Differential winter stemflow generation under contrasting storm conditions in a southern New England broad-leaved deciduous forest

Despite the importance of stemflow as a hydroecological process, differential winter stemflow generation among and within precipitation types (e.g. snow, rain-to-snow) is poorly understood. The purpose of the present study is to understand winter stemflow generation better under contrasting meteorological conditions in a leafless deciduous forest. It is hypothesized that stemflow volume and production, expressed as a funnelling ratio, will differ significantly among and within precipitation event types. Acceptance of this hypothesis would mean that intra-event meteorological conditions have a significant and discernible effect on stemflow production in deciduous forests, differentially affecting soil moisture, groundwater recharge, soil solution chemistry, and nutrient cycling. Stemflow volumes generated from seven canopy trees were monitored in a leafless deciduous forest of southern New England on a precipitation event basis over two successive winter seasons. Stemflow volume was found to differ significantly among different and same-type precipitation events. A rain event that occurred on 8 December 1998 and snow-to-rain event on 18 January 1999 were of similar duration, magnitude, and intensity,yet produced stemflow volumes that differed by a factor of 4. For two snow-to-rain events, stemflow volumes differed by a factor of 11. Stemflow production even varies widely within a discrete precipitation event as a function of meteorological conditions. Significant differential stemflow yield under contrasting storm conditions obviates generalizations concerning stemflow production as a function of precipitation event type and necessitates a deeper, process-level understanding of winter stemflow generation before modelling exercises are undertaken. Copyright (C) 2004 John Wiley Sons, Ltd.