Temperature decouples ammonia and nitrite oxidation in greenhouse vegetable soils

Abstract

The influence of temperature on soil ammonia (NH3) and nitrite (NO2−) oxidation and related NO2− accumulation in soils remain unclear. The soil potential NH3 oxidation (PAO) and NO2− oxidation (PNO) rates were evaluated over a temperature gradient of 5–45 °C in six greenhouse vegetable soils using inhibitors. The values of temperature sensitivity traits such as temperature minimum (Tmin), temperature optimum (Topt), and maximum absolute temperature sensitivity (Tm_sens) were also fitted to the square root growth (SQRT) and macromolecular rate theory (MMRT) models. The ammonia-oxidizing archaea (AOA) and bacteria (AOB) were determined by quantifying amoA, and nitrite-oxidizing bacteria (NOB) were determined by quantifying the nxrA and nxrB. Both models identified that Topt for PAO (34.0 °C) was significantly greater than that for PNO (26.0 °C). The Tm_sens (23.4 ± 2.1 °C) and Tmin (1.0 ± 2.0 °C) for PAO were higher than those for PNO (16.8 ± 3.2 °C and − 11.7 ± 6.7 °C). PAO was positively correlated with AOB-amoA at 20–30 °C and with AOA-amoA at 30–35 °C, while PNO was positively correlated with nxrB at 5–30 °C. Additionally, NO2− and N2O were positively correlated with the (AOA + AOB amoA) to (nxrA + nxrB) ratio, and the concentration of N2O was positively correlated with NO2− accumulation. These results highlight that elevated temperatures resulted in the uncoupling of NH3 oxidation and NO2− oxidation, leading to NO2− accumulation, which could stimulate N2O emissions.