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University of New Mexico (2016)

Experimental drought and soil depth interactively influence fungal community composition in piñon-juniper woodland

Olivas Eric

Titre : Experimental drought and soil depth interactively influence fungal community composition in piñon-juniper woodland

Auteur : Olivas Eric

Université de soutenance : University of New Mexico

Grade : Master of Science (MS) 2016

Résumé
Drought can flip ecosystems between states and in the process alter key systems such as plant biomass and carbon balance. Many drought-related studies have focused on plant responses or charismatic megafauna. Less work has addressed drought in the context of aboveground-belowground feedbacks. Impacts of drought are increasing, particularly in arid environments such as the southwestern United States. Major tree species of these regions, such as piñon pine, are adapted to a wetter and more predictable climate than the projected future climate. The effects of drought on piñon and its ectomycorrhizae have been studied observationally and in laboratories. Soil depth has also been established in other systems to be an important driver of soil processes, but has thus far been ignored in the piñon-juniper system. Our study is the first to address the effects of long-term experimental moisture manipulation and associated piñon mortality on the soil fungal community of the piñon-juniper woodland as well as that of piñon’s obligate ectomycorrhizal partners across soil depth. We used Illumina sequencing to profile the fungal community of piñon pine at two soil depths along an experimentally imposed moisture-stress gradient from 2008-2013 including drought, ambient, and irrigated treatments. We used field collected soil samples expected to include roots, spores, and free-living mycelia to address fungal change community-wide. We found significant effects of moisture treatment and depth in structuring the overall fungal community of piñon-juniper soils. The drought treatment reduced richness by 20% and 38% in surface and deep soils, respectively. We used FUNGUILD to assign functional roles and found a significant reduction in the proportion of ectomycorrhizal fungi in drought plots, particularly on plots with high piñon mortality. The change in guild dominance suggests significant impacts of plant mortality coupled with environmental pressures on ectomycorrhizal fungi. Shifts in climate and plant mortality are likely to alter the distribution of members of the belowground community, particularly ectomycorrhizal fungi, which in turn may limit the establishment and/or recovery of plant species. Based on our findings, we predict greater patchiness of fungi, particularly ectomycorrhizal taxa, in drought-impacted habitats and/or significant retractions in plant and fungal geographic ranges.

Mots clés : next-generation sequencing, Illumina, piñon, pinyon, drougth, depth, ectomycorrhizae, fungi, fungal community, aboveground-belowground feedbacks

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Page publiée le 3 octobre 2016, mise à jour le 17 octobre 2019