Abstract

PAZ PELLAT, Fernando; COVALEDA, Sarah  and  ETCHEVERS B., Jorge D.. Organic carbon distribution on different particle sizes of soil: simple linear kinetic model. Terra Latinoam [online]. 2014, vol.32, n.2, pp.127-142. ISSN 2395-8030.

Modeling soil organic carbon (SOC) dynamic can establish gains and losses associated with vegetation disturbance and management practices. In particular, the estimation of changes in carbon pools, labile and recalcitrant, without considering equilibrium states, raises the need for a distribution model of SOC in physical soil fractions (particle size) that can be parameterized with the information available on national inventories (total SOC and texture). This paper proposes a simplified model of SOC distribution, the product of mass balance between the fractions of soil carbon, which is seen as directly related to size of the particles and not to their mass distribution. The model was calibrated using a database of physical partitioning in Andosols , Cambisols and Acrisols in agricultural and forestry systems in Atécuaro, Michoacán, Mexico, considering only the SOC associated with organic part and total SOC (particulate + mineral). The distribution pattern of SOC by soil particle size was adjusted to experimental data. The model parts from known total SOC and SOC for a reference particle size, estimated experimentally or assumed. The results showed that, in the case of agricultural systems, the model fits well with the measurements (R2 > 0.999). In the case of forest systems, estimates are good (R2 > 0.97). Finally, implications of the developed model are reviewed; the classic concept of SOC saturation of the soil is questioned and explained in terms of the rates of decomposition and assimilation of the particulate and mineral fractions. Also, the relationships between soil texture and SOC associated to particle size is not supported, as texture (mass of soil fractions) is regarded as intrinsic to the relationship between SOC fraction of the soil by particle size and total SOC.

Keywords : physical fractionation; mass balance; SOC dynamic; meta-equilibrium.