Impact of freeze-thaw on the contributions of AOA and AOB to N-flush induced nitrification in meadow soils. (November 2020)

• Record Type: Journal Article
• Authors: Tzanakakis, Vasileios A.; Taylor, Anne E.; Bottomley, Peter J.
• Is Part Of: Soil biology and biochemistry. Volume 150(2020)
• Publication Date: 2020-11
• Subjects: Freeze-thaw -- N mineralization -- Nitrification -- Ammonia oxidizing bacteria -- Ammonia oxidizing archaea; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2020.108015
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: In mid latitude regions of North America, many soils are subjected to freeze-thaw conditions (Fr–Th) during the late winter and early spring months. Fr–Th events are usually accompanied by flushes of C and N mineralization, yet, the concomitant response of nitrification has not been consistently characterized. A laboratory experiment was conducted on three soils that differ in their annual history of exposure to freeze-thaw events, and where both ammonia oxidizing bacteria (AOB) and archaea (AOA) are capable of contributing to nitrification activity at 10 and 16 °C under NH4 + replete conditions. Emergence and rates of N mineralization/nitrification were compared between soils frozen at −20 °C, with non-frozen soils stored at 4 °C. In all soils N mineralization commenced immediately (<1 d) in the Fr–Th soil treatments. Rates and/or amounts of mineralizable N released during the flush differed between soils, but rates for each soil were the same at 10 and 16 °C. Only ammonia oxidizing archaea (AOA)-driven nitrification emerged immediately (<1 d) from the Fr–Th treatment of the two soils with a history of freezing; these rates were higher at 16 than at 10 °C, and were not NH4 + limited. No AOB activity was detected in these soils for up to 3 d. AOB contribute the vast majority (88–92%) of nitrification under NH4 + replete conditions in the soil that rarely freezes. In this soil AOA did not contribute to nitrification in the Fr–Th treatment, and the emergence of AOB activity was delayed for 3 d at 10 °C unless supplemental NH4 + was provided, but commenced immediately at 16 °C with or without supplemental NH4 + ; however, rates of nitrification at 10 and 16 °C did not differ. The dominance of AOA activity immediately after Fr–Th in soils with a history of freezing suggests that AOA handle the transition during the freeze-down phase, and/or recover during the freeze-thaw phase with less constraint of NH4 + availability and temperature, than the AOB. Highlights: Nitrification was fully active in soils with a history of freezing within 1d of thawing. Nitrification emerging from soil with a history of freezing was due to AOA activity. Temperature of incubation affected the rate of AOA activity but not the emergence. Nitrification emerging from soil with no history of freezing was due to AOB activity. Temperature of incubation and NH4 + availability influenced emergence of AOB activity.