Contrasting biomass, dynamics and diversity of microbial community following the air-drying and rewetting of an upland and a paddy soil of the same type

Abstract

We report a preliminary investigation into soil microbial biomass C, ATP, microbial community composition and gaseous emissions when an upland Chinese and an immediately adjacent paddy soil were incubated with increasing percentage water holding capacities (WHC) from 10% WHC to waterlogging for 10 days. The aim was to see what adaptations, if any, occur when a paddy soil is incubated under conditions of increasing soil moisture, from 10% WHC to waterlogging and an adjacent upland soil is subjected to the opposite moisture changes, from waterlogging to 10% WHC. The main differences were that soil ATP remained quite constant in the paddy soil, irrespective of the different WHCs while in the upland soil, it increased from a low level between 10 and 20% WHC to a maximum at 60% WHC declining to a similar low level as 10 and 20% when waterlogged. The most striking feature was that although there were significant changes in biomass C, ATP and biomass ATP concentrations, of up to 3-fold or more, due to changing soil moisture, the changes in relative abundance of the microbial community composition measured by gene sequencing, particularly for fungi, were small and often insignificant, especially between 40% WHC and waterlogging. There were significant changes in bacterial community composition between 10 and 40%, where 45 to 61% of bacteria responded to the change. However, the changes were very few between 40% WHC and waterlogging. Thus, there was no clear link between the large changes in microbial biomass and microbial community composition.