Relationships between the density and activity of microbial communities possessing arylsulfatase activity and soil sulfate dynamics during the decomposition of plant residues in soil

• We identified the dynamics of S in relation with functional microbial communities in soil amended with plant residues.
• Higher decomposition rates and S–SO42−SO42− release from soils amended with low C/S ratio.
• Soil microbial biomass carbon increased more for residues with low C/S ratios.
• Plant residues with low C/S increased the ratio bacteria:fungi possessing arylsulfatase activity.
• The C/S ratio of plant residues incorporated in soil did not influence the arylsulfatase activity.

A laboratory incubation experiment was performed to examine the changes of soil microbial communities possessing arylsulfatase (ARS) activity. Different plant residues were incorporated into soils, and the resulting changes in the density and ARS activity of these communities relative to the sulfate content were studied. Mustard, fescue and wheat plant residues with different biochemical compositions and carbon (C):sulfur (S) ratios ranging from 60 to 486 were tested. Soil lacking residues was included as a control. Among the tested residues, mustard was the most labile and the most rapidly mineralized, leading to a significant 67% increase in the soil microbial biomass C (SMBC) compared with the control. The incorporation of mustard into soil induced a significant shift in the balance of microbes possessing ARS activity (ie. ratio bacteria:fungi) with an increase in the bacterial component producing ARS (ARS-B) but no change in ARS activity. A principal component analysis revealed clear differences between the soil samples according to both the nature of the residues incorporated and the duration of incubation. The correlation coefficients between the different variables showed that the ARS-B:ARS-F ratio was strongly correlated with the soil sulfate content (r = 0.81, p < 0.05). However, ARS activity was more closely correlated with ARS-F density than with ARS-B density (r = 0.63, p < 0.05 and r = 0.29, p < 0.1, respectively). The relative stability of the soil ARS activity, regardless of the nature of the residues incorporated was likely due to non-limiting S conditions for microbial growth in the soil used in this study.