Impact of Pore-Scale Wettability on Rhizosphere Rewetting

Titelangaben

Benard, Pascal ; Zarebanadkouki, Mohsen ; Carminati, Andrea:
Impact of Pore-Scale Wettability on Rhizosphere Rewetting.
In: Frontiers in Environmental Science. Bd. 6 (2018) . - 16.
ISSN 2296-665X
DOI: https://doi.org/10.3389/fenvs.2018.00016

Volltext

Link zum Volltext (externe URL):

Abstract

Vast amounts of water flow through a thin layer of soil around the roots, the rhizosphere,where high microbial activity takes place — an important hydrological and biologicalhotspot. The rhizosphere was shown to turn water repellent upon drying, which hasbeen interpreted as the effect of mucilage secreted by roots. The effects of suchrhizosphere water dynamics on plant and microbial activity are unclear. Furthermore,our understanding of the biophysical mechanisms controlling the rhizosphere waterrepellency remains largely speculative. Our hypothesis is that the key to describe theemergence of water repellency lies within the microscopic distribution of wettability onthe pore-scale. At a critical mucilage content, a sufficient fraction of pores is blocked andthe rhizosphere turns water repellent. Here we tested whether a percolation approach iscapable to predict the flow behavior near the critical mucilage content. The wettability ofglass beads and sand mixed with chia seed mucilage was quantified by measuring theinfiltration rate of water drops. Drop infiltration was simulated using a simple pore-networkmodel in which mucilage was distributed heterogeneously throughout the pore spacewith a preference for small pores. The model approach proved capable to capture thepercolation nature of the process, the sudden transition from wettable to water repellentand the high variability in infiltration rates near the percolation threshold. Our studyhighlights the importance of pore-scale distribution of mucilage in the emergent flowbehavior across the rhizosphere.