Tree traits and meteorological factors influencing the initiation and rate of stemflow from isolated deciduous trees

Tree canopy processes affect the volume and biogeochemistry of inputs to the hydrological cycle in cities. From June 2012 to November 2013, we studied stemflow production from 37 isolated deciduous park trees in a semi-arid climate dominated by small precipitation events. To clarify the effects of canopy traits on stemflow metrics, we analysed branch angles, bark relief (one component of roughness), tree size, canopy and wood cover fraction, median leaf size, and branch and leader counts. High branch angles contributed to stemflow production in both single-leader and multi-leader trees. While bark relief was negatively correlated with stemflow rates in multi-leader trees, it was positively correlated with rates for single-leader trees, possibly reflecting the conducive role of linear furrows once bark of single-leader trees is saturated. The association between numerous leaders, low stemflow initiation thresholds, and high rates deserves further study. Among meteorological variables, rain depth was strongly correlated with stemflow yields; rainfall inclination angle and wind speed were positively correlated with yields, while total intra-storm break duration and vapour pressure deficit were inversely related. For rain depths <3mm, greater stemflow was generally associated with leafless canopies. In support of integrated stormwater management, our results can inform climate-sensitive selection and siting of urban trees with traits that tend to either promote or minimize stemflow, depending on infiltration potential. Copyright (c) 2015 John Wiley & Sons, Ltd.