Environmental Monitoring and Assessment

, Volume 128, Issue 1–3, pp 121–131

Are Nitrogen-Fertilized Forest Soils Sinks or Sources of Carbon?



We developed a simple conceptual model that tracks nitrogen and carbon jointly through an N fertilized forest ecosystem. The stimulation of growth increases the litterfall and imports substrate for soil microorganisms. Microbial biomass forms according to the supply of C and N. The formation of microbial biomass is accompanied by respiratory C losses. The quantity of CO2 efflux depends on the C use efficiency of microbes. When excess N is available, the microbial activity is accelerated and the demand for substrate is high. Litterfall supplies an insufficient amount of C to the soil. In such a case, labile soil C is mineralized and the net effect of N fertilization is a loss of soil C. A strong N fertilization effect on the aboveground biomass can offset the soil C loss. In the case of a low N dosage or high N losses due to leaching or emission of nitrogen oxides, the soil C loss is small. The conceptual model was applied to a case study. The field data, collected over a time span of several decades, could not support sound conclusions on the temporal trend of soil C because the spatial and temporal variability of the chemical data was high. The conceptual model allowed to give an evaluation of the fertilization effect on soil C based on reproducible principles.


Forest soil Conceptual model C sequestration N fertilization 


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Copyright information

© Springer Science+Business Media B.V. 2006

Authors and Affiliations

  1. 1.Department of Wildland ResourcesUtah State UniversityLoganUSA
  2. 2.Federal Office and Training Center for Forests, Natural Hazards and Landscape (BFW)ViennaAustria

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