Utility of Geochemical Normalization Model in Quantifying Significances of Physical Disturbances and Hydrological Processes in Soil Genesis.

Soil is an integral part of biogeochemical and hydrological systems. From biogeochemical and hydrological perspectives, soils and soil materials are often described as a physically immobile medium which water flows thorough and interacts with and organisms inhabit. However, many soils are exposed to recurring physical disturbances such as physical mixing and erosion, and this pedological observation is globally valid. For some soils under active disturbances, large part of soil formation may be understood through two simultaneously operating mechanisms: physical disturbances and hydrochemical processes. Significance of these two mechanisms in soil genesis can be effectively highlighted with geochemical normalization model. This approach can be described as a mass balance model in which losses and gains of elements of interest are quantified by normalizing their concentrations in soils and parent materials against a biogeochemically inert element such as zirconium. In this presentation, the normalization approach is applied to assessing biogeochemical effects of bioturbation along an earthworm invasion chronosequence in a deciduous forest in Northern Minnesota. Another example is drawn from an application to actively eroding hillslopes in SE Australia, where geochemical effects of climate-dependent erosion are assessed. Both model applications highlight the extents and mechanisms that soil geochemistry reflects both physical disturbances and hydrochemical processes. The results also show the important role of organisms in modulating and amplifying the pedological impacts of physical disturbances and hydrochemical processes. These successful applications present the geochemical normalization model as a highly effective tool to bridge soil science with the growing number of process-based land surface models.