title: The unseen iceberg: plant roots in arctic tundra.
abstract: Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits - including distribution, chemistry, anatomy and resource partitioning - play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions.
authors.affiliation: Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA; Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6301, USA.
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Iversen
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Sloan
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Sullivan
authors.forename: Eugenie S
authors.initials: ES
authors.lastname: Euskirchen
authors.forename: A David
authors.initials: AD
authors.lastname: McGuire
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Norby
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Walker
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Warren
authors.forename: Stan D
authors.initials: SD
authors.lastname: Wullschleger
mesh_terms: D001110:Arctic Regions; D001272:Atmosphere; D046448:Ice Cover; D008954:Models, Biological; D018517:Plant Roots / Q000502:physiology*; D065929:Tundra
keywords: arctic; fine roots; model; plant-soil; root biomass; root production; root turnover; tundra