Abstract:Australian native species grow competitively in nutrient limited environments, particularly in nitrogen (N) limited soils; however, the mechanism that enables this is poorly understood. Biological nitrification inhibition (BNI), which is the release of root exudates into the plant rhizosphere to inhibit the nitrification process, is a hypothesized adaptive mechanism for maximizing N uptake. To date, few studies have investigated the temporal pattern and components of root exudates by Australian native plant sp… Show more
“…However, there was a negative correlation between DOC and amoA transcript abundance in our study, which was also observed in estuarine ecosystems ( Happel et al, 2019 ). Many studies have observed that nitrification rates can be inhibited by increased organic C concentration in terrestrial ecosystems due to (1) biological nitrification inhibition ( Elroy & Sunil, 1973 ; Janke, Wendling & Fujinuma, 2018 ; Subbarao et al, 2009 ; White, 1986 ); (2) phenolics, tannins, and monoterpenes promoting heterotrophic immobilization of ammonium and decreasing substrate availability for nitrifiers ( Bremner & McCarty, 1993 ; Paavolainen, Kitunen & Smolander, 1998 ); and (3) the increased competition between heterotrophic and nitrifying bacteria for ammonium caused by high quality C ( i.e., labile carbon) ( Strauss & Lamberti, 2002 ).…”
Background
Fertilizer addition can contribute to nitrogen (N) losses from soil by affecting microbial populations responsible for nitrification. However, the effects of N fertilization on ammonia oxidizing bacteria under C4 perennial grasses in nutrient-poor grasslands are not well studied.
Methods
In this study, a field experiment was used to assess the effects of N fertilization rate (0, 67, and 202 kg N ha−1) and grass species (switchgrass (Panicum virgatum) and big bluestem (Andropogon gerardii)) on ammonia-oxidizing bacterial (AOB) communities in C4 grassland soils using quantitative PCR, quantitative reverse transcription-PCR, and high-throughput amplicon sequencing of amoA genes.
Results
Nitrosospira were dominant AOB in the C4 grassland soil throughout the growing season. N fertilization rate had a stronger influence on AOB community composition than C4 grass species. Elevated N fertilizer application increased the abundance, activity, and alpha-diversity of AOB communities as well as nitrification potential, nitrous oxide (N2O) emission and soil acidity. The abundance and species richness of AOB were higher under switchgrass compared to big bluestem. Soil pH, nitrate, nitrification potential, and N2O emission were significantly related to the variability in AOB community structures (p < 0.05).
“…However, there was a negative correlation between DOC and amoA transcript abundance in our study, which was also observed in estuarine ecosystems ( Happel et al, 2019 ). Many studies have observed that nitrification rates can be inhibited by increased organic C concentration in terrestrial ecosystems due to (1) biological nitrification inhibition ( Elroy & Sunil, 1973 ; Janke, Wendling & Fujinuma, 2018 ; Subbarao et al, 2009 ; White, 1986 ); (2) phenolics, tannins, and monoterpenes promoting heterotrophic immobilization of ammonium and decreasing substrate availability for nitrifiers ( Bremner & McCarty, 1993 ; Paavolainen, Kitunen & Smolander, 1998 ); and (3) the increased competition between heterotrophic and nitrifying bacteria for ammonium caused by high quality C ( i.e., labile carbon) ( Strauss & Lamberti, 2002 ).…”
Background
Fertilizer addition can contribute to nitrogen (N) losses from soil by affecting microbial populations responsible for nitrification. However, the effects of N fertilization on ammonia oxidizing bacteria under C4 perennial grasses in nutrient-poor grasslands are not well studied.
Methods
In this study, a field experiment was used to assess the effects of N fertilization rate (0, 67, and 202 kg N ha−1) and grass species (switchgrass (Panicum virgatum) and big bluestem (Andropogon gerardii)) on ammonia-oxidizing bacterial (AOB) communities in C4 grassland soils using quantitative PCR, quantitative reverse transcription-PCR, and high-throughput amplicon sequencing of amoA genes.
Results
Nitrosospira were dominant AOB in the C4 grassland soil throughout the growing season. N fertilization rate had a stronger influence on AOB community composition than C4 grass species. Elevated N fertilizer application increased the abundance, activity, and alpha-diversity of AOB communities as well as nitrification potential, nitrous oxide (N2O) emission and soil acidity. The abundance and species richness of AOB were higher under switchgrass compared to big bluestem. Soil pH, nitrate, nitrification potential, and N2O emission were significantly related to the variability in AOB community structures (p < 0.05).
“…The expanding body of literature on BNI suggests that many plant species may be capable of reducing nitrification in the rhizosphere (Chowdhury et al, 2017;Coskun et al, 2017a;Janke et al, 2018;Subbarao et al, 2007). In the agricultural setting, direct and indirect suppression of nitrification could reduce NO 3 − losses from annual cropping systems, with the agronomic benefit of increased fertilizer use efficiency and environmental benefits of reduced NO 3 − flow into downstream waterways and N 2 O emissions into the atmosphere.…”
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“…A suitable sediment NH 4 -N range for V. natans has been reported as 5-50 mg/kg (Zhu et al, 2006). Although only a few nitri cation inhibition agents from root exudates have been identi ed, BNI activity was con rmed in different plant species, blocking either the ammonia monooxygenase (AMO) pathway or both the AMO and hydroxylamine oxidoreductase (HAO) pathways (Sun et al, 2016, Janke et al, 2018. BNI function is thought to be triggered by the synergistic effect of NH 4 -N presence and low pH in the root environment (Subbarao et al, 2007).…”
Aims Rehabilitation of submerged vegetation is one of the commonly used techniques for the ecological restoration of shallow lakes. The changes of pollution structure in sediments caused by plant recovery and the rhizosphere chemical process under different sediment organic matter (SOM) levels are theoretical basis for the rational application of plant rehabilitation technology in lake management.Methods A circulating extraction system was designed for in situ collection of rhizospheric metabolites especially for the submerged plants. We explored how Vallisneria natans (V. natans) mediate the changes in sediment N and P through rhizospheric metabolites under low (4.94%) and high (17.35%) SOM levels. Results By analysing 63 rhizospheric metabolites from V. natans, glucitol was found to be 146.82% lower in the low SOM than in the high SOM treatment. NH4-N and NO2-N increased by 57% and 68.39%, respectively, in the high SOM treatment, while approximately one-seventh Inorg-P was transferred from Fe/Al-P to Ca-P in the low SOM treatment. The metabolites lactic acid, 3-hydroxybutyric acid, and phosphoric acid mediated NH4-N accumulation. Additionally, 3-hydroxy-decanoic acid and adipic acid mediated the transformation of Fe/Al-P to Ca-P.Conclusions The growth of V. natans significantly changed Inorg-N or Inorg-P fractions. The changes were SOM level-dependent and rhizosphere metabolites related. This study emphasised the benefit of V. natans rehabilitation at low SOM level. When restoring submerged macrophytes from high SOM sediment, care should be taken due to the release potential of labile N and P forms.
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