1. Controls on Nitrogen Cycling in terrestrial ecosystems: A Synthetic Analysis of Literature Data
Mary S. Booth, John M. Stark, Edward Rastetter
Ecological Monographs, Vol. 75, No. 2 (May, 2005), pp

2. Nitrogen Cycle Nitrification Denitrification Aerobic NO2- NO3- Biomass
Assimilation
Dinitrogen
Fixation
Assimilation
NO3-
Biomass
NH3 , NH4+ N2
Mineralization
Mineralization
Anammox
Denitrification NO
N2O
NO2-
Anaerobic

3. Pool dilution approach
Labeled Product (e.g.: 15NO3-)
Biomass
Gross rate (e.g.:Nitrification)
Substrate
(e.g.: NH3)
Product
(e.g.: NO3-)
Consumption (E.g.: Assimilation, Denitrification)
Product2
(e.g.: NO2-)
3 assumptions:
No discrimination between different isotopes
Rates remain constant
No recycling of labeled product

4. Controls on NH4+ and NO3- production and consumption?
Differences in rates and relationships among various ecosystems?

5. Controls on mineralization

6. Controls on nitrification
Proportion of nitrified N from mineralized N decreases
(63% at 1mg, 28% at 5mg and 19% at 10mg)

7. Controls on uptake of inorganic N
Mineralization, Assimilation and extractable N pool of same magnitude turnover ~1 d
NO3- assimilation was higher in assays done with intact soil cores

8. Controls on uptake of inorganic N

9. Controls on uptake of inorganic N

10. Difference between various ecosystems

11. Summary Mineralization positively related to soil C and N
C:N ratio exerts a secondary negative influence
N mineralization covaries with N assimilation, Nitrification and extractable N
Nitrification strongly related to Mineralization
proportionally most important fate of NH4+ at low mineralization rates

12. Summary Turnover times of Inorganic N pools ~ 1 d
N mineralization higher in grassland than woodland soils at similar C conc.
Grassland soils with lower C:N ratio
N mineralization higher in deciduous than coniferous woodland soils at similar C conc.
Decidous woodland soils with lower C:N ratio

13. Conclusions SOM quality
C:N ratio as index
NH4+, NO3- rates and pools in quasi-equilibrium state with SOM concentration
Nitrifiers and heterotrophs in competition for NH4+ and space
Nitrifiers in C-depleted microsites
Units N per C liberated or serve as proxy for factors like recalcitrance (possibility for microbes to digest) (lignin content)
Higher soil C supports greater populations of heterotrophs which assimilate NH4+ to the detriment of Nitrifiers (folie 9)