International workshop on

  
Koli (c) Metla/Erkki Oksanen

Development of Models and Forest Soil Surveys for Monitoring of Soil Carbon

April 5-8, 2006 at Koli, Finland
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Soil carbon modelling applied for nation-wide forest carbon inventory

Raisa Mäkipää1 , Mikko Peltoniemi, Aleksi Lehtonen, Petteri Muukkonen, Taru Palosuo, Jari Liski

1 Finnish Forest Research Institute (Metla), e-mail: Raisa.Makipaa@metla.fi

Forest carbon sinks were included in the Kyoto Protocol, since they contribute notably to the global GHG budget. The use of C sinks for compensation of emission reductions have created a timely need for more reliable forest C monitoring systems. Reporting of the C sinks should cover all pools including soil C. Methods to assess the changes in soil C stock are still under discussion, even in the countries with extensive soil surveys. Heterogeneity of forest soil together with small expected changes, may lead to costly and time consuming sampling scenarios in large-scale inventories. Therefore, many countries have to find means other than direct soil measurements to fulfill the reporting requirements under the Climate Convention.

Our objective was to develop a method to assess the changes in the C stock of forest vegetation and soil that can be applied in various regions across the temperate and boreal zones. The method integrates information provided by forest inventories, models of biomass allometry and biomass turnover, and dynamic soil C model Yasso (Liski et al. 2005, Lehtonen 2005). The soil model estimates the C content of litter and soil down to 1 meter, which was the depth used in its parameterization. Yasso is based on a conception that chemical compounds existing in litter determine the rate that the litter decomposes. This process has been parameterized and tested only for mineral soils with no peat cover (Liski et al 2005), and other models are therefore needed for the GHG fluxes of peatlands.

This method was applied for Finland where the C budget of the forests over an 80-year period was calculated (Metsätilastollinen 2004, Lehtonen 2005, Liski et al 2006). Forest vegetation and soil had a tendency of increasing C stock over this study period from 1922 to 2004. However, the C sink was highly variable between years depending on climate and the level of harvesting. The estimated changes in soil C were often opposite to those in biomass, which underlines the need of full accounting of C pools of forests.

In addition to component-wise tests of validity of the applied models on allometry of trees, biomass turnover and soil dynamics, this modeling approach as a whole was tested with empirical data from Southern Finland (Peltoniemi et al 2004). Furthermore, the overall uncertainty of the modelled C sinks in vegetation and soil were simulated with Monte Carlo approach (Peltoniemi et al. submitted ms). For the soil C stock change assessment the major source of uncertainty was soil model initialization, but this uncertainty decreases with time elapsed since model initialization. Thereafter, most important factors causing uncertainty were related to decomposition temperature, harvest residues, net forest area change, and soil model parameterization. In many countries soil C monitoring will rely on other methods than direct measurements of repeated soil surveys. Here we demonstrated that the preliminary estimates of soil C sink/source can be provided by modeling. Furthermore, the modeling approach can guide in stratification of the soil sampling when nation-wide soil surveys are conducted.

  • Lehtonen, A. 2005. Carbon stocks and flows in forest ecosystems based on forest inventory data. Dissertationes Forestales 11. 51 p.
  • Liski, J., Palosuo, T., Peltoniemi, M. & Sievänen, R. 2005. Carbon and decomposition model Yasso for forest soils. Ecological Modelling 189: 168-182.
  • Liski, J., Lehtonen, A., Palosuo, T., Peltoniemi, M., Eggers, T., Muukkonen, P. & Mäkipää, R. 2006. Carbon sink of the Finnish forests 1922-2002 estimated by combining forest inventory data with modelling of biomass, litter and soil. Submitted manuscript.
  • Metsätilastollinen vuosikirja 2004. Metsäntutkimuslaitos, Vammalan kirjapaino, 415 p.
  • Peltoniemi, M., Mäkipää, R., Liski, J. & Tamminen, P. 2004. Changes in soil carbon with stand age – an evaluation of a modeling method with empirical data. Global Change Biology 10: 2078-2091.
 
   Päivitetty:   02.03.2006 / EKel Metla : Events   Palaute Metlan etusivulle
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