[Effects of Warming and Straw Application on Soil Microbial Biomass Carbon and Nitrogen and Bacterial Community...

In order to investigate the effects of warming and straw application on soil microbial biomass carbon and nitrogen and bacterial community structure, a randomized block experiment was performed. Four treatments were included, namely a control (CK), warming (WA), straw application (SA), and warming and straw application (WS) treatments. The soils were sampled during the soybean (Sep. 23, 2017) and winter wheat (April 21, 2018) growing seasons. The soils were used to determine the microbial biomass C and N content using chloroform fumigation methods, and the bacterial community structure was evaluated using high-throughput sequencing (Illumina HiSeq). Results indicated that there was no significant difference in microbial biomass C between different warming and straw application treatments (P>0.05). The microbial biomass N of the warming treatment was significantly higher than that of control in the soybean field (P<0.01). There were significant differences in the most dominant soil bacteria between treatments in the soybean growing season (P<0.05) at the class, order, family, and genus levels, while there was no difference in the winter wheat growing season. The percentages of dominant Gemmatimonadales, Gemmatimonadaceae, and Sphingomonas in the CK and WA (or SA) treatments were significantly different (P<0.05) in the soybean growing season. There was a significant (P<0.05) difference in the dominant Gammaproteobacteria between the CK and WA treatments in the winter wheat growing season. The observed number of species, Shannon index, Simpson index, and Chao1 index were lowest in the warming plots in the soybean growing season and highest in the warming and straw application plots in the winter wheat growing season. The Shannon index for the WA plots was significantly higher than in the WS plots in the soybean growing season (P<0.05). The observed number of species, Shannon index, Simpson index, and Chao1 index were significantly higher in the soybean plots than in the winter wheat plots (P<0.05), while the abundance was significantly higher in the winter wheat plots than in the soybean plots (P<0.05). The soybean growing season had significantly higher diversity than the winter wheat growing season. The indexes of α diversity were highly significantly correlated with soil microbial biomass C and N in the soybean growing season (P<0.001), while there was no such correlation in the winter wheat growing season. The indices of α diversity were significantly correlated in both the soybean growing season and winter wheat growing season (P<0.05).