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Pedosphere
2023

Coupling changes of soil functional gene abundances and extracellular enzyme activities across the diagnostic horizons of agricultural Isohumosols

Zhuxiu LIU1,2, Haidong GU1,2, Xiaojing HU1

Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin 150081 (China).

Abstract

Soil functional microbial taxa and extracellular enzymes are involved in a variety of biogeochemical cycling processes. Although many studies have revealed the vertical change patterns of microbial communities along soil profile, the general understanding of the coupling changes in the functional gene abundances (FGAs) and extracellular enzyme activities (EEAs) in soil profiles is still limited, which hinders us from revealing soil ecosystem processes. Herein, we comparatively investigated the FGAs and EEAs in the diagnostic horizons of soil profiles obtained from Ustic and Udic Isohumosols in northeast China based on quantitative real-time PCR (qPCR) and standard fluorometric techniques, respectively. Results showed that the distribution patterns of both FGAs and EEAs were significantly distinguished by two suborders of Isohumosols, and were also separated from A- to C-horizons. Additionally, the variations of EEAs and FGAs were greater in Udic Isohumosols compared to Ustic Isohumosols along soil profile, and greater changes were observed in C- than in A-horizons. The both FGAs and EEAs correspondently decreased along the soil profiles. However, when normalized by soil organic carbon, the specific EEAs were significantly increased in deep soil horizons, suggesting that microorganisms will input more resources to the production of enzymes to ensure microbial nutrient requirements under resource scarcity. More importantly, we revealed that soil microbial nutrient demands were limited by carbon and phosphorus, and the limitation significantly increased along soil profiles with a greater carbon limitation observed in Ustic Isohumosols than that in Udic Isohumosols. Overall, our findings provided solid evidences to link between FGAs, EEAs, and microbial nutrient limitations, which would be helpful for a better understanding of the ecosystem processes in the soil profile.

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