Reduced water repellency of a grassland soil under elevated atmospheric CO2

Abstract Water repellency is a widespread characteristic of soils that can modify soil moisture content and distribution and is implicated in important processes such as aggregation and carbon sequestration. Repellency arises as a consequence of organic matter inputs; as elevated atmospheric CO 2 is known to modify such inputs, we tested the repellency of a grassland soil after 5 years of exposure to elevated CO 2 in a free air carbon dioxide enrichment experiment. Using a water droplet penetration time test, we found a significant reduction in repellency at elevated CO 2 in samples at field moisture content. As many of the processes potentially influenced by repellency have been shown to be modified at elevated CO 2 (e.g. soil aggregation, C sequestration, recruitment from seed), we suggest that further exploration of this phenomenon could enhance our understanding of CO 2 effects on ecosystem function. The mechanism responsible for the change in repellency has not been identified.