Responses of bacterial and archaeal ammonia oxidizers to soil organic and fertilizer amendments under long-term management

Abstract

17Ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) co-exist in soil, 18 but their relative distribution may vary depending on the environmental conditions. Effects of 19 changes in soil organic matter and nutrient content on the AOB and AOA are poorly 20 understood. Our aim was to compare effects of long-term soil organic matter depletion and 21 amendments with labile (straw) and more recalcitrant (peat) organic matter, with and without 22 easily plant-available nitrogen, on the activities, abundances and community structures of 23 AOB and AOA. Soil was sampled from a long-term field site in Sweden that was established 24 in 1956. The potential ammonia oxidation rates, the AOB and AOA amoA gene abundances 25 and the community structures of both groups based on T-RFLP of amoA genes were 26 determined. Straw amendment during 50 years had not altered any of the measured soil 27 parameters, while the addition of peat resulted in a significant increase of soil organic carbon 28 as well as a decrease in pH. Nitrogen fertilization alone resulted in a small decrease in soil 29 pH, organic carbon and total nitrogen, but an increase in primary production. Type and 30 amount of organic matter had an impact on the AOB and AOA community structures and the 31 AOA abundance. Our findings confirmed that AOA are abundant in soil, but showed that 32 under certain conditions the AOB dominate, suggesting niche differentiation between the two 33 groups at the field site. The large differences in potential rates between treatments correlated 34 to the AOA community size, indicating that they were functionally more important in the 35 nitrification process than the AOB. The AOA abundance was positively related to addition of 36 labile organic carbon, which supports the idea that AOA could have alternative growth 37 strategies using organic carbon. The AOB community size varied little in contrast to that of 38 the AOA. This indicates that the bacterial ammonia oxidizers as a group have a greater 39 ecophysiological diversity and potentially cover a broader range of habitats. 40

Efficiency promotion and its mechanisms of simultaneous nitrogen and phosphorus removal in stormwater biofilters

“…2A) and nitrifiers' abundance (especially AOA) (Fig. 2C) although AOA and AOB were considered as autotrophy, which was agreed with the previous study that degradable straw could stimulate the soil nitrification activity (Wessen et al, 2010). Contrary to denitrification, aquatic plant detritus was more effective to nitrification indicated by the higher PNR and higher amoA gene abundance than terrestrial plant detritus.…”

Spatial distribution of ammonia-oxidizing bacteria and archaea across a 44-hectare farm related to ecosystem functioning

“…The negative correlation between AOA and clay content could be indicative of AOA being less abundant in nutrient-rich environments, as clay soils have higher cation exchange capacity and bind more ammonium. Soil pH as a differentiating factor for the AOB and AOA habitats have been discussed previously, but there are conflicting results, with some studies showing a negative correlation to pH, as in our study , and others showing that the AOA are negatively impacted by low pH (He et al, 2007;Hallin et al, 2009;Jia and Conrad, 2009;Bru et al, 2010;Wessén et al, 2010). Contradictory results concerning the effect of pH on AOA abundance could be explained by differences in the physiological diversity within the archaeal communities present in different soils.…”

Dynamics of ammonia-oxidizing archaea and bacteria populations and contributions to soil nitrification potentials

“…Although it is well documented that the ratio of AOA:AOB ranges widely in soils (Leininger et al, 2006;He et al, 2007;Adair and Schwartz, 2008;Shen et al, 2008;Schauss et al, 2009;Di et al, 2010;Wessen et al, 2010;Zeglin et al, 2011), no data exist on what might influence this ratio, or its dynamism. Our study showed that the AOA:AOB shifts were generated by a combination of different phenomena: These observations raise some interesting questions about the environmental drivers of AOA and AOB growth, as well as about their relative stress tolerances.…”

“…A case can be made that the relative contributions of AOA and AOB to soil nitrification might shift in different phases of crop rotation and during different seasons of the year. Although recent studies have evaluated AOA and AOB population sizes, composition and/or their relative growth responses in soils recovered from agricultural cropping systems, the soils were often taken from complex crop rotations in multi-year cycles, and sampled in either spring, fall or unspecified times (Tourna et al, 2008;Hallin et al, 2009;Wessen et al, 2010Wessen et al, , 2011Xia et al, 2011). Clearly, the extent to which phase of the crop rotation or time of soil sampling might have influenced the results cannot be determined.…”