title: Allocation of carbon to fine root compounds and their residence times in a boreal forest depend on root size class and season.
abstract: Fine roots play a key role in the forest carbon balance, but their carbon dynamics remain largely unknown. We pulse labelled 50 m(2) patches of young boreal forest by exposure to (13)CO(2) in early and late summer. Labelled photosynthates were traced into carbon compounds of < 1 and 1-3 mm diameter roots (fine roots), and into bulk tissue of these and first-order roots (root tips). Root tips were the most strongly labelled size class. Carbon allocation to all size classes was higher in late than in early summer; mean residence times (MRTs) in starch increased from 4 to 11 months. In structural compounds, MRTs were 0.8 yr in tips and 1.8 yr in fine roots. The MRT of carbon in sugars was in the range of days. Functional differences within the fine root population were indicated by carbon allocation patterns and residence times. Pronounced allocation of recent carbon and higher turnover rates in tips are associated with their role in nutrient and water acquisition. In fine roots, longer MRTs but high allocation to sugars and starch reflect their role in structural support and storage. Accounting for heterogeneity in carbon residence times will improve and most probably reduce the estimates of fine root production.
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), SE-901 83 Umeå, Sweden.|Present address: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Sonja G
authors.initials: SG
authors.lastname: Keel
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Catherine D
authors.initials: CD
authors.lastname: Campbell
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), SE-901 83 Umeå, Sweden.
authors.forename: Mona N
authors.initials: MN
authors.lastname: Högberg
authors.affiliation: Department of Terrestrial Ecosystem Research, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, AT-1090 Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Richter
authors.affiliation: Department of Terrestrial Ecosystem Research, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, AT-1090 Vienna, Austria.
authors.forename: Birgit
authors.initials: B
authors.lastname: Wild
authors.affiliation: Research Institute for the Changing Global Environment, Fudan University, Shanghai 200433 China.|Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA.
authors.forename: Xuhui
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, SE-901 87 Umeå, Sweden.
authors.forename: Vaughan
authors.initials: V
authors.lastname: Hurry
authors.affiliation: Southern Swedish Forest Research Centre, SLU, PO Box 49, SE-230 53 Alnarp, Sweden.
authors.forename: Sune
authors.initials: S
authors.lastname: Linder
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), SE-901 83 Umeå, Sweden.
authors.forename: Torgny
authors.initials: T
authors.lastname: Näsholm
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU), SE-901 83 Umeå, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Högberg
mesh_terms: D050260:Carbohydrate Metabolism; D002244:Carbon / Q000378:metabolism*; D029791:Ericaceae; D041605:Pinus sylvestris; D018517:Plant Roots / Q000378:metabolism*; D012621:Seasons; D013213:Starch / Q000378:metabolism*; D029801:Vaccinium vitis-idaea
chemical_list: D002244:Carbon; D013213:Starch