BACKGROUND: Soil bacteria play important roles in organic matter decomposition and nutrient cycling during the non-growing season. The purpose of this study was to investigate the effects of soil use intensity and topology on the utilization of carbon resources by soil bacteria in paddy fields.
METHODS AND RESULTS: The Biolog EcoPlate was used for analysing community-level carbon substrate utilization profiles of soil bacteria. Soils were collected from the following three types of areas: plain, interface and mountain areas, which were tested to investigate the topology effect. The results of canonical correspondence analysis and Kendall rank correlation analysis showed that soil C/N ratio and NH4+ influenced utilization of carbon sources by bacteria. The utilization of carbohydrate and complex carbon sources were positively correlated with NH4+ concentration. Cultivated paddy fields were also compared with adjacent fallow fields to investigate the impact of cultivation cessation. The level of utilization of putrescine was lower in fallow fields than in cultivated fields.
Monoculture fields were compared with double cropping fields cultivated with barley to investigate the impact of winter crop cutlivation. Cropping system altered bacterial use of carbon sources, as reflected by the enhanced utilization of 2-hydroxy benzoic acid under monoculture conditions.
CONCLUSION: These results show that soil use intensity and topological characteristics have a minimal impact on soil bacterial functioning in relation to carbon substrate utilization. Moreover, soil chemical properties are important factors determining the physiological profile of the soil bacterial community.