Olusegun_Presentation
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This document summarizes research on soil nitrogen fluxes and root uptake in boreal forests. It finds that amino acids dominated nitrogen fluxes in boreal forest soil. The application of nitrate increased nitrate fluxes, especially in fertilized soils. While diffusive flux may limit nitrogen acquisition by plants, transpiration-induced mass flow also contributes and increases total nitrogen supply. Microdialysis was shown to estimate both diffusive and mass flow nitrogen fluxes in soils, with mass flow enhancing fluxes and changing flux compositions. Transpiration-driven mass flow may significantly contribute to plant nitrogen nutrition.
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- 2. Introduction P. I P. III P. IV ConclusionsP. II N2 , Nox, N2ONH3 Dissolved organic N NH4 + NO3 - Nitrification Denitrification Immobilization Volatilization Complex Organic N Leaching Leaching Leaching Immobilization Dead Microbes & exoenzymes N deposition N fixation Ammonification Litter inputs Microbes & exoenzymes Microbes The soil nitrogen Cycle
- 3. Introduction P. I P. III P. IV ConclusionsP. II Transport of soil nutrients to the roots High concentra>on Low concentra>on Diffusion Mass flow
- 4. Introduction P. I P. III P. IV ConclusionsP. II Transpira>on Diffusion Mass flow Transport of soil nutrients to the roots Mass flow + Diffusion Diffusion
- 5. Importance of diffusion and mass flow to plant N nutri9on? § Roles of diffusion and mass flow in plant nutri>on is controversial Introduction P. I P. III P. IV ConclusionsP. II Transpira>on Diffusion Mass flow
- 6. § Disturbance to soil system § Methodological challenges Tradi9onal methods for es9ma9ng soil N Lysimeter Soil extrac>on Introduction P. I P. III P. IV ConclusionsP. II
- 7. Microdialysis technique Probe Microdialysis set up Introduction P. I P. III P. IV ConclusionsP. II
- 8. Introduction P. I P. III P. IV ConclusionsP. II Limita9ons of microdialysis technique § Microdialysis probe lacks most func>ons of plant root § Underes>ma>on of the availability of some amino acids § Less suitable for determining soil N concentra>ons
- 9. P. IIntroduction P. III P. IV ConclusionsP. II N fluxes in fer9lized and unfer9lized forest soils at the onset of the growing season
- 10. P. IIntroduction P. III P. IV ConclusionsP. II Induced diffusive flux of N in boreal forest soils
- 11. P. IIntroduction P. III P. IV ConclusionsP. II Effect of forest fer9liza9on on soil N flux Control plot Control plot Fer>lized plot Fer>lized plot Addi>on of 10 l m-2 water Addi>on of 1 g N l-1 KNO3 Addi>on of 10 l m-2 water Addi>on of 1 g N l-1 KNO3
- 12. P. IIntroduction P. III P. IV ConclusionsP. II Nitrate application Dynamics of added NO3 - in control and fer9lized forest soils
- 13. P. IIntroduction P. III P. IV ConclusionsP. II Conclusions § Amino acids dominated N fluxes in the boreal forest soil § Nitrate addi>on increases NO3 - flux, but more pronounced in the fer>lized soil
- 14. Introduction P. I P. III P. IV ConclusionsP. II The limi9ng step for plant soil N acquisi9on? Diffusive flux to the roots Root uptake rate
- 15. Introduction P. I P. III P. IV ConclusionsP. II Diffusive flux and root uptake rates
- 16. Introduction P. I P. III P. IV ConclusionsP. II Conclusions § Plant capacity for N uptake greater than diffusive flux in the range of 6 – 27 § Diffusive flux is the rate limi>ng step to plant N acquisi>on
- 17. Introduction P. I P. III P. IV ConclusionsP. II Can microdialysis be use to es9mate mass flow of N? Mass flow
- 18. Introduction P. I P. III P. IV ConclusionsP. II Dextran 40 caused mass flow of water into the microdialysis system
- 19. Introduction P. I P. III P. IV ConclusionsP. II Soil par>cles Soil water Dissolved compounds Microdialysis membrane Dextran + soil water + compounds 20 % (w/v) Dextran 40 solu>on Diffusion Mass flow Es9ma9on of diffusion and mass flow of soil N Mass flow + Diffusion
- 20. Introduction P. I P. III P. IV ConclusionsP. II Mass flow increased N fluxes in standard solu9on and soil Solu>on Soil
- 21. Conclusions Mass flow + Diffusion Diffusion § Using various osmo>c poten>als induced mass flow could be achieved § Mass flow has direct and indirect effects on plant N nutri>on § Transpira>on-induced mass flow may be a driver for N acquisi>on Introduction P. I P. III P. IV ConclusionsP. II Transpiration
- 22. Introduction P. I P. III P. IV ConclusionsP. II Field es9ma9on of mass flow and diffusion • Microdialysis was used to es>mate fluxes of organic and inorganic N Nutrient-poor Pine forest Nutrient-rich Spruce forest
- 23. Introduction P. I P. III P. IV ConclusionsP. II Mass flow increased flux rates of inorganic and total amino acids Nutrient-poor Pine forest soil Diffusion Diffusion + Mass flow Nutrient-rich Spruce forest soil Diffusion Diffusion + Mass flow
- 24. Introduction P. I P. III P. IV ConclusionsP. II Mass flow changes the composi9on of the N fluxes Scots pine forest soil Diffusion Diffusion + Mass flow NO3 - TotAA TotAA NO3 - NO3 - TotAA NO3 - TotAA Norway spruce forest soil Diffusion Diffusion + Mass flow
- 25. Introduction P. I P. III P. IV ConclusionsP. II Conclusions Results from microdialysis suggest that: • Mass flow increases total N flux and may play an important role in plant N acquisi>on • N flux composi>on changes with high propor>on of NO3 - Mass flow + Diffusion Diffusion Transpira>on
- 26. Introduction P. I P. III P. IV ConclusionsP. II Take Home Message § Microdialysis technique provides new insights to understanding intrinsic processes in plant N nutri>on § The induced diffusive flux of N could be the rate limi>ng step in plant N acquisi>on § Transpira>onally-induced mass flow may play an important role in plant N nutri>on
- 28. Introduction P. I P. III P. IV ConclusionsP. II 50 µM June September N-forms Control Fer>lized Control Fer>lized Arginine ∞ ∞ ∞ ∞ Glycine 14 12 63 31 NH4 + 27 6 290 40 NO3 - 16 6 16 0.3 Root uptake rates exceed induce diffusive flux rates
- 29. Introduction P. I P. III P. IV ConclusionsP. II Mass flow increased N supply to Dialysis probe in soil