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UBC Theses and Dissertations

Effects of certain climatic factors on the productivity and availability of forages on the Ashnola bighorn… Harper, Frederick Eugene 1969

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EFFECTS OF CERTAIN CLIMATIC FACTORS ON THE PRODUCTIVITY AMD AVAILABILITY OF FORAGES ON THE ASHNOLA BIGHORN WINTER RANGES by FREDERICK EUGENE HARPER B.S.A., University of British Columbia A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of PLANT SCIENCE We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA June, 1969 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h C o lumbia, I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and Study. I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f fzdauvCt' ^ACAJLMjtty The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date \l/JMJi 9f /?<>? i ABSTRACT The seasonal development c.nd yields of four major plant communities, of the important winter ranges of California bighorn sheep (Ovis canadensis californiana Douglas) in the Ashnola region, and their relation to basic climatic factors, were studied from May 1967 through December 1968. The four communities were: D a bunch grass community dominated by Agropyron spicatum, 2) a sod grass community dominated by Poa pratensis, 3) a tree understory community dominated by Calamagrostis rubescens and 4) a half-shrub community dominated by Artemisia frigida. The climatic variables measured were: ambient air temperature, precipitation, including snow, evaporation and wind. Run-off, soil moisture and soil temperature were also measured. To reduce climatic variations between communities, a l l study sites were located at approximately the same elevation and were close to one another. Virtually a l l forage production in the four communities, in the growing seasons of both 1967 and 1958, occurred before the end of July. After this time, due to shattering, leaching and decay, decreases in herbage weights, ranging from 23 to 35 percent occurred by autumn, and further losses, ranging from 7 to 36 percent occurred over winter. The mean growth rates were essentially the same in the two years, but the cessation of growth two weeks earlier in 1968, resulted in lower production than in 1967. The dates spring grovrth commenced coincided closely with the dates that mean daily temperatures rose to 42 degrees Fahrenheit, whereas the dates growth ceased coincided closely with the dates that available soil water was exhausted. Both ambient air temperatures and i i soil temperatures remained favourable for growth until early autumn. The length of the growing season is the main factor deterroining net productivity of the Ashnola bighorn winter ranges; temperatures determine the beginning of the season and soil moisture deficits terminate the season. Moreover because the growing season is relatively short, climatic influences are important factors determining how much of the forage produced will remain potentially available for overwintering bighorn. i i i TABLE OF CONTENTS Page ABSTRACT i TABLE OF CONTENTS i i i LIST OF TABLES vi LIST OF FIGURES ix ACKNOWLEDGMENTS xi INTRODUCTION 1 SECTION I - VEGETATION 4 METHODS AND MATERIALS 6 Site selection 6 Vegetation measurement 9 Field design 12 RESULTS 13 Species composition of vegetation 13 Range vegetation phenology 19 Forage yield 19 Effect of clipping 28 Crude protein yield 28 DISCUSSION 33 •SUMMARY 39 LITERATURE CITED 42 SECTION II - CLIMATE . 45 METHODS AND MATERIALS 45 Atmosphere near the ground . 4 6 Temperature 46 Precipitation 49 Evaporation 49 Wind 49 iv Pag3 Soil 49 Soil moisture 51 Soil temperature 52 Run-off 52 RESULTS 56 Atmosphere near the ground 56 Temperature 56 Precipitation 58 Evaporation 62 Wind 63 Soil . . 6 4 Soil moisture 64 Soil temperature 68 Run-off 68 DISCUSSION 72 Atmosphere near the ground 72 Soil 74 SUMMARY 77 LrrERATURE CITED 79 SECTION III - INTER-RELATIONSHIPS OF VEGETATION AND CLIMATE : INTRODUCTION GROWING SEASONS Actual growing seasons Factors regulating growing seasons 80 80 83 83 84 V Page COMPARISONS: GROWTH WITH AMBIENT AIR TEMPERATURES, . EVAPORATION, PRECIPITATION AND FORAGE YIELDS SUMMARY LITERATI FRE CITED 89 100 102 APPENDICES 104 v i LIST OF TABLES Table No. Page 1. Elevation, aspect, slope and soil class of each study site 7 2 2. Ratios of mean basal area (cm ) per square meter to percent frequency of major plant species in the three Agropyron spicatum sites 14 3. Ratios of percent crown hits per square meter to percent frequency of major plant species in the three Poa pratensis sites 15 4. Ratios of percent crown hits per square meter to percent frequency of major plant species in the Calamagrostis rubescens site 16 5. Ratios of percent crown hits per square meter to percent frequency of major plant species in the Artemisia frigida site 17 6. Dates in 1967 and 1968 at which various developmental phases were first observed in major plant species 20 7. Mean dry matter yields for 1967 and winter carry-over, from plots clipped at sequential dates in • three plant communities 21 8. Mean dry matter yields for 1968 from plots clipped at sequential dates in three plant communities - 22 9. Comparisons of peak yield, f a l l yield, and winter . carry-over in 1967 in the Agropyron spicatum, . • Poa pratensis and Calamagrostis rubescens mesic exclosures 25 2 10. Comparison of dry matter yields Cgm/m ) for 1967 and 1968, between and within four major plant communities and their moisture sub-communities 27 11. The effect of a single ground level clipping treatment at different dates in 1967 upon subsequent regrowth by August 30, 1967 in the Agropyron spicatum and Poa pratensis mesic sites 29 v i i Table No. Page 12. Crude protein content of forage from three plant communities at sequential dates through 15:67 31 13. Some physical properties of soils from each stud}, site ' 5 3 14. Monthly mean temperatures in degrees Fahrenheit (OF) for the two climatic base stations on Flatiron Mountain and for Keremeos, B .C. , from May, 1967 through December, 1968 57 15. Monthly precipitation (inches) for three climatic stations on Flatiron Mountain and one at Keremeos, B.C. from May 1967 through December, 1968 60 16. Monthly evaporation from May through October in 1967 and 1968 for three Flatiron Mountain sites and for Keremeos, and Cawston, B.C. 62 17. Average wind velocities (miles per hour) from August to December 1968 at two sites on Flatiron Mountain 63 18. Inches of soil'water at sequential dates in 1967 for the top 6 inches of soil at eight study sites on Flatiron Mountain 65 19. Inches of soil water at sequential dates in 1968, for 6 inch soil horizons from 0 to 24 inch soi l depth, at eight study sites on Flatiron Mountain 66 20. Soil temperature in degrees Fahrenheit, at 20 inches depth at sequential dates through 1968, at eight study sites on Flatiron Mountain 69 21. Inches of run-off and precipitation in 1968 for four sites on South Slope and two sites on Juniper Slope 70 22. Actual growing seasons and dry matter yields in 1967 and 1968 at two sites on Flatiron Mountain 84 Table No. 23. Relationships of actual growing seasons and periods when ambient air temperature and soil moisture supplies were favourable to growth 24. Comparisons of dry matter yields for the xeric, mesic and hydric sites in the Agropyron spicatum community, with soil moisture regimes in 1967 and 1968 25. Comparisons of dry matter yields for the xeric, mesic and hydric sites in the Poa pratensis community, with soil moisture regimes in 1967 and 1968 ix LIST OF FIGURES Figure No. Page 1. Aerial photograph showing the locations of slopes and study sites on Flatiron Mountain 8 2. Fenced exclosure on the Artemisia frigida mesic site 10 3. Cage exclosures on the Poa pratensis hydric site " 10 4. Changes in dry matter herbage through 1967 and 1968 at: figure 4(a) the Agropyron  spicatum mesic site, figure 4(b) the Poa  pratensis mesic site, and figure 4(c) the Calamagrostis rubescens mesic site 24 5. Crude protein yields in three plant communities at sequential dates through 1967 32 6. Schematic diagram of locations of climatic equipment within vegetation exclosures 47 7. Stevenson screen and evaporimeter assembly in the Poa pratensis mesic site 48 8 . Sacramento snow gauge in the Agropyron spicatum mesic site - 50 9. Carborundum block evaporimeters 50 10. Run-off gauge in the Poa pratensis mesic site 54 11. Control gauge in the Poa pratensis mesic site 54 12. Mean daily temperatures on a weekly basis at the Agropyron spicatum site from May 1967 through December 1968 59 13. Weekly precipitation from May 10 to October 20 in 1967 and daily precipitation from May 10 to September 30 in 1968, as measured with standard rain gauges (1967) and with tipping bucket rain gauge (1968) at the Agropyron spicatum site 61 Comparisons of cumulative "degree days" above a base of U3°F and cumulative evaporation to plant growth in 1967 and 1968 in the Agropyron  spicatum mesic site Comparisons of cumulative "degree days" above a base of 43°F and cumulative evaporation to plant growth in 1967 and 1968 in the Poa  pratensis mesic site Precipitation patterns in 1967 and 1968, in relation to plant growth in the Agropyron  spicatum and Poa pratensis mesic sites xi ACKNOWLEDGMENTS ! The field work of the project was financed by the Department of Plant Science, University of British Columbia, the B.C. Fish and Wildlife Branch and the Canada Department of Agriculture. Laboratory facilities and office space were provided by the Department of Plant Science, University of British Columbia. I am indebted to Dr. V.C. Brink, Chairman, Department of Plant Science and to Dr. P.J. Bandy, Head of Research Division, B.C. Fish and Wildlife Branch, for suggesting and direct'ing this study. Dr. Ian McTaggart Cowan, Dean of Graduate Studies', Dr. D.P. Ormrod, Professor, Department of Plant Science and Dr. J.R. MacKay, Professor, Department of Geography, gave invaluable assistance, particularly during the preparation of the manuscript. Messrs. A. McLean, L. Farstad and T.M. Lord, Research scientists, Canada Department of Agriculture, made valuable contributions throughout the study. Mr. Ron Erickson, undergraduate student, University of British Columbia, assisted with the 1968 field work and to him I owe a special debt of thanks. His co-operative nature and untiring efforts exceeded any ordinary expectations. The field work was made considerably more pleasant in November of 1967 by the construction of a log cabin in the study area; construction would not have been possible without the able and willing assistance of my father, Richard E. Harper and my father-in-law, Willard .Lynch. The services and hospitality offered by the Quadveleig families of the Harrington Ranch, Keremeos, throughout the study were gratefully X l l appreciated. In the course of this endeavour my wife, Lorraine, has endured without complaint, and provided the necessary encouragement, invaluable help and inspiration, which made possible its ultimate completion. To these people, and many others who contributed both technical and personal assistance, I am deeply indebted. INTRODUCTION , The prime purpose of this study was to investigate the relayionship between the moisture regime and net productivity (principally forage yield) i n the range ecosystem of the Ashnola river basin. The Ashnola region, located in south-central British Columbia (see Figure 1), is semi-arid, and a knowledge of the critical environmental factors determining plant growth i n this region, is essential as a basis for sound management of the range resource. The study is presented in three sections: (I) the seasonal development and yield of major forage species, (II) the climate, with particular reference to components of the moisture regime and (III) the analyses of relationships between climatic data and forage production. On semi-arid rangelands moisture is widely recognized as the primary factor limiting plant growth and net productivity. However, when management programs are formulated the moisture regime and its effects on the vegetation are seldom considered. Numerous studies have shown that the annual variations in yield, which are considerable, are almost entirely attributable to annual differences in available moisture (Blaisdell, 1958; Clarke et a l . 1943; Craddock and Forsling, 1938; Currie and Peterson, 1966; Dahl 1963; Sneva and Hyder, 1962). Grazing should therefore be closely coordinated with the water available for plant growth. Moreover, range improvement programs, such as those involving reseeding or fertilizing, should proceed only when based on a knowledge of the distribution and abundance of moisture. Even range surveys and range classification programs would be more useful i f they made use of moisture data. Synecological classification might also be more meaningful. For example, Daubenmire (1968(a)) showed clearly how climax communities within 2 fairly iarge geographical areas, are often more closely associated with the soil vioisture regime than with any other environmental factor. The grassland ranges of the Ashnola River Valley are heavily used and in n?ed of improvement and better management. Most of the ranges, according to Blood (1961) and Demarchi (1965) are retrogressing and productivity is less than maximum. At present an estimated 350-400 California bighorn sheep (Ovis canadensis califomiana Douglas)''" and a large population the size of which is not known precisely, of Rocky Mountain mule deer (Odocoileus hemionus hemionus Rafinesque) use the ranges during the winter and spring months (D. Spalding personal communication). In addition, the ranges are grazed by approximately 600 cattle during the late spring, summer and autumn months. Previous grazing use, which started in the late 1800's was even greater. Cattle numbers were higher before 1950, up to 1,000 domestic sheep grazed the area intermittently from 1913 to 1923, and at least 250 horses used the ranges prior to 1919 (Buechner 1960; Blood 1961; Demarchi 1965). The present bighorn population, although considerably reduced since the late 1800's, has remained relatively stable since 1910. Earlier workers, notably Blood (1961) and Demarchi (1965) concluded that the main factor limiting the bighorn population is a shortage of winter food. On the other hand, the extensive forested ranges of the Ashnola region have been only lightly grazed and are in excellent condition. These Mammalian nomenclature after Cowan and Guiget (1965) 3 ranges are not used to any extent by the bighorn. However, the understory vegetation, although less productive than the grassland vegetation, could provide valuable forage for domestic stock i f proper management was employed (McLean 1967). The ranges of Flatiron Mountain were chosen for the present study. These ranges presently support most of the Ashnola bighorn population, are located near the geographical center of the area and have been generally described by Blood (1961) and Demarchi (1965). 4 SECTION 1  VEGETATION The Ashnola watershed lies in the transition zone between the Cascade Mountain System to the west, south and east, and the Interior Plateau to the north (Holland 1964). Altitudinal range is great, with a small portion of the area lying below 2,000 feet in deeply entrenched U-shaped valleys, and an upland of moderate relief above 4,800 feet. The entire area was glaciated during the Pleistocene and the soils have been formed largely of glacial material. Excluding the alpine and sub-alpine regions, approximately 90 per cent of the soils fall into two orders of classification; chernozems occur over the open and semi-open grassland areas, and brunisols precbminate over most of the forest lands (T.M. Lord - personal communication). Unfortunately a soil survey has not been conducted in the area and the full array of soils is not known. Demarchi (1965) studied only the chernozem soils and reported several soils ranging between the Orthic black silt subgroup and the Rego dark grey subgroup. The native vegetation of the non-alpine regions of the Ashnola watershed consists predominantly of coniferous trees with an understory of perennial grasses, forbs, and some shrubs. However, the tree cover is not continuous and grasslands have developed on more southerly exposed slopes. As described by Tisdale (1947), marked vertical zonation of the vegetation occurs in both these range types. At elevations below approximately 2,000 feet a "parkland" classifiable as lower Montane forest (Rowe 1959), of open ponderosa pine (Pinus ponderosa) and occasional Douglas f i r (Pseudotsuga menzeisii i ! var. glauca) occurs, with an understory of bluebunch wheatgrass (Agropyron spicatum var. inerme). Where the understory is heavily grazed weedy vegetation has developed. Above 2,000 feet, Douglas f i r becomes the dominant tree of the Montane forest, with an understory vegetation dominated by pine grass (Calamagrostis rubescens). The Douglas fi r zone merges with an Engelmann spruce (Picea engelmanni) zone at elevations between 5,000 and 6,000 feet, depending on aspect and exposure. The latter zone extends up to the alpine regions, which begin at elevations of approximately 7,000 to 7,600 feet (Rowe 1959). Grasslands occur at al l elevations and occasionally extend up to the alpine tundra. When in climax condition they are dominated by bluebunch wheatgrass (Demarchi 1965). Between elevations of 2,000 and 4,500 feet this forage species is associated predominantly with Junegrass (Koeleria  cristata) while at elevations between 4,500 and 6,200 feet, the associate species is Idaho fescue (Festuca idahoensis). Both of these communities have developed on Rego dark grey soils. Where as a result of heavy grazing, these communities are serai, the lower grasslands are dominated by Junegrass and Sandberg bluegrass (Poa secunda), while at higher elevations pasture sage (Artemisia  frigida) and Junegrass are common. ^Nomenclatural lists of plant species are given in Appendix I. 6 Other communities which have developed on the Orthic black ^oils I are dominated by Kentucky bluegrass (Poa pratensis), or downy brome (Bromus tectorum), together with Columbia needlegrass (Stipa Columbiana). METHODS AND MATERIALS Site selection Four plant communities, each characterized rather well by a single forage species, were chosen for intensive study by reconnaissance in April, 1967. All communities were located roughly on the same contour of elevation and represent quite completely the forage resource of the study area. In the first community, characteristic of the grassland area known as "South Slope", Agropyron spicatum is the principal species, and in the second community, characteristic of the grassland area known as "Juniper Slope", Poa pratensis is the principal species. The third community, characteristic of the ridges of both South Slope and Juniper Slope, is dominated by Artemisia frigida and the fourth community, characteristic of the nearby montane forest undercover, is donunated by Calamagrostis rubescens. On the premise that the ridge soils were probably driest, those of the slopes average and those of the swales or basins wettest, moisture subcommunities, designated as "xeric", "mesic" and "hydric" sites respectively, were located in the communities dominated by Agropyron  spicatum and by Poa pratensis. Only a mesic site was selected for the Artemisia frigida community and for the Calamagrostis rubescens community. At each site, soil pits were excavated and the soils classified according to the National Soil Survey Committee of Canada (1968). The elevation, slope, aspect and soil type for each study site are presented in Table 1. The location of each slope and the position of the study sites are depicted in Figure 1. Table 1. Elevation, aspect, slope and soil class of each study site. Site Elevation (ft.) Aspect Slope (%) Soil Class Agropyron S D i c a t u m 1. Mesic 5,750 S • S • E • 28 Rego dark grey 2. Xeric 5,800 South 7 Rego dark grey 3. Hydric 5,650 S • S • E * 8 Orthic black silt Poa pratensis 4. Mesic 5,525 South 5 Orthic black silt 5. Xeric 5,600 S.W. 36 Orthic dark grey 6. Hydric 5,600 S.E. 2 Orthic black silt Calamagrostis rubescens 7. Mesic 5,400 West 48 Degraded eutric brunisol Artemisia frigida 8. Mesic 5,600 S.W. 23 Rego dark grey Figure 1. Aerial photograph showing locations of slopes and study sites Legend: 1. Agropyron spicatum xeric site 2. Agropyron spicatum mesic site 3. Agropyron spicatum hydric site 4. Poa pratensis xeric site 5. Poa pratensis mesic site 6. Poa pratensis hydric site 7. Artemisia frigida mesic site 8. Calamagrostis rubescens mesic site o \ 8 9 Exclosures were established on all sites prior to the advent of spring growth in 1967. Six foot hi^h^seven strand barbed wire fences provided exclosure on all mesic sites (Figure 2), while wire cages were used on the xeric and hydric sites. The cages were of a design described by Dobb and Elliot (1964) and briefly are of quonset shape, six feet long, three feet wide and twenty inches high at the center. One inch wire mesh provided the cage covering (Figure 3). Dobb and Elliot (1964) reported this type of cage to have altered the microclimate and to have increased forage yields of a cultivated and dense crop of creeping fescue (Festuca rubra) by 15 per cent. Such influences were not considered applicable in this study due to the relatively sparse vegetation measured. Vegetation measurement Measurements of the growth, development and productivity of the four communities were made regularly from May 1967 to September, 1968. Only the current year's growth of each year was measured and contiguous plot areas were used for the 1967 and 1968 observations. Each year just prior to the advent of spring growth, the appropriate plot area was clipped to ground level and the old vegetation removed. A one meter square quadrat was the sample unit for al l harvests. On each harvest date the stage of development of each forage species was noted and the quadrat then clipped to determine yield. Also, the species composition of all quadrats measured after July 1 was described. Most species had flowered and were readily identifiable by that date. The "list and chart" method described by Brown (1954) was Figure 3. Cage exclosures on the Poa pratensis hydric site 11 employed to measure species composition on the three Agropyron spicatum sites. Using a one meter square wooden frame gridded by wire into 1H0 squares, the location and basal area size of each plant was sketched onto seven inch by seven inch squared paper to give a quadrat facsimile. The basal area estimate was made at one inch above the ground surface. Areas occupied by species were later determined by superimposing on the quadrat facsimile a transparent grid with 400 dots per square inch. On the remaining five sites, the "point" method as described by Brown (1954) was used to determine species composition. A one meter long wooden frame supporting 10 pins at an angle of 60° to the ground surface, was moved at 10 centimeter intervals across the quadrat to give 100 point measurements. Only root crown "hits" were recorded, for they are least affected by the action of wind or by the growth form of the plant, two common sources of error of the point method (Brown 1954, Daubenmire (1968(b)). After the standing vegetation was measured each quadrat was hand clipped to ground level. The clipped samples were then air dried in the field on a screened drying rack and stored. Later, usually within two weeks, the samples were oven dried at 105°C for 24 hours, cooled in a dessicator, and weighed to the nearest 1/100 gram. No attempt was made to separate the clip sample into species or species groups, hence the yield was a measure of the total standing crop of a quadrat produced from commencement of spring growth to harvest date. Production under-ground was not measured and doubtless invertebrate and vertebrate users of forage, not excluded by the exclosures, were unaccounted for components 12 of production. ! Finally, crude protein analyses were made on the 1967 forage samples collected from the Agropyron spicatum, the Poa pratensis and the Calamagrostis rubescens mesic sites. The macro-Kjeldahl method described by the Association of Official Agricultural Chemists (1960) was used. Field design Randomized block designs of square meter quadrats were employed at all sites. The blocks served as replicates and the treatments were different dates of plant measurements. A given harvest date appeared only once in each block and was randomly located.^ Each meter quadrat was permanently marked at the corners with steel pins and was separated from neighbouring quadrats to reduce border effect. Within the fenced exclosures the quadrats were spaced 2.1 centimeters apart, while in the cages, the quadrats were centered to leave a 10 centimeter border. Also the cages at any one site were spaced approximately 30 centimeters apart. Time and resources did not allow equal study at all sites and the intensity of sampling varied from site to site. The mesic sites of the Agropyron spicatum and Poa pratensis communities were studied most intensively and the design here included 8 replicates. Plot measurements commenced shortly after the advent of spring growth and continued at biweekly intervals until summer dormancy of the vegetation Plot designs for each site are given in Appendix 2. 13 occurred. After this measurements were made at longer intervals and continued i;mtil late autumn. Also, to obtain some estimate of the effect of the clipping treatments upon subsequent regrowth in the same year, four of the eight replicates selected at random, were reclipped on August 30 , 1967. The Calamagrostis rubescens site was studied less intensively. Eight replicates were also used but measurements were made at four week intervals from spring through to late autumn. In the Artemisia frigida site and in the xeric and hydric sites of the Agropyron spicatum and Poa pratensis communities, only three replicates were incorporated in the field design. Two harvests only were made, one at the onset of summer dormancy and a second in the late fall. Finally, to determine the dry matter losses through the winter of 1967-68, attributable to weathering and decay, yields were taken in April of 1968 at the Agropyron spicatum, Poa pratensis and Calamagrostis  rubescens mesic sites. RESULTS Species composition of vegetation The species composition of the four plant communities studied are given in Tables 2 , 3 , 4 and 5. For the Agropyron spicatum community, each species listed is described as a ratio of mean basal area per quadrat to per cent frequency of occurrence within quadrats. For the three remaining communities each species is described as a ratio of mean number of basal crown hits per quadrat to per cent frequency of occurrence within the quadrats. The 100 points measured for each quadrat, although a reasonable sample for portraying floristic composition in a sod cover 14 Table 2. 2 Ratios of mean basal area (cm ) per square meter to per cent frequency of major plant species in the three Agropyron spicatum sites. Species Mesic site (N = 72)1 Xeric site (N = 18) Hydric site (N = 18) Grasses: Agropyron spicatum 446/100 352/100 1303/100 Festuca idahoensis 198/100 286/100 ' 269/100 Koeleria cristata 140/100 252/100 75/83 Poa secunda 1.3/19 6.5/50 0.3/16 Stipa Columbiana 46/34 98/66 1003/100 Forbs: Achillea millefolium 13/100 37/100 3.7/100 Lupinus sericeus 4/99 1.8/100 2.8/100 Antennaria rosea 28/62 34/100 0.5/50 Eriogonum heracleoides 0.4/34 0.1/33 1.8/66 Astragalus serotinus 0.3/37 0.2/16 -Oxytropic campestris 0.1/26 0.25/33 -Shrubs: Artemisia frigida ' 1.5/54 1.2/66 0.2/33 N^umber of meter square quadrats charted to derive basal area/frequency ratios. 15 Table 3.' Patios of percent crown hits per square meter to percent frequency of major plant species in the three Poa pratensis sites. Species Mesic site Xeric site Hydric site (N = 72)1 (N = 18) (N = 18) Grasses: Poa pratensis 26/100 Agropyron spicatum T/8 Kbeleria cristata 3/90 Stipa columbiana 2.3/92 Poa secunda Forbs: Achillea millefolium 0.5/38 Potentilla gracilis 2.5/100 Geranium viscosissimum 0.27/21 Taraxacum officianale 0.43/35 Antenaria rosea  Oxytropis campestris Aster spp. 0.3/23 Viola spp. 0.2/18 9/100 T/17 1.5/83 8.3/100 3.0/100 1.2/83 0.5/66 3.2/100 0.50/50 33/100 0.15/17 0.33/17 2.9/100 2.0/100 1.5/83 0.66/66 0.50/50 Shrubs: Artemisia frigida 5.5/100 percent litter 54% percent bare soil or rocks 10% 3% 64% 56% 3% Number of meter square quadrats measured (100 point measurements per quadrat) to derive basal hit/frequency ratios. Table 4. Ratios of percent crown hits per square meter to percent frequency of major planv species in Calamagrostis rubescens site. Species Mesic (N.= 72)' Grasses: Calamagrostis rubescens 9/100 Forbs: Achillea millefolium  Lupinus arcticus  Astragalus serotinus  Aster spp. Antennaria rosea 0.22/19 0.92/59 0.75/41 0.34/28 0.60/44 percent litter 81% percent bare soil or rocks 6% Number of meter square quadrats (100 point measurements per quadrat) to derive basal hit/frequency ratios. 17 Table 5. Ratios of percent crown hits per square meter to percent frequency of major plant species in the Artemisia frigida site Species Mesic (N = 18)" Grasses: Agropyron spicatum  Koeleria cristata  Stipa columbiana Poa secunda 0.5/66 3.7/100 T/33 8.8/100 Forbs: Oxytropis campestris 4/100 Shrubs: Artemisia frigida 10/100 percent litter percent bare soil or rocks 7% 68% Number of meter square quadrats measured (100 points measurements per quadrat) to derive basal hit/frequency ratios. 18 such as prevails on Juniper Slope, sbould not be used comparatively with the basal area determinations obtained for the bunchgrass cover which prevails on South Slope. In the Agropyron spicatum dominated community the predominant associate grass species were Festuca idahoensis and Koeleria cristata (Table 2). The major forb species were Achillea millefolium and Lupinus sericeus. Within the community, the total basal area of individual species varied between sites. For example, Agropyron spicatum occupied 2 2 1,303 square centimeters per square meter (cm. /m. ) in the hydric site, 2 2 . 2 2 446 cm. /m. in the mesic site and 352 cm. /m. in the xeric site. 2 2 On the other hand, Koeleria cristata occupied only 75 cm. /m. in the 2 2 2 2 hydric site, 140 cm. /m. in the mesic site and 252 cm. /m. in the xeric site. In the Poa pratensis dominated community, Stipa columbiana was the only major associate grass species (Table 3). The predominant forb species were Potentilla gracilis and Achillea millefolium. Basal hits of Poa pratensis and Achillea millefolium were greatest in the hydric site and least in the xeric site. Inversely, the number of basal hits of Stipa columbiana, were least in the hydric and greatest in the xeric site. Potentilla gracilis was most prevalent in the mesic site, slightly less prevalent in the hydric site and absent in the xeric site. In the Calamagrostis rubescens community no other species of grass was prevalent (Table 4). Lupinus arcticus and Astragalus  serotinus, although not abundant, were the major forb species. Poa secunda and Oxytropis campestris were the major associate 19 species in the Artemisia frigida community (Table 5). Pea secunda was the most abundant associate. Range vegetation phenology The dates at which various developmental phases were first observed in at least 10 per cent of the individuals of each of the major forage species differed between the two years of the study (Table 6). Due to the predetermined dates of plant measurements (treatments) the dates given in Table 6 do not represent the actual date of occurrence of a developmental phase, rather the date on which a particular phase was first observed. However, the dates of observations were virtually the same in both years, and i t is probable that actual changes in dates of development did occur. The most important information, is that with the exception of Poa secunda none of the grass species flowered in 1968 while al l of them, with the exception of Calamagrostis rubescens flowered and "set" seed in 1967. Calamagrostis rubescens rarely flowers when i t is in the understory of Douglas f i r (Dr. V.C. Brink - personal communication). In general, the forb species flowered and set seed earlier than the grasses, but flowered approximately two weeks later in 1968. The shrub species developed at about the same rate in both years. Forage yields The mean dry matter yields of the Agropyron spicatum, Poa  pratensis and Calamagrostis rubescens mesic sites, from plots clipped at sequential dates through 1967 and 1968 are presented in Tables 7 and 8. At virtually a l l dates the Poa pratensis site yielded more forage than 20 Table 6 Dates in 1967 at which various developmental phases were first observed in major plant species. Flower Flowers Seed stalks in Seed dissemi- Plant Plant Species Year appear bloom ripe nating drying dried Grasses: Agropyron spicatum 1967 1968 7/12 7/26 8/31 9/18 7/26 7/11 8/31 7/22 Festuca idahoensis 1967 1968 6/28 7/26 8/31 9/18 7/26 7/11 8/31 7/22 Koeleria cristata 1967 1968 6/14 6/28 7/26 8/31 7/26 7/11 8/6 7/22 Poa secunda 1967 1968 6/14 6/25 6/28 7/9 7/12 7/22 8/6 8/27 6/28 6/25 8/6 7/22 Stipa columbiana 1967 1968 6/28 7/12 8/6 8/31 7/26 7/11 8/31 7/22 Poa pratensis 1967 1968 6/28 7/12 8/6 8/31 7/26 7/11 8/31 7/22 Calamagrostis rubescens 1967 1968 -- --7/26 7/11 8/31 8/6 :>rbs: Achillea millefolium 1967 1968 6/28 7/11 7/12 7/22 8/6' 8/26 8/31 9/18 7/22 7/11 8/6 7/23 Lupinus sericeus 1967 1968 6/28 7/11 7/12 7/21 J. - 7/22 7/11 8/6 7/23 Potentilla gracilis 1967 1968 7/9 7/20 7/25 8/6 8/31 9/18 9/20 9/18 8/6 7/23 8/31 8/27 Geranium viscossimum 1967 1968 7/25 8/6 8/6 8/31 8/31 9/18 9/20 9/18 8/6 7/23 8/31 8/27 Oxytropis campestris 1967. 1968 7/9 7/10 7/26 7/23 8/31 8/27 9/20 9/18 8/6 7/23 8/31 8/27 hrub: Artemisia frigida 1967 1968 7/9 7/10 7/26 7/23 8/31 8/27 -8/6 7/23 8/31 8/27 Due to apparent insect damage virtually a l l of the Lupinus sericeus flowers fell prior to seed setting. Table 7. Mean dry matter yields for 1967 and winter carryover from plots clipped at sequential dates in three plant communities Mean yields ± standard errors in grams per square meter* Community Agropyron  spicatum Clipping dates May 31 Jun.14 Jun.28 Jul.12 Jul.26 Aug.9 Aug.30 Sep.20 Oct.20, Apr.19/68 47.4 77.0 94.0 117.7 137.3 94.2 112.0 132.0 89.7 57.9 ± 4.7 ± 4.2 +13.7 ± 12.1 + 15.2 ± 3.1 ± 4.9 + 11.2 + 6.4 ± 8.0 Poa pratensis 45.3 ± 14.8 90.5 135.8 173.0 182.2 158.9 160.1 141.4 149.1 114.7 ±6.3 ± ' 8.3 + 17.8 ± 15.1 + 13.3 ± 20.5 ± 10.2 ± 8.5 ± 8.5 Calamagrostis rubescens 51.6 ± 5.5 78.7 + 7.5 (Aug.24) 64.8 : 5.0 66.3 ± 5.9 55.3 + 3.1 50.0 7.4 Each mean yield determined from eight one square plots. Table 8. Mean dry matter yields for 1968, from plots clipped at sequential dates in three plant communities Mean yields ± standard errors in grams per square meter" Clipping dates Community May 30 Jun.13 Jun.27 Jul.11 Jul.25 Aug.27 Sept.17 Agropyron spicatum 46.8 57.0 82.8 115.4 96.1 112.7 100.5 ± 4.1 ± 5.4 ± 10.3 ± 12.5 ±11.8+ 7.9 ± 8.8 Poa pratensis 58.2 98.1 144.4 154.6 152.6 129.2 143.9 ± 4.3 ± 6.0 ± 10.7 ± 13.7 ± 12.7 ± 16.9 ± 10.1 . (Aug.6) Calamagrostis rubescens 21.2 45.6 45.6 44.4 + 1.6 ± 2.7 ± 5.1 ± 3.7 Each mean yield determined from eight one square meter plots The Agropyron spicatum site, and the Calamagrostis rubescens site yielded less than either of the others. At each of these three sites there was an initial phase of rapid growth which terminated with the maximum yield of the year (Figure 4). The date of termination of this phase was the same for all sites in each year, but was measured 15 days earlier in 1968. Within the Agropyron  spicatum site (Figure 4a) and the Poa pratensis site (Figure 4b) the initial growth phase commenced at approximately the same date and proceeded at approximately the same rate in both years. However, termination occurred earlier in 1968 and the maximum yields attained were approximately 15% less than in 1967. In the Calamagrostis rubescens site (Figure 4c) the initial growth phase started an estimated 10 days earlier in 1968, but the growth rate was less and the maximum yield attained was approximately 45% less than in 1967. In the Poa pratensis and the Calamagrostis rubescens sites virtually a l l of the annual forage crop was produced during the initial growth phase in each year. In 1967, the peak yield was followed by a general decrease in yields until autumn in both sites. In 1968 however, decreases in yield after the peak, occurred only in the Poa pratensis site; herbage weights remained constant in the Calamagrostis rubescens site. In the Agropyron spicatum mesic site, there was a second growth phase during the late summer in both years. In the two weeks immediately following the initial peak of production there were substantial forage losses in both years, but these losses were almost completely compensated 24 _ F i g . 4(a) Agropy ron spical'jm CM E \ (A E O Apr . 19/68 1 1 1 1 r I I 1 May June July August Sept. O c t , Winter 180r to 150 ^ 120 >-90 as 60 v- 30 < >-Q 180 Fig. 4 ( b ) Poa pratensis Apr. 19/68 I—~ 1 1 1 1 M a y J u n e July August Sept. O c t . F ig . 4 (c) Calamagrostis r ubescens 1 l ' l " 1 Winter 150 120 90 f-60 30 , JO - — - «4> - -May 4 /68 , _ - , • - , , 1 i | May June July August Sept. Oct . W in te r •1967 o • -©1968 MONTHS F i g u r e 4. Changes i n d r y m a t t e r herbage y i e l d s t h r o u g h 1967 and 1968 a t : F i g u r e 4a t h e A g r o p y r o n s p i c a t u m m e s i c s i t e , •' F i g u r e 4b t h e Poa p r a t e n s i s m e s i c s i t e and F i g u r e 4c t h e C a l a r a a g r o s t T s r u b e s c e n s m e s i c s i t e . 25 for by the secondary growth which followed. Later however, a secon-1 period of losses resulted in the fall yield being substantially less than the peak yield of either growth phase. In addition, substantial forage losses occurred over the winter of 1967-68. The peak, the fall and the winter carry-over yields from the Agropyron spicatum, the Poa pratensis and the Calamagrostis rubescens mesic sites are compared in Table 9. Because yield measurements of the 1968 vegetation ended in September, comparisons are based on the 1967 data only. The losses in these three sites, from peak yield date until fall yield date, were 35, 22 and 23 per cent respectively, while the over-winter forage losses were 36, 20 and 7 per cent respectively. Table 9. Comparisons of peak yield, fall yield and winter carry-over in 1967 in the Agropyron spicatum, Poa pratensis and Calamagrostis rubescens mesic exclosures Mean oven-dried weight ± S.E. (gm./m )* Peak yield Fall yield Winter carry- Difference Site (July 26) (Oct 20) over (Apr 20)Jul-Oct Oct-Apr Agropyron 137.3 89.7 57.9 47.6 31.8 spicatum + 15.2 + 6.4 + 8.0 + 10.8 + 7.2 Poa pratensis 182.2 149.1 114.7 33.1 34.4 + 15.1 + 8.5 + 8.5 + 11.8 + 8.5 Calamagrostis 78.7 55.3 55.3 23.4 5.2 rubescens + 7.5 + 7.4 + 7.4 + 7.4 + 7.4 * Each mean yield determined from eight one square meter plots 26 The mean dry matter yields of all eight study sites, from plots clipped at two comparable dates in each of the two years, are presented in Table 10. The first yield measurements in the xeric and hydric sites and in the Artemisia frigida mesic site may not have been obtained until after peak yield had occurred, and the changes in yield between dates were generally quite small. However there were considerable differences in yields both within and between the four plant communities. The changes in herbage weights between dates, although generally small, appear important at a few sites. From August 9 to October 20, 1967, an increase in herbage weight of 71 per cent was measured in the Agropyron spicatum xeric site, while in the Poa pratensis hydric site, and the Calamagrostis rubescens and Artemisia frigida mesic sites, weight losses of 33, 23 and 27 per cent respectively were measured. From July 25 to September 20, 1968, the only important change in yield occurred in the Agropyron spicatum xeric site; as in 1967 the autumn yield was greater, but the increase in weight was 51 per cent. Within the Agropyron spicatum and Poa pratensis communities the xeric sites generally yielded less forage than the mesic sites, and the hydric sites consistently yielded more. The Agropyron spicatum xeric site yielded appreciably less forage than the mesic site at all dates except for October 20, 1967. At the latter date, the yield measured in the xeric site was approximately 12 per cent greater than that measured in the mesic site. In the Poa pratensis community, the xeric site yielded approximately the same as the mesic site in 1967, but in 1968 the xeric site yields were substantially less than those measured TABLE 10. Comparisons of dry matter yields for two dates in 1967 and 1968, between and within four major plant communities and their rroisture sub-cx>mmunities Mean yields + standard errors in grams per square meter Number of one meter squared 1967 1968 plots clipped Community - sub community at each date Aug. 9 Oct. 20 July 25 Sep. 20 Agropyron spicatum - xeric 3 64.6 + 6.4 110.5 + 21.4 48.5 + 3.5 73.3 + 3.8 - mesic 8 94.2 + 3.1 89.7 + 6.4 96.1 + 11.8 100.5 + 8.8 - hydric 3 224.5 + 10.8 214.2 + 12.8 144.3 + 13.6 193.1 + 36.6 Poa pratensis - xeric 3 162.7 + 25.4 . 148.1 + 19.8 106.4 + 16.7 113.1 + 6.3 - mesic 8 158.9 + 13.3 149.1 + 8.5 152.6 + 12.7 143.9 + 10.1 - hydric 3 389.5 + 33.1 254.8 + 16.2 214.4 + 21.7 202.4 + 24.0 Calamagrostis rubescens - mesic 8 78.7 + 7.5 55.3 + 3.1 45.6 + 5.1 44.4 + 3.7 Artemisia frigida - mesic 3 85.8 + 4.3 51.7 + 1.9 55.9 + 8.6 54.5 + 7.8 rO 28 in the mesic site. Between communities, the Poa pratensis community was the highest yielder, the Agropyron spicatum second highest, and the Calamagrostis rubescens and Artemisia frigida communities, which yielded in approximately the same order of magnitude, the lowest yielders. However, there were some overlaps in yields between communities. The Poa pratensis hydric site yielded more forage than any site, but the Agropyron spicatum hydric site yielded more than the xeric or mesic sites of the Poa  pratensis community. The Agropyron spicatum xeric site yielded less than the Calamagrostis rubescens and Artemisia frigida mesic sites in the summer of 1967, but about the same in the summer of 1968. The autumn yields of the Agropyron spicatum xeric site however, were appreciably greater in both years than those of the latter two sites. Effect of clipping The single ground level clipping treatments, conducted at different dates in the Agropyron spicatum and Poa pratensis mesic sites from May 31 to August 30 of 1967, had l i t t l e effect upon the total forage produced within clipped plots in the same year (Table 11). Measurable regrowth occurred in the Agropyron spicatum site in only those quadrats clipped on May 31 and those clipped on June 13. In the Poa pratensis site there was measurable regrowth in a l l quadrats clipped prior to July 12. However, at neither site, did the combined yield of any in i t ia l clip plus the August 30 reclip differ appreciably from the control. Crude protein yields The percent crude protein content, of the "clip" samples Table 11. The effect of a single ground level clipping treatment at different dates in 1967 upon subsequent regrowth by August 30, 1967 in the Agropyron spicatum and Poa pratensis mesic sites SITE Date of Mean dry matter yields ± standard errors in grams per square meter initial clip Initial clip* Reclip* Total Control** Difference Agropyron spicatum - mesic May 31 June 14 June 28 49.2 ± 8.2 71.7 ± 6.4 94.0 ± 13.7 67.6 ± 30.7 34.9 ± 3.5 0 116.8 + 19.5 106.6 ± 5.0 94.0 ± 13.7 112.5 ± 4.9 + 4.3 ± 12.2 112.5 ± 4.9 - 5.9 ± 5.0 112.5 ± 4.9 - 16.5 ± 9.8 Poa pratensis - mesic May 31 June 14 June 28 July 12 July 26 41.4 99.2 129.6 188.2 ± 9.0 + 7.1 ± 4.2 ± 44.6 91.5 59.1 23.0 11.9 10.1 6.1 3.8 1.4 158.9 ± 13.3 132.9 158.3 152.6 200.1 158.9 9.6 6.6 4.0 23.0 13.3 160.1 160.1 160.1 160.1 160.1 20.5 20.5 20.5 20.5 20.5 - 27.2 - 1.8 - 7.5 + 40.0 - 1.1 15.1 13.6 12.3 21.8 16.9 J. Mean yields determined from 4 one square meter plots ** Mean yields determined from 8 one square meter quadrats 30 collected at sequential dates through 1967 from the Agropyron spicatum, Poa pratensis and Calamagrostis rubescens mesic sites, declined steadily through the season (Table 12). For the Agropyron spicatum site, crude protein content declined from 14.7% on June 14 to 5.5% on October 20 while in the Poa pratensis site the decline between the same two dates was 13.9% to 5.8%. In the Calamagrostis rubescens site crude protein content declined from 12.9% on June 28 to 4.5% on October 20. The results indicate that from June 28 to August 30 the vegetation in the Calamagrostis rubescens site contained a slightly greater percentage protein than the other two sites, but less by October 20. The seasonal yields of crude protein, in grams per square meter, show a different relationship between sites (Figure 5). At virtually all harvest dates, the Poa pratensis site yielded more crude protein than the Agropyron spicatum site, and the Calamagrostis rubescens site yielded less than either. In all these sites, virtually all of the annual crude protein production occurred in the initial four to six weeks of growth. In the Agropyron spicatum site, most protein was produced by June 14, whereas in the Poa pratensis and Calamagrostis rubescens sites, rapid protein accumulation continued until June 28. Protein yields then remained fairly constant at all sites, until July 26, when the respective protein yields were 13.3, 14.8 and 8.26 grams of crude protein per square meter. After July 26, there were general decreases in protein yields and the values for October 20 were 4.9, 8.6 and 2.5 grams per square meter respectively. Table 12. Crude protein content of forage from three plant communities at sequential dates through 1967 Community Agropyron  spicatum Percent crude protein ± standard errors from eight samples collected at each date Sampling date  May 31 June 14 June 28 July 12 July 26 Aug. 9 Aug. 30 Sept. 20 Oct. 20  14.41 14.67 ± 0.501 ± 0.484 12.49 10.72 9.69 7.31 6.19 6.49 5.46 ± 0.239 ± 0.127 ±0.245 ± 0.178 ± 0.255 + 0.308 + 0.163 Poa pratensis 13.42 13.91 11.36 8.35 8.15 7.99 6.40 6.57 5.76 ± 0.464 ± 0.235 ± 0.153 ± 0.198 ±0.445 ±0.210 ± 0.419 ± 0.208 ± 0.159 Calamagrostis rubescens 12.92 ± 0.541 10.96 ± 0.789 7.22 6.65 4.47 ± 0.316 ± 0.307 ± 0.328 CM 16-i ' . £ in 1 4 -£ O : — " 12-Q LU 10->• z 8-LU t— o 6 -Cxi 0-VJ 4 -Q CH 2 -U . . . Poa pratensis mesic site .Agropyron spicatum mesic site »Calamagrostis rubescens mesic site v / M A Y " 1 J U N E I J U L Y I A U G U S T I SEPTEMBER I O C T O B E R I Figure 5. Crude protein yields in grams per square meter for the mesic sites 'l of three, plant communities, at sequential dates in 1967 CO N5 33 DISCUSSION ' Although there is considerable variation in development among plant species, forbs in the study area, generally completed their reproductive processes at an earlier date than grasses. This early reproductive development allows the forbs as a group, to escape the effects of summer drought, but at the same time their stage of maturity renders them more vulnerable to dessication and "weathering" by the summer heat. As a consequence there are often substantial forage losses. Perennial grasses may not complete their reproductive processes due to summer drought, as was apparently the case in 1968, but they are able to escape serious drought injury by entering a stage of summer dormancy (Laude 1953). The growth curves show clearly that forage yields of plant communities are seldom static. Nearly all of the annual forage crop was produced during the initial growth phase and therefore whatever factors affect the length and the growth rate of the initial phase determine to a large extent the amount of forage produced annually. This was evident in 1968 when because the initial growth phase was terminated two weeks earlier, the maximum yields attained were approximately 15% less than in 1967. Immediately after peak yields were reached, herbage losses occurred, and the rate and extent of these losses demand that the factors involved be considered when estimating yields. Obviously, the length and the rate of the initial growth phase and the speed and extent of the weight losses, are all influenced by environmental factors. Each species however, will be influenced in different ways. In this study, yields of individual species were not measured, but 3U other similar studies (Blaisdell 1958 5 Ratliff and Heady 1962) have shown that some species start their most rapid growth earlier than others and some lose weight earlier and faster than others. The latter was observed in the forb species, which virtually disintegrated in the summer heat. Such variations in growth among species probably also explains the second growth phase of the Agropyron spicatum dominated community. The peak of the fi r s t growth phase was the maximum yield of the whole community but?because of weathering of the forbs and ephemeral type species, was followed by a substantial loss. The second growth phase probably represents a continuation of the i n i t i a l growth phase of the deeper-rooted (Weaver 1919, Troughton 1957) and-slower growing bunchgrass species. Presumably, in the Poa pratensis and Calamagrostis rubescens dominated communities, a l l species entered a stage of summer dormancy at approximately the same time in each year. The patterns of seasonal changes in herbage weights varied between sites and years. Undoubtedly, even greater variations in pattern would be observed over a longer period of time, and prediction of the patterns can be made in general terms only. Sampling for herbage weight must therefore be carefully co-ordinated with species composition and with stage of development, and so designed that the herbage weights measured are not confounded by seasonal weight losses. The amount of forage produced annually would be best estimated from several frequent harvests, made at approximately the time when peak yields would normally occur. Yield measurements for calculating carrying capacities, should be made at the time when ranges are being 35 grazed. For wildlife winter ranges, winter measurements would be best, but since snow cover precludes such measurements, a yield measurement in late autumn, with allowances for overwinter losses, would provide a suitable estimate of potentially available forage. The variations in yields between the four communities are difficult to explain. Since the study sites were all in close proximity to one another the macro-climatic influences were similar. However, the varied slope, aspect and soil type, undoubtedly caused considerable microclimatic differences. The plant species composition was also different and the interactions of these variables undoubtedly influenced forage production. Analyses of these interactions and their effects on forage production are beyond the scope of this study. Within communities, the differences in yields between moisture sub-communities, i.e.: xeric, mesic and hydric sites, were often considerable. These sites however, were selected on the premise that the soils at the xeric site were relatively the driest, those at the mesic site average, and those at the hydric site the wettest. Since soil moisture data for these sites is given in Section II,. discussion of the variations in yields between moisture sub-communities is withheld until Section III. A disturbing anomaly in the yield data is that in both years the Agropyron spicatum xeric site yielded appreciably more forage in the autumn than it had in the summer. At all other sites the herbage weights measured in the autumn were less or nearly equal to the weights measured in the summer. Since only two harvests were made in the xeric and hydric sites, and in the Artemisia frigida mesic site, it is not known whether the peak yield and subsequent yield changes occurred at the same time and 36 rate as in the other sites. Obviously, unless a sampling error exists, herbage weight changes in the Agropyron spicatum xeric site were quite different from those in other sites. Although the effect of preclipping the plot areas prior to commencement of spring growth was not tested, the reclipping data indicate that even after growth had started, a single ground level clipping had l i t t l e effect upon total forage production in the same year. Hence, the spring preclipping is assumed to have had no important effect upon the forage yields in that year. The reclipping results also indicate that grazing, prior to the establishment of exclosures in 1967, had no important influence on forage production in 1967. Numerous studies, reviewed by Jameson (1963), have shown that defoliation of perennial species often reduces forage production in subsequent years; retardation of root growth and depletion of carbohydrate root reserves are the main factors responsible. The more frequent and severe the defoliation the more depressed are subsequent forage yields. ' Erickson (1969) showed that in the Ashnola region, the time of defoliation (clipping) is also important and that defoliation during the last four to two weeks of the i n i t i a l growth period in 1967 depressed forage production in 1968 more than at any other time. He concluded that enough time should be left after the last defoliation for the plant to replenish its carbohydrate accumulation before summer dormancy of the vegetation occurs. Stoddart (1946), working with Agropyron spicatum in Utah arrived at the same conclusion. Since the reclipping results obtained in this study show that none of the harvests 37 noticeably reduced regrowth in the same year, i t appears that grazing prior to 1967 did not appreciably reduced root reserves. The 1968 p^ot area was also exclosed in 1967, but the one year protection from grazing is not believed adequate to have appreciably influenced forage production in 1968. Thus, i t is concluded that the yield data for 1967 and 1968 are comparable, and reflect environmental influences other than grazing. The seasonal decreases in percentage crude protein content of the vegetation from the various sites, follow patterns similar to those reported for other rangelands in British Columbia (McLean and Tisdale 1959). During the summer the vegetation from the Calamagrostis  rubescens community contained the highest percentage protein and thus may provide a more nutritive forage than either the Poa pratensis or Agropyron spicatum communities. After August 30, however, percentage crude protein of the Calamagrostis rubescens community was lower than the other two sites, and the community is probably of relatively little nutritive value as a winter forage. Even the vegetation of the Agropyron  spicatum and Poa pratensis dominated communities entered the winter at a lower protein level than the 6 per cent maintenance level recommended by N.R.C. (1964). However, the forage samples analyzed were composite samples of al l species present in a plot and were collected by clipping to ground level. By selectively grazing certain species or certain plant parts, animals may obtain sufficient protein to meet their needs. The protein yield data show clearly that in 1967, virtually all. of the nitrogen fixed, as represented in crude protein, occurred before June 28. Since herbage weights continued to increase until July 38 26, i t is apparent that much of this increase was in the form of carbohydrate accumulation. It was not until after July 26, when the vegetation apparently entered summer dormancy, that nitrogen began being returned to the environment, partly as a result of losses of herbage through shattering and partly through leaching and degradation. Herbage yields and protein yields can only be used as indices of net productivity. Westlake (1963), defines net productivity as the entire photosynthetic production of organic matter by plants, minus the organic matter respired. This includes root production, which was not measured in this study. Troughton (1957) refers to many grassland species in which more than 30 per cent of the living plant was underground. Although the root to top ratio varies greatly within and between species and with growth stage, Troughton's data and others (Weaver and Zink, 1946 (a), 1946(b); Willard and McLue 1932), indicate that for relatively stable perennial grassland communities, the ratio remains fairly constant from year to year. Thus it is assumed that the yield data gathered here, are with the exception of those for the Calamagrostis rubescens site valid indeces of site productivity. The yield data from the Calamagrostis rubescens mesic site only indicate the productivity of the understory vegetation. The Douglas fi r tree overstory produces annually an unknown but undoubtedly large amount of organic matter. 39 SUMMARY 1. The seasonal development and yield, and species composition of four major plant communities, on Flatiron Mountain in the Ashnola region, were measured from May 1967 to October 1968. In a community dominated by Agropyron spicatum and in a community dominated by Poa  pratensis, xeric, mesic and hydric sites were selected. Only a mesic site was selected in an Artemisia frigida community and in a Calamagrostis  rubescens understory community. All sites were excluded from grazing by exclosures. 2. In the mesic sites of the Agropyron spicatum and Poa pratensis communities, all plant measurements were made at two week intervals until summer "dormancy" of the vegetation occurred, after which measure-ments were made at approximately three week intervals until autumn. In the Calamagrostis rubescens mesic site measurements were made at four week intervals throughout the season. At the other sites, measurements were made at only two dates, one shortly after onset of summer dormancy and one in late autumn. 3. Crude protein analysis were conducted in 1967, on the forage collected for yield determinations, from the Agropyron spicatum, Poa  pratensis and Calamagrostis rubescens mesic sites, and the yields of crude protein computed. 4. The forbs generally completed their reproductive development earlier than the grasses. In 1967 nearly all species completed their development cycle, but in 1968 very few of the grasses flowered or "set" seed and the forbs flowered about two weeks later than in 1967. Spring growth commenced on approximately the same date in both years. 40 5. The weight of standing crop through the season was seldom static in the communities studied. Virtually a l l of the annual forage production occurred during an i n i t i a l growth period, which ended in July in both years, after this time there were general decreases in herbage weight ranging from 23 to 35 per cent by autumn. There were further losses, ranging from 7 to 36 per cent over the winter of 1967-68. 6. The exclosures successfully excluded a l l ungulates from the plots and insect damage was not apparent. The losses appear to be entirely due to shattering, leaching and decay. 7. In both years the length of the i n i t i a l growth period determined the amount of forage produced. The rate of growth was essentially the same in the two years, but growth stopped two weeks earlier in 1968, resulting in the yields being 15 per cent less than those in 1967. 8. Within the Agropyron spicatum and Poa pratensis communities, the xeric sites generally yielded slightly less than the mesic sites and the hydric sites yielded considerably more. 9. Between communities, the Poa pratensis mesic site yielded approximately 25 per cent more forage than the Agropyron spicatum mesic site and the latter yielded approximately 80 per cent more than the Artemisia frigida and Calamagrostis rubescens mesic sites, which yielded in approximately the same order of magnitude. There was some overlap of yields between communities; for example,, the Agropyron spicatum hydric site yielded more forage than the Poa pratensis mesic site. 10. The Calamagrostis rubescens mesic site vegetation was higher in percentage crude protein during the summer, than the forage from the 41 Agropyron spicatum or Poa pratensis mesic sites, but appreciably lower by autumn. The forage from a l l sites entered the winter below the six per cent maintenance level recommended by N.R.C. 11. Virtually a l l of the nitrogen fixed for crude protein elaboration occurred during the i n i t i a l four to six weeks of growth. Protein yields then remained static until summer dormancy of the vegetation occurred. After dormancy, nitrogen was again gradually returned to the ambient environment. 42 LITERATURE CITED ASSOCIATION OF OFFICIAL AGRICULTURAL CHEMISTS, 1960. Official methods of analysis of the AOAC. (Washington, D.C.) 9th edition. BLAISDELL, J.P. 1958. Seasonal development and yield of native plants on the upper Snake River plains and their relation to certain climatic factors. USDA Tech. Bull. 1190, 67 pp. BLOOD, D.A. 1961. An ecological study of California bighorn sheep in southern British Columbia. M.Sc. Thesis. Library, University of B.C. BROWN, Dorothy.. 1954. Methods of surveying and measuring vegetation. Commonwealth Agric. Bureaux Farnham Royal, Bucks. England. 223 pp. BUECHNER, H.K. 1960. The bighorn sheep in the United States, its past, present and future. Wildl. Soc. Wildl. Monograph No. 4. CLARKE, S.E., E.W. TISDALE and N.A. SKOGLUND. 1943. The effects of climate and grazing practices on short-grass prairie vegetation. C.D.A. Publ."747. Tech. Bull. 46, 53 pp. COWAN, IAN MCT. and C.J. GUIGET. 1965. The mammals of British Columbia. B.C. Prov. Mus. Hdbk. No. 11. CRADDOCK, G.W., and C.L. FORSLIMG. 1938. The influence of climate and grazing on spring-fall sheep range in southern Idaho. U.S.D.A. Tech. Bull. 600, 42 pp. CURRIE, PAT 0., and Geraldine PETERSON. 1966. Using growing season precipitation to predict crested wheatgrass yields. J. Range Mgmt. 19(2): 284-288. DAHL, B.D. 1963. Soil moisture as a predictive index to forage yield for the Sandhills Range type. J. Range Mgmt. 16(3): 128-132. DAUBENMIRE, R. 1959. Plants and environment, a textbook of plant autecology. 2nd ed. 422 pp. New York, John Wiley and Sons Inc. DAUBENMIRE, R. 1968(a). Soil moisture in relation to vegetation distribu-tion in the mountains of northern Idaho. Ecology 49(3): 431-438. DAUBENMIRE, R. 1968(b). Plant communities, a textbook of plant synecology. Harper and Row Publ. N.Y. 300 pp. 43 DAVIS, R.J. 1952. Flora of Idaho. Wm. C. Brown Co. (Dubeque, Iowa). DEMARCHI, R.A. 1965. An ecological study of the Ashnola bighorn winter . ranges. M.S.A. thesis. Librery, University of B.C. DOBB, J.L., and C.R. ELLIOTT. 1964. Effect of pasture sampling cages on seed and herbage yields of creeping red fescue. Can. J. Plant Sci. 44(1): 96-99. ERICKSON, R. 1969. The effect of time of clipping upon forage yields in the subsequent year for two plant communities in the Ashnola region. B.Sc. thesis, University of B.C. HITCHCOCK, A.S. 1950. Manual of the grasses of the United States. 2nd ed. U.S.D.A Misc. Publ. No. 200. HITCHCOCK, C. Leo., A. CRONQUIST, Marion OWNBEY and J.W. THOMPSON. 1961. Vascular plants in the Pacific Northwest. Univ. Wash. Publ. in Biology Vol. 17. Univ. of Wash. Press, Seattle. HOLLAND, S.S. 1964. Land forms of British Columbia, a physiographic outline. Bull. 48. B.C. Dept. Mines and Natural Resources. HUBBARD, W.A. 1955. The grasses of British Columbia. Pro v. Mus. Victoria, B.C. Hndbk. No. 9. JAMESON, D.A. 1963. Responses of individual plants to harvesting. Botanical Review 29: 532-594. . LAUDE, H.M. 1953. The nature of summer dormancy in perennial grasses. Botanical Gazette 114: 284-292. McLEAN, Alastair, and E.W. TISDALE. 1959. Chemical composition of native forage plants in British Columbia in relation to grazing practices. Can. J. Plant Sci. 40: 405-423. McLEAN, Alastair, 1967. Beef production on lodgepole pine-pinegrass range in southern British Columbia. J. Range Mgmt. 20(4): 214-216. NATIONAL RESEARCH COUNCIL U.S.A. 1964. Nutrient requirements of sheep. Publ. 1197. 40 pp. NATIONAL SOIL SURVEY COMMITTEE OF CANADA. 1968. Report (rnimeo) of meeting of National Soil Survey Committee of Canada. 1968. Edmonton, Alberta. Chairman: W.A. Ehrlich. RATLIFF, R.D., and H.F. HEADY. 1962. Seasonal changes in herbage weight in an annual grass community. J. Range Mgmt. 15(3): 146-149. 44 ROWE, J.S. 1959. Forest regions of Canada. Bull. 123. Can. Dept. Northern Affairs and Natural Resources (Ottawa). SNEVA, F.A. and D.N. HYDER. 1962. Estimting herbage production on semi-arid rangelands, in the Inteiinountain region. J. Range Mgmt. 15(2): 88-93. STODDART, L.A. 1946. Some physical and chemical responses of Agropyron  spicatum to herbage removal at various seasons. Utah Agr. Exp. Sta. Bull 324: 24 pp. TISDALE, E.W. 1947. The grasslands of the southern interior of British Columbia. Ecol. 28: 346-382. TROUGHTON, A. 1957. The underground organs of herbage grasses. Bull. Bur. Past., Aberystw. No. 44, pp. 163. WEAVER, J.E. 1919. The ecological relations of roots. Carnegie Inst., Wash. Fubl. 286. WEAVER, J.E., and ELLEN ZINK. 1946. Length of life of roots of iospecies of perennial range and pasture species. Plant Physiol. 21: 201-217. WEAVER, J.E. and ELLEN ZINK. 1946. Annual increase of underground materials in three range grasses. Ecol. 27: 115-127. WESTLAKE, D.F. 1963. Comparisons of Plant Productivity. Biol Rev. 38: 385-425. WILLARD, C.J. and McLUPE, G.M. 1932. The quantitative development of tops and roots of bluegrass with an improved method of obtain-ing root yields. J. Amer. Soc. Agron. 24: 509-514. 45 • -.SECTION: i i CLIMATE The Ashnola region as a whole is relatively dry due to the "rain shadow" effect of the Coast Mountains, but the rugged topography of the region itself causes wide variations in local climate. Long term climatological data for the area are lacking except for a few valley bottom stations, but in the Interior Plateau region in general, there are increases in precipitation, and decreases in temperature and evaporation with increases in elevation (for general descriptions see Chapman 1952, Kerr 1952, Kendrew and Kerr 1955 and Scheffler - personal communication)^. A major objective of this study was to measure climate, particularly the components of the moisture regime on some of the critical rangelands in the Ashnola region. Because the study area is in "wilderness",. being approximately 6 miles distant (by trail which climbs some 3,000 feet in elevation) from the nearest road, and 15 miles from a settlement), only basic climatic variables could be measured, and some of the records were intermittent. METHODS AND MATERIALS . Measurement of the climate of the study area was undertaken E.G. Scheffler: (M.Sc. thesis, in preparation) measured some climatic variables at different elevations in the area in 1966 and 1967. 46 from May of 1967 to December of 1968. Climatic stations of varied instrumentation were established within the exclosures of the vegetation sites, described in the previous section of this presentation. A typical layout of a climatic station is presented ii. Figure 6. Station readings were taken at 7 to 10 day intervals during the growing season but during the winter months the station readings were taken once a month. Atmosphere near the ground Ambient air temperature, evaporation, wind and precipitation were the variables measured. Two climatic "base" stations of equal instrumentation, one at the Agropyron spicatum mesic site and one at the Poa pratensis mesic site, were established. A third climatic station, with fewer instruments was installed at the Calamagrostis rubescens site and is henceforth referred to as the climatic sub-station. Temperature Daily records of air temperature were obtained at the-climatic base stations from thermographs'1", each housed in a "Stevenson screen" placed at four feet above the ground surface (Figure 7). A maximum, a nunimum and a standard thermometer were included in each screen. These were used to calibrate the thermograph. A thermograph was not available for the climatic sub-station until July of 1968, although maximum and "*A list of the meteorological instruments used, including the manufacturer and model is given in Appendix 3. EVAPO RI M E T E RS S A C R A M E N T O SNOW G A U G E B O U Y O U C O S B L O C K I N S T A L L A T I O N S A N E M O M E T E R / , S O I L T H E R M I S T O R T 7 T 19 68 / V E G E T A T 1 / / ON P L O T A R E A X A X X X 196 7 V E G E T A T I ON P L O T A R E A * N T I P P I N G B U C K E T RAIN G A U G E S T E V E N S O N S C R E E N STANDARD R A I N G A U G E S Figure 6. Schematic diagram of climatic equipment within the vegetation exclosures-49 minimum Temperatures within a Stevenson Screen were taken at weekly intervals prior to that date. Precipitation At each climatic base station, two standard rain gagues and one tipping bucket raingauge, (the latter in 1968 only) were used to measure rainfall from May through October. Seven standard rain gauges, randomly distributed, were used in the climatic sub-station. All rain gauges were placed on the ground surface. Winter precipitation was collected at each climatic base station with one Sacramento type (Codd 1947), snow gauge at each station (Figure 8). To avoid coverage by snow, each gauge was placed on a.three foot high stand. Two gallons of calcium chloride solution in the gauge prevented freezing of the collected precipitation. Evaporation Two carborundum block evaporimeters using a 22 per cent methanol solution, as described by Wilcox (1967), were used at each macro-climatic station (Figure 9). The evaporimeters were placed four feet above the ground surface and were operated from May through October. They were flushed out weekly to prevent clogging of the carborundum block, which otherwise is a source of error with this type of evaporimeter (Wilcox 1967). Wind One 3-cup totalizing anemometer, mounted four feet above the ground was installed at each climatic base station in July of 1968. Soil Soil moisture content and soil 'temperature were the only 50 Figure 9. Carborundum block evaporimeters. 51 variables measured. These were measured at a l l eight vegetation study sites. Soil moisture In 1967 the per cent soil moisture of the upper six inches of the soil profile was measured gravimetrically. Two soil samples, each an aggregate sample from 10 samplings, were collected from each site at two week intervals throughout the growing season. Each sample was placed in a can, sealed, weighed, unsealed, oven- dried at 105WC for 48 hours and reweighed. The moisture content was then calculated in percentage of oven dry soil. Both gravimetric and electrical resistance methods were employed to measure soil moisture in 1968. "Nylon-gypsum" electrical resistance blocks, as described by Bouyoucos (1956) were buried at 3, 9, 15, and 21 inch soil depths at each installation. Four such installations were placed in each of the mesic exclosures (see Figure 6) and two installations were placed near each of the xeric and hydric exclosures. Resistance readings from the blocks were taken at approximately one week intervals from May through September, using a Beckman "Bouyoucos Model C. Bridge". To calibrate the block readings, soil samples were taken from each depth through the year, and the percent soil moisture determined gravimetrically. By charting on semi-logarithmic paper the absorption block readings in ohms, against percent moisture determined gravimetrically, a curve for each site and depth was formed showing percent moisture according to block response. Available soil water, defined by Baver (1956) as the moisture 52 content between wilting point and field capacity, was determined for the soil from each site, using the pressure plate method as described by Richards (1948). Duplicate soil samples, each a composite sample from • five samplings, of the A and B Soil horizons of each study site, were subjected to 0.33 and 15.0 atmospheres pressure to determine the field capacity and permanent wilting points respectively. The rugged topography, the remoteness of the area and the coarse texture of the soils, precluded actual bulk density determinations. However, an approximate specific gravity for the soil of each site was estimated from standard tables, presented by "Israelsen and Hansen (1962). These values, and the field capacity and permanent wilting points for each soil, are presented in Table 13. The volume of soil water, in inches (V), at each sampling date and for each soil depth was then determined from the formula: V = Specific gravity x Soil depth (inches) x % Soil moisture 100" Soil temperatures Soil temperatures were measured in 1968 only. A thermistor was buried at 20 inches in each site and the soil temperature recorded at weekly intervals from May through September. At this depth diurnal temperature changes are iTi inimal (T.M. Lord - personal communication). Run-off At six sites, run-off gauges fabricated largely in the field, were established in May 1968. -The gauges, constructed of 10 gauge galvanized iron, were V-shaped, one meter wide, and included a collecting trough at the back edge (Figure 10). The front edge of the gauge was inserted one inch into the soil surface and the entire gauge tilted so 53 Table 13. 1 Some physical properties of soils from each study site Field Wilting Estimated' Soil Capacity Point Specific Site Horizon % % Gravity Agropyron spicatum xeric A 23.1. 11.5 1.45 B 17.6 5.9 1.50 Agropyron spicatum mesic A 12.9 7.3 1.55 B 10.5 5.0 1.60 Agropyron spicatum hydric A 25.1 10.4 1.40 B 18.3 7.1 1.45 Poa pratensis xeric A 26.8 15.2 1.45 B 27.0 12.1 1.50 Poa pratensis mesic A 40.5 20.3 1.30 B 38.1 17.4 1.35 Poa pratensis hydric A 40.5 22.4 1.30 B 34.6 18.2 1.35 Calamagrostis A 33.8 12.7 1.35 rubescens B 25.. 9 8.3 1.40 Artemisia frigida A 20.8 11.5 1.40 B 18.5 . 7.5 1.45 Values taken from Israelsen and Hansen 1962. 5u Figure 11. Control gauge in the Poa pratensis mesic site 55 that water would drain into the collecting trough and then into a can. Two types of gauges were employed, and at each site two of each type were installed. Two of the gauges were operating and the other two were controls. The latter were identical in design and installation except that a fold of metal at the front edge prevented entrance of run-off water (Figure 11). In effect the control gauges were simply precipitation gauges and the difference in volume of water collected between the control and the run-off gauge was the amount due to run-off. To provide a known area from which the run-off was collected, a 6 inch high plastic barrier was imbedded approximately 1 inch into the soil surface, 3 meters above the gauge and down both sides of the one meter strip. Hence, run-off from a 3 square meter rectangle was being collected. Run-off gauges were installed in the Poa pratensis, Artemisia  frigida and Agropyron spicatum mesic exclosures. A fourth installation was at the Agropyron spicatum hydric site and the- remaining two installations were in an Agropyron spicatum dominated community, located on two very steep slopes of 43 and 52 per cent. 56 RESULTS Atmosphere near the ground  Temperature Mean temperatures were above 40C" from May through September in both 1967 and 1968, at the two Flatiron Mountain stations (Table 14). At Keremeos, B.C., mean temperatures were above 40°F from March through October.''" From May through September, temperatures at Keremeos, averaged 15°F warmer than at the Agropyron spicatum site, and 16°F warmer than at the Poa pratensis site. This represents an average temperature lapse rate of 3.7°F per 1,000 feet elevation. The annual mean temperature is available for 1968 and from the Agropyron spicatum site only, and was 11.4°F less than at Keremeos. This is an annual temperature lapse rate of 2.6°F per 1,000 feet elevation. Maximum and minimum temperature extremes during the study period were: 83°F in August of 1967 and -22°F in December of 1968 at the Agropyron spicatum site, and in the same months, 81°F and -38°F at the Poa pratensis site. Comparable temperature extremes at Keremeos were 106°F and -22°F respectively. Temperature changes of considerable amplitude over short periods were common during both years. Mean weekly temperatures fluctuated ^he weather station at Keremeos is the closest active station operated by the Canada Department of Transport, Meteorological Branch. Keremeos is approximately 10 "map" miles distant from the study area, and is located in the Similkameen River Valley, at an elevation of 1,410 feet. TABLE 14. Monthly mean- temperatures in degrees Farhenheit °F for the two climatic "base" stations on Flatiron Mountain and for Keremeos, B.C., from May, 1967 through December, 1968 Mean monthly temperatures °f : Mean Station Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Temp. Agropyron spicatum site 1967 M. M. M. M. I. 52.5 53.2 64.3 56.3 34.2 29.2 15.2 43.6 (South Slope-5750 ft) 1968 31.7 32.3 32.9 36.6 42.1 45.8 56.8 49.3 45.3 39.8 25.9 21.9 38.4 Poa pratensis site 1967 M. M. M. M. I. 48.8 52.3 60.4 57.7 39.7 30.9 I. 48.3 (Juniper Slope- 1968 I. I. I. I. 40.3 45.9 55.3 52.6 46.2 44.8 27.2 9.3 39.5 5525 ft) Keremeos 1957 34 40 41 47 58 68 72 76 68 51 39 30 52.0 (1410 ft) 1968 30.5 38.5 45.4 48.6 57.1 62.4 72.6 66.0 61.6 48.7 39.4 26.5 49.8 30 yr. . ave. 26 31 41 51 59 64 71 69 62 50 36 30 49.2 M. Missing data T. Incomplete data - entire months data not obtained 58 as much as 18 at the Agropyron spicatum site (Figure 12) and similar fluctuations occurred at the Poa pratensis site. During July and August of 1968, when a thermograph was available for the Calamagrostis rubescens station, mean temperatures averaged approximately the same as at the Poa pratensis station. However, maximum temperatures were about 2°F lower and minimum temperatures about 2°F higher than those measured at the Poa pratensis station. Prior to thermograph measurements the maximum and minimum temperatures, recorded on a weekly basis, showed similar differences. Precipitation In nearly all months and in both years, precipitation was substantially higher at the study area than at Keremeos (Table 15). Within years, there was little difference in the amount of precipitation received at the Agropyron spicatum site and at the Poa pratensis site, but at the Calamagrostis rubescens site monthly precipitation measured under the forest canopy, averaged approximately 12 percent less than the other two sites. The average precipitation received at the two climatic base stations, from June through December of 1967 was 9.17 inches as compared to 5.35 inches for the same period at Keremeos. In 1968 the average annual precipitation at the two base stations was 12.43 inches as compared to 7.89 inches at Keremeos. In the study area, there was considerable variation in the precipitation pattern between years (Figure 13). In 1967, from May 18 to October 1, the precipitation at the two climatic base stations M O N T H S Figure 12. Mean daily temperatures on a weekly basis at the Agropyron S D i c a t u m site, from May 1967 through December, 1968. Table 15. Monthly precipitation (inches) for three climatic stations on, Flatiron Mountain and one at Keremeos, B.C. from May, 1967 through December,, 1968. • I n c h e s P r e c i p i t a t i o n T o t a l S t a t i o n ( e l e v a t i o n ) Y e a r J a n Feb Mar A p r May J u n J u l Aug Sep Oct Nov Dec : P P f n snow f a l l A esp. s i t e l 1967 M. M. M. M. I . 3.13 0.38 0.16 0.33 1.63 1.13 2.25 9.01 30.37 (5750 f t . ) 1968 0.50 1.00 0.83 0.50 2.42 1.06 0.54 2.12 1.22 0.48 0.75 0.95 12.37 40.83 P o o r , s i t e 1967 M. M. M. M. I . 3.30 0.31 0.16' 0.35 1.58 1.13 2.50 . 9.33 30.63 (5525 f t . ) 1958 0.75 1.03 0.86 0.62 2.18 1.19 0.59 2.15 1.27 0.48 0.63 0.75 12.50 40.02 Caru. s i t e 1967 M. M. M. M. I . 2.88 0.22 0.11 0.29 1.44 M. M. 4.94 M. (5400 f t . ) • • 1963 M. M. M. M. •1.79 0.96 0.47 1.56 1.43 M. M. M. • 6.21 M. Keremeos. 1967 0.81 0.22 0.73 0.45 0.54 1.34 0.25 0.00 0.08 1.10 0.34 2.24 8.10 15.4 (1410 f t . ) ' 1968 0.47 0.84 0.19 0.10 1.77 0.95 0.27 0.94 0.23 0.22 0.32 1.59 11.6 30 y r Mean 1.09 0.83 0.64 0.57 0.90 1.27 0.81 0.78 0.73 0.74 0.95 0.96 10.16 26.0 1 Key t o code symb o l s : Agsp. - A g r o p y r o n s p i c a t u m s i t e P o p r . - Poa p r a t e n s i s s i t e C a r u . - C a l a m a g r o s t i s r u b e s c e n s s i t e M. M i s s i n g d a t a I I n c o m p l e t e d a t a 2.0 1.5 1.0 0.5 7o~ 7o — i — 2 0 1967 —r-10 1 0 M a y J u n e 10 2 0 J u l y ~T~ 20 August 10 Sept. r -20 10 ~T— 20 Oc t. ^ 2.0 h t— E 1-5 u ca  l , u a . 0.5 \-0 i k . - — r 10 20 J u n e f) I) r) I 1 0 1968 i 10 20, M a y i 20 T 20 J u l 10 August i— 20 1 0 S e p t . - r ~ 10 Oct . - r -20 Figure 13. Weekly precipitation from May 10 to October 20 in 1967 and daily precipitation from May 10 to September 30 in 1968, as measured with standard rain gauges in 1967 and with a tipping bucket rain gauge in 1968 at the Agropyron spicatum site. 62 averaged 4.1 inches, of which approximately 75 per cent was received during June. During the same period in 1968, there were 7.4 inches of precipitation, ?f which 31 per cent was received in May, 16 per cent in June, 29 per cent in August and 17 per cent in September. Evaporation On Flatiron Mountain, evaporation was greatest at the Agropyron spicatum site, and least at the Calamagrostis rubescens site (Table 16). Evaporation was considerably higher in 1967, with a peak monthly evaporation of 18.7 inches in August. The highest monthly Table 16. Monthly evaporation from May "through October in 1967 and 1968 for three Flatiron Mountain sites, for Keremeos and Cawston,B.C. Evaporation in inches Station Year May June July Aug. Sept. Oct. Agropyron spicatum site (South Slope - 5,750 ft.) 1967 1968 5.1 3.6 8.8 9.2 12.9 11.4 18.7 8.0 9.5 6.3 5.1 5.0 Poa pratensis site CJuniper Slope - 5,525 ft.) 1967 1968 4.8 2.8 7.9 8.5 11.8 10.3 14.2 5.4 8.8 6.3 4.6 4.7 Calamagrostis rubescens (forest slope - 5,400 ft.) 1967 1968 M 1.7 5.9 4.3 6.4 5.3 8.5 4.4 5.5 3.9 2.4 2.2 Cawston, B.C.* (1,016 ft.) 1967 16.7 17.8 20.9 22.4 14.1 6.2 Keremeos, B.C.** (1,450 ft.) 1968 15.1 14.3 20.4 12.4 10.8 7.5 M - missing data * - data for 1968 not available for Cawston :* - data for 1967 not available for Keremeos 63 evaporation in 1968 was 11.4 inches, which occurred in July. Evaporation data for Keremeos, B.C. are available for 1968 only. However date for 1967 are available for Cawston, B.C., which is located approximately 5 miles distant from Keremeos. Evaporation at these two stations should be similar, and is included here for comparison with the data from the Flatiron Mountain stations. During all months evaporation was greater in the Similkameen Valley than at any station on Flatiron Mountain; the greatest difference occurring in May with only slight differences occurring in October. Wind Wind movement from July through December in 1968 at the two climatic base stations, is shown in Table 17. The average wind velocities during July, August and September were quite similar at the two climatic base stations, but during October, November, and December wind velocities were substantially higher at the Poa pratensis station. Winds were lowest in July and August, averaging 3.7 miles per hour at each site, and highest in November and December, averaging 6.5 miles per hour at the Agropyron spicatum site and 11.0 miles per hour at the Poa pratensis site. Table 17. Average wind velocities (miles per hour) from August to December 1968 at two sites on Flatiron Mountain Station July Aug. Sept. Oct. Nov. Dec. Agropyron spicatum site 3.7 3.5 4.6 5.5 7.2 5.9 Poa pratensis site .3.9 3.7 4.6 6.7 10.4 11.7 64 Soil Soil moistiire The soil water content in the top 6 inches of soil from each study site, at sequential dates from May 15 to September 19 of 1967, are presented in Table 18. The data show that at al l sites except for the Calamagrostis rubescens site, available soil water (i.e. above permanent wilting point) was exhausted by July 12. At the Artemisia  frigida site and at the Poa pratensis xeric site the soil moisture content measured was always less than the permanent wilting point. The soil water content at the Calamagrostis rubescens site however, remained above the permanent wilting point until August 29. Once the available soil water was depleted, it remained so through the rest of the season. During the same period in 1968, the date that available soil noisture was exhausted varied between sites and soil depths (Table 19). Nevertheless, the period when soil moisture was available was short at all sites and the lower soil horizons (6-12 in., 12-18 in., and 18-24 in.) were usually exhausted of available soil moisture later than the 0 to 6 inch horizon. Except for the 6 to 24 inch soil horizon at the Agropyron spicatum hydric site, and the 18 to 24 inch horizons at the Poa  pratensis mesic site and at the Calamagrostis rubescens site, the available soil moisture supplies, in the top 24 inches of soil, had been depleted by July 10. By July 22 no soil water was available within the top 24 inches of soil at any site. In contrast to 1967, there v/as available soil moisture in the Table 18. Inches of soil water at sequential dates in 1967 of the top six inches of soil at eight study sites on Flatiron Mountain Soil Perm Soil moisture (inches) at sequential dates Depth Wilt. May Ray Jun Jun Jul . Jul Aug Aug Sep Site (inches) (inches) 15 30 14 28 12 26 8" 29 19 Agsp.* "xeric" 0-6" 1.00 1.99 1.31 1.51 1.66 0.49 0.45 0.31 0.17 0.32 Agsp. "mesic" 0-6" 0.68 1.25 1.04 1.03 0.98 0.37 0.38 0.24 0.17 0.29 Agsp. - "hydric" • 0-6" 0.87 2.03 1.86 1.41 1.74 0.54 0.73 0.32 0.24 0.33 Popr. "xeric" 0-6" 1.32 M. ' 1.02 1.07 1.24 0.43 0.35 0.39 0.18 0.38 - "mesic" 0-6" 1.58 M. 2.64 2.82 2.63 1.46 0.95 0.69 0.53 0.68 "hydric" 0-6" 1.75 M. 4.12 3.91 3.65 1.76 1.29 0.85 0.49 0.73 Caru. - "mesic" 0-6" 1.03 M. M. 2.84 2.34 1.68 1.18 1.22 0.60 0.83 Arfr. - "mesic" 0-6" 0.97 M. M. 0.79 0.97 0.39 0.28 0.21 0.23 0.26 * Key to code symbols: Agsp. - Agropyron spicatum Popr. - Poa pratensis Caru. - Calamagrostis rubescens Arfr. - Artemisia frigida Missing Data M. & Table 19. Inches of soil water at sequential dates in 1968, for six inch soil horizons from 0 to 24 inch soil depth, at the eight study sites on Flatiron Mountain Soil Perm Soil moisture content (inches) at sequential dates Depth Wilt. May May Jun Jun Jun Jun Jul Jul Aug Sep Sep Site (inches) (inches) 18 30 3 10 21 26 10 22 9 4 19 Agsp.* Agsp. Agsp. Popr. Popr. xeric 0 - 6 1. 00 0.67- 1.61 1. 47 1. 91 1. 65 . 1. 60 0. 50 0. 44 0. 29 0.36 0. 62 6 - 12 0. 53 M. 1.19 1. 07 1. 47 1. 44 1. 46 0. 55 0. 45 0. 31 0.37 0. 36 12 - 18 0. 53 M. 1.16 1. 00 1. 32 1. 38 t 44 0. 60 0. 47 0. 33 0.39 0. 36 18 - 24 0. 53 M. 1.34 1. 38 1. 38 1. 62 1. 65 0. 55 0. 46 0. 29 0.36 0. 36 mesic 0 6 0. 68 0.48 1.08 1. 00 1. 10 0. 83 0. 58 0. 31 0. 30 0. 25 0.58 0. 39 6 - 12 0. 48 M. 0.92 0. 91 0. 95 0. 91 0. 43 0. 32 0. 31 0. 30 0.57 0. 38 12 - 18 0. 48 M. 0.81 0. 82 0. 91 0. 91 0. 84 0. 33 0. 30 0. 29 0.36 0. 38 18 - 24 0. 48 M. 0.83 0. 85 0. 95 o. 95 0. 96 0. 36 0. 33 0. 32 0.38 0. 38 hydric 0 6 0. 87 1.24 1.83 1. 72 1. 90 1. 75 1. 71 0. 87 0. 54 0. 49 0.76 0. 54 6 - 12 0. 62 M. 1.21 1. 21 1. 35 1. 34 1. 35 0. 80- 0. 65 0. 51 0.75 0. 52 12 - 18 0. 62 M. 1.20 1. 18 1. 43 1. 39 1. 43 0. 84 0. 64 0. 49 0.39 0. 52 18 - 24 0. 62 M. 1.27 1. 31 1. 43 1. 43 1. 51 0. 96 . 0. 70 0. 53 0.52 0. 52 xeric , ' 0 6 1. 32 0.48 M. • M. 1. 97 1. 57 0. 98 0. 76 0. 52 0. 49 1.11 0. 75 6 - 12 1. 05 M. M. V !. 2. 03 1. 65 1. 05 0. 78 0. 63 0. 50 0.87 0. 87 12 - 18 1. 05 . • M. M. M. 1. 92 1. 64 1. 03 0. 77 0. 62 0. 53 0.59 0. 87 18 - 24 ; 1. 05 M. M. M. 2. 01 1. 82 1. 34 0. 82 0. 61 0. 56 0.87 0. 87 mesic 0 6 1. 58 2.71 2.62 2. 94 3. 05 2. 85 2. 83 1. 07 0. 78 0. 77 1.56 1. 28 6 — 12 1. 41 M. 2.47 2. 64 2. 74 2. 70 2. 62 1. 30 1. 00 0. 77 1.21 1. 21 12 - 18 1. 41 . M. 2.41 2. 46 2. 59 2. 62 2. 55 1. 37 1. 06 ' 0. 87 0.55 1. 21 18 _ 24 1. 41 M. 2.47 2. 51 2. 62 2. 69 2. 63 2. 35 1. 38 0. 83 1.21 1 -L • 21 Continued Table 19 (continued) Soil rnoisture content (inches) at sequential dates Soil . Perm. — ; '. _ Depth Wilt. May May Jun Jun Jun Jun Jul Jul Aug Sep . Sep (inches) (inches) 18 30 3 10 21 26 10 22 9 4~ 19" Popr. hydric 0 - 6 1.75 3.38 M. M. .3.09 2.99 3.07 1.27 1.21 1.10 2.45 1.23 6 - 12 1.47 M. M. M. 2.75 2.70 2.87 •1.22 1.10 0.97 1.26 1.21 12 - 18 1.47 M. M. M. 3.04 2.68 2.71 1.24 1.08 0.98 1.03 1.21 18 - 24 1.47 M. M. M. 2.70 2.67 2.72 1.22 1.22 1.13 1.21 1.21 Caru. mesic 0 6 1.03 2.72 2.15 2.38 2.72 2.62 2.76 0.70 0.74 0.51 0.98 0.94 6 - 12 0.70 M. 1.51 1.71 2.01 2.11 2.21 0.75 0.51 0.48 1.13 1.13 12 - 18 0.70 M. 1.50 1.55 1.85 1.92 2.06 0.67 0.58 0.57 0.69 0.67 18 - 24 0.70 M. • 1.41 1.55 1.86 2.07 2.14 0.87 0.76 0.56 0.67 0.67 Arfr. mesic 0 _ 6 0.97 0.46 1.46 1.39 0.83 0.54 0.33 0.32 0.40 0.30 0.87 0.60 - 6 - 12 0.65 M. 1.48 1.48 1.02 0.76 0.37 0.33 0.32 0.30 0.64 0.43 12 - 18 0.65 M. 1.49 1.63 1.32 0.92 0.36 0.31 0.30 0.29 0.37 0.43 18 - 24 0.65 M. •1.25 1.32 1.31 1.21 0.54 0.32 0.30 0.28 0.43 0.43 * Same symbols as for Table 17 M. Missing data 68 top 6 inches of soil at the Poa pratensis xeric site and at the Artemisia frigida site in 1968. The period when \ater was available was short however, with the supplies being depleted by June 26 and June 10 respectively. Soil temperatures Soil temperatures in 1968 at 20 inches depth, at each study site, from May 30 to September 19, are presented in Table 20. The lowest temperature was 40.6°F, recorded at the Calamagrostis rubescens site on June 3. The highest temperature was 63.5°F, recorded on July 10, at the Agropyron spicatum xeric and mesic sites, the Poa pratensis xeric site and the Artemisia frigida site. Soil temperatures averaged the highest at the Artemisia frigida site, averaging 56.1°F, while a lowest average temperature of 45.7°F occurred at the Calamagrostis rubescens site. Run-off Run-off in 1968, was measured on few occasions and when measured was almost negligible (Table 21). The greatest run-off occurred at the Agropyron spicatum hydric site (Site 1), during the period from August 9 to August 26, when 2.12 inches of precipitation fell and 0.07 inches or 3.0 per cent was lost to run-off. As determined from tipping bucket rain gauges, the maximum intensity of rainfall during this period was 0.80 inches in 2.5 hours on August 17 (See Figure 13, page 61). Oddly, at this same site, when 0.86 inches of rain fell between September 4 and September 19, of which 0.65 inches of rain fell in 3 hours, 0.05 inches or 5.9 per cent was lost to run-off. Run-off of almost equal magnitude Table 20. Soil 1 temperatures in degrees Fahrenheit, at 20 inches depth, at sequential dates through 1968 at eight study sites on Flatiron Mountain Soil: Temperatures F at sequential dates Site May 30 Jun 3 Jun 10 Jun 21 Jun 26 Jul 10 Jul 22 Aug 9 Aug 26 Sep 4 Sep 19 Ave. To. Agropyron spicatum — ' — J — I I « it - xeric 48.0 49.1 50.5 52.8 56.8 63.5 55.2 57.2 53.2 56.3 49.8 53.9 - "mesic" 48.2 50.5 50.5 55.4 58.7 63.5 55.6 62.6 52.5 58.5 52.4 55.3 - "hydric" M. 51.8 52.5 53.6 56.8 60.8 53.4 60.8 52.5 58.1 53.0 55.3 Poa pratensis - "xeric" M. 51.8 52.4 55.8 M. 63.5 56.8 63.0 52.1 56.7 51.8 56.0 - "mesic" 48.2 48.2 50.5 52.4 M. 56.3 51.6 54.0 55.2 55.4 50.9 52.3 - "hydric" M. 47.5 48.6 50.5 M. 53.6 50.9 53.8 49.8 51.6 49.6 50.7 Calamagrostis rubescens - "mesic" , M. . 40.6 41.2 44.2 46.4 48.2 45.5 M. 46.2 55.4 44.0 45.7 M. 50.5 45.5 48.2 52.1 48.2 46.4 M. 46.6 55.6 45.0 48.7 Artemisia frigida - "mesic" M. 50.5 54.0 55.4 56.8 63.5 60.6 60.6 50.9 56.8 51.8 56.1 M. - Missing data Table 21. Inches of run-off and precipitation in 1968, for four sites on South Slope and two sites on Juniper Slope South Slope Watershed Juniper Slope Watershed Mean* : —, ; — Precipi- Site 1** Site 2 Site 3 Site 4 Site S Site 5. Time Period tation 8% Slope 23% Slope 43% Slope 52% Slope 5% Slope 23% Slope May 30 to June 10 0.47 M. 0 M. M. 0 0 June 10 to June 21 0.50 M. 0 M. M. 0 0 June 21 to June 26 0.25 M. 0 M. M. 0 0 June 26 to July 10 0 0 0 0 0 0 0 July 10 to July 22 0.63 0 0 0 0 0.02 0 July 22 to August 9 0.12 0 0 0 0 0 0 August 9 to August 26 1.95 0.07 0 0 0 0.05 0 August 26 to September 4 0.35 0 0 0 0 0 0 September 4 to September 19 0.89 0.05 0.01 0 0 0.04 0.01 M. - missing data * - mean precipitation measured by the 12 "Control" gauges key to sites: g i t e 1 _ Ag^py^n s pi Catum hydric - Agropyron spicatum mesic Agropyron spicatum community -- Agropyron spicatum community -- Poa pratensis mesic Artemisia frigida mesic Site Site Site Site Site Orthic black silt soil type Rego dark grey soil type Rego dark grey soil type Rego dark grey soil type Orthic black silt soil type Rego dark grey soil type 71 was measured at the Poa pratensis mesi^ site (Site 5) during the same two periods. Both sites were characterized by a very moderate slope and an • Orthic black silt soil type. At the remaining four sites, virtually no run-off was measured, although the percentage slope was considerably greater. The soil type of all the latter sites was Rego dark grey. The precipitation data given in Table 21, is the mean of that measured by al l control gauges for each time interval. These gauges measured precipitation within 5 percent of that measured by standard rain gauges, where the latter were present at run-off sites. 72 DISCUSSION Atmosphere near the ground Since climatic data were gathered for only 20 months, only a few inferences ep.n be made in describing the climate of the Ashnola region. In general though, the climate appears to be typical of the Interior Plateau region, as described by Chapman (1952). Mean temperatures were lower at the study sites than at Keremeos, which lies some 4,000 feet lower in elevation, and as might be expected the growing season was considerably shorter. Rapid temperature changes appear to be characteristic of the Ashnola region and undoubtedly are an important aspect of the range ecosystem. Precipitation averaged higher at the study area than at Keremeos, but no constant monthly difference was observed, particularly during the summer months. This appears to be mainly due to the convective nature of most of the summer precipitation. Presumably because of the mountainous topography of the Ashnola region,convective precipitation, although irregular, occurred more frequently than in the Similkameen Valley. Interception of precipitation by the Douglas f i r tree "overstory", probably explains the lower precipitation amounts measured at the Calamagrostis rubescens site. Similar interceptions of precipitation by trees were reported by Penman (1963) and i t is doubtful that there was any "real" difference in the amount of precipitation which fell at this site and at the other sites. The Calamagrostis rubescens site is less than 1/3 mile from the Poa pratensis site, and at approximately the same elevation. 73 . Precipitation is not likely that local. From May through September, the amount and distribution pattern of precipitation differed considerably between years'; Such wide variations, are normal in mountainous regions (Chapman 1952; Kerr 1952; Kerr and Kendrew 1956). Winter precipitation was measured monthly using "Sacramento" type snow gauges, hence the frequency and intensity of winter precipitation are not known. Monthly winter precipitation at the study sites, usually differed from that received at Keremeos. However, despite the Alter shield present, high winds reportedly (Griffiths, 1966), result in a loss of "catch" of precipitation with this type of gauge. In this study such errors may have occurred (see Figure 9, page 50). Evaporation was considerably lower at the study area than in the Similkameen Valley, and since carborundum block evaporimeters were used at all locations, the results are comparable. Wilcox (1967) found a good correlation between evaporation from this type of evaporimeter, with that from the black Bellani plate, that from the Class A pan and with evapotranspiration. Using a 22 percent methanol solution this evaporimeter performs accurately to temperature above 0°F (Wilcox 1967). During the six month period that wind movement was measured, winds were common, and from casual observation during the study this is probably true during all months. The difference in wind movement 74 during November and December between the Agropyron spicatum and the Poa  pratensis sites was probably the result of the location of the stations, and the direction of the prevailing winds. The Agropyron spicatum site is located just over the crest of a south, south-east facing slope of 28 per cent, and consequently is somewhat sheltered from north and north-west prevailing winds. The Poa pratensis site however is situated on a south facing slope of only 5 per cent and therefore more exposed to wind. Wind direction was not recorded, but northerly winds were observed to be common during the winter. Most summer winds were from the west, hence, as the data indicates, both sites probably are exposed to equal wind movement. During the summer the. winds undoubtedly combine with temperature to cause substantial losses of water from both soils and vegetation, while during the winter they are an important factor in reducing the snow cover on exposed areas. The latter is extremely important to overwintering bighorn sheep, which might otherwise be unable to obtain forage due to snow cover. Soil The relatively short period during which.soil moisture was available to plants, illustrates the aridity of the study area. In neither 1967 or 1968 was the soil water content in the upper soil layers (0-6 inches in 1967 and 0-24 inches in 1968) above the permanent wilting point after mid-July. Assuming that this short term availability of soil water is typical, then only xeric plants, as defined by Daubenrtiire (1959(b)) could survive. 75 Accurate and representative soil moisture data is difficult I to obtain however (Wang 1967, Ehrenleich 1963 and others)} and certain errors may exist in the data presented here. Of the many possible errors only two seem to be plausibly important. First, electrical resistance units are subject to errors from the hysteresis effect in wetting and drying, to soil temperature variations, and to high salt concentrations. The latter can probably be excluded, as soils in the Ashnola are apparently not high in salt (Demarchi 1965). The hysteresis effect and the soil temperatures at each resistance block were not measured and no corrections for these influences could be made. Second, for any given depth within sites, there was considerable variation in the resistance readings obtained at al l measurement dates, but particularly during the soil drying period. Such variations might be expected in such rocky soils as these and, except for occasional aberrations, the mean resistance reading for each depth at each date was used. The number of installations of resistance blocks at each site are assumed sufficient to be representative of the average soil moisture regime. Run-off It appears from the data that no appreciable run-off occurred on the study area in 1968. However, the accuracy of the gauges used is open to question. A certain amount of soil erosion, at the point where the operating gauges were inserted into the soil, was observed at some sites and substantial sediment accumulated in the collecting cans. This was particularly true at the sites installed on Rego dark grey soil (sub-group) profiles, and may be a.reason for no run-off being measured at 76 those sites. Run-off water may have run under, rather than onto, the collecting pan of the gauge. On the other hand this soil type is more permeable to infiltration than the Orthic black s i l t type (T.M. Lord -personal communication). These gauges require, further testing before any conclusions can be safely drawn. Run-off has occurred in the past, as evidenced by the presence of large erosion gulleys, particularly on the steeper parts of South Slope (see Blood 1961). No such erosion was observed during this study and presumably the gulley erosion resulted from more torrential rains than occurred in 1967 or 1968. 77 SUMMARY 1. Measurements of major climatic variables, at 5,500 feet elevation on Flatiron Mountain in the Ashnola region, were made from May 1967 through December 1968. Ambient air temperature and precipitation were measured throughout the study. Evaporation and soil moisture were measured from May to October in each year. Soil temperatures were only measured from May through September 1968 and wind movement only from July through December 1968. Run-off was measured at six sites in 1968. 2. All climatic measurements were made within the vegetation exclosures described in the previous section of this presentation. 3. Mean monthly temperatures were above 40°F from May through September at the study area and from March through October at Keremeos, B.C. (elevation 1,410 feet). Daily mean temperatures for the study area, from May through September, averaged 15.5°F cooler than for Keremeos, and the mean annual temperature, available for 1968 only, was 11.4°F cooler. These differences respectively represent temperature lapse rates of 3.7°F and 2.6°F per 1,000 feet elevation. 4. Precipitation patterns in the two years differed markedly. In 1967, from May 18 to October 1 precipitation in the study area was 4.1 inches, of which 75 per cent was received during June. During the same period in 1968 precipitation was 7.4 inches, of which 31 per cent was received in May, 16 per cent in June, 29 per cent in August and 17 per cent in September. At Keremeos, 2.2 inches of precipitation were received in 1967 and 4.6 inches were received in 1968, during the same period. 78 5. Evaporation was measured from May through October in both years and was considerably less than that measured at Keremeos and Cawston, B.C. The greatest differences were recorded in May with only slight differences in October. On Flatiron Mountain the highest evaporation rates were measured at the Agropyron spicatum station located on a south facing slope and the lowest rates were measured at the Calamagrostis  rubescens station, located under a Douglas f i r canopy. 6. Wind was measured only from July through December of 1968; but substantial wind mileage characterized all seasons. From July through September wind velocities averaged 4.0 miles per hour and from October through December averaged 7.8 miles per hour. Wind direction was not measured but westerly winds seemed to be most common during the summer, while northerly winds seemed to be most common during the winter. No wind data were available for Keremeos, B.C. 7. At all study sites, virtually a l l of the soil water available to plants, was exhausted prior to the end of July in both years. Since temperatures were favourable for growth well into September, water deficits would obviously terminate plant growth and forage accumulation. 8. Soil temperatures at 20 inches depth were above 40°F from May 30 to September 19, 1968, and thus were favourable to plant growth. 9. No appreciable run-off, even on steep slopes, was measured between May 30 and September-19, 1968, despite some quite intense rain storms. The gauges used were simple and some errors may have occurred. However, no appreciable erosion was observed and run-off, i f it occurred, was probably of minor extent. 79 LITERATURE CITED BAVER, L.D..1956. Soil physics 3rd ed. 439 pp. New York, John Wiley and Sons, Inc. BOUYOUCOS, G.J. 1956. Improved soil moistu.ro meter. Agr. Eng. 37(4): 261-262. CHAPMAN, J.D. 1952. The climate of British Columbia. Paper presented to Fifth B.C. Natural Resources Conference. CODD, G.D. 1947. Seasonal storage precipitation gauge. Trans. Amer. Geo. Phys. Union 28(6): 899-900'. EHRENREICH, John H. 1963. Measurement and evaluation of soil moisture and temperature and inicroclimate in ecological studies. U.S.D.A. Misc. Publ. 940: 83-95. GRIFFINS, J.F. 1966. Applied Climatology. Oxford Univ. Press, Toronto. ISRAELSEN, Orson W., and Vaughn E. HANSEN. 1962. Irrigation principles and practices 3rd ed. New York, John Wiley and Sons Inc. KENDREW, W.G. and D.P. KERR. 1955. The climate of British Columbia and the Yukon Territory. Queen's Printer, Ottawa. KERR, D.P. 1952. Climate of British Columbia. Can. Geog. Journ. 45(4): 143-148. PENMAN, H.L. 1963. Vegetation and hydrology. Commonwealth Bureau of Soils, Harpenden Tech. Comm. 53, 124 pp. RICHARDS, L.A. 1948. Porous plate apparatus for measuring moisture retention and transmission by soil. Soil Sci. 66: 105-110. WANG, J.Y. 1967. Agricultural meteorology. Agric. Weather Info. Ser. 693 pp. Omega Enterprises, Palo Alto, Calif. WILCOX, J.C. 1967. A simple evaporimeter for use in cold areas. Water Resources Research 3(2): 433-436. 80 SECTION III INTER-RELATIONSHIPS OF VEGETATION AND CLIMATE INTRODUCTION • Despite the complexity of environmental factors regulating plant growth on semi-arid rangelands, variations in annual forage production can most often be ascribed to variations in the water supply during the growing season. More precisely, water deficits can result in-physiological conditions which truncate growth processes, and thus largely determine how much and when during a temperature determined growing season new tissue can be formed (Slatyer 1957(a); Zabner 1963; Kozlowski 1967). For arid and semi-arid rangelands the dependence of forage production upon the moisture regime has been well documented. For examples, Blaisdell (1958), Craddock and Forsling (1938) and Hutchings and Stewart (1958), reported highly significant correlations between precipitation and annual herbage production. Campbell and Rich (1961) did not find a significant correlation between crop year precipitation and annual herbage yields, but did obtain a highly significant correlation between soil moisture and yield. Rogler and Hass (1947) and Dahl (1953) also report soi l moisture to be more significantly correlated than precipitation with annual forage production. Correlation coefficients and regression equations however, have only descriptive importance, and man's inability to use these relation-ships to determine appropriate grazing capacities, is the major reason for 81 the present overgrazed condition of most of the world's arid and semi-arid rangelands. In the past, grazing capacities have been mainly determir»ed from synecological studies. Such an approach cannot efficiently allow for the wide variations in annual moisture supplies and consequent productivity, and as a result, severe overgrazing has frequently occurred in dry years. Recently, there have been attempts to apply climatic data to carrying capacity determinations. Most of the attempts have been only partially successful due to the treatment of weather variables singly. Sneva and Hyder (1962) devised a method for estimating median annual herbage production based on crop year precipitation, for the semi-arid rangelands in the Inter mountain regions of the Western United States. This method, however, is of little more value than the synecological approach, since it only 'predicts' long-term median yields and does not'allow for adjustments of stocking numbers within and between seasons (from year to year). Spring-field (1963), under a medium rate of grazing on seeded ranges in New Mexico, obtained a correlation coefficient of 0.97 between annual forage production and the preceding October through May precipitation. Eahl (1963) reports that spring soil moisture supply in a Sandhills range type in Colorado, is the best predictive index of annual herbage yield. However none of these methods explained a large portion of the yield variance. Moreover all of the methods were only suitable for an average or range in expected herbage production for an entire growing season. Such predictions neglect the "effective production" - herbage that is available for consumption at a par-ticular time. A knowledge of effective production is of critical importance due to the wide variety of animals which use most rangelands and the different seasons of use. Thus, a more realistic method is required, one which will 82 detect the effects of environmental factors upon plant growth of various stages of development and therefore be suitable for predicting the amount of herbage available for consumption as the season progresses. Originally it was hoped that a prediction model could be developed from the data gathered in this study. However, the data are few, and at this time techniques for model construction have been fully explored. Several methods were investigated, for examples, Currie and Petersen (1966), Baeir and Robertson (1966) and Campbell and Rich (1961), but at the present stage, the data appears' inadequate for the development of a useful model. Neither are there sufficient quantitative expressions for all the crop events, for example, transpiration rates at various developmental stages, nor is the microclimate sufficiently well measured. Moreover, long term data' is desirable. Thus the only possible approach in the time available, is to obtain a first approximation; which i t is hoped will help direct further research towards establishing more precise relationships. Two approaches to the approximation are taken: (a) analysis of the environmental factors regulating the lengths of growing seasons and (b) comparisons of some meteorological variables with plant growth. 33 GROWING SEASONS • . j • The seasonal yield data are used as the measure of plant growth. Since the most detailed yield and climatic data are available for the Agropyron spicatum and Poa pratensis mesic sites, these data are used for the analyses. The data from the xeric and hydric sites and the data from the Artemisia frigida and Calamagrostis rubescens mesic sites are used for secondary comparisons. Both physical and physiological principles are involved in the evaluation of a true growing season. Climatic changes are physical processes while the response of plants to these changes are physiological processes. In a l l plants the commencement of growth is associated with climatic conditions, usually temperatures. Although growth may be physiologically and genetically regulated, climatic factors are of obvious importance and commonly determine the beginning and end of growth, growth rates and sometimes developmental events. Actual growing seasons The actual growing seasons for each site and year were determined from observation and from the yield data. The dates that continuous spring growth commenced were estimated visually, whereas growth cessation was assumed when the change in herbage weights between harvest dates was a zero or minus value. It was shown in Section I of this presentation that virtually a l l of the annual growth occurred during an in i t ia l growth period, which ended in July in both 1967 and 1968. As shown in Table 22, growth started on approximately the same dates in the two years but in 1968 the growth 84 Table 22 Actual growing seasons and dry natter yields in 1967 and 1968 at two sites on Flatiron Mountain Date length Mean continuous of Forage growth growth growing produced rate Site Year started period (gms/m?) (gms/day) Agropyron spicatum - mesic 1967 '1968 May 10 May 10 77 62 137.3 115.4 1.79 1.86 Poa pratensis - mesic 1967 1968 May 15 May 10 72 62 182.2 154.6 2.52 2.52 period in the Agropyron spicatum site was 15 days shorter than in 1967, and in the Poa pratensis site, 10 days shorter than in 1967. At each site the mean growth rate was essentially the same in the two years. Therefore whatever factors terminated the growing period largely determined. the amount of forage produced. In the Agropyron spicatum site there were also important periods of secondary growth of 41 days in 1967 and 31 days in 1968 \ these periods produced 37.8 and 16.6 grams of dry matter per square meter respectively. Factors regulating growing seasons Ambient air temperature and available soil water were the two physical factors believed to be most important in determining how long and when growth could occur. Soil temperatures are undoubtedly also important (Wang 1967), but these are only available for the period May 30 to September 19, 1968. The lengths of the thermally regulated growing seasons were 85 computed by means of climatic diagrams, as described by Conrad (1950). As a limiting value, a mean daily threshold temperature of 42°F was selected. The lower threshold temperatures for growth initiation of range plants are not well established but 42°F has been found satisfactory for many perennial plants (Conrad 1950). The highest mean daily temperature recorded was 70°F, therefore an upper threshold temperature was not considered in the computations. The dates of exhaustion of soil moisture were also computed from climatic diagrams. As a limiting value the soil moisture level at 15 atmosphere, as measured by the pressure plate apparatus described by Richards (1948) was used. Slatyer (1957(b)) showed that this value does not always represent the true wilting point, and reports species variation of from 12 to 30 atmospheres. However moisture characteristic curves were determined for the soil from each study site, using values obtained at 0.33, 0.9, 4.0 and 15.0 atmospheres pressure and the difference in moisture content between 4.0 and 15.0 atmospheres was very slight for all soils. Thus, the values derived from 15.0 atmospheres pressure, are believed close approximations of the true wilting points. The dates that spring growth commenced coincide closely with the dates that mean daily temperature rose to 42°F, whereas the dates that growth ceased, coincide approximately with the dates that available soil water was exhausted (Table 23). The commencement of growth occurred within five days of that estimated from the temperature data and needs no further elaboration. However, the dates that growth stopped in relation to available soil water exhaustion, were not so precise and require further Table 23. Relationships of actual growing seasons and periods when ambient air temperatures and soil moisture supplies were favourable to growth. Event Ag.sp.* mesic site Po. pr. mesic site 1967 1968 1967 1968 Actual growing season Date continuous growth started5'"'' May 10 May 10 May 15 May 10 Date continuous growth stopped*** July 26 July 11 July 26 July 11 Length in days 77 62 72 62 Temperature regulated growing season - 42°F threshold Date season started > May 9 May 14 May 19 May 15 Date season ended Oct. 16 Sept. 20 Oct. 17 Sept. 20 Length in days 160 129 151 128 Date available soil moisture exhausted 0-6 inch depth July 5 June 22 July 12 July 6 6-12 inch depth M. June 23 M. July 10 12-18 inch depth M. July 5 M. July 10 18-24 inch depth M. July 7 M. July 20 * Key to code symbols Ag. sp. - Agropyron spicatum Po. pr. - Poa pratensis ** Visual estimate *** As determined from forage yield data M. Missing data 87 analysis -In addition, to the permanent wilting point, valid interpretation of soil moisture-plant growth relationships requires a knowledge of the depth that the soil is moist and the depth of the rooting system. The depths to which the soils of the study area were moistened in 1967 and 1968 are not known. The soil moisture data show that in 1968 soils were wet at least to 24 inches (see Table 19, page 66). This was probably also true in 1967, but data are not available for depths below 6 inches. Similarly the depths of the rooting systems are not known precisely. It is known as a result of the soil sampling for gravimetric soil moisture determinations, that in the Poa pratensis site nearly al l of the roots were confined to the upper 12 inches of soil and virtually no roots were present below 18-20 inches. The latter may have been due to a hardpan or a very dense " t i l l " layer at about 20 inches depth. In the Agropyron spicatum site most of the roots were in the upper 12-16 inches but were not uncommon in the 16 to 24 inch layer. Also, during soil pit excavations occasional roots were observed at depths to 36 inches. On this basis the role of soil moisture in limiting the length of the growing seasons, can be fairly accurately determined from the data available. In the Poa pratensis site only water in the upper 18 inches is available to plants, and in 1968, as shown in Table 23, this moisture was exhausted on July 10, exactly the same date that growth cessation was measured. In the Agropyron spicatum site soil moisture in the upper 24 88 inches of soil was exhausted on July 7, just four days prior to the date that the initial growth period ended. Presumably the secondary growth in this site, resulted from the deeper rooted plants obtaining water from depths greater than 24 inches. It is noteworthy that in the 0-6" soil layer, available soil moisture in the Agropyron spicatum site was exhausted 21 days before growth stopped in 1967 and 19 days before in 1968. In the Poa pratensis site available soil water in the 0-6 inch layer was exhausted 12 days before cessation of growth in 1967 but in 1968 only 6 days before growth stopped. Since lower soil depths were depleted of available moisture later than the upper 6 inch layer, the longer time lag before grovrth stopped in the Agropyron spicatum site, indicates that the plants in that site v/ere obtaining water from greater depths than in the Poa  pratensis site. Although the preceding discussion strongly suggests that water deficits terminated growth, it is possible that the vegetation in these sites entered a stage of summer dormancy independent of moisture conditions. Certainly the nature of summer dormancy in perennial grass is obscure. Laude (1953) investigated factors affecting summer dormancy' for 20 perennial grasses in California and found that dormancy of 13 species was caused by drought; in the other 7 species high temperatures and long day length caused dormancy, even when adequate water was supplied. However, the temperatures employed to induce dormancy ranged from 120°F to 135°F and the photoperiod was 18 hours, neither of which occurred in the study area. Moreover, assuming that there is no periodicity of 89 reproductive development, the failure of most of the grass species to flower in 1968 suggests that moistuie deficits terminated growth. Furthermore, when growing conditions are favourable reproductive development generally only induces temporary senescence in perennial plants (Jameson 1963). Thus it is concluded that cessation of growth i n both years was determined by water deficits. COMPARISONS: GROWTH WITH AMBIENT AIR TEMPERATURE, EVAPORATION, PRECIPITATION AND FORAGE YIELDS . The mean growth rates in 1967 and 1968 were of approximately the same order of magnitude for each site, and appear to be essentially linear. However, there were some variations in growth rates between harvest dates, which appear real; therefore the comparisons herein are based on unsmoothed growth curves. Since plants respond differently to the same environmental factors at various stages of their life cycle (Wang 1967) and since only two years climatic and growth data are available, correlation and regression analysis have not been computed. Instead graphical comparisons between growth and meteorological factors are presented, i n the hope that they will help in further research. Air temperature, evaporation and precipitation were the meteorological variables compared to plant growth. Soil moisture was not compared since,throughout the actual growing season, except for the last 2 to 5 days, soil moisture levels were greater than the 75 per cent availability value. Once exhausted, soil moisture supplies were never recharged to available levels in either 1967 or 1968. Neither wind nor soil temperatures were compared since data are only available for a 90 portion cf 1968. The "heat unit system" was used for comparing growth to temperatures. Daily mean temperatures above a threshold temperature of 42°F were accumulated on a weekly basis over the actual growing season. Similarly, evaporation was compared to the growth curves by accumulating evaporation in inches overthe actual growing season. Precipitation is compared with the growth curves for the period May through September. The precipitation data for 1967 is presented on a weekly basis whereas in 1968 it is presented on a daily basis. Although precipitation is only directly related to plant growth through the soil moisture regime, the comparisons are made to show how the date of occurrence is of importance to plant growth. As shown in Figure 14, there appears to be a good relationship between growth rate and "degree days" in the Agropyron spicatum site. From May 30 to June 13, 1968, there was only very slight accumulation of heat units and only a slight increase in yields. By comparison, during the same period in 1967, both heat units and forage weight were rapidly accumulating. After June 13, 1968, "heat units" began increasing more rapidly and there was a positive growth response. The relationship suggests that once mean temperatures rise to 43° or 44°F growth proceeds at probably near optimum rates, i.e. long days, optimum soil moisture and good daily maxima provide very favourable growing conditions. In the Poa pratensis site (Figure 15) there was only a slight difference in "heat unit" accumulation between years and similarly, growth 91 120 9 0 6 0 30 1000 8 0 0 6 0 0 4 0 0 2 0 0 0 50 4 0 30 20 10 . 1 r GROWTH ( G M S . / M 2 ) growth stopped C U M U L A T I V E D E G R E E D A Y S C U M L A T I V E E V A P O R A T I O N ( I N C H E S ) M A Y J U N E T J U L Y A U G U S T 1967 1968 F i g u r e 14. Comparisons o f c u m u l a t i v e "degree d a y s " above a base o f 43°F and c u m u l a t i v e e v a p o r a t i o n t o p l a n t g r o w t h I r 1967 and 1968 i n t h e A g r o p y r o n s p i c a t u m m e s i c s i t e . 92 I80| I5p 120 90 60 30 lOOOl 8 00 60 0| 400 200 0 5.01 40 ... '30| 20 10 0 G R O W T H ('GMS. M 2 ) ' growth stopped CUMULATIVE DEGREE DAYS X. CUMULATIVE EVAPORATION ( INCHES ) M A Y J U N E J U L Y A U G U S T F i g u r e 15. •1967 H 9 6 8 Comparisons o f c u m u l a t i v e "degree d a y s " above a base •. o f >430F and c u m u l a t i v e e v a p o r a t i o n t o p l a n t g r o w t h i n 1957 and 1968 i n t h e Poa p r a t e n s i s m e s i c s i t e . 93 proceeded essentially at the same rate in both years. However, temperatures were lower than, in the Agropyron spicatun site particularly in 1967, suggesting that Poa pratensis has a lower threshold temperature. This would also explain why growth started earlier than was estimated from temperature data (see Table 23). Evaporation in the Agropyron spicatum site, was lower in 1968 at the beginning of the growing season than in 1967. From May 30 to August 9, 1968, evaporation proceeded at essentially the same rate as in 1967, but from August 9 to August 26, 1968, evaporation was lower than in 1967, probably due to the cool temperatures during that period. In the Poa pratensis site evaporation accumulated at almost exactly the same rate from May 10 to August 9 in^both years. From August 9 to August 26, 1968 evaporation was considerably less than during the same period in 1967. These comparisons would suggest that there are definite relationships between both temperature and evaporation with rates of growth, with temperature appearing to give a better simple relationship. However, more data are required to test these relationships. The "heat unit system" has been subject to serious criticisms, questioning its theoretical soundness (Wang 1960). The main criticism is that threshold temperatures change with stages of development, and the response of the plants to the same temperatures, varies during different stages of development. However, no other system has been found which can adequately replace it and it continues to be the most suitable method As shown in Figure 16, the pattern of precipitation is of extreme importance to plant growth. Since the dates of available soil MAY JUN ' JUL ' AUG ' SEP ' OCT A g r o p y r o n s p l c c f u r n s i t e MAY ' JUM ' JUL ' AUG ' SEP • - - - • P o a p r a t e n s i s s i t e Figure 16. Precipitation patterns in 1967 and 1968, "in'relation to plant-growth in the Agropyron spicatum'and Poa pratensis mesic sites. 95 soil moisture depletion coincided v/ith the dates that the grand period of growth erded and was never replenished, all precipitation after the end of the true growing season was apparently evaporated almost as soon as it was received.- Undoubtedly during the heavier rains of August, 1968, there were short periods during the interval between soil moisture measurements when moisture was available, but these were of short duration and of little value to the plants. It is also noteworthy that during the secondary growth period in the Agropyron spicatum site in 1967 there was no precipitation throughout the entire period. This indicates further that the plants were obtaining water from deeper soil depths than those measured. In 1968 there were rain storms during the secondary growth period but not until near the end of the period. It is more likely that the cool temperatures which were associated with these rains, (see Figures 12 and 14) stopped growth or at least reduced the growth rate. Precipitation during May and June appears to be the most important to plant growth. However the time within these two months that precipitation is received appears to be extremely important. Precipitation from May 10 to June 30 was 3.54 inches in 1967 and 3.58 inches in 1968, thus a yield prediction model based on precipitation during these two months would be inaccurate. The main reason for the actual growing season in 1967 being approximately two weeks longer than in 1968 was the 2.07 inches of precipitation received during the last week in June. This precipitation recharged a soil moisture supply which was beginning to be depleted. In 1968 there was no appreciable precipitation during the last week of June 96 or until July 13. These three "rainless" weeks were coupled with high temperatures and consequently, available soil moisture supplies were exhausted. Had soil moisture supplies in 1968 been recharged in early July, plant growth almost certainly would have continued and higher forage production realized. The different yields measured at the xeric, mesic and hydric sites in the Agropyron spicatum and Poa pratensis communities are difficult to explain. These sites were selected on the basis of estimated relative aridity and, except for the Agropyron spicatum xeric site, the soil moisture data showed the moisture holding capacities to be least at the xeric and greatest at the hydric sites. The hypothesis was that the soils of the xeric sites would contain less moisture, be exhausted of available moisture sooner and as a result produce less forage than the other two sites. Conversely, the hydric sites were predicted to yield more forage than the other two sites. Within years there was generally little difference in the dates of soil moisture exhaustion between moisture sub-communities, i.e. xeric, mesic and hydric sites. However, two exceptions did occur. In the Agropyron spicatum community (Table 24), soil moisture exhaustion in the hydric site in 1968 occurred approximately. 14 days later than in the xeric and mesic sites; in 1967 soil moisture exhaustion in the upper six inches of soil occurred at virtually the same dates as occured at the other two sites. In the Poa pratensis community (Table 25) soil moisture exhaustion in the mesic and hydric sites occurred at the same Table 24. Comparisons of dry matter yields for the xeric, mesic and hydric sites in the Agropyron spicatum community, with soil moisture regimes, in 1967 and 1968. Xeric site Mesic site Hydric site Item 1967 . 1968 1967 1968 1967 1968 2 Dry matter yields (gms/m ) for Aug. 9, 1967 and July 25, 1968 64.6 48.5 94.2 96.1 224.5 144.3 Dates available soil moisture exhausted 0- 6 inch depth 6-12 inch depth 12-18 inch depth 18-24 inch depth July 4 M. M. M. July 4 July 8 July 9 July 9 July 5 M. M. M. June June July July 22 23 5 7 July 8 M. M. M. July 8 July 22 July 22 July 23 Estimated length of actual growing season (based on soil moisture and temperature data) 65 70 66 68 69 84 M. - Missing data Table 25. Comparisons of dry matter yield for the xeric, mesic and hydric sites in the Poa pratensis community, with soil moisture regimes, in 1967 and 1968. Item Xeric site Mesic site Hydric site 1967 1968 1967 1968 1967 1968 Dry matter yields (gms/m ) for August 9, 1967 and July 25, 1968 Dates available soil moisture exhausted 0- 6 inch depth 6-12 inch depth 12-18 inch depth Estimated length of actual growing season (based on soil moisture and temperature data) 162.7 106.4 158.9 152.6 389.5 214.4 May 17 June 23 July 12 July 6 July 12 July 6 M. June 26 M. July 10 M. July 8 M. June 26 M. July 10 M. July 9 47 58 61 58 60 M. - Missing data 99 date in each year. In the Poa pratensis xeric site however, available soil moisture in the upper six inches was not measured at any time in 1967, but in 1968 soil moisture was present in the upper 18 inches of soil until June 23. As a result, the 1968 grov.dng season for the xeric site was about 13 days shorter than for the mesic and hydric sites. Despite the generally equal lengths of predicted growing seasons, the xeric sites did, with one exception, yield less dry matter than the mesic sites and the hydric sites consistently yielded more. The dry matter yield measured in 1967 in the Poa pratensis xeric site is a disturbing anomaly. The yield was essentially equal to that of the mesic site, even though there was never any available.moisture in the upper 6 inches of the soil. Presumably water for plant growth was being obtained from greater soil depths. Despite a few exceptions, soil moisture exhaustion appears to have occurred simultaneously throughout the two communities. Since soil moisture levels were constantly high until shortly before exhaustion, moisture was not likely limiting the rate of growth. The sites were all close to one another, therefore climatic influences were similar. The variations in yields are therefore believed attributable to the variations in plant density and species composition (see Tables 2 and 3); both of which are probably closely associated with the soil moisture regime (Daubenmire, 1968). 100 SUMMARY 1. Two aspects of the inter-relationships of vegetation and climate were investigated; a) factors affecting the lengths of actual growing seasons and b) factors affecting plant growth. 2. The forage yield and climatic data from the Agropyron spicatum and Poa pratensis mesic sites were used for the analysis. Seasonal herbage yields were used as an index of plant growth. 3. The dates of commencement of continuous spring growth coincided very closely with the dates that mean daily air temperatures rose to 42°F, whereas the date growth ceased coincided very closely with the dates available soil moisture supplies were exhausted. 4. The rates of growth at each site were essentially the same in the two years, but the soil moisture supplies were depleted two weeks earlier in 1968, resulting in less forage being produced than in 1967. 5. Plant growth was compared to ambient air temperatures, evaporation and precipitation. The forage yields of the xeric, mesic and hydric sites of the Agropyron spicatum and Poa pratensis communities were also compared to their soil moisture regimes. 6. Both cumulative "degree days" and cumulative evaporation showed good relationships to plant growth, with "degree days" appearing to give a better simple relationship. 7. Precipitation during the actual growing season was essentially identical in 1967 and 1968. However the timing of precipitation was very different. In 1967 most of the precipitation was received during the latter two weeks in June, whereas in 1968 most was received in late 101 May. As a result soil moisture exhaustion was earlier in 1968 than in 1967. 8. The variations in yields between the moisture sub-communities of the Agropyron spicatum and Poa pratensis communities could not be directly associated with their soil moisture regimes. Although the moisture holding capacities were relative, i.e. least at the xeric, and greatest at the hydric sites, soil moisture was available to plants for an essentially equal length of time at all sites. However, there were variations in species composition,and plant density was least in the xeric sites and greatest in the hydric sites. The differences in yields were therefore attributed to the plant cover present at each site, which probably is closely associated with the relative moisture holding capacities of the soils. 102 LITERATURE CITED BAELR, W. and 6.W. ROBERTSON. 1966. A new versatile soil moisture budget. Can. J. Plant Sci. 47: 299-316. BLAISDELL, J.P. 1958. Seasonal development and yield of native plants on the upper Snake River plains and their relation to certain climatic factors. U.S.D.A. Tech. Bull. 1190, 67 pp. CAMPBELL, R.S. and R.W. RICH. 1961. Estimating soil moisture for field studies of plant growth. J. Range Mgmt. 14(3): 130-134. CONRAD, V. and L.W. POLLAK, 1950. Methods in climatology. 2nd ed. Harvard Univ. Press, Cambridge, Mass. 459 pp. CRADDOCK, G.W. and CL. FORSLING. 1938. The influence of climate and grazing on spring-fall sheep range in Southern Idaho. U.S.D.A. Tech. Bull. 600, 42 pp." CURRIE, PAT 0. and Geraldine PETERSON. 1966. Using growing season precipitation to predict crested wheatgrass yields. J. Range Mgmt. 19(2): 284-288. DAHL, B.D. 1963. Soil moisture as a predictive index to forage yield for the Sandhills range type. J. Range Mgmt. 16(3): 128-132. DAUBENMIRE, R. 1968. Soil moisture in relation to vegetation distribution in the mountains of Northern Idaho. Ecology 49(3): 431-438. HUTCHINGS, S.S. and G. STEWART. 1953. Increasing forage yields and sheep production on Intermountain winter ranges. U.S.D.A. Circ. 925, 63 pp. JAMESON, D.A. 1963. Responses of individual plants to harvesting. Botanical Review 29: 532-594. KOZLOWSKI, T.T. - Editor. Water deficits and plant growth. Academic Press, New York, Vol. 2 333 pp. f LAUDE, H.M. 1953. The nature of summer dormancy in perennial grasses. Botanical Gazette 114: 284-292. RICHARDS, L.A. 1948. Porous plate apparatus for measuring.moisture retention and transmission by soil. Soil Sci. 66: 105-110. 103 ROGLER, G.A., and H.J. HAAS. 1947. .Range production as related to soil moisture and precipitation on uhe Northern Great Plains. J. Amer. Soc/-Agron. 39: 378-389. SLATYER, R.O. 1957(a). The influence of progressive increases in total soil moisture stress on transpiration, growth, and internal water relationships of plants. Austral. J. Biol. Sci. 10; 320-336. SLATYER, R.O. 1957(b). The significance of the permanent wilting percentage in studies of plant and soil water relations. Bot. •Rev. 23: 585-636. SNEVA, F.A. and D.N. HYDER. 1962. Estimating herbage production on semi-arid ranges in the Intermountain ranges. J. Range Mgmt. 15(2): 88-93. SPRINGFIELD, H.W. 1963. Cattle gains and plant responses from spring grazing on crested wheatgrass in Northern New Mexico. U.S.D.A. Prod. Res. Rep. 74, 46 pp. ZAHNER, R. 1963. Internal moisture stress and wood formation in conifers. Forest. Prod. J. 13: 240-247. WANG, J.Y. 1960. A critique of the heat unit approach to plant response studies. Ecology 41(4): 785-790. WANG, J.Y. 1967. Agricultural meteorology. Agric. Weather Info. Ser. 693 pp. Omega Enterprises, Palo Alto, Calif. APPENDIX 1 SCIENTIFIC AND COMMON NAMES AND AUTHORITIES FOR PLANT SPECIES MENTIONED References include: Davis (1952), Hitchcock (1950), Hitchcock et al. (1961), and Hubbard (1955). Where conflicts arose Davis' (1952) was taken as the authority 105 Grasses: Agropyron spicatum (Pursh) Scribn. and Smith, var. inerme Heller, beardless wheatgrass Bromus tectorum L. downy chess Calamagrostis rubescens Buckl. pinegrass Festuca idahoensis Elmer. Idaho fescue Festuca rubra L. Creeping red fescue Koeleria cristata (L.) Pers. Junegrass Poa pratensis L. Kentucky bluegrass Poa secunda Presl. Sandberg bluegrass Stipa columbianan Macoun. Columbia needlegrass Forbs: Achillea millefolium L., var. lanulosa Nutt. yarrow Antennaria rosea Greene. rose pussytoes Astragalus serotinus Gray, timber milk vetch Lupinus sericeus Pursh. silky lupine Geranium viscossissimum Fish, and Mey. sticky geranium Lupinus articus Wats, blue bonnet Oxytropis campestris (L.) D.C. Locoweed Potentilia gracilis Daryl. fivefinger cinquefoil Taraxacum officinale Weber, common dandelion Shrubs and trees: Artemisia frigida Willd. pasture sage Picea engelmanni Parry. Engelmann spruce Pinus ponderosa Laws, ponderosa pine Pseudotsuga menziesii (Mirb.) Franco var.. glauca. Interior Douglas f i r . APPENDIX 2 FIELD PLOT DESIGNS OF EACH STUDY SITE Randomized block designs: The blocks are replicates (designated by alphabetic letters) and the treatments are clipping dates, with number 1 being the first clip, number 2 the second, etc. /REPLICATES TREATMENTS ,FENCE 4 FT. BUFFER ZONE Y. ~7 V9S 7 P L O T A R E~A A S IS 12113 III] 1*30 H l L I H ^ E H L I j t a ® B @ [I] H E LI Si l l [ID® E E S 0^^ F c sstiHmEtira^ 0 Harass ^ G D 0 H ED H 0 0 IL1H H E H 0 B A H [ 5][7][8] 1 9 6 8 P L O T A R E A [ I E [J] [3 LID [13 \" 13 E [?a S S IS III If] 113 Lsl E B S B H L I I slight swale area ]ol[^ ][4]rD not sampled I3EL1DLI [5][7J[9]@[4l|T]gi[6|[i] F cn d] [u n] in m D§ n] H m H Sca le : I inch = 16 feet FIELD PLOT DESIGN OF AGROPYRON SPICATUM MESIC SITE R E P L I C A T E S T R E A T M E N T S ' . F E N C E 4 FT. BUFFER ZOHE 19 6 8 P L O T • A S K S ® ffl U\ CD SI CH CU 0 DO \M IJ8 ISCD (3 LU LULDE BlIJHStl l l f f lLlIH^S (3S[lI[115nOIS[llLS]lSF c H ii] a m III iii H Lii a ia .^jjoicsHticiisLiiLTiQa G D t s j E a L i i i i i t E S E a m L i [ i r 'Li iSHnEQaSELII« 1 9 6 7 P L O T A R E A A S C I I S [®I QlISSIIl ES H S IIIILX EQlffltlo] © S I S IS Gil Dill] El B Jill LslGiE B[[§LIDICE I] LIDS [E[ Ml 511H13 [j^  Ll] H Oil c^GiJIIi S L O E S H E E LU H 03 uU LI] LU OH STCz] LHI Us] ILQ] 03 G o H I S O g M [H^}[MMM-\s\M^U}[ElM fill ED ISO CHS] EICD [SJ-IIQI LXDffilSI Qal [H JS H S c a l e : I i n c h = 16 f e e t FIELD PLOT DESIGN OF POA PRATENSIS MESIC SITE REPLICATES J REATME NTS .F E NC E TREES 7J LT 19 6 7 P L O T A R E A E H S H I M E E B E ® HII] (13 E H Ell] LI Hill-A F iii B as a a Em iiiiiiatiiLimESELiiB G ass m a s siii EII] iimiiiLisiiisLiiiiiogc Htaaatiiiiiaijfliiijiiiii] asaLiima^tiiHa D H G F E [AiELiia LSJEIIILII LU0HL11 D C B A S L I M 19 6 8 O 0 LULUS 1 HQ] LI] • S H E asms P L O T A R E A EHHLj] HLULHEl GASH LI o o FIELD PLOT DESIGN OF CALAMAGROSTIS RUBESCENS MESIC SITE o 1.0 FE NC E R E P L I C A T E S A B C A B C m [DCI1CD-Lnni 2 P l l 3 l H][3 |3 3 4 4 3 4 4 196 8 1 9 6 7 T REATMENT S Scale v I inch = I 6 feet A 2 B i r R E P L I C A T E S Sea le : I inch = 6 feet I METER SQUARE Q U A D R A T ( d i m e n s i o n s 5 70 cm. x 143 cm.) F I E L D P L O T D E S I G N OF A L L X E R I C A N D H Y D R I C S I T E S APPENDIX 3 MODEL NUMBERS AND KANUFACTURERS OF METEOROLOGICAL INSTRUMENTS USED 112 "INSTRUMENT MODEL NUMBER MANUFACTJRER 1. Thermographs j weekly (used in 1967 only) monthly (used in 1968 only) 2. Precipitation gauges standard rain gauges tipping bucket gauges Sacramento snow gauges 3. Evaporimeters 4. Anemometer 5. Bouyoucos Bridge T-9158 252 3 inch orifice Cassela Inst. Ltd., London, England Lambrecht Instruments Overseas Instruments of Canada, Kingston, Ontario. Canada Department of Transport, Ottawa. Ikeda - longterm Ogana Seika Co. Ltd., Tokyo, Japan. carborundum block (tank type) Custom made in Vancouver B.C. Wilcox - Canada Dept. of Agriculture, Summerland, B.C. 3 cup totalizer Canada Department of Transport, Ottawa. C Beckman Instruments Inc., Fullterton, California. 6. Tele-thermometer 42 SL Yellow Springs Inst. Co. Inc., Yellow Springs, Ohio. 

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