Rice straw decomposition affects diversity and dynamics of soil fungal community, but not bacteria

Straw decomposition increased amounts of soil organic carbon and changed microbial biomass. But the different impacts of rice straw decomposition on the succession of bacterial and fungal community composition in field conditions were poorly understood. The objective of this study was to investigate the development of soil bacterial and fungal communities during rice straw decomposition in field conditions, and the relationship between soil chemical/physical properties and the evolution of microbial communities. A 1-year field study (90, 180, 270, and 360 days) was conducted, including the straw decomposition soil and control (no straw decomposition soil). The bulk soil samples (0-15-cm depths) from three replicate plots per treatment were collected for the analysis of soil properties and of microbial diversity parameters. Soil bacterial and fungal community structures and population sizes were determined by applying PCR-denaturing gradient gel electrophoresis (DGGE) and quantitative PCR (qPCR). The bacterial and fungal community diversity was evaluated using the following parameters: Shannon-Wiener diversity index, richness, and evenness. Moreover, the relationship between soil properties and the changes of microbial communities was analyzed using redundancy analysis (RDA). The results showed that, in contrast to bacteria, the soil fungal population size and diversity indices were significantly increased during different time points of rice straw decomposition, and reached to the highest value at 360 days. When compared with the bacterial DGGE profiles, the fungal DGGE profiles significantly changed between the straw decomposition soil and control, and the dominant soil fungal genera varied apparently. Bacterial 16S ribosomal RNA (rRNA) and fungal 18S rRNA gene sequences obtained from the main DGGE bands were further sequenced, among which Penicillium sp., Aspergillus sp., and Acremonium sp. have the ability to degrade cellulose. RDA suggested that the soil available P, organic C, pH, and bulk density were the main factors influencing the variation in the fungal community structures and diversities. The fungal community structures displayed distinct successions during rice straw decomposition. But such finding was not observed in bacterial communities. The ratio of fungi to bacteria measured by qPCR was higher in the straw decomposition soil compared with the findings in control, indicating that fungi predominated in straw decomposition. Especially, our study deduced that the diversified cellulolytic fungal genera highly enriched in rice straw decomposition soils had great potential of mining novel cellulose-decomposing enzymes.