Soil dissolved organic matters mediate bacterial taxa to enhance nitrification rates under wheat cultivation.

Studies have shown that dissolved organic matters (DOMs) may affect soil nutrient availability to plants due to their effect on microbial communities; however, the relationships of soil DOM-bacterial community-N function in response to root exudates remains poorly understand. Here, we evaluated the DOM composition, bacterial taxonomic variation and nitrogen transformation rates in both acidic and alkaline soils, with or without the typical nitrate preference plant (wheat, Triticum aestivum L.). After 30 days' cultivation, DOM compositions such as sugars, amines, amino acids, organic acid, and ketone were significantly increased in soil with wheat vs. bare soil, and these compounds were mainly involved in nitrogen metabolism pathways. Soil core bacterial abundance was changed while bacterial community diversity decreased in response to wheat planting. Function prediction analysis based on FAPROTAX software showed that the bacterial community were significantly (p < 0.05) affiliated with nitrification and organic compound degradation. Additionally, db-RDA and VPA analysis suggested that the contribution of soil DOM to the variance of bacterial community was stronger than that of soil available nutrients. Furthermore, the N-transformation related bacteria like Burkholderiales and ammonia-oxidizing bacteria (AOB) were positively correlated with soil gross nitrification rate, confirming that the soil N transformation was enhanced in both acidic and alkaline soils. Our results provide insight into how soil DOM affects the community structure and function of bacteria to regulate the process of nitrogen transformation in plant-soil system.