Soil properties impacting denitrifier community size, structure, and activity in New Zealand dairy-grazed pasture

Abstract

Abstract. Denitrification is an anaerobic respiration process that is the primary contributor of the nitrous oxide (N 2 O) produced from grassland soils. Our objective was to gain insight into the relationships between denitrifier community size, structure, and activity for a range of pasture soils. We collected 10 dairy pasture soils with contrasting soil textures, drainage classes, management strategies (effluent irrigation or non-irrigation), and geographic locations in New Zealand, and measured their physicochemical characteristics. We measured denitrifier abundance by quantitative polymerase chain reaction (qPCR) and assessed denitrifier diversity and community structure by terminal restriction fragment length polymorphism (T-RFLP) of the nitrite reductase (nirS, nirK) and N 2 O reductase (nosZ) genes. We quantified denitrifier enzyme activity (DEA) using an acetylene inhibition technique. We investigated whether varied soil conditions lead to different denitrifier communities in soils, and if so, whether they are associated with different denitrification activities and are likely to generate different N 2 O emissions. Differences in the physicochemical characteristics of the soils were driven mainly by soil mineralogy and the management practices of the farms. We found that nirS and nirK communities were strongly structured along gradients of soil water and phosphorus (P) contents. By contrast, the size and structure of the nosZ community was unrelated to any of the measured soil characteristics. In soils with high water content, the richnesses and abundances of nirS, nirK, and nosZ genes were all significantly positively correlated with DEA. Our data suggest that management strategies to limit N 2 O emissions through denitrification are likely to be most important for dairy farms on fertile or allophanic soils during wetter periods. Finally, our data suggest that new techniques that would selectively target nirS denitrifiers may be the most effective for limiting N 2 O emissions through denitrification across a wide range of soil types.

Variation in denitrifying bacterial communities along a primary succession in the Hailuogou Glacier retreat area, China

“…Rangwala & Miller (2012) indicated that soil phosphorus limits plant productivity and indirectly affects soil microbial communities. Jha et al (2017) found that nosZ community structure had the strongest correlation with soil moisture content and available phosphorus. Those results were in agreement with our findings showing the relationship between nosZ- denitrifiers and soil properties.…”

“…Those results were in agreement with our findings showing the relationship between nosZ- denitrifiers and soil properties. While we focused specifically on nosZ abundance, previous studies have indicated that nirS and nirK communities are also strongly structured along gradients of soil water and phosphorus contents (Jha et al, 2017).…”

Variation in the nitrous oxide reductase gene (nosZ)-denitrifying bacterial community in different primary succession stages in the Hailuogou Glacier retreat area, China

“…A previous study has shown that organic carbon is the limiting factor in microbial processes and activities in the early successional stages without vegetation cover, and carbon accumulation affects the availability of soil nitrogen (Wardle et al, 2004), in this sense, soil organic carbon and nitrogen levels in retreating glaciers can become the main driving factor in shaping the composition of nitrogen-related microbial communities, and soil pH is the most important factor impacting denitrification processes (Zeng et al, 2016;Čuhel et al, 2011 ;Kim et al, 2015). Jha et al (2017) have pointed out that the nosZ gene community structure had the strongest correlation with soil moisture content and available phosphorus. In a similar study, Tang et al (2016) showed that phosphorus had a strong influence on the abundance of nitrogencycling microorganisms in forest plantations, with a strong positive correlation between soil available phosphorus and nitrogen cycling-related microbial functional gene abundance.…”

Metagenomic reconstruction of nitrogen and carbon cycling pathways in forest soil: Influence of different hardwood tree species

“…More recent studies have used quantitative polymerase chain reaction (qPCR) to measure the abundance of key functional genes involved in N cycling (28), including amoA (nitrification) (31,32), narG (nitrate reduction) (33), nirK and nirS (nitrite reduction) (34), norB (NO reduction) (35), nosZ (N2O reduction) (36), and nifH (N2 fixation) (37). A growing body of evidence supports functional gene abundance as a useful index for predicting biogeochemical rates, particularly when applied to N process rates (33,(38)(39)(40).…”