Grazing Effects on Snow Accumulation on Rough Fescue Grasslands

Abstract

Snow accumulation is an important process that defines the hydrological characteristics of grasslands and is mediated by vegetation structure. Grazing also affects those processes, but its relationship to snow accumulation is poorly understood. We conducted a study in the rough fescue grasslands in southwestern Alberta (lat 50 degrees11ʹ30 degreesN, long 113 degrees53ʹ30 degreesW) to determine the effect of grazing pressure on snow accumulation and its relationship with selected meteorological variables. Snow accumulation (mass per unit area) was measured throughout the winter from 1998 to 2004 within each of 3 watersheds that had different historical grazing pressures (high, moderate, and zero). In a second study, we examined the effect of artificially created patch sizes (0.5-, 1.0-, and 1.5-m diameter) on snow accumulation from 1998 to 2000. The yearly average of the heavily and moderately grazed watersheds was about 42% and 20%, respectively, less snow than the ungrazed watershed. Of the meteorological variables we tested, only average daily temperatures, average daily maximum temperatures, and snowfall were influenced by the watershed. Snowfall was about half as effective in predicting snow accumulation in the heavily grazed watershed as in the moderately grazed or ungrazed watersheds. Patch size was generally not effective, except at single observations in both 1998 and 1999 when the 1.0-m diameter patch captured the most snow mass per unit area. The ungrazed grassland captured a similar amount to that captured in the cut patches. The study indicates that increased grazing intensity reduces the ability of grasslands to capture snow.