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Conference paper, 2006

Modeling soil C storage of forest soils for different N fertilization and deposition levels

Gärdenäs, Annemieke; Eckersten, Henrik

Abstract

The long-term effects of N fertilization and N deposition on the carbon and nitrogen balances of forest stands in Sweden were studied (Gärdenäs et al. 2003; Gärdenäs & Eckersten 2006). Fluxes of carbon and nitrogen were dynamically coupled with the SOILN model (Eckersten et al. 1998) and calculated as a function of water and heat fluxes, which in their turn were simulated with the CoupModel (Jansson & Karlberg, 2001). Three main forested vegetation zones in Sweden (pine in northern and central Sweden, and spruce in southern Sweden) were represented with their own climate, soil type, stem production and N deposition level. The simulations were done for a whole forest rotation period (75-100 years). The tested N deposition levels were 50 %, 100 % and 150 % of the level in 1996 for each region. A single N fertilization dose was set to 150 kg/ha. The maximum total fertilization for each region followed the fertilization recommendations by the National Board of Forestry Sweden with 0, 300 and 600 kg N per ha and rotation period for southern, central and northern Sweden, respectively. The uptake of organic N by the plant (presumably by symbiosis with mycorrhiza) was shown to be essential to simulate biomass production and plant N content of the same magnitude as that found in the literature. We found that soil C sequestration increased most with N deposition level in central Sweden. Increasing deposition level enhanced plant growth and N demand to such a degree that uptake of organic N was also stimulated. The uptake of organic N caused less soil respiration than uptake of mineral N and had a positive feedback on C sequestration (see also Aber et al. 1998; Beier et al., 2001). The effect of N fertilization on soil C sequestration depended on the N deposition level. We conclude that C sequestration is, in a complex way, sensitive to N addition rate, plant growth and climatic conditions. These relationships need to be considered in assessments of climate and management (change) impacts on soil C sequestration

Keywords

Modelling; carbon; nitrogen; forest ecosystems; climate; climate change; organic N uptake

Published in

Title: Workshop 'Development of models and forest soil surveys for monitoring of soil carbon' Abstracts
Publisher: METLA, Finland

Conference

Development of models and forest soil surveys for monitoring of soil carbon’