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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Modelling soil carbon balance at large scales

Jari Liski

Finnish Environment Institute, P.O. Box 140, 00251 Helsinki, Finland, e-mail: jari.liski@ymparisto.fi

It is often necessary to rely on models when estimating the carbon balance of soils at large geographical scales. Measurements may not be available for even the current balance because they are laborious to take. To estimate the balance in the future, models are the only option.

To be useful, the model-estimates must be reliable. Their reliability depends on, first, how realistically and comprehensively the models describe the processes and factors controlling the carbon balance and, second, how accurately the effects of the chosen processes and factors are quantified in the models. The first requirement calls for complex models whereas the second limits their usefulness as data available may be inadequate to determine the values of their numerous parameters. This is the dilemma between the complexity of models and possibilities to determine their parameter values in obtaining reliable estimates for the carbon balance of soils at large scales. A useful model contains the most important process and affecting factors which rates and effects are still possible quantify based on the data available.

What is an appropriate compromise between the complexity of a model and the possibility to determine its parameter values? A way to answer this queston is to validate the output of the model, both the whole model and its parts, against various measurements. How well this can be done depends on the availability of different measurements.

These two issues that affect the reliability of the model-calculated estimates for the carbon balance of soils at large scales, namely the complexity of models vs. the determination of their parameter values and possibilties to validate the results of the model, are discussed in this presentation with the help of examples.

 
   Päivitetty:   02.03.2006 / EKel Metla : Events   Palaute Metlan etusivulle
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