Soil Water Repellency in Natural and Semi-Natural Habitats: A Nexus Between Abiotic Factors and Prokaryotic Communities

Soil water repellency (SWR) significantly impacts water infiltration and soil health, influencing ecological processes across various habitats. Although the mechanisms behind SWR remain partially unclear, it is influenced by both soil and biological properties. While several studies have examined SWR in agricultural soils, fewer studies have focused on natural habitats. This study examines the relationships between soil properties (electrical conductivity (EC), pH, and total carbon (TC)), prokaryotic communities, and potential SWR (measured by the molarity of ethanol droplet test, 60°C pretreatment) in 1153 soil samples spanning 33 habitat types across Denmark. Using path model analysis, we show that both biotic and abiotic factors contribute significantly to SWR. A model including pH, EC, TC, and prokaryotic community composition (β-diversity) could explain ~50% of the variation in SWR, with β-diversity and TC being the most important properties. Furthermore, we reveal distinct variations in SWR across habitat types, which cover a wide range of SWR, from not water repellent to strongly water repellent. Prokaryotic α-diversity was negatively correlated to the degree of SWR, and we found a clear gradient in β-diversity from the highest to the lowest degree of SWR. The degree of SWR was divided into five classes, and we identified 69 genera indicating one or a combination of the SWR classes, which could potentially be used as indicators of the degree of SWR. This research underscores the importance of including the microbial communities in studies examining SWR. In perspective, the observed relations between SWR and soil prokaryotic diversity and community composition also imply that SWR could become a key biophysical indicator of soil health.