Changes in soil microbial community activity and composition following substrate amendment within the MicroResp (TM) system

Purpose The aim of study was to revisit the assumptions of the MicroResp (TM) method and to determine the factors that control the substrate induced respiration (SIR) profiles. The following hypotheses were addressed: (1) SIR changes as a result of substrate form, incubation duration and soil type and (2) prolonged incubation of soils within the MicroResp (TM) assay results in shifts in the microbial community composition and consequently produces different SIR profiles. Materials and methods Two different soils (paddy soil and forest soil) were selected, and combined MicroResp (TM) and highthroughput sequencing were used to explore the relationships between SIR patterns and microbial diversity during 72 h of incubation in the two distinct soil types. Results and discussion The results confirmed that SIR pattern of soil was sensitive to substrate, incubation duration, and soil type. However, both soils showed similar responses to most substrates applied. Principal coordinates analysis showed that the SIR patterns shifted over 72 h in both soils. The structure of the microbial community in soils, when treated with D-glucose, L-arginine, or protocatechuic acid, shifted significantly after only 6 h incubation. Conclusions The results indicated the SIR profiles were determined by microbial community characteristics, incubation duration, and soil type. Especially, the duration of incubation should be carefully considered when applying MicroResp (TM) to soil, in which prolonged incubation (> 6 h) might prompt biases to microbial structure through growth and community alteration.