Effects of management on species dynamics of Canadian aspen parkland pastures

The effects of grazing, fertilizing, and seeding on persistence of herbaceo us species was monitored by point quadrat about every second year from 1975 to 1989 in a low-fertility pasture in the aspen parkland vegetation zone o f east-central Saskatchewan, Canada. Ground cover response to continuous gr azing was contrasted with that of 4- and 6-paddock rotationally-grazed area s fertilized in the fall of every other year with 90 kg N, 45 kg P2O5, 10 k g S ha(-1). The original vegetation in 2 paddocks of the 6-paddock system w as replaced with Russian wildrye (Psathyrostachys juncea (Fisch,) Nevski) i n 1976, and in 1 of the other 4 paddocks in turn with smooth brome (Bromus inermis Leyss.)-alfalfa (Medicago sativa L.) in 1979 and 1981, crested whea tgrass (Agropyron cristatum (L.) Gaertn.) in 1983, and a meadow brome (Brom us riparius Rehm.)-alfalfa mix in 1985. Initially, smooth brome and creepin g red fescue (Festuca rubra L.) dominated the vegetation with ground cover estimates of 10-20 % and 40-60 %, respectively. Alfalfa ground cover was le ss than 1%. With the changes in management, Kentucky bluegrass (Poa pratens is L,) replaced creeping red fescue. Alfalfa increased until 1980 and then declined to its original level, apparently in response to precipitation tre nds. Russian wildrye almost died out and was replaced by brome and Kentucky bluegrass. Reseeding with smooth bromegrass-alfalfa did not consistently i ncrease brome ground cover beyond that obtained by rotational grazing and f ertilization, and increased alfalfa only temporarily. Cultivation during th e summer before spring seeding resulted in partial recovery of the old vege tation and invasion by Kentucky bluegrass. Total ground cover varied from y ear to year in response to spring precipitation. Forbs usually increased af ter reseeding, but declined to their original levels within 5 years.