Adaptive root foraging strategies along a boreal–temperate forest gradient

• Published in: New Phytologist
• Main Authors: Ostonen, I., Truu, M., Helmisaari, H.-S., Lukač, M., Borken, W., Vanguelova, H., Godbold, D. (Douglas), Löhmus, K., Zang, U., Tedersoo, L., Preem, J.-K., Rosenvald, K., Aosaar, J., Armolaitis, K., Frey, J., Kabral, N., Kukumägi, M., Leppälammi-Kujansuu, J., Lindroos, A.-J., Merila, P., Napa, Ü., Nöjd, P., Parts, K., Uri, V., Varik, M., Truu, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2017
• Subjects: boreal and temperate forests; climate gradient; ectomycorrhizal (EcM) mycelium; fine and ectomycorrhizal root biomass; root foraging; root morphology; soil and rhizosphere bacteria; soil C; N ratio; Subarctic
• Online Access: https://doi.org/10.1111/nph.14643; http://hdl.handle.net/11104/0275898

The tree root-mycorhizosphere plays a key role in resource uptake, but also in the adaptation of forests to changing environments. \nThe adaptive foraging mechanisms of ectomycorrhizal (EcM) and fine roots of Picea abies, Pinus sylvestris and Betula pendula were evaluated along a gradient from temperate to subarctic boreal forest (38 sites between latitudes 48 degrees N and 69 degrees N) in Europe. Variables describing tree resource uptake structures and processes (absorptive fine root biomass and morphology, nitrogen (N) concentration in absorptive roots, extramatrical mycelium (EMM) biomass, community structure of root-associated EcM fungi, soil and rhizosphere bacteria) were used to analyse relationships between root system functional traits and climate, soil and stand characteristics. \nAbsorptive fine root biomass per stand basal area increased significantly from temperate to boreal forests, coinciding with longer and thinner root tips with higher tissue density, smaller EMM biomass per root length and a shift in soil microbial community structure. The soil carbon (C) : N ratio was found to explain most of the variability in absorptive fine root and EMM biomass, root tissue density, N concentration and rhizosphere bacterial community structure. \nWe suggest a concept of absorptive fine root foraging strategies involving both qualitative and quantitative changes in the root-mycorrhiza-bacteria continuum along climate and soil C : N gradients.