Publication date: 15 April 2017
Source:Geoderma, Volume 292
Author(s): Juliane Struecker, Jens Dyckmans, Rainer Georg Joergensen
Decreasing O2 and increasing CO2 concentrations in the soil atmosphere with depth are one possible factor controlling C sequestration in subsoil. This study aimed to investigate the impact of these subsoil-specific gas conditions, which were measured in the field, on the decomposition of native soil organic C (SOC) and plant residues. Soil samples were taken on two neighbouring arable sites; one with high and the other with low SOC contents below 302 and increased CO2 , matching gas conditions measured in subsoil. Three different gas concentrations were used in the experiment: Ambient, medium (17% O2 ; 4% CO2 ) and extreme (13% O2 ; 8% CO2 ). These gas treatments were applied to samples with and without the addition of C4 plant residues to the sampled soil. We determined the effects of these treatments on contents of SOC, microbial biomass C (MBC) and fungal ergosterol. Plant residue addition caused negative priming effects on SOC mineralisation in the subsoils. The contribution of plant-derived to total MBC was reduced under medium and extreme gas conditions (topsoil: 31%; subsoil: 54%). However, neither medium nor extreme gas conditions had general effects on MBC and microbial activity indices. There was no evidence that changes in the soil atmosphere are a major factor controlling C sequestration in subsoil. However, some results indicate that changes in soil atmospheric conditions do have an impact on microbial substrate use, which should be considered in C sequestration research in subsoil.
Source:Geoderma, Volume 292
Author(s): Juliane Struecker, Jens Dyckmans, Rainer Georg Joergensen