Isotopic labelling of enchytraeids under FACE conditions: A possible way to analyse the residue-enchytraeid-soil system considering elevated atmospheric CO2 concentrations

Titelangaben

Puppe, Daniel ; Schrader, Stefan ; Giesemann, Anette ; Gebauer, Gerhard:
Isotopic labelling of enchytraeids under FACE conditions: A possible way to analyse the residue-enchytraeid-soil system considering elevated atmospheric CO2 concentrations.
In: Landbauforschung / Sonderheft. Bd. 357 (2012) . - S. 21-26.
ISSN 0376-0723

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Abstract

A soil microcosm experiment was conducted in the laboratory with enchytraeids to assess the carbon (C) and nitrogen (N) turnover when feeding on barley straw. The straw originated from a field experiment where the crop was cultivated under elevated atmospheric CO2 conditions (FACE = Free Air Carbondioxide Enrichment). The CO2 concentration amounted to 550 ppm compared to ambient air with 380 ppm. CO2 applied to the crop in the enrichment plots was depleted in 13C; its δ13C value was -21‰. Additionally, one subplot of plants was labelled with 15N in both ambient air and elevated CO2 treatments. The aim of our study was to evaluate if straw from plants grown under elevated CO2 conditions and treated with labelled fertilizer can be used to trace carbon and nitrogen from the plants to the enchytraeids. Microcosms (n = 5) were filled with a previously defaunated silt loam soil, topped with ground barley straw and inoculated with a mixture of the two enchytraeid species Enchytraeus crypticus and E. buchholzi s.l.. One treatment without enchytraeids served as control. After 50 days of incubation at constant 20°C in darkness, the remaining straw was collected; the enchytraeids were extracted and counted. Samples of soil, straw and enchytraeids were analysed for C and N contents as well as 13C and 15N signatures. While the C/N ratio in the remaining straw material was significantly reduced, no change was observed in the enchytraeids. Under ambient air conditions, δ15N values of the enchytraeids were 27.6‰ in animals from plots with non-N-labelled straw, while those from labelled-N-treatments showed 52.2‰. In the FACE treatments δ15N-values of 15.7‰, and 29.3‰ were measured for animals from unlabelled and labelled treatments, respectively. The δ13C-values of the enchytraeids were as well significantly different reflecting isotope signatures of the consumed straw.