title: δ13C-variations of leaves in forests as an indication of reassimilated CO2from the soil.
abstract: An attempt has been made to evaluate the contribution of soil respired CO2to the total assimilation of a forest tree, by heeding the13C-concentrations of CO2from the free atmosphere and from mineralization processes within the soil respectively. An expression has been derived, according to which the assimilated fraction of CO2from the soil at a particular height of a tree is given by the δ13C-value of the corresponding leaves, δ13C of atmospheric CO2, δ13C of soil respired CO2and the physiological state of the leaves expressed as the ratio of total respiration over gross photosynthesis and internal over external CO2-concentration. In the particular case investigated, a δ13C-difference of 5‰ has been determined from bottom to top of a beech tree which results in a CO2contribution from the soil of about 22% for the lower forest strata, while the total contribution of soil respired CO2accounts for about 5% of the overall assimilation.
authors.affiliation: Institut für Chemie 2, Kernforschungsanlage Jülich GmbH, P.O. Box 1913, D-5170, Jülich, Federal Republic of Germany.
authors.forename: G H
authors.initials: GH
authors.lastname: Schleser
authors.affiliation: Institut für Chemie 2, Kernforschungsanlage Jülich GmbH, P.O. Box 1913, D-5170, Jülich, Federal Republic of Germany.
authors.forename: R
authors.initials: R
authors.lastname: Jayasekera