SHOOT POPULATION-DYNAMICS OF BEAKED SEDGE FOLLOWING CATTLE GRAZING

We studied the effect of cattle grazing on shoot density and flux in 4 southwest Montana beaked sedge (Carex rostrata ex With.) stands for 2 years. Forty plots were protected and 40 plots were grazed by cattle in June and September of 1989 and 1990. The effect of grazing vs. no grazing on mean shoot density and emergence varied over time (treatment by time interaction P < 0.001 and P = 0.003, respectively). About 90% of the time by treatment interaction for shoot density occurred from September 1989 through July 1990. Mean shoot density increased more in grazed plots than in ungrazed plots in spring 1990, and remained 12-16% higher during the last 6 months of the study. Mean shoot emergence was 20% greater (P = 0.006) in the grazed than in the ungrazed plots, with the greatest monthly differences occurring after 3 of the 4 grazing treatments. Mean shoot height declined similarly from June 1989 to June 1990 in the grazed and ungrazed plots (6 and 5%, respectively), indicating that productivity per shoot was similar between treatments. Beaked sedge in our study site was tolerant of light to moderate grazing, given adequate regrowth between spring and fall treatments.