Modeling organic transformations by microorganisms of soils in six contrasting ecosystems: Validation of the MOMOS model

CDCHTULA (project C-765-95-01-B) and FONACIT (F-2002000424). We would like to thank Zulay Mendez for her technical assistance in the laboratory and Yann Martineau (SETEC International, F-13127 Vitrolles, France) and Klaas Metselaar (Soil Physics, Wageningen University, Netherlands) for the orientation in the modeling process. Amer geophysical union Washington

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Inglés. The Modeling Organic Transformations by Microorganisms of Soils (MOMOS) model simulates the growth, respiration, and mortality of soil microorganisms as main drivers of the mineralization and humification processes of organic substrates. Originally built and calibrated using data from two high-altitude sites, the model is now validated with data from a (14)C experiment carried out in six contrasting tropical ecosystems covering a large gradient of temperature, rainfall, vegetation, and soil types from 65 to 3968 m asl. MOMOS enabled prediction of a greater number of variables using a lower number of parameter values than for predictions previously published on this experiment. The measured (14)C mineralization and transfer into microbial biomass (MB) and humified compartments were accurately modeled using (1) temperature and moisture response functions to daily adjust the model responses to weather conditions and (2) optimization of only one parameter, the respiration rate k(resp) of soil microorganisms at optimal temperature and moisture. This validates the parameterization and hypotheses of the previous calibration experiment. Climate and microbial respiratory activity, related to soil properties, appear as the main factors that regulate the C cycle. The k(resp) rate was found to be negatively related to the fine textural fraction of soil and positively related to soil pH, allowing the proposition of two transfer functions that can be helpful to generalize MOMOS application at regional or global scale.