SEASONAL-CHANGES OF HERBAGE BIOMASS ON THE FESCUE PRAIRIE

Knowing the amount of herbage on rangeland is basic to management deci sions related to livestock grazing. However, the amount of herbage ava ilable for grazing changes seasonally. Therefore, changes in herbage b iomass were examined in different communities of the fescue prairie. T he study was conducted at 2 sites in southwestern Alberta. In the Porc upine Hills near Stavely, changes in herbage biomass components were e xamined in 3 communities: rough fescue (Festuca campestris Rydb.), Par ry oat grass (Danthonia parryi Scribn.)-Kentucky bluegrass (Pea praten sis L.), and Kentucky bluegrass-sedge (Carex spp.) by sampling at mont hly intervals from April or May to late September. Observed trends amo ng the rough fescue, Parry oat-grass-Kentucky bluegrass, and Kentucky bluegrass-sedge communities were, for peak current year's standing pro duction, 398, 305, and 226 g m(-2), respectively; for spring current y ear's standing production as a percent of its peak, 73, 50, and 35%, r espectively; and for percent losses of total herbage biomass, from fal l to spring, 24, 43, and 56%, respectively. In the foothills near Pinc her Creek, the standing crop of grasses and forbs was sampled using pa ired subplots. One subplot was harvested in October and the other in A pril. Dry matter losses over winter averaged 27 and 58% for grasses an d forbs, respectively. Of the 3 communities examined, production on th e rough fescue community was the greatest, least dependent on precipit ation during the growing season, and least susceptible to weathering l osses and, therefore, had the greatest forage values. The Kentucky blu egrass-sedge community had the lowest forage values.