RAPID SOIL MOISTURE RECHARGE TO DEPTH BY ROOTS IN A STAND OF ARTEMISIA TRIDENTATA

Abstract

The temporal patterns of soil water potential in a stand of Artemisia tridentata in central Utah, USA, were monitored during the summer, which included small periodic rainfall events, and over the winter, when most of the soil recharge occurs in this environment. The pattern of recharge, when compared to an area cleared of aboveground vegetation, strongly indicated that the downward movement of water to 1.5 m was primarily conducted via roots by the process known as hydraulic redistribution. Rainwater was moved rapidly downward shortly after the rain event and continued over a period of a few days. For rainwater reaching a 0.3–1.5 m depth, the portion redistributed by roots was estimated to range from 100% for small rainfall events (<8 mm) to 74% for a 36-mm event. Simulations with a model of soil water movement that compared situations with and without hydraulic redistribution by roots, indicated that during the fall–spring recharge period, 67% of all water moved downward below 0.1 m was via roots, while 87% of the water moved below 0.3 m was via roots. These results indicate that rapid downward movement of rainwater by roots can be a significant mechanism of soil water recharge to depth in arid and semiarid ecosystems. Corresponding Editor: F. C. Meinzer