Double funneling in a mature forest in coastal British Columbia: Where does stemflow water go?

Double funneling is the combination of the above ground process of stemflow initiation and the below ground infiltration of this water via macropores around tree roots. It affects soil moisture, nutrient dynamics, groundwater recharge, and plant water uptake. In this study, stemflow and soil moisture were measured and dye tracer experiments were conducted to better understand double funneling in a mature forest in coastal British Columbia, Canada. Stemflow accounted for 1% of gross incident precipitation and increased linearly with precipitation. Funneling ratios depended on tree size. Dye tracer experiments showed that stemflow infiltrated primarily along roots and was found more frequently at depth than at the soil surface. However, both stemflow and throughfall infiltrated to 6–14 cm above the bedrock. The side of the tree along which most of the stemflow flowed, influenced surface soil moisture dynamics around the tree.