The Effect of Drought and N Availability on Soil Microbial Production, Respiration, and Carbon-use Efficiency

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Published on December 22, 2016

Author: NIFA_IBCE

Source: slideshare.net

1. The Effect of Drought and N Availability on Soil Microbial Production, Respiration, and Carbon-use Efficiency John M. Stark Dept of Biology, & the Ecology Center Utah State University

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3. CHO

4. CO2 ATP + NADH CHO

5. CO2 ATP + NADH BiomassCHO

6. CO2 ATP + NADH BiomassCHO CUE

7. CO2 ATP + NADH BiomassCHO CUE = 0

8. CO2 ATP + NADH BiomassCHO CUE = 0.8

9. CO2 ATP + NADH BiomassCHO CUE = 0.8 C sequestration

10. How do environmental factors regulate CUE? • Temperature ?

11. How do environmental factors regulate CUE? • Temperature Maintenance E requirements

12. How do environmental factors regulate CUE? • Temperature • Substrate supply ?

13. How do environmental factors regulate CUE? • Temperature • Substrate supply type of substrate C:N stoichiometry

14. How do environmental factors regulate CUE? • Temperature • Substrate supply type of substrate C:N stoichiometry Limiting resource

15. How do environmental factors regulate CUE? • Temperature • Substrate supply type of substrate C:N stoichiometry • Soil moisture ?

16. How do environmental factors regulate CUE? • Temperature • Substrate supply type of substrate C:N stoichiometry • Soil moisture soil water potential soil water content

17. How do environmental factors regulate CUE? • Temperature • Substrate supply type of substrate C:N stoichiometry • Soil moisture soil water potential soil water content Microbial physiology

18. How do environmental factors regulate CUE? • Temperature • Substrate supply type of substrate C:N stoichiometry • Soil moisture soil water potential soil water content Microbial physiology Diffusion of substrates

19. How do environmental factors regulate CUE? • Temperature • Substrate supply type of substrate C:N stoichiometry • Soil moisture soil water potential soil water content Microbial physiology Diffusion of substrates Soil texture

20. Objective Determine how microbial CUE changes with: • Substrate supply (C & N) • Soil moisture (water potential & content) • Substrate x moisture

21. Approach • Range of soil water potentials & contents in soils of different textures • Tracer and isotopic dilution assays with 13C and 15N-labeled substrates • Gas-phase additions of substrates (13C-acetic acid vapor & 15NH3) Measure microbial respiration, C & N assimilation, and CUE using:

22. Approach Two methods for calculating CUE: 13C-acetate assimilation: CUE = 13C in microbial biomass 13C-biomass + 13CO2 15N immobilization (by 15NH4 +-pool dilution): CUE = Inorg N immob * C:Nmicrob Inorg N immob * C:Nmicrob + CO2

23. Approach Preliminary Experiment:

24. Approach Preliminary Experiment: Can microbes assimilate C and N supplied through the gas phase in acid, dry soils?

25. Approach Preliminary Experiment: Can microbes assimilate C and N supplied through the gas phase in acid, dry soils? • Sitka spruce forest soil, pH 3.8 • Moist (-0.03 MPa) and dry (-3.6 MPa) soils • Gas-phase additions of substrates (13C-acetic acid vapor & 15NH3) • 0 to 48-h incubations

26. Approach Preliminary Experiment: Can microbes assimilate C and N supplied through the gas phase in acid, dry soils? Herron et al. 2009 SBB

27. Approach Preliminary Experiment: Can microbes assimilate C and N supplied through the gas phase in acid, dry soils? Glass beads w/ 13C-acetic acid Aquarium pump (90 mL/min) Herron et al. 2009 SBB

28. Approach Preliminary Experiment: Can microbes assimilate C and N supplied through the gas phase in acid, dry soils? Glass beads w/ 13C-acetic acid Aquarium pump (90 mL/min) Soil cores Herron et al. 2009 SBB

29. Approach Preliminary Experiment: Can microbes assimilate C and N supplied through the gas phase in acid, dry soils? Glass beads w/ 13C-acetic acid Aquarium pump (90 mL/min) 15NH3 Herron et al. 2009 SBB

30. Can acetic acid vapor supply 13C substrate to soil microbes in acidic and/or dry soils?

31. Can acetic acid vapor supply 13C substrate to soil microbes in acidic and/or dry soils? Dry soil (-3.6 MPa) Moist soil (-0.03 MPa)

32. Can acetic acid vapor supply 13C substrate to soil microbes in acidic and/or dry soils? Dry soil (-3.6 MPa) Moist soil (-0.03 MPa) • Yes. 13C-acetate was readily respired. • Respiration rates were higher after injection of larger amounts of acetic acid vapor.

33. Can acetic acid vapor supply 13C substrate to soil microbes in acidic and/or dry soils? Dry soil (-3.6 MPa) Moist soil (-0.03 MPa) • Yes. 13C-acetate was readily respired. • Respiration rates were higher after injection of larger amounts of acetic acid vapor. • Acetic acid injections had no negative impact on respiration of native SOC.

34. Can acetic acid vapor supply 13C substrate to soil microbes in acidic and/or dry soils?

35. Can acetic acid vapor supply 13C substrate to soil microbes in acidic and/or dry soils? • 13C assimilation rates were higher after injection of larger amounts of acetic acid vapor and in moister soil.

36. Does acetic acid vapor affect N cycling rates?

37. Does acetic acid vapor affect N cycling rates? • Mineralization: No

38. Does acetic acid vapor affect N cycling rates? • Mineralization: No • Microbial N immobilization: Yes • Addition of larger quantities of acetic acid vapor stimulated microbial immobilization of N in both moist and dry soil.

39. So, what about microbial CUE?

40. So, what about microbial CUE? 15NH3 13C-acetic acid

41. So, what about microbial CUE? 15NH3 13C-acetic acid • 15N and 13C methods gave very similar results after 24 to 48 h

42. So, what about microbial CUE? 15NH3 13C-acetic acid • 15N and 13C methods gave very similar results after 24 to 48 h • CUE in different C-addition and soil moisture treatments converged to the same values (0.4 to 0.5) after 24 to 48 h

43. Conclusions • Gas-phase additions of substrate can be used to provide isotopically labeled C & N to microbes, and to manipulate substrate supply

44. Conclusions • Gas-phase additions of substrate can be used to provide isotopically labeled C & N to microbes, and to manipulate substrate supply • 15N and 13C methods gave similar CUE estimates after 24 – 48h

45. Conclusions • Gas-phase additions of substrate can be used to provide isotopically labeled C & N to microbes, and to manipulate substrate supply • 15N and 13C methods gave similar CUE estimates after 24 – 48h • Surprisingly, C-partitioning into biomass and respiration did not appear to be affected by C supply or soil moisture.

46. Acknowledgments Jeanette Norton Jennifer MacAdam Katrina Slabaugh Shay Peterson Funding from: Collaborators: Technicians:

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