A Taxonomic and Ecologic Study of the Riverbottom Forest on St

Great Basin Naturalist

Volume 36 Number 3 Article 1

9-30-1976

A taxonomic and ecologic study of the riverbottom forest on St. Mary River, Lee Creek, and Belly River in southwestern Alberta, Canada

Robert K. Shaw Cardston, Alberta, Canada

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Recommended Citation Shaw, Robert K. (1976) "A taxonomic and ecologic study of the riverbottom forest on St. Mary River, Lee Creek, and Belly River in southwestern Alberta, Canada," Great Basin Naturalist: Vol. 36 : No. 3 , Article 1. Available at: https://scholarsarchive.byu.edu/gbn/vol36/iss3/1

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Volume 36 September 30, 1976 No. 3

A TAXONOMIC AND ECOI.OGIC STUDY OF THE RIVERBOTTOM FOREST ON ST. MARY RIVER, LEE CREEK, AND BELLY RIVER IN SOUTHW^ESTERN ALBERTA, CANADA

Robert K. Shawi

Abstr.\ct. — The riverbottom forest community of St. Mary River. Lee Creek, and Belly River in southvvestern Alberta. Canada, is a unique ecological entity characterized by poplar species having their major Alberta distribution along these streams. Stands in the community are dominated by three tree species, six shrub species, and nine herb species. Establishment of the community is dependent on climate and substrate; destruction is the result of progressive lateral stream-flow erosion. Soils are sandy loams above gravel, with pH values of 1.1 to 8.0 and soluble salt concen- trations of 176 to 458 parts per million. Trees in mature stands averaged 23.0 cm in diameter and 40 3'ears in age; ma.ximum tree age was 250 years. The vascular flora consists of 291 species of whicb 41 are woody and 250 herbaceous. One species {Prunus nigra Ait.) new to Alberta and range extensions for 12 species are cited. There are no true community endemic species. Recreational and livestock-raising uses are present community modifiers. Fire is not important in current forest dynamics.

The riverbottom forest community of about 1,235 km- of northwestern Montana southwestern Alberta, Canada, is usually and southwestern Alberta. less than 0.8 km in width and occurs on Monthly water flow in all three streams only certain lengths of each stream. It has varies widely throughout the year. From been utilized for pasture and, to a minor late July through autumn and winter the extent, for firewood and timber, leaving flow is fairly constant, but during March much of the woodland free from excessive warmer weather causes snow melt in the disturbance. This study treats several as- foothills and on the lower mountain slopes pects of the riverbottom forest community to increase stream flow. The most rapid including the vascular flora, community melting of deep mountain snow occurs in stratification and composition, successional late May and early June. This coincides patterns, seasonal aspect, climate, geog- with the season of highest precipitation raphy, geology, and soils. when stream flow is swollen to its max- St. Mary River, Lee Creek, and Belly imum, which is four to five times the River originate in alpine tundra (ele- winter flow rate. Stream flow generally vation 2,000-3,200 m) on the Lewis Range peaks rapidly in late May or earlj^ June of the Rocky Mountains in Glacier Na- followed by a rapid decline throughout tional Park, Montana (Fig. 1). From al- July. Maximum flow in any year seldom pine tundra these streams flow northeast persists for more than 24 hours. Irrigation into the Province of Alberta, Canada, water is in low demand at the high run- through montane forest and aspen park- off season, and the six small weirs and land into the treeless stretches of fescue diversions on the three streams exert little prairie (elevation 900-1,400 m) where, control on downstream flooding. In spite along the stream courses, the poplar-domi- of these uses, near normal flow does pre- nated riverbottom forest community be- vail in the three streams in all months comes a unique ecological entity (Fig. 2). of the year except July, August, and St. Mar\' River drains about 3,440 km-, September. Lee Creek about 290 km-, and Belly River Pollution of the waters varies. No in-

'Box 364, Cardston, Alberla, Canada.

243 244 GREAT BASIN NATURALIST Vol. 36, No. 3

Porcupine Hills Monarch 1580 m k» Oldman River I 17 km

• Fort Lethbr^dge M Macleod 896 m 950 m

Standoff

Waterton

Belly River

Waterton St. Mary Reservoi] rj-^'SI Reservoir 1113 m

Cardston 1151 m^

• Mountain St. Mary View Lee Creek River 1312 m Zi Milk River Ridge 1433 m Alberta, Canada Montana, U.S.A.

Lewis Range 3200 m

Fig. L Streams of soiifhwoslcrii Allx-itii. Cariiidii. 'Ilic mnioi- ci olof^ic and taxoiiotnu stiidv •^ites

are niimberorl 1 through 10. September \'^76 SHAW: HIV1,HIU)TT()M IX)UEST 245

Fig. 2. Site 4 on St. Mar\' River, a typical climax stand of riverbottom forest on the second terrace. The background farmland is on the third terrace, and the foreground road crosses the fourth terrace grassland.

(lustrial wastes reach these streams, al- brother, Mike, for being a very willing though municipal sewage and some agri- field crew during the study. cultural feedlot effluent cause local prob- lems. Early snowmelt combined with per- Geology .\nd Geogr.^phy colation and leaching of water through old vegetation and manure on the up- The headwaters of the three streams lands causes discoloration and objec- originate on the Continental Divide over tionable odor in the water during March geological formations of the Belt Series and April of each year. High runoff in the Lewis Range of the Rocky Moun- from rain and melting snow in late May tains (Wyatt 1939). These strata, nearly and early June produces a high particulate all of sedimentary origin, were formed content in the water at this time. For the during the Proterozoic Era of 510,(300,000 rest of the year stream water in St. Mary years ago when much of western Alberta, River, Lee Creek, and Belly River tends eastern British Columbia, Montana, and to be clear, clean, and free from con- Idaho were covered by a shallow^ sea. taminants. These rocks, with a maxinnmi thickness of more than 6,100 m, are in the form of Acknowledgments a large syncline, the east edge of which forms the Lewis Range. The greatest thick- The author wishes to extend his thanks nesses of limestone .show numerous fossils to all those who have helped make this of calcareous algae and primitive marine work possible. Gratitude is expressed to [ilants. Dr. S. L. Welsh, Dr. J. R. Murdock, and The mountains themselves, of more re- Dr. C. Lynn Hayward of Brigham Young cent origin, are about 58.000,000 years University for their counsel and guidance f)ld. Thev resulted when tremendous during the course of this study. The use cru'^tal forces, principally from the west, of the Herbarium of Brigham Young Uni- w^ere directed against the geosyncline. The versity and the assistance rendered by its Proterozoic rocks were uj)lifted and moved curator, Dr. S. L. Welsh, in identifying some 80 km to the east where they were plant specimens are gratefully acknowl- warped into a great anticline, the Lewis edged. Overthrust, which overlies the younger The author also wishes to express his Cretaceous shales and sandstones of the appreciation to his wife, Shirley, and his plains. It is because of the Lewis Over- 246 GREAT BASIN NATURALIST Vol. 36, No. 3 thrust that there are no significant foot- Much of southwestern Alberta is ve- hills on the east side of the Lewis Range. neered with glacial deposits (Wyatt During Miocene and Pliocene time the 1939). Glaciation was general over most mountains were deeply eroded by streams. of the area. There is also widespread dis- Several thousand meters of Belt rocks tribution of reworked glacial deposits as were removed during the course of valley well as alluvial and lacustrine deposits formation. Near the close of Pliocene time transported by rivers and creeks. Retreat the climate cooled, vegetation disappeared, of the glaciers is presumed to have oc- and mountain glaciers formed from the curred for the last time about 9,000 years snow and began to move down the stream- ago (Dyson 1949). caned valleys where they met the con- Soils on the prairie section of south- tinental glaciers advancing from the western Alberta are generally fertile. As- north. pen parkland and some adjacent fescue The prairie section of St. Mary River, prairie are in the black soil zone and Lee Creek, and Belly River flows through east of this are the shallow black soils and over a variety of consolidated and which grade gradually into dark brown unconsolidated deposits, from the trans- soils of the mixed grass prairie and short- ported Belt series rocks of Proterozoic grass plains. The dark brown and most time to the more recent Cretaceous series. of the shallow black zones underlie tree- The geological formations which occur at less prairie. The soils along the river and the surface or immediately below the un- creek bottoms are of alluvial deposition in consolidated deposits the plains and and some, still liable to frequent flood- foothills zone of southwest Alberta are ing, are quite variable in texture and Cretaceous and Tertiary in age. A large utilization (Wyatt 1939). area of southwestern Alberta prairie, Undoubtedly the Lewis Range of the which includes the Porcupine Hills and Rocky Mountains on the west side of the Willow Creek formations, is underlain by area is the most prominent topographic formations of Tertiary age. Through feature of the landscape. In this part of Cardston and southward to the interna- Alberta the break from mountains to tional boundary, the soft sandy shales plains is fairly rapid, there being no wide and sands have influenced the soils range of foothills. The Porcupine Hills where they occur near the present surface. (elevation 1,580 m) is a prominent topo- The St. Mary River nonmarine strata graphic feature bordering Oldman River underlie the Willow Creek formation of on the north. East of St. Mary River the early Tertiary age and represent the land gradually rises to Milk River Ridge, uppermost Cretaceous strata in southwest which has the appearance of a high Alberta. This formation consists mainly of north-south plateau with a maximum ele- highly calcareous light gray sandstones vation of 1,433 m. Between these three and sandy shales. Irregular bedding and landmarks lies the area of study, which is crossbedding are common. Soils influenced in the of large plain of level to by these beds have a pronounced lime con- nature a in elevation 900 tent. Freshwater oyster shells and coal rolling land ranging from beds are common in this formation. Much to 1,200 m. of the prairie section of the three study streams cuts through the St. Mary River Climate formation. Bounded on the west by the mountains The marine Bearpaw formation consists and foothills of the Rocky Mountains, the mainly of dark gray clay shales and whole of the three prairie provinces—Al- sandy shales. A large area of Bearpaw berta, Saskatchewan, and Manitoba—con- extends from Township 1 Range 21 north- sists of vast plains deeply cut by river ward to Township H Ranges 22 and 23. valleys and gently sloping toward the east Much of the lower half of St. Mary River, and northeast. The western mountains where there is no riverbottom forest, flows form a fairly effective barrier to the mar- through this formation. A narrow band Pacific, and at the of Bearpaw shale extends from Cardston itime influence of the south beyond Kimball, and from Kimball same time the area is left exposed to the upstream on St. Mary River to the mouth inflow of cold Arctic air masses from the of Coalmine Coulee. north (Canada 1969). September 1976 SHAW: RIVF.RBOTTOM FOREST 247

Summers are normally warm, but win- Temperatures may fall to C or lower ters are usually long and intensely cold. in every month of the year in less favored Throughout southwestern Alberta mean locations in the southern prairies. temperatures are below C from Novem- The average frost-free period in south- ber through March. Winter cold across ern Alberta ranges from 80 to 120 days, the province increases from southwest to which is critically close to the minimum northeast. Winter temperatures on the required for cultivated grain crops to reach prairies may vary widely from month to maturitv. The growing season to which month during a single winter, or from the native flora has adapted is 85 days at vear to year, depending on the character Mountain View, 100 days at Cardston, and path of air masses passing over the 110 days at Lethbridge, and 120 days at region. In some winters, with a steady Medicine Hat, the progressive lengthen- flow of cold polar air, a cold spell may last ing occurring with increasing distance for several weeks. On the other hand, in from the mountains and with decreasing other winters the southerly flow of Arc- altitude (Longley 1968). tic air may be quite weak allowing air The prairie provinces are fortunate in of Pacific origin to move eastward at the receiving a high average of sunshine for surface, thus bringing mild weather. the latitude; the annual total ranges from Winter temperatures in the lee of the 2,000 to 2,350 hours in the prairies. July Rockies reflect the warming effect of the is the sunniest month with total exceeding "chinook" wdnd which occurs from the 300 hours at most stations in southern Northwest Territories to the United States Alberta. December is the dullest month but is most pronounced in southern Al- of the year with all stations showing total berta with effects noticeable as far east as less than 100 hours. There is a noticeable Regina, Saskatchewan. Characteristically, tendency for the sky to be either cloudless the chinook occurs as a westerly or south- or completely overcast on the prairie westerly wind and is brought about by (Canada 1969). the subsidence east of the western moun- Lying in the center of the continent tain ranges of maritime Polar air from the and shielded from the Pacific by the west- Pacific. This air is cooled adiabatically ern mountain ranges, the Canadian prai- at the saturated lapse-rate in its ascent ries lack available sources for abundant over the mountains. In its descent to the precipitation. The region is favored, plains, however, it is warmed again adia- however, by the fact that cyclonic activity batically at the dry lapse-rate which is is fairly vigorous and the hot summers are twice the cooling rate during the ascent. conducive to convection. The heaviest pre- Consequently, this air reaches the foothills cipitation results from the lifting of ex- at a much higher temperature than it had tensive masses of moist air moving north- at a corresponding level on the western ward from the Gulf of Mexico and ad- slopes. The chinook is most striking when joining regions. Droughts are usually as- it occurs following a cold wave that has sociated with abnormally low pressure been accompanied by snow. The sky in the Northwest Territories, which pro- clears abruptly and temperatures may rise duces only a weak southward flow of cold as much as 30 C in 24 hours. The bright air. sunshine and above-freezing temperatures In marked contrast to the Pacific Coast cause the snow to melt rapidly and some with its winter maximum, the prairies plants may be stimulated to begin growth have a rainy season from late May to prematurely with subsequent deleterious early October, although no season is with- effects. out some precipitation. The light precip- Temperatures rise rapidly from winter itation is somewhat mitigated bv the fact to summer and decline with equal rapidity that 60 to 75 percent of the year's pre- from summer to winter. The transition cipitation ('45.8 cm at Cardston) falls periods are usually confined to April and during the growing season when it can be October. Monthly mean temperatures in utilized by plants. southwestern Alberta are above 10 C for Precipitation shows wide variations the five months May to September. Ex- from year to year, with differences be- treme maximum temperatures have ex- tween the extreme annual amounts ex- ceeded 38 C over most of the prairies. ceeding the mean annual total in most 248 GREAT BASIN NATURALIST Vol. 36, No. 3 areas. Monthly precipitation totals are Ware and Penfound (1949) studied more often in deficit than in excess. June the floodplain of the South Canadian and July are most likely to have high River in Oklahoma and found sparse rainfall totals. vegetation due to annual destruction by

Winter snowfall is com])aratively light floods, shifting of sand, a high rate of with amounts ranging from 76 to 127 cm evaporation, the intense heat of the sand over the central j)rairies. This amount in- surface, and the drying out of sand. A creases to 180 cm in the foothills of the total of 85 species of plants was found. Rockies and at least twice that amount Dominant tree species were Populus in the highest ranges. Snow may fall in dcltoides, Salix interior, and lamarix gal- any month except July and August, al- lica. though measurable snow is unusual in The Mississippi River floodplain in June. The first snow cover usually ap- northwestern Tennessee has been given pears in late October and snow disappears special study by Shelford (1954). The in early April. A combination of heavy two dominant large tree species were snowfall and wind causes drift buildup Populus deltoides and Salix nigra. The in coulees and along the streams through- climate of the area was favorable for out winter. the rapid growth of trees on the higher terraces of the floodplain. Annual rainfall was 112 to 125 cm and the mean an- Literature Review nual temperature was 16 C. Nearly every year two or more early stages of the The riverbottom forest commimity in floodplain forest were inundated, the southwestern Alberta is found on stream length of submergence varying from one floodplains which show characteristics of week to two and one-half months. Usu- Melton's classification. Melton (1936) ally flooding came early in the spring proposed one category containing flood- but sometimes as late as May or June. plains seldom or never subject to over- The herb layer was usually poorly de- bank floods. These lack sedimentary de- velojied. Cottonwoods of 50 to 60 cm di- posits on the surface, and lateral cor- ameter at breast height showed 20 annual rosion results in the formation of meander growth rings in the Donaldson area north loops. A second category included flood- of Tiptonville. In the Reelfoot I-ake area plains frequently subject to over-bank cottonwoods grew in diameter at the rate i floods with considerable sedimentary de- of 2.1 cm or more per year, but in Iowa, posits on the surface. farther north, growth was measured at In a study of the Coeur d'Alene River only 1.0 cm per year. The cottonwood floodplain in Idaho, Humphrey (1924) stand near the Tiptonîlle Ferry was came to the conclusion that the êgetation estimated about 40 years old, counting on the floodplain of that river had spread from the time the cottonwoods were seed- from the south and east into Idaho be- lings. The area was a sandbar island in cause of the constancy of the moisture the river 52 years earlier. Estimated time factor along the river floodplain. Actual for the complete development of the cli- transfer of dissemiiuiles probably came max Tulip-Oak Forest was 600 years. about through winds and the movements In a survey of the vegetation of Al- of birds. berta, Moss "(1955) described the flats Lee (1945) rejKJrted 40 species of tall of rivers in the prairie parkland of south- trees, 9 s[)ecies of small trees, and 14 spe- \^(^stern Alberta as being connnonly dom- cies of shrubs from the flood])lain forest inated In- poplars and willows with as- of the White River in Indiana. A well sociated birch, al(l(>r, and a variable as- developed small tree-shrub layer was s(Miil)lage of herbaceous sj)ecies. The lead- lacking in the stratigraphic develnpnictil iiii; [)()plar sp(>cies designated were Pop- of the forest and stands along the river ulus angi/s/ifolia. P. acuminata. P. sar- showed striking similarity e\en though grnfii. P. trichorarpa (near the moun- the river passed throiigli four- i)ot;nii(.il tains), and P. halsarnift'ra. There was evi- areas of striking diffcrciK c in llic up ilence of liNbridi/ation bc^tween certain of land forest. Micnx lirnate was lliought to the cottonwoods and also between the two be of more imj)orlan(e than macro- balsam poplars. The chief willow species climate. indicated were Sali r lutca. S. caudata. S. Sei)tenil)('r l^Tf) SHAW: KIVI.HHOTTOM FOREST 249 interior \ar. pcdircUata. S. rtwlanopsis. the vegetation of Alberta which preceded iiiid S. nryiygdaloidcs. his monumental work (1959), the Flora Wistondahl (1958) doscribed the of .Mberta. a most comprehensive work floodplain of th(> Raritan River, New for the time and still the most useful Jersey, as flowing through three of four- taxonomic tool for the province. Supple- geologic provinces with floods luipredict nieiitary accounts of southwest Alberta able from to 16 days per year, March plants are to be found in Budd (1957), having the most floods. High preci])itation Booth (1950). and Booth and Wright oicurrod in the summer when floods were (1959). scarce. Succession trends on new^ alluvium Some hel|) in understanding the plants reflected the dynamics of stream action. of the upper reaches of Belly River and The dominant tree species on the levee Lee Creek was provided by Breitung's were willow, river birch, sycamore, and (1957) enumeration of the plants of box elder. Waterton Lakes National Park, Alberta. Hosner (1958) found that cottonwood Popular treatments including some of (Populus deltoidcs) seedlings could sur- the riverbottom species are Cormack's vive only with fewer than eight days (1967) Wild Flowers of Alberta and complete inundation by flood water with Kuijt's (1972) Common Coulee Plants of variable rates of recovery. Southern Alberta. A detailed and com- Weaver (1960) reported that the ]ii- })lete account of the northern great oneer tree species on the floodplain of the plains flora was provided in Boivin's Central Missouri Valley were SnJix (1967) Flora of the Prairie Provinces. nrny^daloides. S. nigra, and Populus sar- Specific treatment of the woody vascu- gentii. The floodplains were subject to lar plants found along southwest Alberta occasional or frequent flooding but were streams was done in Shaw's (1968) Guide nloderatol^' to well drained between over- to the Woodv Plants of the Lee Creek flows. Pie concluded that it was not the Valley and (1972) Guide to the Woody soil type alone that determined the kind Plants of the Prairies, Foothills and and amount of native vegetation but Valleys of Southwest Alberta. rather aeration and constancy of water Brayshaw (1965) has provided the supply of these mostly productive soils necessary treatment of native poplars of that directly affected their vegetation. southern Alberta and their hybrids, Lindsay et al. (1961) reported 629 which is most valuable in both taxonomic species of plants from a study of the vege- and ecologic evaluations of streamside tation and environment along the Wa- communities. bash and Tippecanoe Rivers in Indiana. Pioneer tree species were cottonwoods Methods and M.aterials (Populus spp.) and black willow (Salix nigra). A medium-sized island largely The riverbottom forest community of built by a major flood supported both St. Mary River, Lee Creek, and Belly cottonwoods and willows up to 33 cm River was chosen for this ecologic and diameter after 15 years. There were from taxonomic study of the vascular flora be- four to seven stages in succession from cause of a ])ersonal interest of long stand- pioneer grass-forb to the floodplain ing in these streams and their vegetation. edaphic climax. Discounting plant collecting and eco- Early taxonomic studies, w^hich in- system observations spanning the decade cluded accounts of the plant species of 1959 to 1969, the actual planned research stream vallevs. include the wôrk of for this paper covered the years 1970 Macoun (1883-1909) on plants of the through 1973. Intensive field data col- western prairies. Standley (1921) on the lection was carried out during the grow- flora of Glacier National Park in Mon- ing seasons of 1970. 1971. and 1972 with tana, and Rvdberg ri922, 1932) on the followup and fill-in studies completed by floras of the Rocky Mountains and plains autumn 1973. and prairies of central North America. Study sites along the stream systems An early edition of Native Trees of were chosen with two purposes in mind: Canada (1956) gave good accoimts of (1) intensive plant collection only, and tree species taxonomv and distribution. (2) both plant collection and ecosys- In 1955 Moss presented an overview of tem data collection. Within this frame 7

250 GREAT BASIN NATURALIST Vol. 36, No. 3 of reference, sites were evaluated from study sites and these in upstream to headwaters to outlet on each of the three downstream order were (5) Town Dam, study streams during the summer of NEY^ S26 T2 R26 W4 (Fig. 3); and 1970. Some sites were discarded because (6) Slaughter Hole, NW14 S4 T3 R25 they did not fall within the riverbottom W4. forest community proper, being in up- Belly River had four major study sites stream transition zones. Others were not and from upstream to downstream they selected because of community alteration were (7) Highway 5 bridge, SWI4 Si by livestock overgrazing, timber cutting, T2 R28 W4; (8) Hillspring Park, NEI/4 farmstead site, and cattle feedyards. and NW14 SI 3 T3 R28 W4; (9) Glen- Final sites meeting standards of reason- wood Bridge, SWI/4 S6 T5 R26 W4; and able expectation of similarity to pre-1870 (10) Standoff, S27 S28 S33 S34 T6 R25 climax community aspect numbered 19. W4 and S2 T7 R25 W4. A major objective of the study was to de- Nine minor taxonomic sites were cho- scribe the species of vascular plants and sen. On St. Mary River these were at their ecological relationships in the ap- Coalmine Coulee, SE14 S22 Tl R25 W4; parent edaphic-climatic climax of the Kimball Park, SW^i SI T2 R25 W4; east present. of Cardston, unsurveyed Blood Indian Re- There were 10 numbered major eco- serve; Christensen Farm, SW^^ S27 T5 logic-taxonomic sites (Fig. 1). Four were R23 W4; and Blood Reserve Cut-off, chosen on St. Mary River. From up- SW14 S30 T6 R22 W4. stream to downstream, with the assigned Minor sites on Lee Creek were the name and legal description, the sites were Dugway, S5 Tl R27 W4; the Narrows, (1) Cook's Ranch, SW14 S9 Tl R25 S20 T2 R26 W4; and Cardston, town of W4; (2) east of Aetna, SE14 SI 9 T2 Cardston. R24 W4; (3) Cardwell's Island, NEI4 The one minor site on Belly River was S30 T2 R24 W4; and (4) Woolford Park, at the Belly River-Oldman River conflu- NE14 S31 T2 R24 W4. ence, S27 S28 T9 R23 W4. On Lee Creek there were two major Since prior to this study no precise

vfc^^

Fig. 3. iSite 5 on Lee Creek with the climax stand of riverbottom forest on the second terrace at right and a pioneer site on the first terrace gravel bar at loft. September 1976 SHAW: RIVERBOTTOM FOREST 251

evaluation of the vascular flora of the canopy diameter for clumped shrubs. riverbottom forest had ever been made, All measurements were based on esti- intensive plant collecting was done mates with frequent tape measure checks throughout the growing season, beginning to insure reliability. in early May and ending in late Septem- The line-intercept method, using a ber. Important sites were collected thor- 30-meter steel tape placed at right angles oughly from five to seven times to insure to the line of travel at 30 m intervals, complete records of all species. Specimens proved to be satisfactory for obtaining were preserved according to standard information on clonal thicket shrubs. Ten herbarium practice. After careful check- 30-meter lines were sampled per stand. ing and comparison with known material, Bare ground and litter intercepts were all specimens collected—some 1500 num- not recorded; these were left for inclusion bers—were deposited in the Herbarium in quadrat herbaceous plant sampling. of Brigham Young University, Provo, A 2-dm-by-5-dm quadrat supported on Utah (bry). a duplicate set of specimens legs and made from small welding rods remains in my private herbarium at was used for herbaceous plant sampling. Cardston, Alberta. Sides of the quadrat were painted alter-

Taxonomy of the poplars follows Bray- nating colors at 1 dm intervals for ease shaw (1965), the genus Cryptantha after in estimating percentage cover. Fifty Higgins (1971), the genera Astragalus quadrats were sampled per stand at 10- and Oxytropis follow Welsh (1960), and step intervals. Bare ground and litter the remainder are after Moss (1959). estimates were obtained for the entire Boivin (1967), Booth (1950), and Booth stand by this method. and Wright (1959). From all data, calculations of absolute After several field trials, using various and relative density, absolute and relative methods, a standard procedure for ob- dominance, and absolute and relative fre- taining numerical data on forest stands quency were made with a final sum- evolved. Information leading to density, mation of relative values to yield im- dominance, and frequency was desired portance value. throughout. Each forest stand was Soil characteristics were evaluated in sampled by following a predetermined several ways on the 10 sites chosen for pattern—travel parallel to the stream, intensive study. To determine soil phys- sample at intervals, interrupt the interval ical characteristics, 100 samples per stand whenever nonforest terrain was crossed. were taken at 10-step intervals with a Field data were recorded on data sheets steel rod penetrometer and penetration similar to those suggested by Cox (1967). depth was recorded to the nearest deci- Data on trees, tree reproduction, and meter. Physical characteristics of the clumped shrubs were best obtained by gravel on gravel bars occupied by pioneer using the point-centered quarter method forest stands were determined by taking recommended by Cottam and Curtis three to five samples with a shovel, (1956). Point-to-plant distance determi- screening each sample with a sieve of 0.5 nation by tape measure proved quite dif- by 0.5 cm with square-hole design, and ficult because of the brush; so an optical calculating percentage rock and percent- range finder (Edscorp), also recommend- age sand, sand being all particles passing ed by Cottam and Curtis (1956), was sub- through the sieve mesh. Comparative stituted for the tape with the operator samples were also taken from sites oc- standing beside the plant and sighting cupied by sandbar willow. back to a two-meter rod painted alter- Five soil samples per site were collected nately red and green at decimeter inter- in plastic bags at (1) surface on pioneer vals set at the point of quadrant inter- community gravel bar, (2) surface in section. interval betw^een The travel mature forest, (3) 2 dm depth in mature points was 30 m, and three strata —trees, forest. (4) surface on adjacent fescue tree reproduction, shrubs and clumped prairie grassland, and (5) 2 dm depth on —were sampled from the same point. fescue prairie grassland. All rocks greater Dominance calculations were based on than 0.5 rm in diameter were removed diameter-breast-high for trees, tree re- from the samples. These samples were production dominance on height, and analvzed in the soils laboratorv of the .

252 GREAT BASIN NATURALIST Vol. 36, No. 3

Brigham Young University Department fescue prairie portion of the grassland of Botany and Range Sciences for per- biome. Riverbottom forest is continuous centage sand, percentage silt, percentage along 48 river km to St. Mary Reservoir clay, type, pH, and parts per million except for one short discontinuity at the soluble salts following the directions of mouth of Coalmine Coulee. Below St.

Bouyoucos ( 1 936) Mary Reservoir riverbottom forest is lack- To determine average age of trees in ing for the 80 river km to the river's con- a stand as well as the age of the oldest- fluence at Lethbridge. The lack of river- appearing trees, samples were taken with bottom forest on St. Mary River coin- a 46 cm increment borer and the corings cides w^ith river channel restraints im- were stored in glass tubing until rings posed by the Bearpaw Shale formation. could be counted in the laboratory. So Streamfall along the river length aver- many of the trees cored had heart rot ages 3.4 m per km. Where glacial and/or (about 40 percent) that much of the cor- alluvial gravel deposits occur, riverbottom ing was unproductive. However, suf- forest has developed. ficient growth ring information was ob- On Lee Creek, riverbottom forest be- tained to justify the construction of aging gins 1.6 km above the hamlet of Beazer. formulae for tree species. These formulae It is continuous for 20 stream km to the were based on the average number of mouth of Lee Creek below Cardston. annual growth rings per centimeter of Riverbottom forest development is coin- xylem and the tree trunk diameter at cident wdth gravel bar formation. Stream- breast height. fall averages 0.75 m per km. Valley profiles were developed for each Riverbottom forest development begins of the 10 major study sites utilizing a on Belly River 1.6 km above the Highway hand-held 30-meter steel tape, optical 5 bridge. As with St. Mary River and Lee range finder, and pacing estimates. From Creek, the transition forest changes these profiles the fraction of the river abruptly to riverbottom forest which is valley occupied by riverbottom forest was continuous to the Belly River-Waterton derived, plus forest height above stream River confluence at Standoff. River- level and terrace arrangement. bottom forest development coincides with General observations and photographic gravel bar formation for the 48 stream work were carried out during all seasons km. Streamfall averages 3.2 m per km. of the years 1970 through 1973. Impor- The channel pattern of the three tant phonological dates were recorded to streams is similar. They are "meander- yield seasonal development trends. The ing" streams in the definition of Neill effects of stream flooding were noted with and Galay (1967). The potential energy special attention to poplar seedling sub- of moving water has given these streams mergence and survival, channel alter- the ability to carve channels to their ation, silt deposition, mature forest de- present sha])e. The flow ])attern obeys struction bv erosion, and gravel bar for- the laws of stream morpholog^' described mation. by Yang (1971). Riverbottom forest is Historical data on river changes and found on streams that have not reached forest evolution and use were obtained a final static equilibrium but are still in through correspondence and interviews a state of dynamic equilibrium, contin- as well as library sources. General ob- ually adjusting to achieve an ajiproximato servations on bird and mammal life balance bot\veen work done and load ini- were also made thoughout the study j)osed. Stream flow is such that degrada- years. tion and aggradation occur each year. Th(> |)oak periods of channel alteration Results and gravel bar formation were found to (oiiicidc witli peak streaniflow in late General Features of River Valleys .May and early June. The inability of and Ri\('rl)ottoni Forest these streams to adjust widths in accor- Typical ri\orbottf)m forest begins on dance with velocity has led to the alter- first on St. Mary River 3.2 km south of the in- nate disposition of gravel bars, ternational boundary where the river one side of the stream and tlien on the abruptly leaves the aspen parkland-fescue other wherever the water has had access prairie transition and winds through the to transportable gravels. Gravel deposits Septemhor 1976 SHAW: HlVI.nnOTTOIM FORKST 253

nltoniatiiifj; with degraded banks are char were available to forest invasion and de- acteristic of the meander pattern. velopment bv late .Tune. Successful invad- Pioneer stands of riverhottom forest ers were able to cope with a few days were observed pfrow^ing on gra^el bar for- of submergence during flooding each mations but never on sand bars. On nine spring. In 1971, 1972, and 1973 average such pioneer riverhottom forest sites the number of flooddays per year was four, 0.1 graveL on which many small poplars ") lliese occurred with greatest frequency to O.fi m tall were growing, consisted of (luring late May and early .Tune. The ()1.1 percent rocks greater than 0.5 cm po|)l;H- species on pioneer riverhottom in diameter and 38.9 percent of particles forest sites are well leafed out by the time less than 0.5 cm in diameter, in other annual flooding commences. Three pio-

words, sand (Fig. 4) . On sites occupied neer riverhottom forest stands on gravel by small sandbar w^illows, 100 percent bars between site 3, Cardwell's Island, oiF each soil sample passed through the 0.5- and site 4. Woolford Park on St. Mary cm mesh screen. River, were observed for flood damage Depth of easy penetration by the pene- effect on the poplar species in late spring trometer on gravel bars occupied by pio- of 1972. On each of the three sites poplar neer riverhottom forest ranged from 0.0 seedlings and saplings 0.15 to 0.6 m tall dm to 1.0 dm, the mean being 0.4 dm were numerous prior to flooding. There Ten gravel bars were sampled, one at were also many herbaceous plants. All each major site, with 100 penetrometer sites were subjected to over-site flooding readings per site. for three days. After flood water subsi- Gravel bars formed bv annual flooding dence the pioneer tree stands w^ere intact on two of the three gravel bars. Seedlings were somewhat muddy and bent over; otherwise thev appeared to be uninjured. One week later they were thriving. A shallow layer of silt and sand 0.6 to 1.2 cm in depth had been deposited over the original gravel by the flood water. On the remaining gravel bar, largest of the three, not a trace of the former pioneer tree stand could be found. The flood water had been directed over this gravel bar. altering its shape completelv. All plant life had been buried or washed away, leaving several hundred square meters of fresh new gravel bar ready for re-invasion and establishment of the riverhottom forest community. Lee Creek and the St. Marv and Belly rivers are principally degrading streams with several different terrace levels. Riverhottom forest is confined to the narrow band of gravel of the first and second terraces. The first terrace or "first bottom" of Tindsay et al. (1961) is un- stable from modern river cutting and deposition and endures partial or total annual flooding. It supports the pioneer stages of riverhottom forest. The second terrace or "second bottom" is inundated only by floods of unusual proportions, such as the one of 1964. This second terrace supports the climax riverhottom forest commnnitv. Fig. 4. Recently formed first terrace gravel bar on St. Mary River open to invasion by river- Elevation increase from terrace to ter- bottom forest tree, shrub, and herb species. race was measured. From low water 254 GREAT BASIN NATURALIST Vol. 36, No. 3 level in the stream to mean level of the this damage being a direct function of first terrace is 0.3 to 1.0 m. The second streamflow velocity. Under ideal condi- terrace is 0.9 to 1.5 m higher than the tions, doubling the water velocity may in- first, and the third and fourth terraces crease abrasive power by four times are 1.2 to 2.4 m higher than the second (Flint et al. 1941). and third terraces. The third and subsequent terraces are occupied by the same The Climax Forest fescue prairie grassland community that is climax on the surrounding rolling hills Major emphasis was placed on the sta- of southwestern Alberta. tus of the climax riverbottom forest com- At the 10 study sites, mature river- munity occurring on St. Mary River, Lee bottom forest occupied 1 7 to 50 percent of Creek, and Belly River in southwest Al- the rim-to-rim valley width. The average berta, Canada. Numerical analyses, using riverbottom forest occupancy of the rim- standard methods, were performed for to-rim valley width was 32 percent. the mature tree canopy, tree reproduc- No evidence was found of invasion of tion, clumped shrub understory, thicket grassland terraces by tree species. Evi- shrub understory, and herbaceous under- dence was found in several locations of story. the invasion of the forest by grassland Following the example of Rice (1965), species, the invasion being accelerated by dominants in strata categories with very localized high intensity sheep grazing. few species were designated as those spe- Reproduction of tree species at high in- cies having importance value of 75 or tensity grazing sites was nil. more, based on the maximum impor- Long unused river channels higher in tance value possibility of 300. Average elevation than the present river channel number of species per stand for the tree were devoid of forest development. canopy stratum was three, for tree re- The longevity of riverbottom forest production three, and for clumped shrubs stands was investigated and found to be three. Therefore, an importance value of dependent on factors other than possible not less than 75 designated stand dom- age attainment and reproduction of its inants in these three strata. species. Few forest stands were found Designation of dominants for remain- where tree species had grown to maturity, ing strata followed the reasoning that died, were dying, or were being replaced with more (or fewer) species the im- by forest or grassland. Most stands portance values expected of dominants showed evidence of destruction during would decrease (or increase) proportion- some stage of development by the eroding ately. Average number of species per action of water on the forest-supporting stand for the thicket shrub stratum was gravel bar. Trees and shrubs washed away 7.5. Applying the inverse proportion rule, during the course of lateral degradation a stand dominant would be so designated were deposited on newer gravel bars or if it had an importance value of at least were lodged against other plants farther 30. downstream. Some had been lodged for There was an average of 30 species per several years, were partly decayed, and stand for the herbaceous plant stratum. had trapped sand, gravel, and river de- The inverse proy)ortion rule designates bris. 7.5 as the least importance value for The abrasiveness of transported gravels stand dominants. was found to have been most effective in Identification of plant species was debarking woody stems and roots of based on collections made during the transported plants and thus limiting their course of field work. The 1971 growing regeneration. Woody })lant fragments season was largely devoted to learning were checked on gravel bars at each of field identification characters of her- the three study streams for regenerative baceous species not in flower at the time growth following uprooting and transport of data sampling. Tree species identifi- by the water. No accurate count was kept, cation, based on Brayshaw (1965), in but the majority had not regenerated this study recognized narrowleaf cotton- even following partial burial in gravel wood (Populus nnpustifolia), balsam pop- by flooding. All showed abrasion damage lar (P. balsam ifera), and the hybrids be- to the bark, smaller branches, and roots. tween these two, called herein "AB hy- September 1976 SHAW: RIVERBOTTOM FOREST 255

Table 1. Summary of the mature tree stratum Table 3. Summary of the clumped shrub data data from 10 riverbottom forest stands in south- from 10 mature riverbottom forest stands in western Alberta. southwestern Alberta.

'O «3 »,

Species PC ^ Species CC

Populus angustifolia 91.5 32.3 29.5 32.7 94.5 Betula occidentalis 79.6 P. bahamifera .9 31.4 27.7 30.8 89.9 P. X bahamifera 96.9 34.2 41.9 34.7 110.8 P. tremuloides 5.4 1.9 0.5 1.3 3.7 Picea glauca 0.6 0.2 0.4 0.5 1.1 Total 283.4 100.0 100.0 100.0 300.0 brid" (P. angustifolia X bahamifera). Populus trichocarpa. long considered a species in its own right, has recently been designated by Brayshaw (1965) as P. bahamifera subsp. trichocarpa. Recog- nizing only one species of balsam poplar greatly simplified fieldwork inasmuch as the fruiting capsules necessary for the identification of P. trichocarpa as a species were produced infrequently. Summary data for the mature tree stratum are presented in Table 1. Density is expressed as the number of trees per hectare, and relative dominance was derived from stem basal area and density. Tree reproduction data for the 10 stands are summarized in Table 2. Tree reproduction included tree species individuals with a stem diameter at 1.4 m above ground of 5 cm or less. Relative dominance was derived from average sapling height and density. Clumped shrub data for the 10 stands are summarized in Table 3. Relative dominance for clumped shrubs was derived from average canopy coverage area and density.

Table 2. Summary of the tree reproduction data from 10 stands of mature riverbottom forest in southwestern Alberta.

^ "«

a -d ni Species EC ^

Populus angustifolia 113.3 42.0 38.3 38.6 118.9 P. bahamifera 81.5 30.2 32.4 28.1 90.7 P. X bahamifera 65.0 24.1 25.2 29.8 79.1 P- tremuloides 9.2 3.4 3.9 3.1 10.4 Picea glauca 0.8 0.3 0.2 0.4 0.9 Total 269.8 256 GREAT BASIN NATURALIST Vol. 36, No. 3

Table 5. Summary of herbaceous species stand dominants based on a minimum importance value of 7.5 or more in at least 1 of the 10 stands. Community dominants, designated "CD" in the table, have an average importance value of not less than 7.5 and are dominant in at least 4 of the 10 stands.

r-. -CJ

Species September 1976 MI AW: RIV1:HH0TT0M IX)IU-.ST 257

tant species was narrowleaf cottonwood, Nine ( oinniLuiitv dominants were found a (loniinant in 8 of 10 stands with an av- among the herbaceous species in the 10 erage importance valne of 118.9. Balsam stands. Forty-nine species were dom-

poplar was second, a dominant in () of 10 inants in at least one stand. The com- stands, with an average importance valne nuniitN' dominants in descending order of 90.7. Third was the AB hybrid poplar, followed by frequency of dominance and a dominant in 6 of 10 stands, with an average importance value are: Poa pra- average importance value of 79.1. The tensis. 8 of 10, 41.9; Medicago lupulina. three dominant species in the tree repro- 6 of 10, 26.3; Poa comprcssa, 5 of 10, duction stratum are the same as the dom- 12.1; Chrysopsis villosa, 5 of 10, 11.1; inant species in the mature forest tree Solidago mollis, 5 of 10, 10.6; Phleum stratum with closely grouped average im- pratcnse, 5 of 10, 10.4; Oxytropis viscida, jK)rtance \alues and stand-dominant val- 6 of 10, 10.1; Aster laevis, 5 of 10, 9.3; ues. and Fragaria virginiana, 4 of 10, 7.5. The minor tree species, quaking aspen, All of the dominant tree and shrub and white spruce, were also the minor species are native to Alberta. Five of the species in the tree reproduction stratimi. herbaceous species community dominants Absolute density of tree species ranged are native and four are e.xotics. from a low density of 122.6 trees per hec- Penetrometer readings throughout the tare at site 1, Cook's Ranch, to a high forest stands tended to reflect the sand density of 517.8 trees per hectare at site and silt deposition brought about by 7, Highway 5 bridge. Average density of earlier overbank flooding. The litter layer, all stands was 283.4 trees per hectare. even imder the highest density forest at Of the six species of clumped shrubs site 7, Highway 5 bridge (517.8 trees per encoinitered in sampling, onh' two oc- hectare), did not exceed 5 cm. The minimum penetrometer reading at most curred in 1 or more of the 10 stands and none in 10 of 10. River birch {Betula oc- stands was 0.0 dm, and maximum read- cidentolis) was the number one dominant ings of 9.0 dm were not uncommon. chmiped shrub for the ri"\'erbottom forest Mean penetration of soil under mature community of this study. It occurred as forest was 2.5 dm, in considerable con- a dominant in 9 of the 10 stands and had trast to the 0.4 dm mean obtained from an average importance value of 171.8. pioneer gravel bar sites. The other community dominant was red- The pH of gravel bar soil was very osier dogwood {Cornus stolonifera) , a close to 8.0 at all sites, with a moderation dominant in 7 of 10 stands and with an toward a slightly less alkaline reaction average importance value of 72.1. Yellow in the forest sites where pH values aver- willow (SaJix lutca) was a dominant in 3 aged 7.6 at the surface and 7.8 at a depth of 10 stands, but its average importance of 2 dm. Neighboring grassland soils on value of 44.5 was too low for considera- terrace three w^ere more moderate yet tion as a community dominant. with an average surface pH of 7.5 and a

Of the 14 species of thicket shrubs en- 2-dm-depth pH of 7 .7 . A decrease in sand countered in sampling, 8 were dominants and an increase in silt and clay fractions in at least 1 stand. Only 4 were judged occurred from gravel bar to forest to communitv dominants. First was silver- grassland, these data complementing [lenetrometer data. Parts per million of berry (EIocagnus romrnutata) , a dominant in 8 of 10 stands and with an aAer- soluble salts increased markedly, from age imj)ortance value of 80.5. Second the gravel bar surface average of 176 was snowberry (Syrnphoricarpos occidcn- ppm, to 458 ppm in forest surface soils, talis) occurring in 8 of 10 stands as a to 409 ppm in grassland surface soils. No dominant and \vith an average importance analyses were undertaken for organic car- value of 59.0. Third was wood rose bon, total nitrogen, or total phosphorus. (Rosa woodsii). dominant in 7 of 10 An age determination formula was de- stands, average importance value 55.3. vised to facilitate approximating average Fourth was serviceberry (Amelanchier tree age and age of the largest tree in each oln/folia). a dominant in 4 of 10 stands stand. The basic formula was: Age in and with an average importance value (d-bd) of 30.9. years = 2 r+5; where d equals 258 GREAT BASIN NATURALIST Vol. 36, No. 3 the diameter in centimeters of the tree Another large AB hybrid, with a diam- trunk at 1.4 m above ground, b equals eter of 129 cm and approximate age of the fraction of the diameter that is bark, 200 years, was found at the Kearl Ranch r the average number of annual rings on Lee Creek three miles southwest of per centimeter of xylem, and "plus 5" Cardston. Other large trees in Kearl's pri- is an approximation of the number of vate picnic ground were a narrowleaf years the tree took to reach a height of cottonwood 160 years old and a balsam 1.4 meters. Values for b and r were con- poplar 100 years old. structed through the use of an increment The largest tree found on St. Mary borer, with no fewer than 20 samples River, near Woolford Park, was an AB being taken for each tree species through- hybrid poplar with a 102 cm diameter out the range of the 10 study sites. For at 1 .4 m above ground and an approx- narrowleaf cottonwood b equals 0.2 and imate age of 160 years. Nearby was a r equals 3.74; for balsam poplar b equals balsam poplar 97 cm in diameter and ap- 0.184 and r equals 3.70; for the AB hy- proximately 155 years old. brid poplar b equals 0.193 and r equals Height of the large trees ranged from 3.78; and for quaking aspen b equals 13 to 22 m. At no site were trees tall 0.073 and r equals 5.5. Values for b and enough to project much above the valley r were not determined for white spruce. rim. Bark thickness for the AB hybrid poplar First leaf-out of tree species began at was intermediate between those of its par- site 10, Standoff, on 13 May 1972. One ent species and growth rate of the AB week later tree leaf-out was beginning hybrid was slowest of the three. on the upper St. Mary River at site 2, Smallest average diameter and lowest east of Aetna, on Lee Creek at site 5, average age species was narrowleaf cot- Town Dam, and at site 8, Hillspring tonwood with an average diameter of 20.8 Park on Belly River. cm and average age of 36 years for all Leaf-out was not simultaneous at any stands. Second oldest species was balsam one site for all poplar species. For ex- poplar with an average diameter of 21.8 ample, on 14 May 1972 balsam poplar cm and average age of 38 years. The AB and prevernal aspen were leafing out at hybrid poplar had the largest average site 10, Standoff. By 18 May the same diameter, 26.2 cm, and the highest aver- species were beginning leaf-out at site 4, age age, 45 years. Woolford Park. The AB hybrids were just Narrowleaf cottonwood was the largest beginning leaf-out at site 10, Standoff, on tree sampled in two stands. Largest diam- 21 May and at site 4, Woolford Park, eters of 36 and 43 cm for this species on 28 May. By 21 May narrowleaf cot- were found in two stands. Corresponding tonwoods were leafing out at site 10, ages were 58 and 69 years. Balsam poplar Standoff, but had not yet begun to do so was the largest tree sampled in one stand. at site 4, Woolford Park, nor at any sites This tree, 48 cm in diameter, was 78 upstream from there. Leaf-out sequence years old. The AB hybrid poplar was of community tree dominants at any the largest tree sampled in eight stands. given site is first, balsam poplar; second, The average diameter of these large pop- the AB hybrids; and third, narrowleaf lars was 53 cm and average age 85 years. cottonwood. The largest tree in any sample, an AB The shrub species followed a leaf-out hybrid, was 89 cm in diameter with an sequence that began, in 1972, on 21 May age of 141 years. The average age of at site 10, Standoff, and worked from the largest trees sampled in the stands there upstream and toward the moun- was 40 years. tains on all stream sites. Woody plant A search was conducted on each of leaf-out progressed upstream at the rate the three streams for very large and, of five river kilometers per day under presumably, very old trees. These would mild weather conditions. provide some indication of the possible The im})ortance of riverbottom forest age attainment of dominant tree species. to man in the early days of the Canadian Through actual increment boring the west was variable. Certainly use of the oldest tree found was an AB hybrid pop- forest for shelter and firewood was made lar on Lee Creek three miles below by aboriginal man. Prior to 1877 this Beazer that was, in 1973, 250 years old. j)art of the northern great plains was September \976 SHAW: RIVI.RBOTTOM FOREST 259

controlled by Indian tribes of the Black- riverbottom forest on a second terrace feet Confederacy. Ewers (1958) reported of St. Mary River east of Cardston. With- that Indian use of riverbottom forest was in 10 years the home had to be aban- principally limited to winter season en- doned and was ultimately destroyed by camj)ments. Ewers also reported the feed- the river, which had initially seemed ing of the inner bark of cottonwood trees far enough away for safety (P. C. Shaw to horses when snow was too deep for pers. connn.). grassland feeding. My grandfather, Vernon S. Shaw, re- Walter McClintock (1910). who lived marked in the early 1950s that the huge with the Blackfeet Indians from 1896 (AB hybrid) cottonwood at the Kearl to 1900, wrote that the Indian name for Ranch on Lee Creek seemed just as large St. Mary River meant "Green Banks" to him when he w-as a boy in 1885 as it because of its gallery forests of poplars. did at present. This tree, estimated to be He also reported riding through groves 200 years old in 1973, would have been of large cottonwoods along the Belly about 114 years old in 1885 and a very River. large tree even then. Between 1870 and 1900 many settlers Today, of 13 ranch homes in Lee arrived from eastern Canada and United Creek valley, only 1 is built in riverbot- States to take up homesteads offered by tom forest on a second terrace, and that the Canadian government. Since many of one is protected from flood damage by these people came from forested regions, a road serving as a dike. Of the 14 ranch to feel more at home they settled in the homes on St. Mary River between the river valleys, occasionally in the river- international boundary and St. Mary bottom forest itself. Reservoir, not 1 is built in riverbottom The town of Cardston, founded in 1887 forest. Along Belly River 3 out of 10 by Charles Ora Card from Cache Valley ranch homes and several homes on the in Utah, was built in part of the river- Blood Indian Reservation at Standoff are bottom forest of Lee Creek. Photographs in riverbottom forest and are annually taken of Cardston during the period 1887 in danger of flood damage. to 1900 show the riverbottom forest in During the years from 1950 to 1970 much the same position and with the provincial and municipal boards estab- same general appearance as today (Ma- lished picnic and camp grounds at four cleod 1900). Major floods of 1889, 1903, riverbottom forest sites. On St. Mary and 1964 taught the residents about the River parks were established at Kimball hazards of living in riverbottom forest. and Woolford, on Belly River at a site Settlers in southwestern Alberta re- near Hillspring, and on Lee Creek at ported that cottonwood logs made poor Cardston. Woolford Park has been sub- building material, being crooked and subjected to frequent and serious flood dam- ject to early decay. Lumber of quality age with over half of the original acreage could not be cut from them. Cottonwood on the second terrace lost to river erosion made poor firewood; the logs tended to in spite of attempts made to divert the smoulder rather than burn and smaller river. Streambank stabilization using branches burned too quickly. Building broken concrete slabs has been necessary logs, lumber, and shingles came from the at the Cardston park to prevent erosional forests of spruce and pine on lower moun- loss. Hillspring Park is protected from tain slopes 20 miles to the southwest. flood damage by the United Irrigation Coal was found in abundance, further re- District diversion dam. ducing the need for trees as fuel (Hud- Preservation of intact riverbottom for- son 1963). A cottonwood log cabin built est has been fortuitous. in 1885 on Lee Creek by E. N. Barker has Throughout the years of this study, long since rotted away with no trace of 1970 to 1973, observations of a general its logs remaining. Cabins built of pine nature were made on common bird and and spruce logs at the same time still mammal species of the riverbottom forest. stand (Barker 1937). The most frequently sighted birds, in the In 1896 Collector of Customs Frederick order in which they appear in Salt and D. Shaw, an immigrant from wooded Wilk (1958), were: great blue heron, Nova Scotia, built his beautiful home red-tailed hawk, killdeer, spotted sand- "Woodgrove Park" in a mature stand of piper. California gull, ring-billed gull, 260 GREAT BASIN NATURALIST Vol. 36, No. 3 mourning dove, great horned owl, com- (pers. comm.), was deleted because no mon nighthawk, kingfisher, red-shafted specimens could be found to substantiate flicker, black-billed magpie, common the report. This report of Prunus nigra crow, house wren, catbird, robin, starling, in southwestern Alberta is now verified yellow warbler, house sparrow, and (Cody and Shaw 1973). American goldfinch. The black-billed Range extensions for 12 species were magpie is the most typical bird of the obtained from the collection data of this riverbottom forest. study, these being noted in the species The most frequently sighted native list. mammals, in the order in which they appear in Soper (1964), were: white-tailed prairie hare, American varying hare. Species List Black Hills cottontail rabbit, pale-striped PoLYPODIACE.\E ground squirrel, buff-bellied chipmunk, Cystopteris fragilis (L.) Bernh. Canada beaver, white-footed mouse, Equisetace.\e meadow vole, jumping mouse, porcupine, Equisetum laevigatum A. Br. northern plains skunk, mule deer, and Equisetum pratense Ehrh. white-tailed deer. Sel.'\ginellaceae Selaginella densa Rydb. Taxonomic Treatment PlN.'VCE.'\E Juniperus communis L. Vascular plants were collected at the Juniperus horizontalis Moench 10 major study sites and at 9 minor sites Juniperus scopulorum Sarg. (Range extension) on St. Mary River, Lee Creek, and Belly Picea glauca (Moench) Voss var. River during the growing seasons of alberliaria (S. Brown) Sarg. Pinus 1970, 1971, 1972, and 1973. Plants in- flexilis James Pseudotsuga menziesii (Mirb.) Franco cluded as riverbottom forest species were collected from pioneer forest sites on grav- Typhace.'^e Typha latijolia L. el bars and from the riverbottom forest- fescue prairie grassland transition as well Ausmace-ae as from the area of major interest, the Sagittaria cuneata Sheld. mature riverbottom forest. Gramineae The southwestern Alberta riverbottom Agropyron dasystachyum (Hook.) Scribn. forest community contained 291 species Agropyron inerme (Scribn. & Smith) Rydb. of vascular plants in 165 genera represent- Agropyron smithii Rydb. Agropyron smithii Rydb. var. ing 50 plant families. Of these, 41 are molle (Scribn. & Smith) Jones woody plant species and the remaining Agropyron subsecundum (Link) Hitchc. 250 are herbaceous plant species. Agropyron trachycaulum (Link) Malte The most important plant families rep- Agrostis alba L. Agrostis variabilis Rydb. resented were: Compositae, 30 genera, 61 Beckmannia syzigachne (Steud.) Fern. species; Leguminosae, 12 genera, 39 spe- Boutrloua gracilis (HBK.) Lag. cies; Gramineae, 16 genera, 28 species; Bromus ciliatus L. Rosaceae, 8 genera, 16 species; Salicaceae, Bromus inermis Leyss. Bromus /ectorum L. 2 genera, 13 species or species hybrids; Calatnagrostis incxpansa A. Gray and Umbelliferae, 8 genera, 12 species. Dactylis glomcrata L. One species new to the province of Al- Deschamj)sia cacspilosa (L.) Beanv. berta was found. Prunus nigra Ait. was Descliampsia cacspitosa (L.) Beauv. var. glauca (Hartm.) Sam. collected in 1971 from a small population F.lymus cinrreus Scribn. & Merr. on Lee Creek at site 6, Slaughter Hole F.lymus glaucus Biukl. (Shaw 1218). In earlier editions of Native Glyceria borcalis (Nash) Batchehler Trees of Canada (1949, 1956, 1961), Glyceria grandis S. Wats. Korlrria cristata (L.) Pers. Canada Plum i Prunus nigra) was re- Oryzopsis hymrnoidrs (R. & S.) Ricker ported from New Brunswick west into Phalaris arundinacra L. Manitoba. It was also reported from Phlrum pralrnse L. ". Poa comprrssa L. . . fords of several rivers in southern Alberta." The seventh edition (Hosie Poa cusickii Vasey Poa interior Rydb. no of 1969) made mention the Alberta Poa pratensis L. report. This, according to T. C. Brayshaw Stif)a Columbiana Macoiin September 1976 SHAW: RIVKIUJOTTOM KORF.ST 261

Cypfji.\ce.\e Clematis rrrticellaris DC. var. Carex flava I^. Columbiana fNutt.) A. Gray Eleocharis palustris (L.) R. & S. Ranunculus acris I.. Scirpus acutus Miihl. Ranunculus cymbalaria Pursh Scirpus paludosus A. Nols. Ranunculus pedatifidus J. E. Smith var. affinis (R. Br.) L. Benson JUNC.\CE.\E Ranunculus repens L. (Range extension) Juncus alpinus Vill. vai". rariflorus Harlin. Thalictrum renulosum Trel. /uncus lonpistyUs Torr. Juncus torrryi Coville Capparid.\ce.ae Cleome serrulata Pursh I.ir.IACE.'^E Allium crrnuum Roth Crucifehae

Allium scfjornnprasum I,, vac. Arabis hirsuta (L.) Scop. var. sihiricum (T..) Hartni. plabrala T. & G. Allium rex tile Nols. & Macbr. Arabis holborllii Hornem. Disporum orcpanum (A.. Wats.) B. & H. Arabis holboellii Hornem var. Fritillaria pudica (Pursh) Spreng. retrofracta (Graham) Rydb. TAlium philadelphicum L. var. Draba aurea Vahl (Range extension) andinum CNiitt.) Ker Erysimum cheiranthoides L. Smilacina racemosa (L.) Desf. var. Lesquerella alpina fNutt.) S. Wats. var. amplrxicaulis (Nutt.) S. Wats. spalhulata TRydb.) Pay.son Smilacina slellata (L.) Desf. Lesquerella arenosa (Richards.) Rydb. Zypadenus pramincus Rydb. Physaria didymocarpa (Hook.) A. Gray Sisymbrium loeselii L. Irid.\ce.\e Thlaspi arvense E. Sisyrinchium mnntanum Greene Crassulaceae Orchid.\cr\e Sedum sfenopetalum Pursh Calypso bulbosa (L.) Oakes (Range extension) Sa x I fr Cnrallorhiza striata Lindl. agaceae Parnassia palustris Habenaria hyperborea (L.) R. Br. L. var. neopaea Fern. Ribes inerme Habenaria viridis (L.) R. Br. var. Rydb. (Range extension) Ribes braeteata (Muhl.) A. Gray oxyacanthoides E.

S.\LIC.\CE.\E Ros.ace.\e Populus acuminata Rydb. Amelanchier alnifolia Nutt. Populus anpustifolia James Chamaerhodos erecta (E.) Bunge ssp. nuttallii (Pickering) Hulten Populus anpustifolia .Tames X balsamifcra L. Crataepus Populus balsamifcra L. subsp. chrysocarpa Ashe Fraparia virpiniana trichocarpa (T. 8z G.) Brayshaw Duchesne var. Populus sarpentii Dode plauca S. Wats. Populus tremuloides Michx. Fraparia rirpiniana Duchesne var. Salix amypdaloides Anderss. platrpetala (Rydb.) Hall Salix bcbbiana Sarg. (Range extension) Salix caudata fNutt.) Heller Potentilla anserina L. Salix interior Rowlee Potentilla concinna Richards. Salix lutea Nutt. Potentilla fruticosa L. Potentilla (gracilis Salix petiolaris J. E. Sm. Dougl. Salix scouleriana Barratt Potentilla hippiana Eehm. Prunus nipra Ait. Betul.'\ce.\e (New record for Alberta) Betula occidentalis Hook. Prunus virpiniana E. var. melanocarpa (A. Nels.) Sarg. Urtic.'VCeae Rosa acicularis Eindl. Vrtica lyallii S. Wats. ("Range extension) Rosa woodsii Eindl. Rubus striposus SaNTAL.ACE.'VE Michx. Comandra pallida A. DC. Eeguminosae Astrapalus aboripinum Richards. Polygonaceae Astrapalus adsurpens Pall. Erioponum ssp. flavum Nutt. robustior (Hook.) Welsh Rumex crispus L. Astrapalus aprestis Dougl. Rumex mexicanus Meisn. Astrapalus alpinus E. Caryophyli.ace.'^e Astrasalus bisulcatus (Hook.) A. Gray Astrapalus bourpovii Arenaria lateriflora Poir. A. Gray (Range extension) Cerastium arvense L. Astrapalus canadensis E. Ranuncul.\ce.ae Astrapalus crassicarpus Nutt. var. Actaea rubra (Ait.) Willd. paysoni (Kelso) Barneby Actaea rubra (Ait.) Willd. forma Astrapalus drummondii Dougl. neplecta (Gillman) Robins. Astrapalus flexunsus Dougl. Anemone multifida Poir. Astrapalus miser Dougl. var. Clematis lipusticifolia Nutt. serotinus (Gray) Barnebv 262 GREAT BASIN NATURALIST Vol. 36, No. 3

Astragalus missouriensis Nutt. Oenothera biennis L. var. Astragalus robinsii A. Gray var. hirsutissima Gray minor (Hook.) Barneby Oenothera caespitosa Nutt. Astragalus terwllus Pursh Astragalus vexilliflexus Sheld. Umbellifer.'ê Glycyrrhiza lepidota Pursh Bupleurum americanum Coult. & Rose Cicuta douglasii (DC.) Coult. Rose Hedysarum alpinum L. var. & americanuni Michx. Heracleum lanatum Michx. Hedysarum boreale Nutt. Lomatium dissect um (Nutt.) Mathias Hedysarum sulphurescens Rydb. & Constance var. muUifidum (Nutt.) M. & C. Lornaliuni foeniculaceum (Nutt.) Lathyrus ochroleucus Hook. Lathyrus venosus Muhl. var. Coult. 8z Rose Lomatium simplex (Nutt.) Macbr. var. intonsus Butters & St. John Lupinus argenteus Pursh leptophyllum (Hook.) Mathias depauperata Philippi Lupinus sericeus Pursh Osmorhiza Osmorhiza longistylis (Torr.) DC. Medicago falcata L. Osmorhiza occidentalis (Nutt.) Medicago lupulina L. Torr. Perideridia gairdneri Medicago saliva L. (Hook. & Arn.) Mathias Melilotus alba Desr. Sanicula marilandica L. Melilotus officinalis (L.) Lam. Cornace.\e Oxytropis campestris (L.) DC. var. Cornus stolonifera Michx. gracilis (A. Nels.) Barneby Oxytropis sericea Nutt. var. Pyrolace.ê spicata (Hook.) Barneby Pyrola asarifolia Michx. Oxytropis splendens Dougl. Pyrola asarifolia Michx. var. Oxytropis viscida Nutt. purpurea (Bunge) Fern. Petalostemon candidum (Willd.) Michx. Petalostemon purpureum (Vent.) Rydb. Ericace.'\e Thermopsis rhombifolia (Nutt.) Richards. Arctostaphylos uva-ursi (L.) Spreng. Trifolium hybridum L. Primul.'^ceae Trifolium pralense L. Androsace septentrionalis L. var. Vicia americana Muhl. subumbellata A. Nels. Vicia sparsifolia Nutt. Lysimachia ciliata L. Gf,R.'\NI.'\CEAE Gentianace.\e Geranium richardsonii Fisch. & Trautv. Gentiana affinis Griseb. Geranium viscosissimum Fisch. & Mey. Gentianclla amarella (L.) Borner ssp. LiNACEAE acuta (Michx.) J. M. Gillett Linum lewisii Pursh Apocynace.'ê EuPHORni.\CE.Ê Apocynuni cannabinum L. Euphorbia esula L. Polemoniace.\e Anacardiaceae Phlox hoodii Richards. Rhus trilobata Nutt. Polernonium pulcherrimum Hook.

ACERACE-AE Boraginaceae Acer negundo L. var. Cryplantha celosioides (Eastw.) Payson interius (Britt.) Sarg. Cynoglossuni officinale L. Hackelia americana (A. Gray) Fern. Malvaceae (Range extension) Sphaeralcea coccinea (Pursh) Rydb. Hackelia floribunda (Lehm.) I. M. Johnston Lappula rchinata Gilib. VlOI..\CE.\E Lithospermum incisum Loiun. Viola (idunca J. E. Smith Lithospermum ruderale Eehni. Viola rugulosa Greene Onosmodium occidentale Mackenzie

Loasaceae Lahiatae

Mentzelia decapetnla f Pursh) Urban & Gilg Galeapsis letrahit L. Mentha arvensis I-,, var. villosa Ri,aea(;nac:e.\e (Benth.) S. R. Stewart FAaeagnus commulata Bernh. Monardu fistulosa I>. var. Shepherdia argen tea Nutt. men/haefolia (Graham') Fern. Shepherdia canadensis (I,.) Nutt. Prunella vulgaris I,.

()nagraci-:ai-: Scrophui-ariackae Epilobium angusiifoUum L. Castilleja miniata Dougl. Epilobium glandulosum I. chin. (\istilleja septentrionalis I.indl. Epilobium latifolium I,. Linaria vulgaris Hill Gaura coccinea Putsh Orthocarpus luteus Nutt. Gaura coccinea Pursh var. Penstemon confertus Dougl. glabra (Lehm.) Torr-. & Gray Pensteiuox\ nilidus Dougl. September 1976 SHAW: RIVI.HBOTTOM FOREST 263

Penslrnion procerus DourI. Lygodesmia juncea (Pursh) D. Don Rfiinanthus crista-galli L. Ratibidu columnifcra (Nutt.) Wooton Verbascuni thapsus L. & Standi. Rudbcckia serotina Nutt. RUBIACF.XK Senecio canus Hook. Galium aparine L. var. Senecio integerrimus Nutt. var. echinospermum (Wallr.) FarwcU exaltalus (Nutt.) Cronq. Galium boreale I.. Senecio lugens Richards. Senecio pauperculus Michx. Caprifoliace.\e Solidago giganlea Ait. Lonicera dioica L. var. Solidago graminifolia (L.) Salisb. var. glaucescens (Rydb.) Butters major (Michx.) Fern. Lonicera involucrata ( Ridiards.) Banks. Solidago missouriensis Nutt. Lonicera tartarica L. Solidago multiradiala Ait. (Range extension) Symphoricarpos occidentalis Hook. Solidago spalhulata DC. Sonchus asper (L.) Hill CaM pa N U LAC E.\ E Sonchus uliginosus Bieb. Campanula rotundifolia L. Taraxacum officinale Weber Townsendia parryi D.C. Eat. COMPOSITAE Tragopogon dubius Scop. Achillea millefolium L. var. lanulnsa (Nutt.) Piper Agoseris glnuca (Pursh) Raf. Antennaria rosea Greene Discussion Arctium minus (Hill) Bernli. held belief that na- Arnica rordifolia Hook. The rather \\ddely Arnica fulgens Pursh tive Cottonwood species have not pop- Aster ciliolatus Lindl. ulated the prairies of southwestern Alberta Aster laevis L. var. geyeri A. Gray because of lack of shelter from the wind Aster occidentalis (Nutt.) T. & G. poplar Aster pansus (Blake) Cronq. is open to closer scrutiny. Native Artemisia biennis Willd. and Cottonwood species have been success- Artemisia campeslris L. ssp. fully transplanted from natural river- \caudata (Mirh.x.) H. & G. bottom forest populations to prairie grass- Artemisia longifolia Nutt. hybrid exot- Artemisia ludoiiciana Nutt. land sites. Furthermore, and Balsamorhiza sagittata (Pursh) Nutt. ic poplar species have been planted with Chrysanthemum leucanthemum L. excellent success on the prairies during Chrysopsis villosa (Pursh) Nutt. var. the past 80 years. The barrier to native hispida (Hook.) Gray invasion of the grasslands is partly Crepis intermedia A. Gray poplar Cirsium arvense (L.) Scop. a reproductive one. Mature trees in yard Cirsium undulatum (Nutt.) Spreng. and shelterbelt plantings produce quanti- Cirsium vulgare (Savi) Airy-Shaw ties of seed, but these observedly have Erigeron acris L. failed to plants. The seeds Erigeron caespitosus Nutt. produce new Erigeron compositus Pursh var. glabrata Macoun of native poplars are transported far and Erigeron glabellus Nutt. var. wide by the generous wind. If lack of pubescens (Hook.) Cronq. shelter is the only factor responsible for Erigeron peregrinus (Pursh) Greene ssp. failure of poplar seedling survival, callianthemus (Greene) Cronq. the (Range extension) then there must surely be evidence of Erigeron philadelphicus L. seed germination and partial seedling Erigeron speciosus (Lindl.) DC. growth on some parts of the prairie grass- (Range extension) land. No such evidence was found. Erigeron strigosus Muhl. Gaillardia aristata Pursh However, seeds from southwestern Al- Grindelia squarrosa (Pursh) Dunal var. berta riverbottom forest poplar species quasiperennis Lunell will readily germinate and grow if they Gutierrezia sarothrae (Pursh) Britt. & Rusby environ- Helianlhus annuus L. ssp. are provided with two essential lenticularis (Dougl.) Cockerel! mental conditions in addition to the ob- Helianlhus laetiflorus Pers. var. vious ones of temperature, etc. First, there subrhomboideus Fern. (Rvdb.) must be gravel beds or bars with a make- Helianlhus nuttallii T. & G. Hierncium canadense Michx. up of about 40 percent sand (particles Hieracium cynoglossoides Arv.-Touv. less than 0.5 cm in diameter) and 60 Hieracium umbellalum L. percent rock; and, second, these gravel Hymenoxys acaulis (Pursh) Parker beds or bars must be water saturated to Hymenoxys richardsonii (Hook.) Cockerell intervals during Lactuca serriola L. the surface at frequent Liatris punctata Hook. the growing season, and there must be a 264 GREAT BASIN NATURALIST Vol. 36, No. 3 high water table, within 4 to 10 dm of the thickets where wind velocity decreases. surface, at other times. Bird activities provide other transport The necessity of the gravel being in mechanisms. Downstream species are able streamside bars is not absolute since pop- to extend their ranges upstream nearly as lar seeds have readily germinated and de- readily. In spite of its constancy of veloped into trees in abandoned high change, the riverbottom forest floodplain water table gravel pits on the [)rairies, is a very uniform habitat where macro- for example, 1.5 km west of Fort Alacleod climate and substrate definitely determine and 1.5 km west of Cardston. These trees the establishment of plant species, where are poorly sheltered from the wind. soil moisture conditions are less rigorous New gravel bars saturated with water than in the uplands, and where the hab- on the streams of southwestern Alberta itat can be quite uniform over wide geo- are quickly populated by seedlings of riv- graphical areas. erbottom forest poplar species. These are Riverbottom forest species are oppor- capable of developing into mature forest tunists who take advantage of pioneer trees if the gravel bar or terrace remains sites offered and survive for greater or intact. lesser periods of time as successional High quality loam soil with high soil trends and competition dictate. The nimi- moisture will not produce forest growth. ber of plant species found in any stratum Such sites on the sheltered high banks of the riverbottom forest community is of rivers and coulees may have tangled a direct function of the number of species thickets of serviceberry, chokecherry, adapted to survive the climatic and soil honeysuckle, and hawthorn but rarely regimes. There are many more species of are there poplars growing with them. herbaceous plants than woody ones on the In southwestern Alberta, streams such northern great plains, and a pioneer site as Rolph Creek, Snake Creek, and Bound- such as a gravel bar is a prime target for ary Creek, plus some sections of the colonization by many more herbaceous north and south forks of Milk River, species than woody ones. In this study have high water tables in bankside sand- the ratio of the riverbottom forest woody silt soils; yet they are without riverbot- species to herbaceous species was 41 to tom forest. They are well within the sur- 250. vival and seed dissemination ranges of Plant survival in the floodplain hab- native poplars. itat is considered from the standpoints of Gravel banks and perched ancient survival of the individual and survival of river valley terraces, with gravel in abun- the species. The woody jierennials sur- dance, having subsurface drainage, are vive as individuals for periods of time as without riverbottom forest. River valley short as one growing season or as long as gravel bars formed by unusually high 250 years. Species populations survival flood waters and left too high for sub- is insured because only small portions of surface water saturation will also fail to the total ri\'erbottom forest connnimity develop riverbottom forest stands. Her- area are destroyed each year and the an- baceous S7)ecies may be quite successful nual re-establishment of species on pio- on such sites, however. neer sites offsets population destruction. Streams flowing in very shallow val- The occurrence of many perennial leys, for example the Little Bow River, forbs, as well as annuals, on pioneer or in very open coulees like Pinepound gra\el bar sites is probably due as nuich Coulee are without riverbottom forest to reseeding each year as to renewed not entirely because of exposure to the growth from perennating buds. This is wind but because the necessary liigh true on the many first terrace sites where water table streamside gravels are not iuiiiual high water results in erosion of available. tli(> substrate and consequent removal of Stream systems iiKo provide excel Ifiit most overwintering organs of herbaceous seed dis[)ersal mechanisms. Flowing water s[)(H ies, with the exception of more will bring mountain or submontane spe- (lenseK- intertwined and matted root sys- cies to greater range extensions down the tems. Tbus. abundant sood production is valleys. Wind -borne seeds are readilv a [)rin( ipal species-survival nuM iianism, dropped in the lee of sheltering l)anks and provided such s(H'(Is are imt subiect to September 1976 SHAW: HIVl.HHOTTOM IT)HKST 265

damage by water. Abimrlant seed })ro- fimiously inundated for periods longer duction is a characteristic of members of than four days. The rapid drainage and the most important jilaiit families repre- aeration of gravel soils following flooding sented on pioneer gravel bar sites: Com- also prevents death by root drow^ning. positae, Leguminosae, and Gramineae. Water availability to the roots of trees While survival of the species popula- and shnd:)s in mature riverbottom forest tion is of primary significance in terms is good to excellent throughout the grow- of the vegetation, in terms of mature itig .season. Spring flooding and rainfall riverbottom forest stands survival and recharge of soil moisture are coincident life span of the individual are important. with earlv season leaf-out and photosyn- Hence, the successional trend from f^mvel thesis. High water tables and water seep- bar pioneer site to mature riverbottom ing through the gravels from the upstream forest has, as its parallel, a trend from to downstream sides of a riverbottom herbaceous annuals or short-lived her- forest stand are evident from two observa- baceous perennials with high seed ])roduc- tions: (1) Seepage channels originating tion toward longer-lived woody species in low^ spots in the gravel (i.e., "springs") and herbaceous understory perennials. were flowing or wet throughout most of The ei)hemeral nature of the riverbot- the growing seasons of 1970, 1971, and tom forest community is most favorable 1972. During the summer of 1973, when for establishment of anv edaphically and precipitation and streamflow were below climatically adapted species of plant normal, these springs and seepage chan- capable of producing viable seed. Coloni- nels dried up by early August, but no zation of a new gravel bar by poplars observable woody plant damage due to may be dependent on the production and drouth was noticed. In the same summer distribution of seed in the same year as many herbaceous species in the riverbot- gravel bar formation. Which poplar spe- tom forest failed to develop sufficiently cies or species hybrids dominate the early to flower. (2) During the course of ob- stages in riverbottom forest development taining tree trunk cores for age determi- may be a function of which of them pro- nations, it was commonly noted that as duced the greatest or indeed anv amount the stem core was removed from the in- of seed during the year of colonization. crement borer, varying amounts of tree Poplar species in southwestern Alberta sap would run out the end of the borer do not flower and produce seed every for varying lengths of time. This indicated year. plentiful supplies of water in these trees. Seeds of the southwestern Alberta Boring was done during 1971 and 1972 riverbottom forest community poplar throughout the growing season and into dominants when produced are out of autumn, even as late as mid-October dehiscing capsules by mid-.Tune to mid- after all leaves had dropped. At no time July, just at the time when advantage did sap fail to flow from the tree trunks. can be taken of newly formed gravel By autumn in the very dry year 1973, bars, high water tables in gravels, and sap flow from trees sampled with the high precipitation rates. Survival is thus increment borer was very slow to nil. enhanced. Corings from the driest tree trunks were still wet enough to indicate that no ex- If poplars are to be successful in pop- treme water stress had been placed on the ulating new gravel bars, they nmst be trees. able to survive complete inundation by flood waters several times during the The river valleys originated during gla- years of advancement of the first terrace cial and postglacial times, and the gravels stage to the second. It is doubtful if seed- supplied for riverbottom forest develop- ling survival for all species of poplars ment are glacial in origin (Wyatt 1939). under inundation is the same. If the The higher valley terraces are seldom eight-day survival with complete recovery influenced by the river, and riverbottom reported for P. deltoides by Hosner forest does not develop on them. The (1958) can be applied as a guideline, deepening of the valley by stream erosion then forest species of southwestern Al- is a very slow process. River erosion de- berta riverbottoms are reasonablv safe stroys existing riverbottom communities from drowning since thev are seldom con- and at the same time builds new sites 266 GREAT BASIN NATUKALIST Vol. 36, No. 3

available for community colonization nd deposit Ion (Figure 5). Investigators of floodplain forests in temperate North America (Lee 1945; Ware and Penfound 1949; Shelford 1954) have been in agreement that the pioneer stands of such forests include poplar species. Unlike the riverbottom forest of southwestern Alberta, other riverbottom forests of more temperate climates are capable of successional development beyond the pioneer poplar stage to

stages dominated by other species, such Fig. 5. Successional schema for the river- as maple, ash, and elm. Maple, ash, and bottom forest community of southwestern Alberta, elm are not part of the native flora of Canada. southwestern Alberta, and riverbottom forests here go through a sere of poplar cent forest regions and partly from the species only. These poplar-dominated riverbottom forests on other streams to stands are capable of self-perpetuation if the south, east, and north. Balsam poplar the stability of the substrate permits. {Populus balsarnifera trichocarpa) has Therefore the successional pathway to the followed the streams down through the climax may be very short; the pioneer foothills from Rocky Mountain popula- stage to a climatic-edaphic climax with tions. Narrowleaf cottonwood {Populus the same species and perhaps even the angustifoUa) seems to have spread from same individuals as codominants. stream to stream along the edge of the Acer negundo, Fraxinus pennsylvanica, foothill zone from the south (Brayshaw Lonicera tartarica. Populus sargentii, and 1965). Narrowleaf cottonwood has not some exotic poplar hybrids have been in- extended its range into the transition and troduced into southwestern Alberta by montane forests of the lower mountain man. In spite of these introductions and slopes, nor has it extended its range more the success of the individuals, no exotic than casually east and north beyond Leth- species of woody plants have become im- bridge. portant members of the southwestern Al- Narrowleaf cottonwood-balsam poplar berta riverbottom forest community. This hybrids have their population centers is true despite their importance in flood- within the areas of overlap of the parent plain forests of other regions. species. Brayshaw (1965) found scattered It is doubtful that any of the 291 species AB hybrids in eastern Alberta well be- of plants found in this study are truly yond the distribution limits of the parent riverbottom forest endemics. Even the species. dominant species of the four different Plains cottonwood {Populus sargentii), strata are not limited to the riverbottom a most important eastern and northern forest community. Each of the poplar spe- species of floodplain forests, has been un- cies can be found in some other habitat, able to colonize the valleys of St. Mary from abandoned gravel pit to home River and Lee Creek. Its range does ex- shelterbelt. River birch and dogwood can tend up Belly River to near Monarch. be found on moist sandy soil sites in Quaking aspen {Populus trcrfiuloides) other plant communities, and snowberry, is a ubiquitous species, finding any moun- silverberry, rose, and serviceberry are tain and foothills climate to its liking, likewise scattered across the plains and re([uiring only adequate soil moisture, and coulees of the grasslands and aspen park- [)ersisting in small stands on the better land. Four of the nine herbaceous stratum soils along river valleys where conditions dominants are intrfxiuced exotics found are similar to those of its population in a wide variety of other habitats. Of centers in the Rocky Mountain foothills the five native herbaceous dominants not and tlie northern half of Alberta. one is truly endemic to the southwestern Superficial estimates of jioplar species Alborta riverbottom forest connnunity. ill pioneer stands indicated that seedlings The riverbottom forest poplar dom- of narrowleaf j)oplar, balsam poplar, and inants are derived partly from the adja- AB hybrids were jiresent. Colonization of Soptembor 1976 SHAW: RIVKRBOTTOM FOREST 267

new gravel bars does not seem to be the zation ability and its greater average prerogative of any one poplar species, longevity than to its reproductive ability but this is only a tentative conclusion and in the mature forest. must be verified through further study. I'he growth in diameter of poplars on In the mature riverbottom forest com- the three study streams is not nearly munity a comparison of importance val- so rapid as the growth of other poplar ues for the three poplar dominants shows species in better climates. Shelford's that there is little difference between (1954) report of Populus deltoides on the those values for mature trees (narrowleaf Mississippi River floodplain growing to a Cottonwood 94.5. balsam poplar 89.9, AB diameter of 60 cm (24 in ) in 20 years hybrid 110.8) and for tree reproduction is in great contrast to the 13 and 16 cm (narrowleaf cottonwood 118.9, balsam (5 and 6 in) diameters achieved by St. poplar 90.7, AB hybrid 79.1). The dif- Mary River, Lee Creek, and Belly River ferences in importance values for trees poplars in the same span of time. during early stages of riverbottom forest Mature ri\erbottom forest stands that development can best be accounted for b}' have been under a heavy grazing regime, considering that such differences are the by sheep in particular, are quite open, product of the random colonization of and one can walk through them with new sites by available seeds. Succession only minor deviations in his course (Fig. in mature stands seems to favor one 6). Shrubs occur singly or in small poplar slightly, the AB hybrid. patches, and between these are low- At the beginning of this study, my pre- growing herbaceous species. This "English conceived opinion was that narrowleaf Park" appearance contrasts with other cottonwood was unable to compete \^dth stands grazed lightly or not at all. These other poplar species when forest maturity can be most difficult to walk through. was reached. If this hypothesis were true, Rose thickets, silverberry thickets, dog- then it should be expected that narrow- wood clumps, and snowberry patches can leaf cottonwood importance values would be so dense, continuous, and high as to be very low in sampled mature stands of be impenetrable to all but the most de- riverbottom forest. To the contrary, in termined person. each of the 10 study stands this species No correlation could be found between was a very important constituent of the the average age of trees in a stand and mature tree stratum. Its importance value average penetrometer readings for stands. average of all stands, 94.5, made it more Alluvium buildup is a product of the important than balsam poplar (I.V. number of over-bank floods that have 89.9) and only slightly less important occurred during the life of the terrace than the AB hybrid (I.V. 110.8). In its and these vary from stand to stand. ability to reproduce and perpetuate itself Observation of exposed root systems, within the community narrowleaf cot- undercut, and fallen trees shows that lat- tonwood had the highest average impor- eral stream migration is a major factor tance value (118.9) in comparison to with which floodplain plants must con- balsam poplar (I.V. 90.7) and the AB tend (Lindsay et al. 1961). It is due to hybrid (I.V. 79.1). this erosion on the one side and deposition As for absolute values, narrowleaf cot- on the other that the floodplain owes its tonwood ranked intermediate in density existence. The proportion of over-bank (91.5 trees per hectare) between balsam deposits is very small compared to chan- poplar (88.9 trees per hectare) and the nel deposits.

AB hybrid (96.9 trees per hectare). Island formation on St. Mary River, Absolute density values in tree repro- Lee Creek, and Belly River is rare in duction for all stands put narrowleaf cot- contrast to its importance on other streams tonwood well ahead (113.^ saplings per (Lindsay et al. 1961). hectare) of balsam poplar (81.5 saplings In spite of the quantities of tree and per hectare) and the AB hybrid (65.0 shrub leaves and other herbaceous debris saplings per hectare). falling to the ground each autumn, only The relative success of the AB hybrid shallow layers of organic material have in the mature tree stratum may be due accumulated on the surface of mature more to its greater pioneer site coloni- riverbottom forest soils. Autumn winds 268 PREAT BASIN NATURALIST Vol. 36, No. 3

Fig. 6. Riverbottom forest stand on St. Mary River at Woodgrove Park. Clumped and thicket shrubs have been largely killed out through sustained high intensity grazing by domestic sheep. blow the leaves away or pile them in that clearing of riverbottom forest by sheltered spots. Saprophytic reduction is inan for farming has never been an agri- rapid and by leaf-out of the next spring cultural practice. Third and higher grass- the previous year's organic debris is little land terraces wdth good soil are suf- in evidence. ficiently removed from flood danger to Mechanical damage to standing trees make farming them no more hazardous during over-bank flooding appeared to than farming the surrounding prairies. be minimal, based on a survey of trees in The effect of prairie v\ildfire. long stands flooded in 1964. Trees torn away known to be devastating to Indian and by lateral corrosion are badly abraded settler alike, on riverbottom forest is un- by transported and bottom gravels as they known. Various accounts of prairie wild- are tumbled downstream. Over-bank fires in southwestern Alberta settlement floods with slower moving water transport days tell of the importance of creeks and only the finer sands and silts that do not rivers in stopping the fire but do not damage tree stems. Ice blocks were fre- mention what effect the fire had on trees quently pushed or floated out on to first along these streams. Poplars a:?e not terrace pioneer sites during unusual notably fire-resistant sjjecies; thus the winter and normal early spring break up. probability of damage or death to them Hydraulic pressure exerted from below is great. The high percentage of bare by increased streamflow will break heavy ground luider the forest probably afforded ice into cakes, and these float down- some fire protection. stream until the receding water leaves Riverbottom forest stands grazed by them stranded on gravel bars. The general cattle tend to remain heavily brushed. and unsupported hypothesis is that ice Grass forage is minimal and use is made does not cause appreciable damage to j)i()- of the forest for shade ckiring hotter sum- neer or mature riverbottom forest stands. mer days. Sheep have been effective in Soils under riverbottom forest stands reducing shrub densities and promoting are gravelly and topsoil layers .so thin grass cover in several riverbottom forest — — ——

SepU'inher 1976 SHAW; lUVKUHOTTO.M JT)HKST 269 stands. Heavy grazing by sheep can re- interwoven pattern of (1) new gravel duce tree reproduction to nil and promote bar, the first terrace, formed by river de- development of a grassland which as- position; (2) pioneer riverbottom forest sumes dominance as the forest trees reach on the first terrace gravel bar floristically maturity and die. composed of herb species and poplar species' seedlings; (3) maturing riverbottom Summary and Conclusions forest stands on first and second terraces with poplar saplings, clumped and thicket Ten stands in the riverbottom forest shrub invaders, and herbs; and (4) pop- community of St. Mary River, Lee Creek, lar-dominated climax stands capable of and Belly River in southwestern Alberta, self-iier[)etuation, with mature clumped Canada, were analyzed for plant species and thicket shrubs and perennial herbs. com})osition during the period 1970-1973. Any stage in succession may be destroyed Four vegetational strata in the commu- (hiring progressive lateral erosion by the nity are recognized: (1) the tree canopy ri\er, and this is the usual fate of the and its reproduction, (2) clumped shrubs, climax forest. (3) thicket shrubs, and (4) herbaceous Unoccupied space (bare ground and understorv. Vegetational anal^'sis methods litter) accounted for 66.2 percent of the were: ( 1 ) the point-centered quarter total herb stratum area. method for trees, tree reproduction, and Riverbottom forest soils range from clumped shrubs; (2) the line-intercept gravel (61.1 percent rocks greater than method for thicket shrubs; and (3) the 0.5 cm diameter and 38.9 percent sand) quadrat method for herbaceous vegetation to sandy loams above a gravel base of and unoccupied space. Data were sum- unknow^n thickness. The sandy loam sur- marized and reported in absolute terms face layer is the result of a buildup of (density, dominance) and relative terms water-borne particles deposited during in- (percent density, percent dominance, per- frequent over-bank flooding. Mean pene- cent frequency, importance value). Simi- tration of the soil by the penetrometer larities between the 10 stands outweighed averaged 0.4 dm on gravel bar pioneer the dissimilarities, and all 10 stands were forest sites and 2.5 dm in mature forest deemed to be parts of a southwestern Al- sites. The pH values averaged 8.0 on berta riverbottom forest community. gravel bar pioneer sites, 7.7 in mature Dominant species and their importance forest soils, and 7.6 in neighboring fescue value, based on a maximum possible of prairie grassland soils. Soil soluble salts 300, in the four vegetational strata of the averaged 176 parts per million on gravel mature riverbottom forest community bars, 458 ppm in mature forest soils, and were: (1) trees Popidus X balsamifera 409 ppm in the neighboring grassland I.V. 110.8. P. ongustifolia I.V. 94.5, P. soils. balsamifera I.V. 89.9; tree reproduction The average diameters and ages of the ~P. angustifolia I.V. 118.9, P. balsam- poplar dominants in mature riverbottom ifera I.V. 90.7, P. X balsamifera I.V. 79.1; forest stands were ( 1 ) Populus X bal- (2) clumped shrubs Betula occidentalis samifera 26.2 cm, 45 years; (2) P. bal- I.V. 171.8. Cornus stolonifera I.V. 72.1; samifera 21.8 cm, 38 years; and (3) P. (3) thicket shrubs Elaeagnus com- angustifolia 20.8 cm, 36 years. Maximum mutata I.V. 80.5, Symphoricarpos occi- age for any single tree of the dominant dentalis I.V. 59.0, Rosa woodsii I.V. 55.3, poplar species was (1) P. X balsamifera Amelanchier alnifolia I.V. 30.9; (4) 250 years, (2) P. angustifolia 160 years, herbs Poa pratensis I.V. 41.9, Medicago and (3) P. balsamifera 155 years. Height lupulina I.V. 26.3, Poa compressa I.V. of the mature poplar dominants ranged 12.1, Chrysopsis villosa I.V. 11.1. Solidago from 15 to 22 meters. mollis I.V. 10.6, Phleum pratense I.V. The climate of southwestern Alberta 10.4, Oxytropis viscida I.V. 10.1, Aster is typically continental and cool, with laevis I.V. 9.3, Fragaria virginiana I.V. warm summers and cold winters. Average 7.5. All of the woody plant dominants annual precipitation is 45.8 cm (18.04 and five of the nine herb dominants are in.) with 65 percent of the total falling species native to southwestern Alberta. during the growing season. Succession in the southwestern Alberta Development of riverbottom forest is riverbottom forest community follows an conditional on climate and substrate. The 270 GREAT BASIN NATURALIST Vol. 36, No. 3

climate determines the species that are BoiviN, B. 1969. iFlora of the Prairie Provinces able to survive in southwestern Alberta, I, II, III, IV. Canada Dept. of Agriculture, Ottawa. Ontario, Canada. and the continually forming gravel bars Booth, W. E. 1950. Flora of Montana. I - of the streams provide the necessary sub- Conifers and monocots. Montana State Univ., strate. Development of the forest is cor- Bozeman. related with May-June flooding and grav- Booth, W. E., .^nd J. C. Wright. 1966. Flora of Montana. II - el bar formation; May-June precipitation; Dicots. Montana State Univ., Bozeman. June-July poplar seed production, dispers- BouYoucos, G. J. 1936. Directions for making al, and germination; and a high water mechanical analyses of soils by the hydro- table in the gravel substrate. The gravels meter method. Soil Sci. 42: 225-229. BR.'VYSH.Awr, are of mountain and continental glacial T. C. 1965. Native poplars of southern Alberta and their hybrids. The Queen's origin and overlie strata of Upper Cre- Printer, Ottawa. Ontario, Canada. taceous and Tertiary ages. . 1971. Unsubstantiated i-eport of Pru- The riverbottom forest flora is com- nus nigra Ait. in Alberta. Pers. comm. to the posed of 291 species of vascular plants in author. Breitung, a. J. 1957. Plants of Waterton 165 genera representing 50 families. Of Lakes National Park. Canadian Field-Nat- these 291 species, 41 are woody plant uralist 71: 39-71. species and 250 are herbs. The plant BuDD, A. C. 1957. Wild plants of the Canadian families contributing most to the river- prairies. Canada Dept. of Agriculture, Ottawa. Ontario, Canada. bottom forest community flora are Com- C.'>iNAD.A Department of Regional Economic Ex- positae, Leguminosae, Gramineae, Rosa- pansion. 1971. Streamflow data for south- ceae, Salicaceae, and Umbelliferae. These west Alberta river systems. Pers. comm. to six families account for 76 (46 percent) of the author. Canada Department of the genera and 172 (58 percent) of the Transport. 1967. Temperature and precipitation tables for species. prairie provinces III. Ottawa, Ontario, One species new to Alberta was found. Canada.

Canada Plum {Prunus nigra Ait.) is now . 1969. The climate of Canada. Toronto. known from Lee Creek, 0.5 km southwest Ontario. Canada. Cody, W. J., and K. Shaw. 1973. Canada Plum of Cardston, Alberta. Range extensions for in southwestern Alberta. Blue Jav 31: 217- 12 species were provided by this study. 219. No species of plant is truly endemic to Cormack, R. G. H. 1967. Wild flowers of Al- the riverbottom forest in southwestern Al- berta. Queen's Printer, Edmonton, Alberta. Canada. berta. Plant species in the riverbottom CoTTAM. G.. and J. T. Curtis. 1956. Use of forest community are opportunists able to distance measures in phytosociological sam- take advantage of the continuing avail- F)ling. Ecology 37:451-460. ability of new gravel bars for colonization. Cox. G. W. 1967. Laboratory manual of general ecology. Wm. C. Brown Co.. Dubuque. Iowa. The riverbottom forest community of Dyson, J. L. 1949. The geologic story of Gla- southwestern Alberta has little economic cier National Park. Glacier Natural History value. Livestock grazing and shelter are iA.ssociation. West Glacier, Montana. the major uses with recreation as a minor Ewers, .1. C. 1958. The Blackfeet: Raiders on use. This community provides some wild- the northwestern plains. University of Okla- homa, Nonnan. life habitat, especially for white-tailed Fmnt, R. F., C. R. Longwem., and A. Knopf. and mule deer. 1941. Outlines of physical geology. .lohn Fire is unimportant in riverbottom Wi!e>- and Sons, New York. forest dynamics at the present time. The HiGGiNs, L. C. 11971. A revision of Cryptantha; greatest altering force of riverbottom subgenus Oreocarya. Brigham Young Uni- forest stands is water erosion. versitv Scieiue Bulletin. Biologicid Series 13 (4). The riverbottom forest community of HosiE, R, C. 1969. Native trees of Canada. St. Mary Ri^er, Lee Creek, and Belly Dominion Forest Service, Ottawa, Ontario. River in southwestern Alberta, Canada, Canada. is a unique ecological entity characterized HosNKH, ,r. F. 1958. The fffect-; of complete by poplar species that have their major inundation u|)on seedlings of six bottomland Alberta distribution along these streams. tree species. Ecology 39:371-373. Hudson. A. .1. 1963. Charles Ora Card: Pioneer and colonizer. Privately Literati IRK Citkd printed. Cardston. Alberta. Canada.

Barker, E. N. 1QS7. T}i.> Lifo of E. N. Barker, Humphrey, H. B. 1924. Tiie |)livt(igc()gi;ii>hy Lethbridge Herald. EethbridRc, Alberta. of the Couer d'Alene flood plain of jiortlierii Canada. Idaho. Ecology 5:6-13. Soptoinbor 1076 SHAW: RIVERBOTTOM FOREST 271

KtTi.iT. I. 1072 Conininn ronloo plants of Salt. W. R.. and A. E. Wii.k. 1058. The soutlioiii All)orta. Uiiivorsit\' nf I.othbriHgo. birds of Alberta The Queen's Printer. Ed- I.othliiidgo, Alberta. Canada. monton. Alberta. Canada. I.F.E. M. B. 1945. An erologiral study of the Shaw, P. C. 1972. The location of "Woodgrove flood plain forest along the White River sys- Park." Pers. comm. to the author. tem of Indiana. Butler University Botanical Sii.\w. R. K. 1968. Guide to the woody plants Studies 7:15'5-16'5. of the Lee Creek Valley. Privately printed. I,iNDS.\Y. A. A., R. O. Petty. D. K. Sterling. Cardston. Alberta, Canada.

.•\ND W. V.\nA.sd.\li.. 1061. Vegetation and ——— . 1972. Guide to the woody plants of environment along the Wabash and Tippc the prairies, foothills and valleys of south- canoe riv(>rs. Ecol. Monog. 31:10t-1'^6. west Alberta. Privately printed. Cardston. I.oNGi.EY. R. W. 1068. Climatic maps for Al iAlberta, Canada. berta. T"^niversity of Alberta. Edmonton. SitEMnRD. V. E. 1954. Some lower Mississippi Maci.eod. N. W. 1000. Picturesque Cardstoii Valley flood plain biotic communities; their and environments. Privately printed. Cards- age and elevation. Ecology 35:126-142. ton. Northwest Territories. SoPER. .T. D. 1064. The mammals of Alberta. Macoun. J. 188^-1000. Catalogue of Canadian Tlie Queen's Printer, Edmonton. Alberta. plants. Geological and Natural Histon' Sur- Canada. vey. Ottawa. Ontario. Canada. Standi.ey. P. C. 1921. Flora of Glacier National McCi.iNTOCK. W. 1010. The Old North Trail Park. Contr. U.S. Nat. Herb. 22: (5). I^niversity of Nebraska. Lincoln. 1949. Mei.ton. F. a. 1036. An empirical classifica- Ware. G. H.. and W. T. Penfound. tion of flood plain streams. Geog. Rev. 26: The vegetation of lower levels of the flood •)03-600. plain of the South Canadian River in central Moss, E. H. 105^). The vegetation of Alberta Oklahoma. Ecology 30:478-484. Hot. Rev. 21:403-'567. We.wer. J. E. 1960. Flood plain vegetation of

. 1959. Flora of Alberta. University of the central Missouri vallev and contacts of Toronto. Toronto. Ontario. Canada. woodland with prairie. Ecol. Monog. 30: Native Trees of Canada. 1049, 1056. 1961. 37-64.

Dominion Forest Service, Ottawa. Ontario. Welsh. S. L. 1960. Legumes of the north- Canada. central states. Galegeae. Iowa State J. Science Neii.i.. C. R.. and V. ,T. Galay. 1967. Syste 35: (2). matic evaluation of river regime. .1. Water- Wistendahl. W. a. 1058. The flood plain of ways and Harbors 03:25-53. the Raritan River. New Jersey. Ecol. Monog. Rice. E. L. 1065. Bottomland forests of north 28:129-153. central Oklahoma. Ecologv 46:708-713. of Lethbridge Rydberg, P. A. 1922. Flora of the Rock v Moun- Wyatt. F. a. 1939. Soil survey I^niversity of tains and adjacent plains. New York Bo and Pincher Creek Sheets. tanical Garden. New York. Alberta. Edmonton.

. 1932. Flora of the prairie and plains Yang. C. T. 1971. Potential energy and stream of central North America. New York Bo- morphology. Water Resources Research I: tanical Garden. New York. 311-322.