ABSTRACT: Scale issues in post-disturbance forest hydrology.

CGRG Bibliography of Canadian Geomorphology
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Abstract

In snow-dominated headwater basins of the Western Cordillera, forest canopy structure strongly affects snow processes at the ground surface. Observed increases in rates of forest change due to insect infestation and wildfire thus significantly alter snow accumulation and melt, and associated basin runoff. Field studies at the plot scale indicate that disturbed stands accumulate more snow and melt faster than undisturbed stands, due to a combination of decreased canopy interception, increased shortwave radiation transmittance, and decreased snow surface albedo as a result of increased forest litter production. Watershed scale field studies in undisturbed basins, however, suggest that topography dominates snow accumulation and melt, thus providing a first order control on snow processes that exceeds the role of vegetation. We combine field and modelling data with hydrologic theory to address this scale issue in the context of ecohydrology and hydrometeorology. Several key questions arise: Can we scale stand-level results up to the watershed scale to understand integrated basin hydrologic response to disturbance? Given a mosaic of post-disturbance stand types distributed across a watershed, will topography or vegetation dominate the snowmelt-driven hydrologic response of the basin? Does increasing heterogeneity in forest structure cancel out mass and energy balance variations between stand types at the watershed scale, reducing effects on basin outflow? By integrating results across research groups, we can begin to address these scale issues and assess their significance for post-disturbance runoff from snow-dominated basins

Bibliography of Canadian Geomorphology