Flow Pathways of Throughfall and Stemflow Through the Subsurface

Net precipitation recharges soil- and groundwater beneath vegetation canopies and litter layers. Interactions between subsurface water and net precipitation fluxes differ, however, as there are multiple types of net precipitation: free throughfall (rain that passes through canopy gaps), throughfall, and stemflow (rain that drains down plant stems). Rates and infiltration areas for these different hydrologic fluxes interact with soil properties to result in complex wetting fronts, preferential flow paths along roots and through macropores, and localized soil water recharge. How far net precipitation travels through the subsurface and whether it contributes to streamflow or groundwater recharge is reviewed in this chapter. Past and current methods for monitoring throughfall and stemflow infiltration patterns are reviewed, and a critical synthesis is provided for our understanding of subsurface–precipitation interactions to date.