RESUMEN
Increasing salinity and sodicity have been recognized as threats to soil fertility and crop yield worldwide. In recent years, salt-affected soils have received great attentions due to the shortage of arable land. This study therefore aims to characterize soil bacterial community, assembly process and co-occurrence network along natural saline-sodic gradients across Songnen Plain, Northeast China. As revealed by Miseq sequencing, 8482 bacterial OTUs were annotated at 97% identity across 120 soil samples. Our results indicated that soil salinity-sodicity not only significantly decreased bacterial richness and but also impacted bacterial community composition. The dominant bacterial phyla included Proteobacteria (28.89%), Actinobacteria (19.96%) and Gemmatimonadetes (16.71%). By applying threshold indicator species analysis (TITAN), OTUs from Gemmatimonadetes were found to be the taxa with the most prevalent and strongest preference for high salinity-sodicity. Null model analysis revealed that the majority (76.4%) of ßNTI values were below -2 or above 2, indicating deterministic process was dominant across all samples. Notably, deterministic process contributed to a greater extent in higher saline-sodic soils. The bacterial co-occurrence network was more complex in slightly saline-sodic soils than in moderately and extremely saline-sodic soils, reflected by more nodes, more hubs and stronger connections, which was mainly driven by soil pH. These results provide strong evidence that salinity-sodicity was a key determinant in shaping soil bacterial community, assembly process and co-occurrence network pattern.
Asunto(s)
Microbiota , Suelo , China , Salinidad , Cloruro de SodioRESUMEN
Organic fertilizer application could have an impact on the nitrogen cycle mediated by microorganisms in arable soils. However, the dynamics of soil ammonia oxidizers and denitrifiers in response to compost addition are less understood. In this study, we examined the effect of four compost application rates (0, 11.25, 22.5 and 45 t/ha) on soil ammonia oxidizers and denitrifiers at soybean seedling, flowering and mature stage in a field experiment in Northeast China. As revealed by quantitative PCR, compost addition significantly enhanced the abundance of ammonia oxidizing bacteria (AOB) at seedling stage, while the abundance of ammonia oxidizing archaea was unaffected across the growing season. The abundance of genes involved in denitrification (nirS, nirK and nosZ) were generally increased along with compost rate at seedling and flowering stages, but not in mature stage. The non-metric multidimensional scaling analysis revealed that moderate and high level of compost addition consistently induced shift in AOB and nirS containing denitrifers community composition across the growing season. Among AOB lineages, Nitrosospira cluster 3a gradually decreased along with the compost rate across the growing season, while Nitrosomonas exhibited an opposite trend. Network analysis indicated that the complexity of AOB and nirS containing denitrifiers network gradually increased along with the compost rate. Our findings highlighted the positive effect of compost addition on the abundance of ammonia oxidizers and denitrifiers and emphasized that compost addition play crucial roles in shaping their community compositions and co-occurrence networks in black soil of Northeast China.