A continuous labelling approach to recover photosynthetically fixed carbon in plant tissue and rhizosphere organisms of young beech trees (Fagus sylvatica L.) using 13C depleted CO2

Abstract

A continuous labelling approach to recover photosynthetically fixed carbon in plant tissue and rhizosphere organisms of young beech trees (Fagus sylvatica L.) using 13 C depleted CO 2 Abstract A continuous labelling experiment using 13 C-CO 2 was set up in open-top chambers in order to follow fluxes of assimilates from the plant into the rhizosphere. Labelling was performed for one growing season by adding low amounts of CO 2 depleted in 13 C to the atmosphere of the open-top chambers, resulting in a difference of Δ 13 C 5‰ V-PDB compared to ambient conditions. The label was recovered in both plant parts and soil microbial communities, analysed via phospholipid fatty acid (PLFA) side chains. PLFA 18:2ω6,9 showed a significant incorporation of the 13 C label in October, indicating that fungi utilized plant derived carbon. In bacterial PLFA no label incorporation was detected, probably due to a lower use of rhizodeposits or a preference to older carbon compounds as energy sources. This experimental setup represents a low-cost continuous labelling method for field experiments with only minor increase of CO 2 concentrations.

Allocation and dynamics of C and N within plant–soil system of ash and beech

“…Microbial biomass is composed of a large number of various microorganisms and includes the extraradical mycelium of mycorrhizal fungi. A rapid transfer of photosynthate to ectomycorrhiza has indeed been reported (Leake et al, 2001;Esperschü tz et al, 2009;Hö gberg et al, 2010). The results in our experiment corroborate those findings.…”

“…Beech is associated with ectomycorrhiza, while ash associates with arbuscular mycorrhiza (Meinen et al, 2009). A rapid transfer of photosynthates to ectomycorrhiza has indeed been reported (Leake et al, 2001;Esperschü tz et al, 2009;Hö gberg et al, 2010). Callesen et al (2013) discovered in ash and beech that the δ 15 N pattern reflected tree species-related traits affecting the N cycling as well as site fertility and former land use, and possibly differences in N leaching.…”

13C PLFAs: a key to open the soil microbial black box?

“…The δ 13 C values determined by GC-C-IRMS are therefore those of the methyl esters (δ 13 C FAME). A mass balance equation is used to account for the one carbon added in the methyl group during the derivatisation process (Esperschütz et al 2009) to determine the isotope ratio of the PLFAs themselves (δ 13 C PLFA).…”

“…With steady state labelling of 13 CO 2 the labelling periods used have varied greatly. In laboratory experiments periods of days to weeks have been utilised, whilst in free air CO 2 enrichment (FACE) experiments the labelling periods are typically much longer (Esperschütz et al 2009;Grams et al 2011). For example, Esperschütz et al (2009) used a steady state approach to trace 13 CO 2 into soil PLFA pools following the labelling of young beech trees in open top chambers over an entire growing season.…”

Influence of chronic ozone stress on carbon translocation pattern into rhizosphere microbial communities of beech trees (Fagus sylvatica L.) during a growing season

“…However, these concentrations are known to cause direct CO 2 effects on plants and soil microbes. In a recent paper Esperschütz et al (2009) described an approach for free air fumigation of trees using only 75 µl*l −1 CO 2 fossil , added to the ambient air resulting in a CO 2 concentration that did not exceed 400 to 500 µmol*mol −1 CO 2 .…”