Soil is a heterogeneous and structured environment that is characterised by variable geometry, composition and stability, across spatial scales spanning several orders of magnitude. The physical structure of solid and pore space results in a complex distribution of oxygen, water films and gradients of solutes spanning distances as small as a few micrometers, all of which have a profound effect on the ecological and hydrological functioning of soil.
The soil structure is determined by an interplay of physical, chemical and biological mechanisms, the quantitative role of which is still poorly understood. Soil structure is difficult to study as it is a 3D opaque matrix. To shed light into soil structure, the concept of aggregate has often been used and defines “pieces” of soil structure, that remain bounded under disrupting forces. Microaggregates (250µm) are larger soil units, composed by microaggregates and primary particles, bound together by biological agents, such as roots, fungal hyphae or even earthworm activity. Cutting edge imaging techniques are as well used to observe “in situ” associations of mineral and organic material at micro- and macro-scales and the resulting ever changing pore space, which is partly destroyed when focusing on aggregates, even though it has a fundamental role in soil ecology and functioning.

In this session we integrate the description of structure and its dynamics, using new imaging techniques, with the ecological, functional and physical consequences of the spatial arrangement of soil constituents. A strong interdisciplinary approach is thus required, merging soil physicists, chemists and ecologists. The ultimate aim is to understand how soil structure, from micro-architecture to macropores, emerges from interactions within soil and how it determines the outcome of soil processes, in order to create models of soil functioning that integrate structure dynamics.
This session is divided into two oral blocks, one focusing more on the micro-scale in relation to microbial activities and the other accounting for micro- and macro-scale in relation to soil ecology of larger organisms and soil functioning. Carsten Mueller is the solicited speaker of the first oral block and Matthias Rillig is solicited for the second oral block.