Disentangling CO2 fluxes: direct measurements of mesocosm‐scale natural abundance 13CO2/12CO2 gas exchange, 13C discrimination, and labelling of CO2 exchange flux components in controlled environments

• DOI: 10.1046/j.1365-3040.2003.01102.x
• Publication Date: 2003-11-13T23:59:09Z
• Authors: H. SCHNYDER; R. SCHÄUFELE; M. LÖTSCHER; T. GEBBING
• Keywords: Darkness

ABSTRACT A 13 C/ 12 C mass spectrometer was interfaced with a open gas exchange system including four growth chambers to investigate CO 2 components of perennial ryegrass ( Lolium perenne L.) stands. Chambers were fed air containing known δ CΟ2 −2.6 or −46.8‰). The did not fractionate isotopes and no extraneous leaked into chambers. on‐line discrimination (Δ) stands in light independent when constant. exchanged by the Nd ) darkness Rn differed 0.7‰, suggesting some Δ dark respiration at stand‐level. However, decreased ∼ 10‰ switched from −46.8 −2.5‰, increased following shift −46.7‰ due isotopic disequilibria between photosynthetic respiratory fluxes. Isotopic imbalances used assess (non‐photorespiratory) replacement substrate pool(s) new photosynthate. Respiration partially inhibited light, but during period darkness, association temperature changes. labelling kinetics indicated existence two major pools: fast pool which within hours, slow accounting for 60% total having mean residence time 3.6 d.