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Diffusive fractionation complicates isotopic partitioning of autotrophic and heterotrophic sources of soil respiration
Author(s) -
MOYES ANDREW B.,
GAINES SARAH J.,
SIEGWOLF ROLF T. W.,
BOWLING DAVID R.
Publication year - 2010
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2010.02185.x
Subject(s) - diel vertical migration , soil respiration , heterotroph , flux (metallurgy) , respiration , autotroph , environmental science , environmental chemistry , stable isotope ratio , soil science , chemistry , atmospheric sciences , soil water , ecology , botany , geology , biology , paleontology , physics , organic chemistry , quantum mechanics , bacteria
Carbon isotope ratios ( δ 13 C) of heterotrophic and rhizospheric sources of soil respiration under deciduous trees were evaluated over two growing seasons. Fluxes and δ 13 C of soil respiratory CO 2 on trenched and untrenched plots were calculated from closed chambers, profiles of soil CO 2 mole fraction and δ 13 C and continuous open chambers. δ 13 C of respired CO 2 and bulk carbon were measured from excised leaves and roots and sieved soil cores. Large diel variations (>5‰) in δ 13 C of soil respiration were observed when diel flux variability was large relative to average daily fluxes, independent of trenching. Soil gas transport modelling supported the conclusion that diel surface flux δ 13 C variation was driven by non‐steady state gas transport effects. Active roots were associated with high summertime soil respiration rates and around 1‰ enrichment in the daily average δ 13 C of the soil surface CO 2 flux. Seasonal δ 13 C variability of about 4‰ (most enriched in summer) was observed on all plots and attributed to the heterotrophic CO 2 source.