Influence of soil 3D architecture on soil organic matter stabilization as revealed by the combination of X-ray CT and biological approaches

Introduction

Soil organic matter (SOM) stabilization is strongly influenced by its availability to decomposers, which is related to its spatial location in the soil matrix. In order to investigate the three dimensional architecture of this matrix and its relationship with SOM stabilization I will use X-ray computed tomography (X-ray CT). This non-destructive imaging technique allows me to investigate the soil matrix at the smallest relevant scales. With the state-of-the-art scan equipment at the UGent Centre for X-ray Tomography (UGCT) we can make scans with a resolution of 0.3µm. As a consequence high quality scans can be obtained from which it is possible to make detailed 3D visualizations of the pore structure and the location of OM in the soil matrix.

fig1_peter.jpg

X-ray CT

Scanning of a soil sample results in a multitude of X-ray scans which are subsequently processed by a software program that generates cross-sectional gray scale images. The grey values are representations of the different X-ray attenuation coefficients, which are specific for each material in the soil sample and depend on their density and atomic number. Contrasts between these grey values strongly determines the degree to which we are able to distinguish soil organic matter (SOM) from pore space and soil mineral fraction.

fig2_peter.jpg

Objectives

A first objective of my PhD is to investigate the potential of certain heavy element staining agents to enhance the contrast of organic matter in X-ray CT scans. Because the binding selectivity to mineral particles is an important feature of an appropriate staining agent, different mineral soil fractions will be used.

In a second part of my PhD I will combine the X-ray CT technique, that has limited disturbance on soil microbial functioning, with soil incubation experiments. By using artificially created soil samples I will be able to investigate the interactive effect of soil pore structure and microbial community on SOM stabilization and degradation. This will provide new insights in the mechanisms that regulate the last mentioned processes.

 

Researcher: ir. Peter Maenhout
Period: 2013-2017
Financing body: FWO project
Promoter: Prof. Steven Sleutel and Prof. Stefaan De Neve