Modelling of Soil Organic Matter and Elements of Soil Nutrition Dynamics in Mineral and Organic Forest Soils: the ROMUL Model Expansion

Soil organic matter (SOM) dynamics is an important pool in biological turnover of carbon and other elements of plants nutrition in forest ecosystems. Problems at its modelling are: quantification of SOM fractions which are decomposing with specific rates; description of humification, obtaining dependencies of SOM rates of transformation in dependence on external factors. Different methods of fractionating of SOM are now in use based on different solubility of fractions/ This approach presents difficulties at model's initialization. We expanded a model of SOM dynamics ROMUL based on successive stages of mineralization and transformation of fresh litter, which correspond to SOM pools in horizons L, F and H of forest floor. A1 et al. are horizons in mineral soil. Rates of transformation of one SOM pool into another in these horizons can be obtained from experimental data. The dynamics of N, Ca and Mg is described using main equations of SOM transformations with inserting of additional constants or functions as independent multipliers for rates of transformation. Pools of elements available for plants nutrition, and some intermediate pools such as secondary soil minerals have been added to the model. New ROMUL has been successfully applied to ICP Forest plots in Russia.