CUAHSI CyberSeminar: Snowmelt processes in forests: Apparent paradoxes and implications for advancing hydrologic understanding in complex terrain
Presenter: Dr. Timothy E. Link - University of Idaho, Department of Forest, Rangeland, and Fire Sciences
In mountainous, forested environments, vegetation exerts a strong control on snowcover dynamics that in turn affect ecohydrological processes, streamflow regimes, and riparian health. Snowcover deposition and ablation patterns in forests are controlled by a complex combination of canopy interception processes coupled with radiative and turbulent heat flux dynamics related to topographic and canopy cover variations. Recent research has elucidated variations that can result in snowcover dynamics that run counter to conventional wisdom, but which are important for advancing the understanding of hydrological processes in complex terrain. In most seasonal snow environments, snowcover ablation dynamics in forests are dominated by net radiation. In discontinuous forests however, net radiation in forested areas may exceed radiation in open sites, whereas in other cases, net radiation may be less than in closed canopy forests. The low-radiation paradox most pronounced early in the winter, at high latitudes and on north-facing slopes due to low solar elevation angles relative to the ground. Physically-based simulations of snowpack dynamics indicate that desynchronization of snowmelt by approximately 3 weeks can occur between north and south facing discontinuous forests relative to continuous canopies, whereas timing differences are minimal between east and west facing slopes. These results indicate that forest thinning may be used to reduce snowmelt rates and/or alter melt synchronicity, but that the exact configuration will be highly spatially variable. This evolving line of research holds important implications for a wide range of disciplines including water resources management, fire hazard risk reduction, vegetation regeneration, forest entomology, soil processes and winter recreation.