Stemflow and Soil Water Redistribution in Intact and Disturbed Plants of Larrea divaricata in Southern Argentina

Abstract

The interception of rainfall by the shrub canopy and its redistribution via stemflow to deep soil layers represents an important source of deep-soil-water. Therefore, reductions in stemflow caused by shrub canopy disturbance should be reflected in less moisture in the deeper layers of the soil. The objectives of this study were to determine (1) stemflow, (2) soil moisture next to the root crown at three depths (10–25 cm; 25–45 cm; 45–75 cm), and (3) predawn plant water potential in intact and sprout regrowth after mechanical clearing of Larrea divaricata in southern Argentina. Stemflow was collected and measured through funnels placed at the plant crowns. Soil moisture was measured by time-domain reflectometry and water potential with a pressure chamber. Stemflow was lower (P ≤ 0.01) in disturbed (3.6% precipitation) than in intact (7.2% precipitation) plants. Soil moisture next to the plant crown was similar or lower (P ≤ 0.05) in disturbed compared to intact plants, particularly at deep soil layers. Variations of predawn water potential in intact plants were accounted for (P ≤ 0.05) by variations in soil water content at the 45–75 cm depth, whereas variations of predawn water potential in disturbed plants were accounted for (P ≤ 0.05) by variations in soil water content at both the 45–75 cm depth and 10–25 cm soil depth. Sprouts of L. divaricata after mechanical clearing showed reduced stemflow, similar or lower soil moisture next to the root crown at different soil depths, and stronger association of predawn water potential with shallow water, compared to intact plants of the same species.