• Effect of native prairie, crested wheatgrass (Agropyron cristatum (l.) Gaertn.) and Russian wildrye (Elymus junceus Fisch.) on soil chemical properties

      Dormaar, Johan F.; Naeth, M. Anne; Willms, Walter D.; Chanasyk, David S. (Society for Range Management, 1995-05-01)
      Crested wheatgrass and Russian wildrye are used estensively as seeded pastures in the prairie region of western Canada. Their long-term impact on soil quality was studied at 4 sites, each including plant communities of native mixed prairie rangeland and 17- to 27-year-old monocultures of crested wheatgrass and Russian wildrye, in southern Alberta, Canada. Root mass and soil chemical properties mere determined on the soil samples collected. Native rangeland had about 7.6 times more root mass than the seeded species from the 0- to 7.5cm depth and about equivalent mass from the 7.5 to 40-cm depth. For the seeded species, root mass was significantly less between rows than within rows. Soils in the native rangeland community had significantly greater soil organic matter and lower NOs-N, chemical index, urease activity, and available phosphorus than those in the seeded pastures. Altering the plant community from native mixed prairie to either a sequence of cropping followed by an introduced grass monoculture, or directly to an introduced grass monoculture, resulted in decreased root mass and organic matter, and monosaccharide content of dry aggregates. The seeded grasses could neither return nor maintain the chemical quality of the soils in relation to that of the native rangeland.
    • Grazing and soil carbon along a gradient of Alberta rangelands

      Henderson, Darcy C.; Ellert, Ben H.; Naeth, M. Anne (Society for Range Management, 2004-07-01)
      The regional scale response of soil carbon mass to long-term grazing exclusion was investigated in the Canadian Great Plains. Vegetation, litter, macro-organic matter and soil were sampled in paired grazed and ungrazed treatments from 9 independent locations along an environmental gradient in southern Alberta. Vegetation and litter carbon mass were greater on ungrazed treatments, but no consistent grazing effect was observed for macro-organic matter (roots, subsurface litter) or soil (fine particles 2mm) carbon mass per equivalent soil mass. Soil carbon in mixed grass prairie was positively correlated with clay content, but no grazing effect could be detected when this subset (n = 7) was analyzed by ANCOVA. Comparison of multiple sites with a consistent sampling and reporting method revealed no general trend in the response of soil carbon to grazing. Current range management practices to maintain range types in good to poor condition appear to be consistent with maintaining the soil organic matter pool in the northern Great Plains.
    • Quantification and simulation of soil water on grazed fescue watersheds

      Chanasyk, David S.; Mapfumo, Emmanuel; Willms, Walter D.; Naeth, M. Anne (Society for Range Management, 2004-03-01)
      A 2-year study was conducted at the Agriculture and Agri-Food Canada Stavely Range Substation, Alberta. The objective was to quantify and simulate the soil water status of small grassland watersheds under 3 grazing intensities and 4 topographic positions. The grazing treatments were ungrazed (or control), heavy (2.4 AUM ha-1) and very heavy (4.8 AUM ha-1) grazing and the topographic positions were upperslope, midslope, lowerslope and 5 m away from the collector drain. Moisture readings were taken every 2 weeks between spring and fall using a CPN 503 moisture neutron probe. Readings were taken at the soil surface and at 15-, 25-, 35-, 45- and 55-cm depths. Total annual precipitation in 1998 and 1999 was 648 and 399 mm, respectively. In both years grazing treatments did not affect total soil water in the 0-50 cm (TSW50) depth interval for the upper, middle and lower slope positions, but TSW50 close to the collector drain was significantly (P ≤ 0.05) greater for the heavy grazed compared to the very heavy grazed treatment. Within each grazing treatment, TSW50 differences among slope positions occurred mainly under the heavy grazed treatment. Simulation of soil water at each soil depth and watershed was conducted using the Versatile Soil Moisture Budget Model (VB2000). Statistical and graphical evaluations of the model results were conducted using the volumetric soil water data collected for 1998 and 1999. The statistics determined included average error (AE), root mean square (RMS), coefficient of residual mass (CRM), modeling efficiency (EF) and coefficient of determination (CD). All statistics varied with each soil depth and watershed, indicating the transient nature of the data. This is reflected in the mostly negative CRM values, which ranged between -1.0 and 0.16. Overall model fitting to the whole data for all depths, watersheds and years gave values of CRM = -0.08 and EF = 0.19, indicating a slight over-prediction by the model. Spatial variation due to presence of rocks or cracks and averaging across slopes may have partly contributed to the discrepancies between model results and observed data.