Modelling of Soil Organic Carbon Dynamics in Grassland and Agricultural Ecosystems in Ukraine.

For the better understanding of the dynamics of soil organic matter (SOM) in the natural grassland and agricultural ecosystem, a simple process-based model is proposed and validated using the values of whole soil respiration (WR) and the microbial soil respiration (MR) measured in Chernozem and Kastanozem soils in Ukraine. Measured input values for the validation were light fraction C (LFC), clay content and plant biomass including shoot and root biomass, daily soil temperature and volumetric water content at 15 cm depth and daily air temperature and precipitation. As an influx of C to the soils, NPP was calculated by Chikugo model using annual temperature and precipitation. For the measured whole soil respiration rate, estimated WR value without root respiration showed close fitting under the drier conditions, probably because of the restricted root respiration. Under the wetter conditions, c.a. 50% of the WR would be attributed to root respiration. For the measured microbial respiration rate, the model estimation fitted well with measured values. These results suggested that the proposed model successfully simulated the decomposition processes in the natural grassland and agricultural ecosystems.