
Fisk, Melany C
Finzi, Adrien C
Groffman, Peter M
Morse, Jennifer L
Templer, Pamela H
Keywords: elevation gradient; plant roots; soil N cycle; snowpack; soil bacteria and fungi
Issue Date: 2019
Publisher: Frontiers Media S.A.
Project: Funding for this study was provided by a student award from the Boston University Biogeoscience program and from the National Science Foundation (NSF-DDIG DEB-1406521, NSF DEB-1149929, 1406521, 1114804, and 1637685). PS was in part supported by the Watershed Function Scientific Focus Area funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research under Award Number DE-AC02-05CH11231. JD acknowledges support from the Fundação para Ciência e Tecnologia (IF/00950/2014). Hubbard Brook is a Long-Term Ecological Research site supported with funding from the National Science Foundation. This research is a contribution to the Hubbard Brook Ecosystem Study, administered by the USDA Forest Service, Northeast Forest Experiment Station, Radnor, Pennsylvania. 
Serial title, monograph or event: Frontiers in Microbiology
Volume: 10
Abstract: Rising winter air temperature will reduce snow depth and duration over the next century in northern hardwood forests. Reductions in snow depth may affect soil bacteria and fungi directly, but also affect soil microbes indirectly through effects of snowpack loss on plant roots. We incubated root exclusion and root ingrowth cores across a winter climate-elevation gradient in a northern hardwood forest for 29 months to identify direct (i.e., winter snow-mediated) and indirect (i.e., root-mediated) effects of winter snowpack decline on soil bacterial and fungal communities, as well as on potential nitrification and net N mineralization rates. Both winter snowpack decline and root exclusion increased bacterial richness and phylogenetic diversity. Variation in bacterial community composition was best explained by differences in winter snow depth or soil frost across elevation. Root ingrowth had a positive effect on the relative abundance of several bacterial taxonomic orders (e.g., Acidobacterales and Actinomycetales). Nominally saprotrophic (e.g., Saccharomycetales and Mucorales) or mycorrhizal (e.g., Helotiales, Russalales, Thelephorales) fungal taxonomic orders were also affected by both root ingrowth and snow depth variation. However, when grouped together, the relative abundance of saprotrophic fungi, arbuscular mycorrhizal fungi, and ectomycorrhizal fungi were not affected by root ingrowth or snow depth, suggesting that traits in addition to trophic mode will mediate fungal community responses to snowpack decline in northern hardwood forests. Potential soil nitrification rates were positively related to ammonia-oxidizing bacteria and archaea abundance (e.g., Nitrospirales, Nitrosomondales, Nitrosphaerales). Rates of N mineralization were positively and negatively correlated with ectomycorrhizal and saprotrophic fungi, respectively, and these relationships were mediated by root exclusion. The results from this study suggest that a declining winter snowpack and its effect on plant roots each have direct effects on the diversity and abundance of soil bacteria and fungal communities that interact to determine rates of soil N cycling in northern hardwood forests.
ISSN: 1664-302X
DOI: 10.3389/fmicb.2019.00926
Rights: openAccess
Appears in Collections:I&D CFE - Artigos em Revistas Internacionais

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