The effect of storage on microbial activity and bacterial community structure of drained and flooded paddy soil

Abstract

Logistics and time demands necessitate soil storage under laboratory conditions after sampling because soil properties cannot always be determined immediately. There have been a number of studies about the effects of storage on biophysical properties; however, there has been little reference to paddy soils, which experience the alternation of wetting and drying phases. Our aims were to determine the impacts of sample storage on microbial activity and community structure in paddy field soil. We pre-incubated paddy soil to reach two states: flooded (F) and drained (D). Samples were then stored at −20 and 4 °C or air-dried. After 30 days, one part of the stored soils was used to measure key soil indices and the other part of the soil was incubated for 7 days prior to reassessment. Total phospholipid fatty acid (PLFA) was used to characterize the microbial biomass. MicroResp™ and Illumina next-generation sequencing techniques were adopted to analyze the change of microbial community activity and structure, respectively. Results showed that the various storage treatments did not affect the total PLFA in drained and flooded soil except for the flooded soil stored at 4 °C. Basal respiration was unusually increased in the drained soil after storage but recovered after a 7-day re-incubation. In contrast, the impact on flooded soils was minimal. Further, the soil community-level physiological profile (CLPP) was affected by storage, but microbial community structure remained mostly unchanged. Sequencing also showed that α diversity of the flooded paddy soil was higher than that in the drained soil. The effect of storage on drained paddy soil using these indices was mainly consistent with previous studies on non-flooded cultivated soils, while the effect on flooded soil suggested a different mechanism from that in drained soil. Although the microbial function and community structure were different between drained and flooded paddy soils, the various storage approaches all altered the microbial functional structure to some extent but kept the microbial community structure largely intact.