Browsing Journal of Range Management, Volume 44, Number 1 (January 1991) by Subjects
Now showing items 1-4 of 4
Applicability of the Kostiakov equation to mixed prairie and fescue grasslands of AlbertaThe Kostiakov equation is of interest in rangeland hydrology because it is a simple 2 parameter equation with values of constants easy to determine from measured infiltration data, and because of its reasonable fit to infiltration data for many soils over short time periods. There is, however, some controversy in the literature regarding its applicability to rangelands. The Kostiakov infiltration equation was examined to determine its suitability to characterize infiltration on mixed prairie and fescue grassland ecosystems in Alberta, Canada. The infiltration data from double ring infiltrometers fit the Kostiakov equation very well. Of 26 regressions, 10 had an R2 over 0.95 while another 8 had an R2 over 0.90. The average R2 for all data at a site was 0.931 for mixed prairie, 0.857 for parkland fescue, and 0.938 for foothills fescue grassland. Changes in antecedent soil water and different grazing regimes altered the 2 equation parameters. Intercepts consistently declined with intensity and earliness in the growing season of grazing, although there were no consistent treatment trends with grazing. The Kostiakov equation is considered a good equation for infiltration in the 3 grassland ecosystems studied. Although parameter m had a narrow range of values for all 3 ecosystems and an average value from this study could be used, parameter a limits the equation and field testing is required for its determination.
Cutting frequency and cutting height effects on rough fescue and parry oat grass yieldsA study was made in the Rough Fescue Grasslands of southwestern Alberta to determine the yield response of rough fescue (Festuca scabrella var campestris Rydb.) and Parry oat grass (Danthonia parryi Scribn.) to 5 cutting frequencies and 3 heights over a 1-year period. The same plants were cut either 1, 2, 4, 8, or 16 times over a 16-week period beginning in mid-May, at 16-, 8-, 4-, 2-, or 1-week intervals, respectively, and at heights of either 5, 10, or 15 cm above ground level. Yield response to cutting treatments differed significantly from the flrst to the third treatment year. In the first year, rough fescue and Parry oat grass produced most forage when cut at a height of 5 cm with 1, 2, or 4 cuts. By the third year, rough fescue produced the greatest yields with a single cut after 16 weeks and Parry oat grass produced the greatest yields when cut at 10 or 15 cm at 1-week intervals. The data confirm the high sensitivity of rough fescue to grazing while the plant is growing and suggest that the greatest benefit from the Rough Fescue Grasslands may be derived by grazing in fall or winter. Summer grazing favors Parry oatgrass, which is more tolerant than rough fescue, but forage production on the grassland is reduced.
Grazing impacts on litter and soil organic matter in mixed prairie and fescue grassland ecosystems of AlbertaImpacts of long-term cattle grazing on litter and soil organic matter were assessed in mixed prairie, parkland fescue, and foothills fescue grasslands of Alberta, Canada. Grazing regimes were of light to very heavy intensities, grazed early, late, and continuously during the growing season. Litter and soil organic matter were sampled in 0.1-m2 quadrats and removed as live vegetation, standing litter, fallen litter, and soil organic matter. Litter and organic matter samples were air dried and sorted by size using sieves and an automatic sieve shaker. Organic carbon content was determined by thermal oxidation. Ground cover was determined using point frames, and heights of standing litter and fallen litter were measured. Heavy intensity and/or early season grazing had greater negative impacts on litter and soil organic matter than did light intensity and/or late season grazing. Under the former regimes there were significant reductions in heights of standing and fallen litter, decreases in live vegetative cover and organic matter mass, and increases in bare ground. More large particle-sized organic matter, particularly standing litter, occurred in controls than in grazed treatments since it would not be removed or trampled by grazing animals. More medium and small particle-sized organic matter occurred in grazed treatments than in ungrazed controls since vegetation likely decomposed more rapidly when it was trampled and broken down as animals grazed.
Water holding capacity of litter and soil organic matter in mixed prairie and fescue grassland ecosystems of AlbertaLitter and organic matter accumulations can reduce soil water through interception of precipitation and subsequent evaporation of absorbed water. Interception varies with mass and water holding capacity (WHC) of litter and organic matter, and is highest from small precipitation events. WHC varies with vegetation type, which is affected by grazing regime. Thus long-term grazing could affect WHC of litter and organic matter and would be important in the hydrologic assessment of rangelands subjected to many small precipitation events throughout the growing season. The study was conducted in mixed prairie, parkland fescue, and foothills fescue grasslands in Alberta, Canada. Grazing regimes were of light to very heavy intensities, grazed early, late, and continuously during the growing season. Litter and organic matter were sorted by sieving into various sized categories. Litter-soil cores were also evaluated. WHC of litter and organic matter was lower in mixed prairie than in fescue grasslands. WHC increased with increazed particle size, being higher for roots and standing and fallen litter than for organic matter. WHC of large particle-sized material decreased with heavy intensity and/or early season grazing. WHC was affected more by intensity than season of grazing. Grazing affected WHC through species composition changes, since species have different WHC, and through trampling which affected particle size. It was concluded that litter and organic matter WHC were important in rangeland hydrologic assessments.