Effects of nitrogen deposition rates and frequencies on the abundance of soil nitrogen-related functional genes in temperate grassland of northern China

Abstract

Purpose Microbial processes driving nitrogen (N) cycling are hot topics in terms of increasing N deposition. Abundances of N-related functional genes (NFG) can be most responsive to N deposition and commonly used to represent N transformation rates. However, empirically simulated N deposition has been exclusively conducted through large and infrequent N fertilization, which may have caused contrasting effects on NFGs.Therefore, experiments with small and frequent N additions closed to natural deposition are necessary. ) and two frequencies (2 times per year addition as conventional large and infrequent N fertilization (2 N), and 12 times per year addition simulating small and frequent N deposition (12 N), respectively) were conducted in a long-term field experiment of a semiarid grassland in northern China. Quantification analysis using real-time PCR were carried out for NFGs, including nifH for N fixation, chiA for N mineralization, archaeal (AOA) and bacterial (AOB) amoA for nitrification, and narG, nirS, nirK, and nosZ for denitrification. Results and discussion NFG abundances showed distinct sensitivities to N addition rates. The nifH, AOA-amoA, nirS, and nosZ gene abundances increased due to improved available N at low N rates, but suppressed by salt toxicity and acidification at high N rates. Large changes of chiA and AOB-amoA gene abundances highlighted their great sensitivities to the N enrichment. The abundance of AOB-amoA was more sensitive to N addition than AOA-amoA, but AOA-amoA dominated in absolute numbers and they predominated the ammoniaoxidation under different conditions. The N addition frequencies caused significant lower gene abundances of nifH, nirS, and nosZ under the 2-N frequency due to stronger suppression of acidification and salt toxicity and resulted in significant higher AOB-amoA gene abundances in response to higher N availability under the 2-N frequency. Conclusions The NFGs abundances responded to N addition rates distinctly, highlighting that the driven processes involved in N cycling were altered by the N addition rates.

Community Composition and Abundance of Bacterial, Archaeal and Nitrifying Populations in Savanna Soils on Contrasting Bedrock Material in Kruger National Park, South Africa

“…The strong dominance of ammonia-oxidizing thaumarchaeota within the archaeal communities was further supported by the numerical predominance of archaeal amoA gene abundances (~5 × 10 7 copies g −1 soil) relative to bacterial amoA gene abundances (mostly ≤ 7 × 10 4 copies g −1 soil). To our knowledge, a predominance of archaea within the ammonia-oxidizing communities has not yet been described for savanna soils but is well known for various other soil environments (e.g., Erguder et al, 2009 ; Herrmann et al, 2012 ; Sims et al, 2012 ; Ding et al, 2015 ; Ning et al, 2015 ). AOA tend to dominate over AOB in acidic soils and can also thrive at much lower substrate concentrations than AOB due to a higher substrate affinity (Leininger et al, 2006 ; Martens-Habbena et al, 2009 ; Zhang et al, 2012 ; Yao et al, 2013 ).…”

Nitrogen has a greater influence than phosphorus on the diazotrophic community in two successive crop seasons in Northeast China

“…Many studies have found that N addition increases the richness of diazotrophs 33 , 34 . However, some studies have found that N has no such clear influence 35 .…”

Low Nitrogen Fertilization Alter Rhizosphere Microorganism Community and Improve Sweetpotato Yield in a Nitrogen-Deficient Rocky Soil

“…The reasons for this difference may be that (1) the original N content in the rocky soil and the level of urea applied to the rocky soil were very low, as in the Antarctic soils and semiarid grassland (Jung et al, 2011;Zhang et al, 2019). A previous study also found that nifH gene abundance increased under low N rates (5-15 g N/m 2 /year) but was suppressed under high N rates (50 g N/m 2 /year) (Ning et al, 2015). It was suggested that low N fertilization (0.7 g N/m 2 ) may have promoted the growth of N-fixing microorganisms in the N-deficient soil.…”