Alberta's Prairie Vegetation: Past and Present Use Brian D

56 RANGELANDS16(2), April 1994

Dempsey, Hugh A. 1952. Historic sites of Alberta. An Alberta Jameson,Sheila 5. 1987. Ranches, cowboys, and characters: Birth GovernmentPublication. ofAlberta's westernheritage. GlenbowMuseum, Calgary, Alberta. Dempsey, Hugh A. 1966. Jerry Potts, plainsman. 0cc. Pap. No. 2. Kelly, L.V. 1913. The Range Men. Willow Creek PubI., High River, Glenbow Museum,Calgary, Alberta. Alberta. Hamilton, Jacques. 1971. Our Alberta heritage series: Places. Cal- MacEwan,Grant. 1973. Sitting Bull, the Years in Canada. Hurtig gary Power Ltd., Calgary, Alberta. Publishers, Edmonton,Alberta. lndorwlck, Mary E. 1883. A lady and her ranch. In: The best from MacEwan,Grant. 1975. Blazing the Old Cattle Trail.Western Pro- Alberta history. 1981. H.A. Dempsey, Ed.Western Producer Prairie ducer PrairieBooks, Saskatoon,Saskatchewan. Books.Saskatoon, Saskatchewan.

Alberta's Prairie Vegetation: Past and Present Use Brian D. Olson

Alberta's prairie vegetation has gone through many changes. Glaciation, fire, climate, and bison grazing played important roles in its development before Euro- pean settlement. Since European settlement, fire suppression, domesticcrop production,and the elimination of migratory bison herds have altered Alberta's prairie ecology and changedmuch of the vegetation. Vegetational Changes since Glaciation During Alberta's early history after the last glaciation, coniferous forests dominated the landscape. Even the semiarid grasslands present in southern Alberta today were dominated by coniferous forest. After the glaciers fully retreated, dry weather along with natural wildfire created grasslands and expanded them northward. The amount of grassland expansion that occurred is uncer- tain. Some postulate that the grasslands of the Peace River region in northwestern Albertajoined upwith those in centralAlberta. Thesegrasslands are currentlysepar- ated by nearly 100 miles of borealforest. As the dryperiod became less harsh, forests began invading back into the grasslands until the present equilibriumwas reached. Present Vegetation With the present equilibrium, six vegetation regions occur on Alberta's prairies (Figures 1 to 6). They are the Dry Mixed Grass Prairie, the Mixed Grass Prairie, the Fescue Prairie,the Aspen Parkland, the Montane, and the Low Boreal Mixedwood. The Dry MixedGrass Prairie is a Figure 1. Vegetation Regions Needle-Grama Grass complex of Stipa comata, S. spar- on Alberta's Prairies: tea, and Bouteloua The Mixed Grass Prairie is a 1.Dry Mixed Grass Prairie; grad/is. 2.Mixed Grass Prairie; Needle-Wheat Grass complex of Stipa viridula, S. spar- 3.Montane; 4.Fescue Prairie; S. and A. smith/i. 5.Aspen Parkiand; tea, comata, Agropyrori dasystachyum, 6.Low Boreal Mixedwood Rough Fescue (Festuca scabrella)-Parry Oat Grass (Dan- (Strong & Leggat 1992) thonia parryi) grasslands dominatethe Fescue Prairie. Mountains The Aspen Parkland is a combinationof Rough Fescue grasslands on uplandsites and Trembling Aspen (Popu- lus tremuloides) clones on moist sites. The dominant forests. sites in the Montane are in the Montane is a combinationof ziesii) Dry occupiedby vegetation Lodgepole Fescue or June (Koeleriamacrantha) and men- Rough grass grass- pine (Pinuscontorta) Douglas-fir(Pseudotsuga lands, while moist sites are occupied by Balsam poplar Author is a rangeland manager/ecologistfor the Alberta Department of (Populus balsamifera) or Willow (Salix spp.). Trembling EnvironmentalProtection, Land and Forest Services, Edmonton, Alberta. RANGELANDS16(2). April 1994

FIg. 2. Mixed GrassPrairie.

FIg. 3. FescuePrairie

FIg. 4. Aspen Park/and 60 RANGELANDS 16(2), April 1994

Fig. 5. Montane

Fig. 6. Low BorealMixedwood.

Table 1. PrecipitatIonand temperatureAlberta's prairies (Strong and Leggat 1992).

Annual May-Aug. Ave. May-Aug. Extremesummer precip. precip. max. temp's max. temp's Dried mixed grass 272mm 156mm 23° -28°C 35°C 10.7" 6.1" 73° -82°F 95°F Mixed gras 326mm 176mm 21°-24°C 33°C 12.8° 6.8" 70°—75°F 91°F Fescue 445mm 214mm 19°-23°C 31°C 17.5" 8.4" 66°-73°F 88°F Aspen Parkland 412mm 259mm 19°—22°C 31°C 16.2" 10.2° 64°-72°F 88°F Montane 515mm 210mm 17°-20°C 30°C 20.3" 8.3° 62°—68°F 86°F Low Boreal Mixedwood 380mm 235mm 19°-21°C 30°C 15.0" 9.3" 64°-70°F 86°F RANGELANDS 16(2), April 1994 61

Aspenstands dominate the Low Boreal Mixedwoodwith form small groves and artificial-looking clumps that dot WhiteSpruce (Picea glauca) occurring as a subdominant the rich pasture lands." Frequent fires were also impor- on some sites. tant in maintaining a false parklandstate of Trembling Aspen stands and Rough Fescue grasslands Influences of the Present throughout Vegetation the Low Boreal Mixedwood region. Proof of fire's role in Climate this region is substantiated by early settlers who found There are threesignificant climatic influences on Alber- burntconifer trees in the soil while breakingtreeless land ta's prairies.They are Pacificmoisture systems, thunder- (Dewar 1992). storms, and chinooks. After Alberta was settled, fires were suppressed and Pacificmoisture systems are low pressure weathersys- removed from the Aspen Parkland and Low Boreal tems that bring moistureinland from the Pacific Ocean. Mixedwood regions. With fire suppression, Trembling These systems supply most of the moisturereceived by Aspen stands have expanded, unchecked, into the fire Alberta's Prairies. Generally, most of the moisture in maintained grasslands ata rateof 1% ofthe area per year. these systems is lost crossingthe RockyMountains. Any This has decreased the amountof forageproduced in the remainingmoisture is usually dropped shortly after they AspenPark land and Low Boreal Mixedwoodregions and enterthe prairies.The rainfall patternexhibited by these has created many management problems. moisturesystems forms a moisturegradient of moist to dryfrom the RockyMountains eastward to the DryMixed Pre-SettlementUse Grass Prairie region (Table 1). The Aspen Parkland and Before European settlementthe main use of Alberta's the Low Boreal Mixedwoodare exceptions to this mois- central and southern prairie vegetation was year-round ture gradient because they receive moisturefrom other bisongrazing. Large herds of bison utilizedthese prairies moisture systems known as thunderstorms. in a migratory pattern. During spring and early summer, Thunderstormsare rain showers that form whenthe air bison moved throughout the Dry MixedGrass and Mixed at ground level, that is warmedby daytime heating, rises Grass regions. They chose to graze these areas at this and condenses by colliding with cooler air above it. This time because the snow cover disappears earlier than in form of rain is most frequent in the Aspen Parkland and the otherregions, which allowed succulentspring growth Low Boreal Mixedwood during July and August when to occur earlier. Then, after the vegetation in the Dry daytime heating is at a maximum. Thunderstormsare Mixed Grass and Mixed Grass regions ripened and important to the Aspen Parkland and Low Boreal Mixed- became unpalatable, the bison would move into the wood because they supply the Trembling Aspen stands Fescue Prairie and Aspen Parkland regions.The grass- with needed moistureduring the hottestsummer months. lands in these two regions, which are mainly Rough The Aspen Parkland andLow Boreal Mixedwood have the Fescue grasslands, have the highest nutritional value highestamount of May-Augustprecipitation on Alberta's after curing of any grassland region in Alberta. The prairies (Table 1). The Fescue Prairie also receives high Fescue Prairie and Aspen Parkland regions also tend to amounts of May-Augustprecipitation, but cannotsustain have moreavailable water in the latesummer andfall than Trembling Aspen stands because thunderstormsare not the Mixed Grass regions do. Duringwinter the bisonalso frequent enough and because chinooks desiccate the tendedto stay in the Fescue Prairie and Aspen Parkland Trembling Aspen stands. regions. They chosethese regions because of the nutri- Chinooks are hot, dry winter winds that come over the tious Rough Fescue forage and because frequent chi- RockyMountains from the southwest. Theyare important nooksleft the hills in the Fescue Prairie bareof snow. The because they warm the areaand melt off the snow cover. bisonalso used the Montaneand Low Boreal Mixedwood Early ranchingin Alberta was feasible because chinooks regions to some extent during the winter. Even afterthe cleared the grasslands of snow so that they could be snow cover was established, bison would stay in these grazed year-round. Chinookshave most oftheir influence regions because the tall, dense growth form of Rough closer to the mountainsin the Rough Fescue Prairie and Fescue was easy to reach by cratering throughthe snow. Montane regions. As they move further out into the prair- iesthey lose their warmthand often become bitter winds. Use After European Settlement After European settlement, domestic Fire crop production and livestock grazing became the main activities on BeforeEuropean settlement, wildfires controlledbrush Alberta's prairies. Throughthese activitiesAlberta's prair- and forest expansion throughout Alberta's prairies.The ies have been altered. of fire was significantly importance especially significant in the Aspen The most distinguishablechanges have been caused Parkland and Low Boreal Mixedwood where it controlled annual Most of the the of by crop production. Aspen Parkland, spread Trembling Aspen. With fire, most of the Fescue Prairie, and Mixed Grass Prairie regions have Aspen Parkland was maintainedas RoughFescue grass- been put into annual crop production in order to take lands. Pall iser (1863) described thefire maintained Aspen of their rich soils. Large areas of the Low Parkiand as an advantage area where, "the woods are very scanty Boreal Mixedwood and Dry Mixed Grass Prairie regions and consist almost exclusively of aspen poplar, which have also been put into annual crop production,despite 62 RANGELANDS16(2), April 1994

their poorer soils. More native vegetation might have winterfeed is essential for livestockproduction in Alberta. remained in the Dry MixedGrass Prairie if it had not been With the frequent heavy snow falls that occur during the forthe Homesteader Act which required settlers to culti- winter,grazing is impossible and providingstored forage vate half (80 acres) of their quarter section homesteads. for the livestock is essential. Because of thisAct, many areasthat were notsuitable for Even though agricultural activity has significantly al- annual crop production were cultivated. Most of these teredAlberta's prairies,many sites with nativevegetation areas have since been seeded back to the perennial still exist. From these sites, and even from the sites that forages. have intensive agricultural activity occurring on them, Annual cropping is not the only reason why native you can appreciatethe beauty and productivity of Alber- grasslands have been plowed under. Domestic forage ta's prairies. John Macoun(1882), an early prairie bota- productionfor rangerejuvenation, creatingcomplemen- nist, may have captured the splendour of Alberta best tary grazing systems, and producing winter feed has when he stated, "In all my wanderings, I never saw any caused many native grasslands to be cultivated. Range spot equal in beauty rejuvenation has been usedto increase theproduction on References rangelands choked by Trembling Aspen encroachment and on overgrazed rangelands. Seeding domesticforage Dewar, Bob. 1992. Bob Dewaris a secondgeneration farmer in the has also been used when systems Low Boreal Mixedwood;personal discussions. implementinggrazing John. 1982. and that mimic bison Because the Macoun, Manitoba the great North-west. grazing patterns. of past Moss,E.H. 1955. The vegetationof Alberta. The Bot. Rev. 21:493-567. bison grazing patterns, each vegetation region is best Palliser,J. 1863. Exploration—British North America. suitedto grazingat certain timesduring the grazing sea- Strong, W.L.,and K.R. Leggat.1992. Ecoregionsof Alberta, Alberta son. Therefore, domestic have been used to Forestry, Lands and Wildlife, Edmonton, Alberta,Canada. Publi- forages cation T/245. createspring, fall, or summerpastures that complement the proper use of the available native range. Producing