January 04, 2021

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Impacts of Arctic Shrubs on Root Traits and Belowground Nutrient Cycles Across a Northern Alaskan Climate Gradient

Root traits of Arctic deciduous shrubs vary, indicating differing nutrient acquisition strategies.

Alnus viridis ssp. fruticosa is one of the deciduous shrub species expanding in the Arctic tundra.
[Image Credit: Tyler Refsland, Michigan State University]

The Science

Deciduous shrub species are expanding into parts of the sedge-dominated Arctic tundra where large pools of soil organic nitrogen are stored. To increase understanding of how nutrient acquisition strategies and nutrient dynamics differ among vegetation types, a team of researchers examined f root traits, root biomass, and mycorrhizal associations of three commonly distributed shrub genera (Alnus, Betula, and Salix) and a widespread sedge (Eriophorum vaginatum) along a climate gradient in northern Alaska. The results from this study demonstrate striking differences in multiple root traits, mycorrhizal associations, and root functions between shrubs and sedges and between co-existing shrubs, indicating contrasting nutrient acquisition strategies.

The Impact

Diverse nutrient acquisition strategies and belowground impacts among different Arctic shrubs and sedges portend widespread belowground trait shifts across regions experiencing changes in aboveground vegetation (e.g., shrub expansion). Further identifying the specific shrub genera in the tundra landscape will ultimately provide better predictions of belowground dynamics across the changing Arctic tundra landscape.

Summary

During the past several decades, shrub species have expanded into parts of the sedge-dominated Arctic tundra. Absorptive root traits of shrubs are key determinants of nutrient acquisition strategies from tundra soils, but the variations of shrub root traits among common shrub genera are poorly resolved. Consequently, the impacts of Arctic shrub expansion on belowground nutrient cycling remain unclear. In this study, researchers collected roots from three commonly distributed shrub genera (Alnus, Betula, and Salix) and a widespread sedge (Eriophorum vaginatum) along a climate gradient in northern Alaska. They found consistent differences in root traits among Arctic plant genera along the climate gradient. Alnus and Betula had relatively thicker and less branched absorptive roots more frequently colonized by ectomycorrhizae than Salix roots, suggesting complementarity between root efficiency and ectomycorrhizal dependence among the co-existing shrubs. Shrub-dominated plots tended to have more productive absorptive roots than sedge-dominated plots. These findings reveal diverse nutrient acquisition strategies and belowground impacts among different Arctic shrubs, suggesting that further identifying the specific shrub genera in the tundra landscape will ultimately provide better predictions of belowground dynamics across the changing Arctic.

Principal Investigator

Jennifer M. Fraterrigo
University of Illinois
jmf@illinois.edu

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

This work and associated field data collection campaigns were supported by grant DE-SC0016219 from the Environmental System Science program of the Office of Biological and Environmental Research (BER) within the U.S. Department of Energy (DOE) Office of Science.

References

Chen, W., Tape, K.D., Euskirchen, E.S. et al. "Impacts of Arctic shrubs on root traits and belowground nutrient cycles across a northern Alaskan climate gradient". Frontiers in Plant Science 11 588098  (2020). https://doi.org/10.3389/fpls.2020.588098.