RANGELANDS11(2), April 1989 65

Geology and Soils of Grassland Ranges, Kamloops, British Columbia A.L. van Ryswyk and A. McLean

The Kamloops-Merritt area has been the hub of the The great volumes of spring melt-water eroded and ranching industry in south central British Columbia, redistributedmuch of the rock materialdeposited by the Canada, since European settlements were established in icesheet. Tonguesof remnant ice often blockedoutlets of the mid-1800's. The first ranchers were attracted by the the Thompson and Nicola valleys, creating temporary ready sourceof feed during all seasons on theopen grass- glacial lakes. Layers of sands and gravels, several tens of landsthat lie in the rain shadowof the Coast Mountains feet thick, were deposited as deltas where the glacial and on the Interior Plateau. streams entered the lakes. Silts and clays were carried In manyinstances, this first useof thegrassland ranges further into the lakes, settling out during summer and by domesticlivestock led to their rapid deterioration.To winter as annual layers to form depositsone hundredor develop recommendations for rehabilitation and man- morefeet thick. agementof these ranges, it is necessary to considerthe The last remnant of Ice had melted by about 10,000 roles that geologyand soils play inthe character of range years ago in the Kam loops-Merrittarea. Streams and riv- vegetationand in foragemanagement. ers assumed their presentpattern and have since formed The Interior Plateau lies between the western Coast the recent fine- and medium-textured deposits on their Mountainsand the eastern mountainsystem that includes valley bottoms. the Purcell, Selkirk, and Rocky Mountains.The rolling When the landscape was firstexposed from the iceand plateau upland, at elevations between about 4,000 and before vegetation established, drying winds picked up 5,000 feet, is deeply dissected by valleys of the major fine sands and silts. These were redeposited over the rivers which flow at about 1,000 feet. The grasslands surfacein a layer a few inchesthick on the hillsand up to extend from the valley bottomsup to 3,000 feet at Kam- one or two feet thick in the low parts of the landscape. loops and to 4,000 feet near Merritt. Grassland vegetationthat had existed In southeastern Rocksof the plateau Includethe youngest basalt lava WashingtonState migrated northward as the ice front and the older sedimentaryshale, sandstone and lime- retreated. The British Columbia grasslands therefore stone aswell as igneousgranites. These rocks provideda representthe northern extensionof those in Washington. wide variety of mineralsand materialsthat were distrib- Duringthe last 10,000 years the climate hasfluctuated. uted overthe landscape during theglacial periods to form The extent of grassland increased during a prolongeddry the soil parent materials. period and then decreased during subsequent wetter The last glacial period began about 19,000 years ago periodsas the adjacent forest encroached upon it. During when the climate became cooler and wetter allowing this time, soils developed on the new deposits of the annual snow accumulation in the Coast and eastern glacial period. mountains. This accumulation eventually formed ice Summerdrought is a regularfeature of the climate of (glaciers)that flowed down the mountainvalleys to coa- these grasslands due to the rain shadow effect of the lesce on the plateau creating the Cordilleran ice sheet Coast Mountains. However, precipitation increases and attaining a thickness of about one mile over the major temperature decreaseswith elevation, resultingin greater valleys. At its maximum, the ice sheet flowed to a point moisture effectiveness at higher elevations. Annual cli- just southof Spokane, Washington.It eroded and ground matic moisture deficits (estimated evapotranspiration the rocks on the high parts of the landscape and depos- minus precipitation) rangefrom 16 inches for the lower ited the resulting mixture on the lower parts as a dense grasslands to8 inches forthe uppergrasslands and occur compact layer called basal till. during late spring and summer. Annual precipitation About 15,000years agothe climate warmedand theice ranges from 10 to 12 inches. Thus drought tolerant melted fasterthan it accumulated.The icesheet retreated grasses and shrubsdominate the grasslands. The domi- and became thinner, exposingthe highesthills first. Dur- nant species found in good to excellentcondition stands ing this period of deglaciation, most of the soil-forming of the lower grasslands are bluebunch wheatgrass and materials were deposited on the surface. Rock material big sagebrush; that of the middle grassland is bluebunch that had been carried within the ice was deposited ontop wheatgrass; and those of the upper grassland are blue- ofthe basal tillforming athin looselayer of mixeddebris. bunch wheatgrass and rough fescue.Several otherher- baceous species and clumps of aspen occur consistently Theauthors are soil scientist and ecologist (retired), Agriculture Canada, Research Station,3015 Ord Road, Kamloops, B.C. V2B 8A9. in theupper grassland to providea rich floral mixture.The RANGELANDS11(2), AprIl 1989

Lookingwest, kamloops iies in we miaoie grounosojacant to we connu&nceof the South and North ThompsonRivers. The flowing Cordilleran Icesheet formed the U-shapeof the ThompsonValley. The valley wasfilled with the 'white'silts at the glacial lake stage. They were erodedand redeposited by the riverin recent times.Grasslands extend fromthe valleybottom tomerge with the Douglasfir forest on the glaciatedplateau upland. open Douglas fir forest borders the uppergrassland. textured materials. The long taproots of the pine enables The medium-textured layer of wind-blown deposits it to utilize the moisture in the deeper soil layersand to provided an excellent mediumfor the grasses. Cherno- coexist with bluebunch wheatgrass. Brunisolic (Incep- zemic soils (Mollisols) developedunder the grass. They tisol)soils havedeveloped under theyellow pine-bluebunch are characterized by surface horizons with accumula- wheatgrass vegetation. tions of organic matter derived from the annual produc- Atthe forest-grassland boundary, the roots of Douglas tion of grass roots. Organicmatter content of the surface fir have difficulty penetrating the compactbasil till where horizonsvaries from about 1%for the BrownChernozems it occurs nearthe surface, usually on high parts of the (Aridic Haploboroll) on the lower grasslands to 4% for landscape. Fescue and bluebunchwheatgrass, with shal- Dark Brown Chernozems(Typic Haploboroll) and up to lowerroot systems, are well suitedto establish on thethin 10% for Black Chernozems (Udic Haploboroll) on the wind-blown surface deposits. Douglas fir, however, can upper grasslands. The rich flora of the uppergrasslands establish where deep, loose medium-textured materials are responsiblefor the high organicmatter content ofthe occur in ravines and at the base of steep slopes. The Black Chernozems. Variationsfrom the generalsoil and differencesamong the deposited materials has created a vegetation patternsoccur because of differencesin tex- mosaic of forest and grassland vegetation associated ture,water holdingcapacity, compactionand depth ofthe with respective Brunisolicand Chernozemic soils. materialdeposited during the glacial period. The low growing needle-and-thread grass is the domi- Yellow pine will establish on deep sandy gravellydep- nant grass on sites where gravellysandy stream deposits osits. The low water holding capacityof these materials occur. Sites withvery shallowdeposits over bedrocksup- willallow precipitation to penetratedeeperthan in medium- port mainly the small Sandberg's bluegrass. These sites I1#MIULANL) 11(i), #pni 1 Of

have low water holding capacity so support only species Increases in forage production from applications of that can completetheir growth cyclebefore soil moisture nitrogen fertilizer are greatest on the middle and upper is depletedand therefore have a low forage production grasslands where moistureeffectiveness is greatest. In- potential. Adjacentsites that have deep, medium-textured creased production is also greatest on good condition wind-blownor glacial lake depositswill support produc- stands well stocked with dominant native bluebunch tivestands of bluebunchwheatgrass because they have a wheatgrass and rough fescueor with introducedcrested higher water-holdingcapacity. wheatgrass. Stands dominated by low-growing grasses, CertaIn foragemanagement practicescan berelated to either because of depletion by grazing or because of the different geologic materialsand the soils developed coarse-textured or shallow soil material,show small for- on them. Grazing bluebunchwheatgrass during its criti- age increases to fertilizer application. cal boot to flowering period has been responsible for its A wide variety of geologic materials were deposited in depletion. This has allowed an increase of needle-and- the Kamloops-Merritt area during the glacial period. thread grass, which has a lower forage productivity. Re- Some of the preceding examples have illustrated how covery of bluebunchwheatgrass maytake decades, even these materials, and the soils developed on them, are when grazingpressure is reduced. Seeding these ranges related to the grassland vegetation of the area and to to crested wheatgrass would bean alternativeto reducing certain foragemanagement practices. livestock usage. However, improvedforage production Suggested ReadIng could be expected onlyon the deeper medium-textured with British Columbia Ministry of Environment. 1978. The Soil Land- deposits higher water-holdingcapacity. scapes of British Columbia. K.W.G. Valentine, P.N. Sprout, T.E. Rough fescue on the upper grasslands deteriorates Baker and L.M. Lavkulich (eds.), B.C. Ministry of Environment, rapidly when subjected to grazing at critical periods. ResourceAnalysis Branch,Victoria, B.C. 197 pp. of Forests.1982. Grassland and However, it also recovers in a few years when grazing British Columbia Ministry Ecology Classification. InSymposium proceedings June1982, Kamloops, pressure is reduced. Grazing management is a feasible B.C.,A.C. Nicholson,A. McLeanand T.E. Baker(eds.), B.C. Minis- alternativeto seeding for improving forageproduction on tryof Forests, information ServicesBranch, Victoria, B.C. 353pp. these grasslands.

Recognizing Range Readiness Alfred H. Bawtree During the early years of the range industry, in the Rules-of-thumb were provided for the application of intermountain region of the Pacific Northwest, horses thosetwo guidelines. The rule-of-thumbfor rangeutiliza- and cattle grazed the grasslands year-long. After some tion was take half and leave half. The rule-of-thumbfor severe winters in the late eighteen hundreds, it was range readiness was to allow six to eight inches of new acceptedthat hay was requiredfor feeding of cattle dur- growth on bunch grasses before grazing. By applying ing some winters. In the southern interior of British these rules, a gradual improvement in range condition Columbia, turnout of cattle occurred when the snow took place. By 1960, most of the range deterioration in melted or hay suppliesran out. Horsescontinued to graze British Columbia had been stopped and since that time, year-roundand cattle continuedto graze the grasslands considerableimprovement hastaken place. Much of that season-long untilabout the middleof this century. British Improvement can be attributed to the rules-of-thumb Columbia is fortunate to have both grassland and forest regardingrange readiness and utIlIzation. rangein most of the ranchingcountry with very different Range readiness is a term frequently used by range growing periods.Bunch grasses maystart growthearly in managers. The SAM Range Term Glossary Committee March on the lower grasslands, whereas at higher eleva- (1974) has defined range readiness as the defined stage tions in theforest, the pinegrass doesn'tstart growth until of plant growth at which grazingmay begin undera spe- May or June. citic management plan without permanent damage to The scienceof range management has been develop- vegetation or soil. This definition says range readiness ing through the twentieth century. Initially the objective takes into account the stage of plant growth, the man- wasto developmanagement guidelineswhich wouldstop agementplan to beused, and thepossibility of permanent range deterioration and restore the range to its former damage to vegetationand soil, It does not consider eco- productivity.Two hIghlysIgnIfIcant guIdelines were deve- nomics, nutritive value of the forage or animal require- loped: range utilizatIonand rangereadiness. ments. Should we continue to manage for range improve- Editors Note: A simillar article, "Range Readiness," by Alfred H. Bawtree much more can we appearedin the March 1988 issue ofBeef in B.C. Vol 2, No5. ment? How range improvement