Oxygen and substrate availability interactively control the temperature sensitivity of CO2 and N2O emission from soil

Abstract

We investigated how oxygen availability, substrate amount, and quality affect the temperature dependency of enzymatic processes involved in the production of carbon dioxide (CO2) and nitrous oxide (N2O). Three substrates differing in microbial degradability (glucose with potassium nitrate, glycine, and phenylalanine) were added to a mountain grassland soil at a range of concentrations. Soils were incubated at 21 and 1 % of O2 content and at 10 and 20 °C. Oxygen availability was a main factor controlling the reaction rates and temperature sensitivity of CO2 and N2O production. The temperature sensitivity of CO2 production was higher under aerobic versus oxygen-limited conditions, and the opposite dependency was observed for the N2O production. Substrate availability was a second factor affecting the temperature sensitivity of the processes leading to the production of these gases. The temperature response was reduced under substrate limitation. Apparent activation energy for aerobic CO2 production was similar (E a ~ 30 kJ mol−1) for tested substrates, while E a for anaerobic N2O production increased in the order phenylalanine < glycine < glucose + NO3 − having values 45, 75, and 106 kJ mol−1, respectively. Commonly, the temperature sensitivity of N2O production (2 < Q 10 < 4.5) was much higher than that for CO2 (Q 10 ≤ 1.5).