Deciphering the microbial mechanisms underlying glucose induced soil priming effects under low and high nutrient levels

Soil priming effect, which refers to the impact of labile carbon inputs on the decomposition of soil organic matter, plays a significant role in carbon storage. Investigating substrate induced soil priming effects and the involved microbial mechanisms, particularly under nutrients gradient, is central to the understanding of carbon processes and potential accrual in agriculture soil. Thus, a 7 days laboratory incubation was conducted to assess ¹³C labeled glucose induced priming effects in soil receiving the high (TH) and low nutrient (TL) addition. Also, DNA-SIP coupled with metagenomic were adopted to identify the core microbial groups and functional guild responsible for soil priming effects. Here, we found that i) soil priming effects were significantly larger in TL treatment than in the TH treatment, and ii) the larger priming in TL was likely driven by N-mining processes dominated by K-strategy microbes, whereas less priming in TH might be explained by co-metabolism led by r-strategy microbes. Additionally, functional changes of microbial community were revealed by Shotgun sequencing. Both KEGG, EggNOG and CAZymes showed the relative abundance of the functional genes (e.g., GH13_10 and GH77) encoding cellulase enzymes involved in soil organic carbon decomposition were more abundant in TL compared to TH, suggesting higher priming effects in TL was mainly due to the nutrient constraints on microbial demands. This study revealed the main microbial groups and their functions in glucose induced soil priming effects under low and high nutrient levels.