Quantitative characterization of soil micro-aggregates: New opportunities from sub-micron resolution synchrotron X-ray microtomography

• Main Authors: Voltolini, Marco, Taş, Neslihan, Wang, Shi, Brodie, Eoin L, Ajo-Franklin, Jonathan B
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2017
• Subjects: Environmental Sciences; Soil Sciences; Synchrotron X-ray microCT; Soil microaggregate; Quantitative image analysis; Modeling; Biological Sciences; Agricultural and Veterinary Sciences; Agronomy & Agriculture; Barrow; Alaska
• Online Access: https://escholarship.org/uc/item/58m8d2tm

Soil microaggregates are the fundamental building block, at the micron scale, of the highly hierarchical structure of soils, and can exert a significant control on the local biological metabolism and microbial community partitioning. In this study we propose an analysis protocol for the morphometric characterization of complete soil microaggregates based on sub-micron resolution synchrotron X-ray microtomography. A comprehensive characterization of the aggregate morphology is the first step towards a complete characterization of the soil microaggregates, when trying to correlate morphometric parameters with physical and/or biological properties, or when building models (e.g., effective diffusivity, microbial distribution, etc.). We demonstrate our characterization approach on two single microaggregate samples from dramatically different soil environments: one from Kansas, primarily composed by inorganic particles, and one from Barrow (Alaska) dominated by plant fragments. A series of state-of-the-art morphometric analysis techniques have been employed providing quantitative results highlighting specific differences of the two samples. The role of the microstructure in a scenario microbial population development has been discussed and it has been found that the Barrow microaggregate seems to be more favorable, from a purely geometrical point of view, as also confirmed by a simple model presented in this work. The potential of this approach, when coupled with chemical and biological analysis for a fully comprehensive characterization of soil aggregates in the larger picture of enhanced biological activity, is evident.