Soil micromorphology, by means of the description and analysis of soil thin sections, provides information about soil microstructure, which includes, among other features, morphological data on the aggregates and the porosity derived from structure formation. Soil porosity may be due to both abiotic factors and biological activity (biopores). The aim of this study is to validate a methodology for the quantification of bioporosity in thin sections of Luvic Phaeozems of Argentina, for its use as soil quality indicator. Soil samples were taken from the surface horizon in plots with different uses: reserve (R), agricultural (A), Eucalyptus globulus forest plantation (E), and Pinus radiata forest plantation (P). In each site, bulk density, penetration resistance, structural stability, organic matter, and pH were determined. Three undisturbed samples were taken, impregnated with resin, and treated using routine techniques to obtain soil thin sections. Volume percentages of total porosity and biopores were determined in the thin sections using two methodologies (I: irregular polygon on the outline of the biopore and II point counting), in order to obtain an estimation of the biological activity under the different land uses. Plots R, E, and P showed greater porosity and higher bioturbation compared to plot A. In addition, the percentage of biopores in soils of R, E, and P plots reaches almost 80% of the total porosity, while in soil of plot A plot, it is two times lower (40%). This indicates greater biological activity in the natural and forested plots as compared with the cultivated plot. This activity is linked to the high content of organic matter, high structural stability, low bulk density, and low penetration resistance. These results show that the estimation of the bioturbated volume would be a good indicator of soil quality and, in addition, the methodologies used in this study constitute an easy-to-use tool for the determination of bioporosity in soil. However, methodology II is preferred, because it requires a shorter time of image edition.
