No abstract

their construction, to a stable range condition, took from 14 years in the lightly grazed field to more than the length of the study in the A study was conducted to examine the effects of 4 stocking rates on the vegetation in a Rough Fescue Grassland vegetation in southwestern Alberta. Stocking at a light rate (1.2 AUM/ha) for 32 very heavily grazed field. The duration required for recovery was years did not affect range condition. However, a modest increase in stocking rate (1.6 AUM/ha) led to a marked decline in range related to the original range condition of the exclosures. condition. This was associated with a change in the composition of rough fescue from 38 to 21% of basal area. Rough fescue (FestzCQ ScQbreflQ) was nearly eliminated with a stocking rate of 2.4 AUM/ha. Rough fescue was repiaced by Parry oat grass (DQnthoni~ parryi) which increased from 24% at 1.2 AUM/ha to 48% at 2.4 AUM/ha. However, stocking at 4.8 AUM/ha resulted in severe deterioration of the grassland. This required annual adjustment of the stocking rate to avoid animal losses. The recommended stocking rate for good condition range in the area is 1.6 AUM/ha. Recovery of the vegetation within the exclosures, from the time of setting stocking rates. The stocking rate, expressed in this paper as animal unit months per hectare (AUM/ ha), defines the relative quantity of forage that will be harvested during the grazing period in a given year. The effect of increasing the stocking rate is to increase the proportion of forage utilized, which may lead to changes in species composition of grasslands (Ellison 1960). The species that increase because of an increased stocking rate are often subdominants in the plant community and are potentially less productive than the dominant species (Looman 1969). The purpose of this study was to examine the changes that occur in species composition of a Rough Fescue Grassland as a result of stocking with cattle at different rates. The work described is part of a final assessment of the study which was reported earlier (Johnston 1961, Peake and Johnston 1965). The Rough Fescue Grasslands (Festuca scabrella)t in western Canada are managed primarily for grazing by cattle. They are found on highly productive soils, but cultural practices are limited by steep terrain. Consequently, management of grassland vegetation is through management of grazing by cattle. This is normally accomplished using a continuous grazing system where the cattle are turned onto the range in spring and removed in autumn. The most critical management decision made, with this system, is in ing in elevation from 1,280 to 1,420 met&above sea level (Fig. i). Average precipitation at the substation, over a 30-year period from April to August, was 35 I mm. Average precipitation from April to Site Description August at 2 similar areas within 65 km (Pincher Creek and Pekisko) was 353 mm while the annual precipitation averaged 614 The study area was at the Agriculture Canada Research Substamm over the same 30-year period. Annual precipitation data a...

Highlight Very heavy grazing of fescue grassland range at Stavely, Alberta, compared to light grazing, changed the color of the Ah horizon from black to dark brown and the pH from 5.7 to 6.2, reduced the percent organic matter, reduced percent total P but increased NaHCOs-soluble P, and increased soil temperature but decreased percent soil moisture. Trends indicated that soil of the very heavily grazed field was being transformed to a soil characteristic of a drier microclimate. The importance of soil as a reservoir elf nutrients and moisture for the production of forage has been recognized since the beginning of range management as a science (Klemmedson, 1970). With the development of the range conditioa metho,d of range analysis (Dyksterhuis, 1949; Smoliak et al., 1969), soil became an object of study in terms of soil-plant relations, its potential to produce a vegetative crop, and its resistance to damage. But, in the Fescue Grassland ranges of western Canada, there is still a dearth of soil infolrmation for use in management planning and in the improving or rehabilitating of deteriorated or brush-infested ranges. The purpose of our study was to determine the nature of edaphic change resulting from the grazing of fescue grassland range by cattle.

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The effects of grazing on Stipa-Bouteloua prairie soils in Alberta were evaluated after 19 years of continuous summer use by sheep at three stocking intensities. Analysis of the soils under the heavy grazing treatment showed lower values for pH and percent spring moisture but higher values for total carbon (C), alcohol/b enzene-extractable C, alkaline-soluble C, polysaccharides, and belowground plant material than the soil under light or no grazing. The results were attributed to changes in amounts and kinds of roots due to species changes caused by grazing and to increased amounts of manure deposited by sheep on fields grazed at a higher intensity. Shallow-rooted species replaced the deeperrooted ones on the drier environment induced by heavy grazing. Materials and Methods The study site was at the Canada Department of Agriculture Research Substation, Manyberries, Alberta, where the vegetation is that l

cootiouous stockiog usu8Ily leads to the fonlutioo of grued patclkea. However, the effect of p&bee 00 the grazelMd c0mmunity is related to their stability. Therefore, we ztudied the spatial stability of grazed pat&e oo Rough Fezcue Gramlande by map ping forage remov8l clmuee 00 10 site8 over 8 Cyeu period, tezting stability uzing the Kappa index (H), and characterizing the soila and vegetatioo of overgrazed and undergrazed patches. Spotlal stability of grazed patches between comecutivc yeam wm good (lEO.26) oo &en experieming low grazing prwsure. However, oo dtea having high grazing preezure, spatial stability waz Iese comizteot between comecutive yeuz (DKSO.45) ud low over 8 Cyeu period (K10.10). Overgrazed patches were dominated by graziogresistant zeral speck, but undergrazed patcher were dominated by climu species. Rough feecue (%cstuco SC&&~ 8nd P8rry oat grazs @u&to& porryi) plantz were 50% shorter, and forage production waz about 35% lees, on overgrazed than on undergrazed patches. Soil organic matter, carbohydratea, and depth of Ah horizon were zignificantly greater oo undergrazed patches but ureaze activity, NO& NH,, and available phosphorus were greater oo overgrazed patchez. Overgrazed and undagrazed patches were stable in the long term, although patch bouodariez fluctu8ted.

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The effects of animal impact on soil chemical and physical properties as well as range condition were measured over a 5-year period to test tbc bypotbesls that animal impact can improve the nutrient and water status of the soil and promote grassland succeadon. A seventeen-pasture short-duration graxing system was establlsbed in 1981 on 972 ba. The pastures were stocked on average wltb 278 cows wltb calves from 1982 to 1986, wbicb was about twice to triple tbe recommended rate of 0.8 AUM/ba. Increased grazing pressure reduced range condition as reflected by a loss of de&able species such as rougb fescue (Festuccr scubrelkh Torr.). Soil molsture was always bigber in soils of ungrazed exclosures. Soli bulk density increased wblle hydraulic conductivity decreased with grazing. Litter was not signlflcantiy incorporated into the soll with hoof action. Cbltln-N, as a measure of fungrl biomass, decreased significantly under tbe increased grazing pressure. Tbe bypotbesis that animal impact would improve range condition was rejected since impact, in tbe manner applled during tbe study, resulted ln retrogression of the grasslands.