Perspectives from the Fritz-Scheffer Awardee 2020-The mutual interactions between roots and soil structure and how these affect rhizosphere processes

Roots growing into soil interact with soil structure in numerous ways. They can grow into the soil matrix and leave elongated macropores after decomposition, that is, biopores. Conversely, the soil may already have a large and connected macropore system through which the roots can expand, and thus reach deeper soil layers. Both, the formation of new biopores or the reuse and occupation of existing macropore systems are expected to affect major soil processes like water and gas flow through the soil profile, as well as water flow toward the root. Despite the increasing research interest in the limitation of root growth by soil structure, as well as the modification of soil structure by roots, the mutual interactions between the two are largely overlooked. This study highlights new methodological developments which enable describing interactions between roots and soil structure with X-ray computed microtomography. It further shows how roots affect the pore system and can create a massive biopore system in less than a decade. After this, it is evaluated how the mutual interaction of roots and structure determines the physical properties of the rhizosphere. It is outlined that this has implications for major rhizosphere processes. Thus, it is emphasized, that the role of structure needs to be considered in future experiments with plants, in particular if extrapolation of results from laboratory experiment with sieved, homogenized substrates to field conditions with well-established soil structure is intended. Lastly, in this study, research gaps are outlined remaining in respect to the dynamics of biopore creation and destruction and their consequences for processes in rhizospheres like carbon storage. These reveal the need for novel research approaches that consider the mutual interactions of root growth and soil structure.

Automated summary

Roots growing into soil interact with soil structure in various ways, affecting key soil processes like water and gas flow. Despite growing research interest in this interaction, there are still overlooked aspects which require further investigation.