title: Treeline advances and associated shifts in the ground vegetation alter fine root dynamics and mycelia production in the South and Polar Urals.
abstract: Climate warming is shifting the elevational boundary between forests and tundra upwards, but the related belowground responses are poorly understood. In the pristine South and Polar Urals with shifts of the treeline ecotone documented by historical photographs, we investigated fine root dynamics and production of extramatrical mycorrhizal mycelia (EMM) along four elevational transects reaching from the closed forest to the treeless tundra. In addition, we analysed elevational differences in climate and vegetation structure, and excavated trees to estimate related changes in the partitioning between below- and aboveground biomass. Fine root biomass of trees (<2 mm) increased by 13-79% with elevation, paralleled by a 35-72% increase in ground vegetation fine roots from the closed forest to the tundra. During the first year of decomposition, mass loss of fine root litter from different vegetation types was greater at lower elevations in the forest-tundra ecotone. The ratio between fine roots of trees and stem biomass largely increased with elevation in both regions, but these increases were not accompanied by a distinct production of EMM. Production of EMM, however, increased with the presence of ectomycorrhizal trees at the transition from the tundra to the forest. Our results imply that the recorded upward expansion of forest into former tundra in the Ural Mountains by 4-8 m per decade is decreasing the partitioning of plant biomass to fine roots. They further suggest that climate-driven forest advances will alter EMM production rates with potential feedbacks on soil carbon and nutrient cycling in these ecosystems.
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, Birmensdorf, 8903, Zurich, Switzerland. emily.solly@wsl.ch.
authors.forename: Emily F
authors.initials: EF
authors.lastname: Solly
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, Birmensdorf, 8903, Zurich, Switzerland.
authors.forename: Ika
authors.initials: I
authors.lastname: Djukic
authors.affiliation: Institute of Plant and Animal Ecology, Yekaterinburg, Russia.
authors.forename: Pavel A
authors.initials: PA
authors.lastname: Moiseev
authors.affiliation: Institute of Plant and Animal Ecology, Yekaterinburg, Russia.
authors.forename: Nelly I
authors.initials: NI
authors.lastname: Andreyashkina
authors.affiliation: Institute of Plant and Animal Ecology, Yekaterinburg, Russia.
authors.forename: Nadezhda M
authors.initials: NM
authors.lastname: Devi
authors.affiliation: Institute of Forest Ecology, University of Natural Resources and Life Sciences, Vienna, Austria.
authors.forename: Hans
authors.initials: H
authors.lastname: Göransson
authors.affiliation: Institute of Plant and Animal Ecology, Yekaterinburg, Russia.
authors.forename: Valeriy S
authors.initials: VS
authors.lastname: Mazepa
authors.affiliation: Institute of Plant and Animal Ecology, Yekaterinburg, Russia.
authors.forename: Stepan G
authors.initials: SG
authors.lastname: Shiyatov
authors.affiliation: Institute of Plant and Animal Ecology, Yekaterinburg, Russia.
authors.forename: Marina R
authors.initials: MR
authors.lastname: Trubina
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, Birmensdorf, 8903, Zurich, Switzerland.
authors.forename: Fritz H
authors.initials: FH
authors.lastname: Schweingruber
authors.affiliation: Institute for Botany and Landscape Ecology, University Greifswald, Greifswald, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Wilmking
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zürcherstrasse 111, Birmensdorf, 8903, Zurich, Switzerland.
authors.forename: Frank
authors.initials: F
authors.lastname: Hagedorn
mesh_terms: D018533:Biomass; D017753:Ecosystem; D065928:Forests; D018517:Plant Roots; D012987:Soil / Q000737:chemistry; D014197:Trees; D065929:Tundra
chemical_list: D012987:Soil
keywords: Extramatrical mycorrhizal mycelia; Fine roots; Global change; Treeline shifts; Ural Mountains