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Abstract:
The input of organic substances (e.g., rice straw) in rice field soils
usually stimulates the production and emission of the greenhouse gas
methane (CH4). However, the amount of CH4 derived from the applied rice
straw, as well as the response of bacterial and archaeal communities
during the methanogenic phase, are poorly understood for different rice
field soils. In this study, samples of five different rice soils were
amended with C-13-labeled rice straw (RS) under methanogenic conditions.
Immediately after RS addition, the RS-derived CH4 production rates were
higher in soils (Uruguay, Fuyang) that possessed a stronger inherent CH4
production potential compared with other soils with lower inherent
potentials (Changsha, the Philippines, Vercelli). However, soils with
higher inherent potential did not necessarily produce higher amounts of
CH4 from the RS applied, or vice versa. Quantitative PCR showed copy
numbers of both bacteria and methanogens increased in straw-amended
soils. High-throughput sequencing of 16S rRNA genes showed distinct
bacterial communities among the unamended soil samples, which also
changed differently in response to RS addition. Nevertheless, RS
addition generally resulted in all the rice field soils in a relative
increase of primary fermenters belonging to Anaerolineaceae and
Ruminococcaceae. Meanwhile, RS addition also generally resulted in a
relative increase of Methanosarcinaceae and/or Methanocellaceae. Our
results suggest that after RS addition the total amounts of RS-derived
CH4 are distinct in different rice field soils under methanogenic
conditions. Meanwhile, there are potential core bacterial populations
that are often involved in primary fermentation of RS under methanogenic
conditions.
