| Summary: | In this study, large scale rainfall simulation was used to evaluate runoff generation from canopy
and intercanopy areas within an ashe juniper woodland of the Edwards Plateau. One 3 x 12 m site was
established beneath the canopy of mature ashe juniper trees and two sites were established in intercanopy
areas. At the base of each plot a trench was constructed for capturing and monitoring shallow subsurface
flow. Rainfall simulations on the juniper site produced little surface runoff even though rainfall intensity
exceeded 145mm/hour on some occasions. A total of 82.6% of the water applied to the juniper dominated
site was accounted for as shallow subsurface flow. The dynamic nature of shallow subsurface flow
indicate this process is driven chiefly by macropore flow. On the intercanopy site, 12.67% of the water
left the site as surface runoff and ≤3% left as shallow subsurface flow. Large root channels and conduits,
which were not present on the intercanopy site, within the soil may promote shallow subsurface flow
beneath the juniper canopy. This study is the first to document and suggest shallow subsurface flow
occurs on Texas rangelands. The results of this experiment indicate shallow subsurface flow is an
important mode of runoff generation on the Edwards Plateau.
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