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Fenceline ecology of four grassland sites in the southern interior of British Columbia. Ndawula-Senyimba, Michael Solomon 1969

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FENCELINE ECOLOGY OP POUR GRASSLAND SITES IN THE SOUTHERN INTERIOR OP BRITISH COLUMBIA BY MICHAEL SOLOMON NDAWULA-SENYIMBA .Sc. (Botany), University of East A f r i c a , 1967 A THESIS SUBMITTED IN PARTIAL FULFILMENT OP THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the D i v i s i o n of Plant Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA May, 1969 In presenting this thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. I t i s understood that copying or publication of this thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of P/.fl<vh < c i £rrtc£ The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8 , Canada. Date ^ HPJuy lU?  ABSTRACT An e c o l o g i c a l study of grassland communities sepa-rated by fencelines i n the Southern Interior of B r i t i s h Columbia was conducted from spring 1968 to spring 1969. Measurements to compare plant species composition, herbage y i e l d , growth habits and edaphic features on both sides of the fences were taken i n the f i e l d . S o i l organic matter was determined in the laboratory and moisture penetration patterns were demonstrated i n the greenhouse. Heavy grazing resulted in the removal of the p r i n c i p a l climax caespitose species and their replacement by.shrubs, annuals and rhizomatous grasses. There were reductions i n the composition, herbage y i e l d and vigor of the caespitose species at a l l sites following heavy grazing. The success of the increasers under heavy grazing seemed to be favored by possession of rhizomes, presence of unpalat-able flowering culms and inflorescences, shortness of t i l l e r s and an elaborate means of seed di s p e r s a l . The vegetational changes introduced by grazing on the heavily grazed side, resulted in a high l e v e l of organic matter in the top 25 cm. of s o i l , a high s o i l moisture content and high summer and low winter s o i l temperatures. The dense vegetation on the l i g h t l y grazed side modified both summer and winter s o i l temperatures. A technique was developed to determine the a b i l i t y of caespitose grasses to r e d i s t r i b u t e moisture i n the s o i l . I t was demonstrated that a e r i a l parts of Agropyron spicatum c o l l e c t l i g h t rains and concentrate them i n the rooting zone of the plant. This phenomenon i s l i k e l y to be one of the adaptive features which enables caespitose species to dominate a r i d habitats. I t i s possible that the great s u s c e p t i b i l i t y of Agropyron spicatum and other caespitose grasses to heavy grazing might be related to s o i l moisture disturbances introduced by the removal of a e r i a l parts of the plants. TABLE OP CONTENTS Page INTRODUCTION 1 SECTION I. LITERATURE REVIEW 3 The Plant Community Under Grazing 3 The Individual Plant Under Grazing Conditions . . . . . . . . . 5 The Time Factor Associated With the D e f o l i a t i o n E f f e c t s . . . 7 Grazing and the P l a n t - S o i l Relationship. . 8 The Plant's Reproductive Potentials and the Habitat Factors 10 I I . LOCATION AND DESCRIPTION OF THE STUDY SITES. 13 I I I . METHODS 21 F i e l d Experiments. 21 Climate, s o i l moisture and . temperature instrumentation 21 Vegetation analysis. . 22 Laboratory and Greenhouse Experiments. . . 25 IV. RESULTS 27 F l o r i s t i c s . • - 27 Species Frequency, Canopy Cover, Basal Area and Dry Matter Y i e l d 37 SECTION Page . ' Species frequency 37 Canopy cover 39 Basal area 39 Dry matter y i e l d 42 Growth Habits 43 Vigor 4 8 Phenology 50 Seed productivity 58 Edaphic Features 61 S o i l temperature 61 S o i l moisture 61 S o i l organic matter . . . 6j V. DISCUSSION . 72 Vegetation Structure 72 Growth Habits 75 Edaphic Features , 83 SUMMARY 91 BIBLIOGRAPHY 96 LIST OF TABLES TABLE Page I. Number of species i n categories by s i t e s . . . 7 I I . The l i s t of species found, i n the study area 28 I I I . Species composition ( i n percentage) on four s i t e s on the opposite sides of the fenceline 36 IV. The percentage frequency of the major species 38 V. Canopy percentage cover of the major species 40 VI. Basal area as percentage cover of the t o t a l surface area sampled 4 l VII. Average dry matter y i e l d i n Kgms. per Hectare of the grass herbage present at the end of the growing season 42 VIII. Average t i l l e r heights of Agropyron spicatum and Stipa columbiana measured in J uly 1968 49 IX. Average leafblade length of Agropyron spicatum and Stipa columbiana measured i n July 1908 51 X. Some phenological changes i n some plant species at Hamilton Commonage (Upper grassland zone) 52 XI. Percentage d i s t r i b u t i o n of the Bromus tectorum seeds away from the fenceline on the T i g h t l y grazed side at Quilchena s i t e . . . . 57 XII. Average number of seed stalks per square meter of the sampled area 59 XIII. The F e r t i l e / S t e r i l e shoot r a t i o s of Agropyron spicatum and Stipa columbiana . . . 60 XIV. S o i l organic matter percentage at various depths on both sides of the fence 69 LIST OF FIGURES FIGURE Page 1. (a), (b) and (c) show the fenceline at Hamilton Commonage, Quilchena and Tranquille s i t e s r espectively. (H) heavily grazed side and (L) l i g h t l y grazed side 20 2. A diagram of a grass t i l l e r i n d icating the parts measured for vigor determination 23 3. (a) and (b) i l l u s t r a t e the c h a r a c t e r i s t i c spacing of Agropyron spicatum bunches i n a least disturbed condition at Minnie Lakes and Quilchena r e s p e c t i v e l t . The picture represents two d i s s i m i l a r s o i l surface features 32 4. A mixed stand of Agropyron spicatum, Festuca sp. and forbs i n the l i g h t l y grazed exclosure at Hamilton Commonage s i t e 33 5. (a) and (b) show the difference i n the plant density between the heavily grazed and the l i g h t l y grazed exclosures respectively at Tranquille s i t e . The pictures were taken i n Summer, 1968 34 6. Bunches of Agropyron spicatum at Minnie Lakes s i t e on the l i g h t l y grazed side of the fence. . 44 7 . Stipa columbiana at Hamilton Commonage i n the heavily grazed exclosure 47 8. (a), (b) and (c) are i l l u s t r a t i o n s of vegetative p r o l i f e r a t i o n or vivipary i n Agropyron spicatum 53 9. Spikelets and f l o r e t s of Agropyron spicatum, Bromus tec tor urn and S t ip a~c o lumb fan a 55 10. A dense stand of Bromus tectorum along the fence at QuilchenaTi [H) heavily grazed side and (L) l i g h t l y grazed side 56 ix FIGURE Page 11. . Stipa columpiana and Antennaria dimorpha in the heavily grazed exclosure at Hamilton Commonage 57 12. S o i l temperature by depth and treatment from June 1968 through February 1969 62 13. S o i l moisture change by depth and treatment from July to October 1968 at Tranquille s i t e . . 64 14. The experiment for moisture penetration .beneath bunches of Agropyron spicatum. Bunch B. clipped. . . . . . . . . . 66 15. A mist spray water-system for water penetration experiment 68 16. Depth at which penetrated water was detected. I Bunches A and B in t a c t . II Bunches B clipped 68 17. S o i l organic matter percentage at various '. ...depths and s i t e s for both sides of the fence. . 70 18. Agropyron spicatum bunches with the canopy spread out after mist spraying with water for an hour . 71 ACKNOWLEDGEMENT G r a t e f u l acknowledgement i s e x t e n d e d t o D r . V. C. B r i n k , P r o f e s s o r o f Agronomy and Head o f t h e P l a n t - S c i e n c e D i v i s i o n , U n i v e r s i t y o f B r i t i s h C o l u m b i a f o r s u g g e s t i n g t h i s s t u d y and f o r h i s h e l p f u l d i r e c t i o n o f t h e e x p e r i m e n t a l work and c h e c k i n g o f t h e m a n u s c r i p t . Thanks a r e a l s o due t o Mr. A. McLean, R e s e a r c h S c i e n t i s t , a nd Mr. L. Haupt, T e c h n i c i a n , o f t h e C D . A . R e s e a r c h S t a t i o n K a m l o o p s , B r i t i s h C o l u m b i a , f o r t h e i r g r e a t a s s i s t a n c e i n t h e f i e l d e x p e r i m e n t s and p l a n t i d e n t i -f i c a t i o n . I n a d d i t i o n , t h e members o f t h e a u t h o r ' s committee were a l w a y s a v a i l a b l e whenever t h e y c o u l d be o f h e l p . . T h e i r c o n t r i b u t i o n i s g r e a t l y a p p r e c i a t e d . The a u t h o r i s a l s o i n d e b t e d t o the C a n a d i a n Commonwealth S c h o l a r s h i p and F e l l o w s h i p Committee f o r p r o v i d i n g t h e s c h o l a r s h i p w h i c h e n a b l e d the a u t h o r t o s t u d y i n C a n ada d u r i n g 1 9 6 7 - 1 9 6 9 -INTRODUCTION Ranges where fencelines have been established for many years often show s t r i k i n g physiognomic differences between the plant communities which the fences separate. Yet i n many instances the fence separates communities which a few years e a r l i e r were comparatively homogeneous. In many cases i t i s obvious that the fenceline differences are to be attributed to d i f f e r e n t grazing patterns of the f i e l d s the fence separates. If some judgment i s used and some knowledge of grazing practises i s known, such a r t i f i c i a l "ecotones" associated with fencelines offer an unparallelled opportunity for studying response to grazing of as many plant communi-t i e s , edaphic and climatic conditions as fencelines traverse. At the end of the spring term i n 1968 a number of plant communities (separated by fences), where major differ-ences had obviously been generated as a r e s u l t of fencing, were chosen for study. Four study si t e s were selected to represent the three grassland zones known as the Lower, Middle, and Upper grassland zones. One of the selected s i t e s was located at Tranquille near Kamloops and three others were located on the Nicola grassland. The objective of the study was to assess comparative differences i n species vigor, reproductive p o t e n t i a l , l i f e -2 form, and growth habit of species of the fenceline communi-ti e s and the r e l a t i o n of these to s o i l and some climatic f a c t o r s . I t i s anticipated that a study of this nature w i l l throw more l i g h t on the basic factors associated with the plant-fence-animal rel a t i o n s h i p in the range ecosystem. I. LITERATURE REVIEW The Plant Community Under Grazing Stebbins (1950) emphasized that the individual plant is a phenotype which is the product of a given environment and a p a r t i c u l a r genetic make-up. In their experiments on the Western North American plants, Clause e_t a l . (1940) demonstrated that phenotypes can be altered quite profoundly in some c h a r a c t e r i s t i c s by environmental factors. They reported that p l a s t i c i t y i s often exhibited by the amount of stem elongation, the number of branches, leaves and flowers, the form of the i n d i v i d u a l plant and the nature of the pubescence. The a b i l i t y to adapt to a new environmental condition is more pronounced i n weedy plants. Stebbins (1964) concluded that such a p l a s t i c i t y must reside i n c e r t a i n morphological and physiological c h a r a c t e r i s t i c s of the plant concerned. Some workers on forage plants have often reported that the quality of some herbage species "improve" under "moderate" grazing. Nelson (1934), Canfield (1948), and Hutchings et a l . (1953) observed that plants when regarded as forage respond as "favorably" under grazing as under "no grazing" or as "favorably" under moderate as under l i g h t grazing. Vogel et a l . (1966) reported that four years of 4 either deferred or moderate grazing on the f o o t h i l l sheep range, did not cause major changes i n the vegetation cover. Instead they observed some "improvements" in the y i e l d , composition and vigor of climax dominant perennial grasses such as Agropyron spicatum. Also workers such as Schmutz et a l . (1967) have reported increases of composition and cover of blue grama grass (Bouteloua g r a c i l i s ) under grazing. However, the general b e l i e f i s that grazing cer t a i n species i n a community tends to handicap those species and to favor the ungrazed species. Since Clements (1920) described this e f f e c t of grazing, numerous workers have proved that grazing has adverse effects on the vegetation. Larson et a l . (1942), Johnson (1956), E l l i s o n (i960), Potter et a l . (1967), Pieper (1968) have, i n various ways, demon-strated some appreciable grazing effects even at l i g h t grazing i n t e n s i t i e s . This led E l l i s o n (i960) to conclude that the exact composition of a climax vegetation possibly cannot be maintained by an in t e n s i t y of grazing or selection of species other than those exerted by p r i s t i n e w i l d l i f e . He suspected that the reports which claim benefit to the plants from grazing are for the most part, either specula-t i v e , crude i n experimental design, inadequate i n method or cover so short a time as to r e f l e c t only the i n i t i a l stimulation i n herbage growth. The stimulation that occurs. 5 might be due to the stored food reserves or to the carry-over e f f e c t s caused by other s t i m u l i . He also pointed out that few studies are made of "grazing per se". Most of them are made of "over-grazing" and/or complete protection. The Individual Plant Under Grazing Conditions Petterson (1962) reported that certain changes in structure and ph y s i o l o g i c a l responses induced by prolonged heavy grazing appeared to favor the persistence of Stipa  comata under such treatment. In general a grazing animal removes photosynthetic parts of a plant and thereby reduces the plant's p o t e n t i a l to synthesize "food". In grasses also i f the growing points of the t i l l e r s are elevated to more than 2 cm. above t h e s o i l they may be removed by grazing and new leaves may not be produced thereafter by those shoots (Branson 1953? Booysen et a l . 1963). In some grass species such as Festuca  s c a b r e l l a (Johnston et a l . I967) f l o r a l i n i t i a t i o n occurs in the autumn. This means that early removal of the shoot primordia i n the following spring may deny the plant of t h e opportunity to produce seeds. However, Laude e_t a l . (1968) reported that reduced t i l l e r i n g associated with the flowering stage of Harding grass (Phalaris tuberosa) can be o f f s e t by b y removal of elongating flowering culms. 6 In addition to i n t e r f e r i n g with photosynthetic and reproductive organs, grazing has profound e f f e c t s on roots. Numerous reports have proved beyond doubt that d e f o l i a t i o n stops, root growth (Weinmann 19^8, Curtis and Clark 1950, Crlder 1955, Troughton 1957, Weaver 1958, E l l i s o n i960, Jameson 1963)• Prom his extensive study on the subject, Crider (1953) reported that removal, during the growing season, of at l e a s t half of the foliage of grasses both cool and warm season species including bunch, rhizomatous, and stoloniferous types, caused root growth to stop. He also reported that with the exception of orchard grass (Dactylis glomerata) stoppage occurred within 2k hours of foli a g e removal and continued u n t i l recovery of the top growth. A single cut could cause 6 to 18 days of stoppage. In his review, Jameson (1963) pointed out that d e f o l i a t i o n does not only stop root growth but i t also reduces the a b i l i t y of the e x i s t i n g roots to absorb nutrients. He emphasized that continued grazing reduces dry matter y i e l d , vigor, seed y i e l d and the amount of carbohydrates in the underground portions of the herbage. Although a l l plant species are affected by intensive d e f o l i a t i o n , reports indicate that some species are affected more than others (Schmutz et a l . 1967, Petterson 1962). 7 The Time Factor Associated With the  De f o l i a t i o n E f f e c t s A number of reports have indicated that some plants respond more conspicuously to d e f o l i a t i o n e f f e c t s at c e r t a i n times than at others. Vogel et a l , ( 1 9 6 8 ) reported that c l i p p i n g l i t t l e blue stem, big blue stem and Indian grass for three successive years at the seed-ripening stage or la t e r increased both y i e l d and s p r i n g - i n i t i a t e d t i l l e r i n g . But c l i p p i n g at any time during summer and es p e c i a l l y between f l o r a l i n i t i a t i o n and anthesis reduced the y i e l d . B l a l s e l e_t a l . ( 1 9 ^ 9 ) also.had. reported that whereas Agropyron spicatum was generally reduced i n vigor by c l i p p i n g any time of the year, the greatest damage was done late i n May and early i n June. The e f f e c t was less i n spring and least i n the f a l l . Similar changes were reported by Jameson ( 1 9 6 3 ) to exi s t i n the carbohydrate l e v e l s of some plants. He further noted that i n perennial plants there is a decrease in carbo-hydrate accumulation with the onset of spring growth. During the res t of the season carbohydrate levels may increase, then decline at mid-season and r i s e again to a maximum in the f a l l . He attributed the early spring decline to u t i l i z a t i o n of carbohydrates i n the production of new leaves. The mid-season decline, when i t occurs, might be a tempera-8 ture or moisture response or r e s u l t from i n f l o r e s c e n c e -indeced senescence (Jameson 1963). I t i s therefore suspected that the poor regrowth at mid-season might be due to the low carbohydrate reserves ( M c l l r o y 1967)• The r o l e of carbohydrates as f u n c t i o n a l reserves which can be drawn on when photosynthesis i s reduced by d e f o l i a t i o n was questioned by May e_t a l . (1958). However, M c l l r o y (1967) claimed that i t had been proved beyond doubt that the. c o n c e n t r a t i o n of so l u b l e carbohydrates i n the herbage does i n f l u e n c e re-growth a f t e r c u t t i n g . I t may also be of i n t e r e s t to note t h a t Davidson et a l . (1965) are of the o p i n i o n t h a t although not as important as carbohydrates, p r o t e i n s and mineral s a l t s such as phosphates p l a y a s i g n i f i -cant r o l e i n the re-growth process. Grazing and the P l a n t - S o i l R e l a t i o n s h i p Herbage removal deprives the s o i l of i t s p r o t e c t i v e cover against the d i s p e r s i n g and eroding e f f e c t s of r a i n drops and running water, and some f r o s t and drought e f f e c t s . Trampling may compact the s o i l (Eaver 1956) and the veget-a t i o n change which r e s u l t s from heavy gr a z i n g may a f f e c t the s o i l organic matter l e v e l s . I n a d e t a i l e d study Osborn (1952,53) demonstrated the e f f e c t i v e n e s s of p l a n t cover i n 9 r e s i s t i n g the k i n e t i c energy o f r a i n drops and the speed of r u n n i n g w a t e r . The r o o t s o f p l a n t s b i n d the s o i l and reduce l a n d s l i d e h a z a r d s and a l s o improve the s o i l g r a n u l a t i o n , p o r o s i t y and i n f i l t r a t i o n c a p a c i t y . C l a r k (1937) o b s e r v e d t h a t the a e r i a l p a r t s of herbaceous p l a n t s i n t e r c e p t e d more t h a n 50 per c e n t of the inc o m i n g r a i n and a l l o w e d such i n t e r c e p t e d water t o be e v a p o r a t e d d i r e c t l y back i n t o the a i r . Daubenmire (1942) used t h i s phenomenon t o e x p l a i n why the s o i l m o i s t u r e i n an o l d s t a n d of Agropyron was lower t h a n on a h e a v i l y g r a z e d a r e a . However, Grah and W i l s o n (1944) demonstrated t h a t o n l y p a r t of the i n t e r c e p t e d , water i s l o s t t h r ough e v a p o r a t i o n . The r e s t o f the i n t e r c e p t e d water d r a i n s t o the ground e i t h e r as "stem f l o w " , drops f r o m l e a v e s or i s shaken o f f the p l a n t by win d . Many i n v e s t i g a t i o n s have been made on f o r e s t t r e e s (Wood 1937, Grah e t a l . 1944, K i t t r e d g e e t a l . 1941, N i e d e h o f e_t a l . 1943) , g r a s s l a n d shrubs and crop p l a n t s ( C l a r k 1937, 1940, Haynes 1940, Reimann e t a l . 1946, Spechut 1957). A l s o Gwynne (1966) and Gl o v e r and Gwynne (1962) o b s e r v e d t h a t c o r n and some o t h e r t r o p i c a l g r a s s e s such as Themeda t r i a n d r a use t h e i r a e r i a l p a r t s t o c o l l e c t the l i g h t savanna r a i n s and c o n c e n t r a t e them around the p l a n t base. T h i s means t h a t a spot s o i l l o c a l i t y r e c e i v e s much more r a i n water t h a n would f a l l on the open s u r f a c e . Specht (1957), 10 emphasized that interception of r a i n f a l l by vegetation i s a major factor i n any investigation of the water balance of an ecosystem. Stem flow or f o l i a r drip which can be of con-siderable importance i n a r i d plant communities has a great influence on the d i s t r i b u t i o n of the incoming moisture. Bharucha (1958), Shant (1966), and Daubenmire (1942) emphasized that heavy grazing affected the physical structure, minerals and organic matter of the s o i l . Bharucha found that grazing altered the mechanical composition of the s o i l , and decreased the organic matter and the t o t a l exchangeable b a s e s — e s p e c i a l l y exchangeable calcium. Daubenmire (1942), on the other hand, had reported that the s o i l under grazing had a higher l e v e l of moisture and organic matter content than the s o i l under a protected vegetation. He attributed the higher organic matter-levels i n the top s o i l s to the high percentage of annual plants which grew on the overgrazed range. Since annuals have a short l i f e cycle and shallow root systems their remains tend to increase the organic matter i n the topmost horizons of the s o i l . The Plant's Reproductive Potential and  the Habitat Factors E l l i s o n (i960) commented that a l l the evidence tends to indicate that the r e l a t i o n between the plant and the 11 grazing animal i s one of parasitism by the animal, i n which the plant receives no benefit. Salisbury (1°A2) pointed out that i n general the e f f e c t of adverse conditions such as competition, unless of an extreme character, is to cause a reduction i n the number of seeds per plant rather than to a f f e c t the q u a l i t y of the seeds themselves. He concluded that there was no c o r r e l a t i o n between the seed output capacity and the degree of mortality r i s k s the progeny is to be sub-jected to, although a c e r t a i n minimum of seeds i s required to meet these r i s k s . In his observations, the species which demanded p a r t i c u l a r l y r e s t r i c t e d environmental conditions seemed to possess the more meagre reproductive equipment, while those species which had numerous niches or large area to occupy had capacity for a high p o t e n t i a l progeny. While i t i s true seed output i s not d i r e c t l y proportional•to the mortality r i s k s , plants with a short l i f e span have a repro-ductive pattern suited to the type of conditions they stay i n . Stebbins (1950) observed that there are two correlations which hold r e g u l a r l y i n the plant kingdom. The f i r s t i s that between the l e v e l of compromise and the length of l i f e of the i n d i v i d u a l organism. In short-lived, r a p i d l y reproducing organisms the genetic system is usually one which favors f i t n e s s at the expense of f l e x i b i l i t y , while an.increasing length of l i f e r a i ses the selective value of genetic systems 12 which favor f l e x i b i l i t y at the expense of immediate f i t n e s s . Secondly, in organisms which are s t r u c t u r a l l y simple, the l e v e l of compromise tends to favor f i t n e s s . The f a c t that plants with small seeds tend to dominate open habitats while heavy-seeded plants favor the closed habitats (Salisbury 1942, Laig 1966) seems to correlate the nature of propagule with the habitat factors. Baker (1964) concluded that i n undistributed communities, the native plants which are often aliogamous, have appropriate breeding systems to produce f i n e l y adaptive ecotypes through extensive recombinations. On the other hand, weeds or colonizers to which s e l f - p o l i n a t i o n or even apomixis i s l i k e l y to be important for establishment after long-distance d i s p e r s a l , or i n b u i l d i n g up a large population quickly, would be unable to produce recombinants as r a p i d l y and therefore, depend more upon "general purpose" genotypes. He defined "general purpose" genotypes as the kind of genotypes which provide the plant bearing them with a wide environmental tolerance and give i t the a b i l i t y to grow i n a multitude of c l i m a t i c and edaphic s i t u a t i o n s . Stebbins (1964) observed that i n spite of the f a c t that weedy plants, mainly annuals, have b i g seeds which are not early dispersed, they have b e t t e r chances for germination and establishment. I I . LOCATION AND DESCRIPTION OF THE STUDY SITES The four s i t e s which form the study area of this project are located i n the grassland vegetation of the Southern Central B r i t i s h Columbia, known as the I n t e r i o r . These grasslands occur i n a region l y i n g between the mountains of the Columbian System on the east, the Coast Range on the west, the 53rd p a r a l l e l on the north and the Canadian/United States i n t e r n a t i o n a l boundary on the south. The area i s topographically rugged and represents an ancient plateau which has undergone enormous changes due to u p l i f t s and erosion of the Late Tertiary times (Tisdale ±9^-7, Brink e_t a l . , Bostock 1948, Fulton 1962, 1963) . The area is characterized by numerous v a l l e y s , some of which have bottoms from 6l0 meters to nearly 1524 meters below the l e v e l of the surrounding country. The climate of the major grasslands i s r e l a t i v e l y warm and dry with the average annual p r e c i p i t a t i o n varying from; s l i g h t l y less than 18 em. (7 ins.) i n the d r i e s t parts to 44 cm. (15.5 ins.) i n the wettest parts. The climate i s greatly conditioned by the presence of a mountain b a r r i e r in the west and by the l o c a l topography (Tisdale 1947)• Most of the r a i n f a l l ' comes i n r e l a t i v e l y gentle storms and run-off is not very extensive except on extremely steep or denuded 14 slopes. The f r o s t - f r e e season ranges from 175 to 150 days i n areas where the experiments were conducted. The grassland vegetation i n this region occupies the larger and lower valleys and adjacent slopes of the Okanagan, Nicola, Thompson, Fraser and C h i l c o t i n watersheds. This vegetation was f i r s t described by Tisdale (1947) who c l a s s i -f i e d i t into the following grassland zones: the Agropyron-Art errrisia or Lower Grassland Zone; the Agropyron-Poa or Middle Grassland Zone; and the Agropyron-Festuca or Upper Grassland Zone. The terms--Lower, Middle and Upper--have reference to the v e r t i c a l sequence of the three zones throughout most of the region. The l a t t e r a l t i t u d i n a l c l a s s i f i c a t i o n i s adapted i n this account. The s o i l s of the region are mainly sandy loam of g l a c i a l t i l l o r i g i n . Generally these s o i l s consist of three main zonal types described by Tisdale (1947) as Brown, Dark Brown and Black Earth Zones. These Zones are associated with the three major di v i s i o n s of the grassland vegetation. S o i l descriptions of thi s grassland region, including the study area, have been published by Fulton (1962, 19^3, 1967)• The four s i t e s investigated i n the present study were selected i n conjunction with Mr. A. McLean, Research S c i e n t i s t CD.A. Kamloops and Dr. V. C. Brink, Head o f the 15 Plant Science Department at the University of B r i t i s h Columbia, as representatives of the three vegetational zones of the grasslands of the Nicola-Thompson area. At leas t one s i t e was selected i n each zone. Although these si t e s may not be considered by some to be t y p i c a l of the zones i n which they are located, their status represents the c o l l e c t i v e appearance of some of the fenceline vegetation c h a r a c t e r i s t i c s of the area. The four si t e s together repre-sent a 100-kilometer (approx. 62 miles) transect which runs from the lower grassland to the upper grassland zone. Before the advent of the white man i n the early l800's the grasslands were grazed only by w i l d l i f e possibly mainly small populations of deer and elk. Pasture ungulates apparently did not exert heavy grazing pressures possibly because aboriginal people kept their numbers at a low l e v e l . Cattle ranching i n the Kamloops area started around 1862 but no fencing was done u n t i l the l890's. The fencelines referred to i n this account are related to some of these o r i g i n a l fences which were possibly b u i l t as the good grass-land pasturage was claimed through purchase, lease or other means of land tenure. The s i t e s used are named after the area where they are situated. They are "Tranquille", "Quilchena", "Hamilton Commonage" and "Minnie Lakes". 16 1. The Tranquille s i t e (Tranquille Gov't Range) located i n the lower grassland zone, i s 3 Km. (2 miles) from the Kamloops Research Station and 0.8 Km. from the B.C. Government Farm at Tranquille. The elevation is 335 meters (1100 f t . ) above sea l e v e l . Average annual p r e c i p i t a t i o n i s about 20 cm. (8 in.) and slope 6% S.E. The vegetation i s characterized by the p r i n c i p l e species Agropyron spicatum* and Artemisia t r i d e n t a t a Nutt.** The former dominates the "ungrazed" side and the l a t t e r the "grazed" side of the fence. 2. The Quilchena s i t e on the Guichon Cattle Co. ranch, is situated i n the middle grassland zone and about 77 Km. (48 miles) south of Kamloops on the Kamloops-Merritt road i n Nicola Valley. The elevation i s 647.7 meters (2125 f t . ) above sea l e v e l , average annual p r e c i p i t a t i o n i s between 23-28 cm. (9-12 in.) and slope is 9$ *This name includes both the awned type of the species A. spicatum (Pursch) Scribn. and Smith, and the awnless type A. sp ic atum var. inerme Heller, and other possible intermediate v a r i e t i e s (Passey et a l . 1963) • **The authority for each s c i e n t i f i c name w i l l be given either the f i r s t time the species i s mentioned or i n Table I I . 17 S.W. The vegetation i s characterized by A. spicatum, Poa secunda Pres l and Chrysothamnus  sp. A. spicatum i s the dominant species on the "ungrazed" side and Chrysothamnus sp. i s the dominant species on the grazed side of the fence. 3. The Hamilton Commonage s i t e , on the Douglas Lake Cattle C. range, i s located i n the upper grass-land zone. I t i s l 6 Km. (10 miles) east of Quilchena s i t e on the Minnie Lakes-Pennask Lake road. The elevation i s 1242 meters (4075 f t . ) above sea l e v e l , average annual p r e c i p i t a t i o n i s about 43.2 cm. (15 in.) and slope 6fo S.S.E. The winter-grazed side of the fence i s dominated by Agropyron spicatum, Festuca s c a b r e l l a Torr. and Lupinus sericeus Pursch. The heavily-grazed side i s dominated by Stipa columbiana Macoun and Poa pratensis L. 4. The Minnie Lakes S i t e , on the Douglas Lake Cattle Co. range, i s located i n the middle grass-land zone, about 21 Km. (13 mi.) east of Quilchena s i t e on the Minnie Lakes-Pennask Lake road. The elevation i s 1,112.5 meters (3650 f t . ) above sea l e v e l , the average annual p r e c i p i t a t i o n is about 18 3 C 5 cm. (12 i n . ) and the slope i s 5$ E. on the less grazed plot and 3$ N.N.W. on the grazed p l o t . The dominant plant species on both sides of, the fence are Agropyron spicatum and Festuca  s c a b r e l l a . At each s i t e an old fenceline separates the two sides which have had d i f f e r e n t grazing treatments for a long time-(Fig. l ) . At the f i r s t two s i t e s , the side refer r e d to as " l i g h t l y grazed" or " r e l i c t " had had l i t t l e to no disturbance for over f i f t y years, while the other side had been heavily grazed continuously, e s p e c i a l l y i n spring and f a l l . In the case of the l a s t two s i t e s , the " l i g h t l y grazed" side had been occasionally very l i g h t l y grazed i n the f a l l and winter while the "heavily grazed" or "depleted" side had had continuous heavy grazing. The terms " l i g h t grazing" and "heavy grazing" refer to the state of the s i t e s when experimentation started. After fencing the desired exclosures on each side of the old fenceline no further grazing took place i n either exclosure. For con-venience the terms " l i g h t l y grazed" and "heavily grazed" w i l l be used i n t h i s thesis to refer to the " r e l i c t " and "depleted" exclosures respectively. Although not included in the reported study, grazing study areas have been set up 19 adjacent to the newly fenced area, on the assumption that the present grazing practices i n the general area w i l l continue. ( a ) , (b) and (c) show the f e n c e l i n e a t H a m i l t o n Commonage, Q u i l c h e n a and T r a n q u i l l e s i t e s r e s -p e c t i v e l y . (H) h e a v i l y g r a z e d s i d e and ( L ) l i g h t l y g r a z e d s i d e . I l l . METHODS F i e l d Experiments Exclosures (to exclude ungulate users of the range) were established at each of the aforementioned s i t e s . For p r a c t i c a l purposes, these exclosures consisted of contigu-ous pa i r s divided by the range fenceline and located so that both members of the pair had the same s o i l aspects. Each exclosure i s 30 by 30 meters enclosed i n a f i v e strand barbed wire fence with s t e e l and wooden posts, constructed on each side of the old fenceline. The two exclosures at each s i t e formed a 60 by 30 meter p l o t divided into two smaller plots by the old fenceline. In addition to the barbed wires, the bottom half of whole enclosure was reinforced with a "chicken" wire netting of about 7.5 cm. mesh. Climate, s o i l moisture, and temperature i n s t r u -mentation. P r e c i p i t a t i o n gauges were i n s t a l l e d i n pairs at each s i t e at the vegetation l e v e l . Readings at a l l si t e s were taken weekly. At Tranquille s i t e recording was done by means of a cumulative v i c t o r r a i n gauge. S o i l moisture at the other three s i t e s was monitored by the neutron probes while at Tranquille where the previous years' recordings were made, gravimetric means were used. 22 S o i l temperatures were measured with thermistor probes placed i n each exclosure at 10, 25, 50 and 100 cm. below the s o i l surface•. S o i l samples used for organic matter analysis were c o l l e c t e d i n t r i p l i c a t e at 0-2, 5, 10, 25, 50 and 100 cm. below the s o i l surface i n each exclosure. The organic matter content was determined i n the laboratory at U.B.C. by the Walkley-Black method ( A l l i s o n 1965). Vegetation analysis. The f l o r i s t i c l i s t s were derived from the species l i s t s compiled during the crown cover determinations. The species which could not be • i d e n t i f i e d i n the f i e l d were tagged and brought back to the Kamloops Research Station for comparison with herbarium speciments. The species composition percentages were determined from the values obtained from basal area- measure-ments. Phenological observations were made throughout the growth period. Culm heights and leaf blade lengths were measured on both flowering shoots and vegetative t i l l e r s as i n d i -cated i n Figure 2. At least 30 bunches selected randomly were measured on each side of the fence depending on how well the species was represented. I f fewer bunches than 30 occurred i n the exclosure a l l the available bunches were measured. However, measurement of flowering culm 24 heights was abandoned because there were very few flowering culms of Agropyron at some s i t e s . T i l l e r heights were measured i n August. Counts of the flowering shoots and vegetative t i l l e r s per selected bunch were made at the same time the culm heights were measured. Ratios of f e r t i l e to vegetative shoots on a bunch were used to indicate reproductive p o t e n t i a l of a bunch. Due to shortage of time most of the measurements were confined to A. spicatum. Seed y i e l d per unit area was determined by counting flowering culms i n 5 one-sqare; -meter quadrats scattered randomly i n each exclosure. The basal cover of a l l plants was determined by means of l i n e intercept method (N.A.C. - N.R.C. Pub. 890) using 10 l i n e s of 10 meters long each placed randomly i n each exclosure. In order to keep track of the in d i v i d u a l plant changes permanent one-square-meter-charting quadrats were established, two on each side of the fence (N.A.C. -N.R.C. Pub. 890). The vegetation cover and frequency were determined by "the quadrat method similar to that described by Poulton and Tisdale (1961). The dry matter herbage y i e l d of grasses and forbs was determined by c l i p p i n g eight randomly placed meter-25 square permant quadrats, from each exclosure. Individual species were clipped separately and weighed after oven drying. Clipping was done at the end of the growth season i n October. . Laboratory and Greenhouse. Experiments An experiment to determine the l e v e l at which water penetrates d i r e c t l y under the bunches of Agropyron spicatum was conducted i n the greenhouse at U.B.C. Transplanted bunches were used i n the set-up i l l u s t r a t e d i n Figure 15. . Three sets of Bouyoucos moisture blocks were set up i n the box at the time the box was f i l l e d with garden s o i l . The moisture blocks were placed at 10, 25, 50 and 70 cm. levels and the s o i l was uniformly packed. Two bunches of A. spicatum were planted on the top of two block sets (A) and (B) leaving the middle set of blocks as a control (Figure 15) One month after transplanting a non-run-off mist-spray system was set up 160 cm. above the box. The. height of the sprayers was determined beforehand in several t r i a l s i n which the uniformity of spraying system was determined. Watering lasted one hour each time and measure-ments were taken every two weeks. Every time measurements were done, the i n i t i a l moisture l e v e l was determined before watering and then the 26 change i n moisture l e v e l s was recorded an hour after watering had stopped. Several determinations were made using both bunches and then one bunch was clipped to the ground. Further measurements were made using one clipped and one undipped bunch. IV. RESULTS F l o r i s t i c s There were no marked differences i n the l i s t s of . plant species on the opposite sides of the fenceline. At Tranquille and Quilchena s i t e s , there were s l i g h t l y more forb (broad-leaved) species on the heavily grazed sides than on the less grazed ones. However, at Hamilton Commonage sit e the l i g h t l y grazed area had more forbs' than the depleted area and at Minnie Lakes s i t e both sides had e s s e n t i a l l y the same number of species. The numbers of species i n each plant category present at each s i t e are shown i n Table I and- a complete l i s t of a l l species i s presented i n Table I I . TABLE I NUMBER OP SPECIES IN CATEGORIES BY SITES CATEGORY Tranquille Quilchena Minnie Lakes Hamilton C. Porbs Shrubs Grasses Annuals Perennij L H L H L H L H 4 7 1 1 2 2 Us 3 3 11 18 2 3 1 1 3 5 18 15 l l 5 5 28 19 2 1 1 8 7 TOTALS 10 13 17 27 24 21 37 29 L •= L i g h t l y grazed. H = Heavily grazed. 28 TABLE I I THE LIST OF SPECIES FOUND IN THE STUDY AREA SPECIES Site 1 Site 2 Site 3 Site J 4 L H L H L H L H GRASSES Agropyron spicatum P P P P P P P P Agropyron repens (1) Beauv. P P Bromus tectorum L. P P P P P P Festuca idahoenis Elmer P Festuca o c t o f l o r a Walt. P P Festuca s c a b r e l l a Torr. P P P P K o e l e r i a c r i s t a t a (l) P P P P P Poa' ampla Mer. P P P P Poa compressa L. P Poa pratensis L. P P Poa secunda P r e s l . P P P P P P P P Sporobolus cryptandrus (Torr .) Gr ay P P Stipa columbiana Macoun P P Juncus b a l t i c u s W i l l ' d . P FORBS A c h i l l e a m i l l e f o l i u m L. var. C. Lanulosa (Nutt) Piper P P P P P Agoseris glauca Pursh. P Androsace occ i d e n t a l i s P 29 TABLE II Continued SPECIES Site 1 Site 2 Site 3 Site 4 L H L H L H L H Antennaria dimorpha (Nutt) T. & G. P P P P P P P Antennaria rosea Greene P P P P Arab i s h o l b e l l i i Hornem. P P P P Aster campestris Nutt. P P P P Astragalus p u r s h i i Dougl. P P P Astragalus serotinus A. Gray P P Camelina microcarpa Anderz. P P Cerastium arvense L. P Chenopodium album L. P P C o l l i n s i a p a r v i f l o r a Dougl. P P Collomia l i n e a r i s P P Comandra p a l l i d a A. P Delphinium b i c o l o r Nutt. P Descurainia sophia P P P Epilobium paniculatum Nutt. P P Erigeron compositu-s Pursh. P P P P Erigeron corymbosus Nutt. P P Erigeron l i n e a r i s (Hock) Piper. P Erigeron pumilus T. & G. P P P P P Eriogonum heracleoides N u t t r --30 TABLE I I Continued SPECIES Site 1 Site 2 Site 3 Site 4 L H L H L H L H Geum t r i f l o r u m Pursh. P P Lappula echinata G i l . P P P P i Lithospermum ruderale P P ) Lomatiura macrocarpum (Nutt) G. & R. P P P P P P P Lupines sericeus Pursh. P P P P Opuntia f r a g i l i s Haw. P P P Oxtropis campestris P P P Pentstemon procerus Dougl. P Phlox g r a c i l i s P P P P P P P o t e n t i l l a g r a c i l i s Dougl. P P Senecio caus Hook.. P Sisymbrium altissimum P P Taraxacum o f f i c i n a l e Weber P P P P P P Tragopogon pratensis. L. P P P P P P V i o l a adunca Smith. P P Zygadenus venenosus Wats. P P P SHRUBS Artemisia f r i g i d a Wall'd. P P P P P Artemisia glauca P Artemisia t r i d e n t a t a P P P Chrysothamnus sp. (Pall) B r i t t . P P P \1. Tranquille. 2. Quilchena. 3. Ham i l t o n C. 4. Minnie Lake sv L - L i g h t l y grazed. H-Heavily grazed. p indicates presence. 31 In general the number of species present at the si t e increased from the Lower grassland zone to the Upper grass-land zone. This coincided with the observations made by Tisdale (1947). The difference i n the species number appeared to be more an attribute of the vegetation zone than as a simple response to grazing. Out of a t o t a l of 60 species recorded i n the whole study area (Table II) only Agropyron spicatum, Poa secunda, Antennaria dimorpha, Lomatium macrocarpum and Artemisia  f r i g i d a were represented at a l l s i t e s . A. spicatum dominated a l l the l i g h t l y grazed areas contributing over 50$ of the t o t a l vegetation cover at Tranquille and Quilchena, and 4 6 $ at Minnie Lake s i t e s . Under " r e l i c t " conditions A. spicatum tended to form pure stand with large bunches widely spaced. Usually there were large bare areas between the bunches sometimes only occupied by small short l i v e d , shallow rooting species such as C o l l i n s i a p a r v i f l o r a and Poa secunda (Fig. 3)• However, at Hamilton Commonage s i t e , the charac-t e r i s t i c pattern of A. spicatum bunches i n undisturbed state was less d i s t i n c t . Although the bunches were b i g and widely spaced, there were l i t t l e bare areas between them. The spaces between A. spicatum bunches were occupied (a) F i g . 3 . (a) and (b) i l l u s t r a t e the c h a r a c t e r i s t i c s p a c i n g of Agropyron s p i c a t u m bunches i n a l e a s t disti/nbed c o n d i t i o n at M i n n i e Lakes and Q u i l c h e n a r e s p e c -t i v e l y . The p i c t u r e s r e p r e s e n t two d i s s i m i l a r s o i l s u r f a c e f e a t u r e s . 33 by a v a r i e t y of o t h e r s p e c i e s of g r a s s e s and f o r b s ( F i g . 4) . Among the a s s o c i a t e d s p e c i e s were F e s t u c a s c a b r e l l a , F. i d a h o e n i s , Poa ampla and K o e l e r i a c r i s t a t a . Grasses con-t r i b u t e d 77$ o f the t o t a l c over and the r e m a i n i n g p e r c e n t a g e was made o f f o r b s . L u p i n u s s e r i c e u s was the p r i n c i p a l f o r b c o n t r i b u t i n g 14$ o f the t o t a l v e g e t a t i o n c o v e r . A c h i l l e s  m i l l e f o l i m v a r . l a n u l o s a made up almost 8$ of the c o v e r . and f o r b s i n the l i g h t l y g r a z e d e x c l o s u r e a t H a m i l t o n Commonage s i t e . A l t h o u g h A. s p i c a t u m o c c u r r e d on b o t h the l i g h t and h e a v i l y g r a z e d s i d e s a t a l l l o c a l i t i e s , i t s bunches on the h e a v i l y g r a z e d s i d e s were v e r y s m a l l i n s i z e ( F i g . 5)• At T r a n q u i l l e and Q u i l c h e n a , the s m a l l bunches were f o u n d g r o w i n g near and under shrubs ( F i g . 5,a). At e v e r y s i t e the d e p l e t e d a r e a was dominated by e i t h e r s h r u b s , a n n u a l s or 34 00 F i g . 5 . (a) and (b) show the d i f f e r e n c e i n the p l a n t d e n s i t y between the h e a v i l y grazed and the l i g h t l y grazed exclosures r e s p e c t i v e l y at T r a n q u i l l e s i t e . The p i c t u r e s were taken i n summer 1968 . rhizomatous grasses. At Tranquille Artemisia tridentata contributed 76% of the t o t a l species cover. At Quilchena Chrysothamnus sp., Artemisia f r i g i d a and Bromus tectorum together made up 76$ of the t o t a l species cover. At Hamilton Commonage Stipa columbiana and Poa pratensis were the major species, and at Minnie Lakes Juneus b a l t i c u s and Artemisia f r i g i d a were the apparent increaser species. The f l o r i s t i c composition expressed as percentage of the species basal area to the t o t a l vegetation.cover is shown i n Table I I I . There were- s i g n i f i c a n t differences between the composition of species on the l i g h t l y grazed side and that of the species on the heavily grazed side. There were marked reductions i n the percentage composition of Agropyron spicatum, Festuca scabrella and F. idahoensis on the heavily used side at a l l s i t e s . On the other hand Bromus tectorum, Stipa columbiana, Poa pratensis, Artemisia  tridentanta, Chrysothamnus sp. and Antennaria dimorpha had s i g n i f i c a n t l y greater amounts on the depleted side than on the l i g h t l y grazed side. At a l l s i t e s there was an apparent decrease i n the composition of caespitose grasses under grazing and an increase i n the annuals and rhizomat-ous species. 36 TABLE I I I SPECIES COMPOSITION (IN PERCENTAGE) ON FOUR SITES ON THE OPPOSITE SIDES OF FENCELINES SPECIES L H L H . L H L H ** * #* A. spicatum 65.5 6.3 66.3 1.3.2 4 6 . 8 35.1 13.8 0.1 Festuca s c a b r e l l a 3.2 9.6 29.3 *•* 0.1 Festuca ideahoensis 8.7 <.l Poa secunda 13.8 9.8-* 13.4 12.3 #-* 2.1 6.2 10.0 10.1 Bromus tectorum <J01 1.0 0.04 3.8 <*05 Poa pratensis 9-5 67.8 ** Stipa Columbians 0.7 6.2 Artemisia t r i d e n t a t a 19.3 76.7 Artemisia f r i g i d a - 11.9 14.2 4.6 *•# Chrysothamnus sp • 16.6 44.4 *•* 1 Lupinus sericeus 1.8 0.5 14.3 0.2 Antennaria dimorpha - 1.6 3.3 11.5 12.6 12.5 0.5 •* 3.0 Koeleria c r i s t a t a 7.6- 14.7 5.7 3.0 OTHERS 1.4 4.6 0.4 2.9 11.7 16.8 7.5 9-5 TOTALS OF ALL SP . 100. 100. 100. 100. 100. 100. 100. 100. TOTAL GRASS COMPOSITION 79.3 18.1 79.7 30.3 61.8 68.7 77.7 87.3 **io.dicates a s i g n i f i c a n t differences (P<-0.01) between the l i g h t l y grazed and the heavily grazed area. •^Indicates a s i g n i f i c a n t difference (P<0.05) between the l i g h t l y grazed and heavily grazed area. 37 Species Frequency., Canopy Cover, Basal  Area and Dry Matter Y i e l d Species frequency. Frequency was determined by noting the presence or absence of a given species i n 5 0 sampling plots l a i d out i n each exclosure following the method described by Poulton and Tisdale ( 1 9 6 1 ) . The per-centage of the number of plots i n which the species occurred was used as i t s percentage frequency. The frequency of Agropyron spicatum, Festuca  s c a b r e l l a , F. idahoensis, Poa ampla and Lomatium macro-carp urn was reduced wherever grazing had been i n t e n s i f i e d (Table IV). On the other hand Poa pratensis, Stipa  columbiana, Bromus tectorum, Artemisia tridentata, A. f r i g i d a , Chrysothamnus sp. and Antennaria dimorpha increased as grazing was i n t e n s i f i e d . Lupinus sericeus tended to become rare on the depleted side on Hamilton Commonage site while Poa secunda and A c h i l l e a millefolium did not change much. The percentage of Festuca s c a b r e l l a on the depleted side of the fenceline at Minnie Lakes, was higher than on the l i g h t l y grazed side. I t may be there were reasons other than grazing which o r i g i n a l l y influenced this high percentage. On both sides of the fence, however, the 38 TABLE IV THE PERCENTAGE FREQUENCY OF THE MAJOR SPECIES SITE SPECIES Tranquille Quilchena Minnie Lakes Hamilton C. L H L H L H L H Agropyron spicatum 98 70 100 82 96 98 78 12 Festuca s c a b r e l l a 16 50 76 10 Festuca idahoensis 32 -Koeleria c r i s t a t a 56 72 64 48 Poa ampla 26 10 • 5 25 Poa secunda 9^ 94 52 54 6 34 ' 70 84 A c h i l l e a m i l l e f o l i u n - 25 16 36 80 50 Poa pratensis 14 32 Stipa columbiana 16 82 Bromus tectorum 25 36 10 98 25 -Sporobolus cryptandrus _ 20 Artemisia tridentat a 66 88 Artemisia f r i g i d a 25 50 40 50 Chrysothamnus sp. 8 78 Antennaria dimorpha - 12 10 50 26 64 25 38 Opuntia f r a g i l i s 18 26 25 25 Lupinus sericeus 10 4 90 25 Taraxacum o f f i c i n a l e 25 25 28 16 16 32 JuncuS b a l t i c u s - 88 Lomatium macro.carpum 14 8 40 34 22 . 25 25 -s p e c i e s was r e p r e s e n t e d by b i g bunches whose c e n t e r s had d i e d l e a v i n g t h i n r i m s o f t i l l e r s m a rking the o t h e r l i m i t s of the o r i g i n a l crowns.. Canopy c o v e r . W i t h the e x c e p t i o n of H a m i l t o n Commonage s i t e , the p e r c e n t a g e canopy cover of a l l g r a s s e s was lower on the h e a v i l y used s i d e t h a n on the l i g h t l y used s i d e , a t a l l s i t e s (Table V ) . On H a m i l t o n Commonage, though the t o t a l c o v e r of g r a s s e s was h i g h e r on the d e p l e t e d s i d e , t h e r e was a marked r e p l a c e m e n t o f c a e s p i t o s e s p e c i e s by sod f o r m e r s . B a s a l a r e a . B a s a l a r e a measurements were made by the l i n e i n t e r c e p t method d e s c r i b e d i n the "Range R e s e a r c h B a s i c Problems and Techniques" p u b l i s h e d by N.A.C.-N.R.C. The b a s a l a r e a o f each s p e c i e s was c a l c u l a t e d f r om the pe r c e n t a g e o f the sum o f a l l d i a m e t e r s , of the i n d i v i d u a l p l a n t s o f t h a t s p e c i e s i n t e r c e p t e d by l i n e t r a n s e c t s , to the t o t a l l e n g t h of a l l t r a n s e c t s used. As f a r as the pe r c e n t a g e o f the bare ground was concerned, t h e r e was no marked change f o l l o w i n g heavy g r a z i n g . Some s p e c i e s such as A. s p i c a t u m d e c r e a s e d as g r a z i n g was i n t e n s i f i e d but a t the same time the d e c r e a s e r s were r e p l a c e d by the apparent i n c r e a s e r s and i n v a d e r s . Poa p r a t e n s i s g r e a t l y i n c r e a s e d i t s coverage on the d e p l e t e d s i d e thus r e d u c i n g the p e r c e n -tage o f bare ground (Table VI) a t H a m i l t o n Commonage. 4o TABLE V CANOPY PERCENTAGE COVER OF THE MAJOR SPECIES SITE SPECIES Tranquille • Quilchena Minnie Lakes Hamilton Commonage L H L H L H L H Agropyron spicatum 65 16 59 18 48 33 4o 3 Festuca s c a b r e l l a 4 9 35 1 Festuca idahoensis 8 -Koeleria c r i s t a t a 7 10 15 11 Poa secunda 17 23 7 12 1 4 13 26 Poa amp l a 3 1' 4 1 A c h i l l e a millefolium 1 4 6 21 13 Poa pratensis 8 20 Stipa columbiana 4 4l Bromus tectorum 1 6 1 l Sporobolus cryptanarus 1 3 Artemisia t r i d e n t a t a 19 34 Artemisia f r i g i d a 8 6 9 1. Chrysothamnus sp. 2 27 Antennaria dimorpha 2 1 6 2 6 l 5 Opuntia f r a g i l i s Lupinus sericeus 3 3 1 l l l 47 1 Taraxacum of f ic i n ale . 2 1 1 2 41 TABLE VI BASAL AREA AS PERCENTAGE COVER OF THE TOTAL SURFACE AREA SAMPLED SPECIES SITE Tranquillel Quilchena L H L H Minnie Lakes L H Hamilton Commonage L H Agropyron spicatum 19.1 2 Festuca s c a b r e l l a Festuca idahoensis Koe l e r i a c r i s t a t a Poa amp l a Poa secunda A c h i l l e a m i l l e f o l i u m Poa pratensis Stipa columb iana Bromus tectorum Sporobolus  cryptanclrus Artemisia tridentata Artemisia f r i g i d a Chrysothamnus sp. Antennaria dimorpha Opuntia f r a g i l i s Lupinus sericeus Taraxacum o f f i c i n a l e Juncus b a l t i c u s Lomat ium macro carp urn  Oxtropis campestris 4 .1 0.3 0.1 1 7 24 l 1 l .1 .1 .1 0.1 16 .1 7 4 l 3 11 3 0.2 .1 .1 0 . 2 1 10 1 7 2 2. 3. 0.4 1 0.4 1 .1 0.2 0, 6 0.1 12 0.1 3 .1 2 2 0.2 0.2 4 7 2 2 2 4 48 0.3 6 .1 -3 1 0.3 0 0 . 1 0 - 1 0 . 2 2 1 6 0 . 2 l - l 1 1 1 0 Total veget. covers 31 3; 24 25 21 20 41 7; 42 Dry matter y i e l d . The dry herbage y i e l d of the major grass species sampled at the end of the growing season i s given i n Table VII. The herbage y i e l d of forbs was not determined because at the time of measuring a l l forbs had dried out. Shrubs, too, were not measured because they were too big to be measured by the c l i p p i n g method. A better measure of shrubs i s expected to be used in future determinations. TABLE VII AVERAGE DRY MATTER YIELD IN Kgms. PER HECTARE OF THE GRASS HERBAGE PRESENT AT THE END OF THE GROWING SEASON SPECIES SITE Tranquille Quilchena Minnie Lakes Hamilton Commonage L H L H L H L H Agropyron spicatun Festuca s c a b r e l l a Festuca idahoensis Poa ampla Poa pratensis Stipa columbiana 1498 129 1166 196 924 393 36 66 -* * 6 13 885 35 34l 20 130 * 5 4 194 340 * 475 TOTAL 1498 129 1166 196 966 472 1555 874 •^Indicates presence i n the exclosure but not in the sampling quadrats. 43 Growth Habits In several ways an attempt was made to f i n d out whether the growth habit of some major plant species res-ponded to management differences represented along the fences. Owing to the shortage of time, detailed measure-ments were confined to Agropyron spicatum and other species were measured only when comparison with A. spicatum was required. Agropyron spicatum, a dominant species i n the. grass-land climax (Tisdale 1947), has a very high grazing value (U.S.D.A. Forest Service 1966). When not greatly disturbed on open semi-arid s i t e s , the species usually produces more herbage than a l l other associated species combined. I t is a perennial grass and generally caespitose (Fig. 6), although some rhizomatous v a r i e t i e s exist (Passey e_t a l . 19^3) . Its culms are slender and tufted and i t s leaves are narrow and smooth with the inner surface (upper) grooved and s l i g h t l y pubescent. The awnless variety, sometimes c a l l e d Agropyron spicatum var. inerme, was commonest at a l l s i t e s . However, .a f a i r proportion of the awned s t r a i n (generally c a l l e d A. spicatum) was found at Minnie Lakes and Quilchena s i t e s . Old bunches of A. spicatum l i v e for a number of years and at Tranquille and Quilchena s i t e s , where the 44 s t a n d s have not been markedly d i s t u r b e d f o r many y e a r s , no s e e d l i n g s were o b s e r v e d growing among o l d bunches. N o r m a l l y new p l a n t s are e s t a b l i s h e d f r o m seeds and d e f e r r e d g r a z i n g i s s a i d t o f a c i l i t a t e seed s e t t i n g . New t i l l e r s on the o l d bunches grow I n the a x i l s o f the o l d t i l l e r s and f l o w e r i n g culms on the lower most nodes. The new buds emerged out o f the ground e a r l y i n the f a l l , subtended by s c a l y l e a v e s , and c o n t i n u e d t o grow u n t i l w i n t e r tempera-t u r e s p r e v e n t e d f u r t h e r growth. The same t i l l e r s n o r m a l l y c o n t i n u e growth i n the s p r i n g when c o n d i t i o n s became f a v o r a b l e a g a i n . F i g . 6 . Bunches o f Ag r o p y r o n s p i c a t u m a t M i n n i e Lakes s i t e (on the l i g h t l y g r a z e d s i d e of the f e n c e ) . A l t h o u g h no h r a t e measurements of the t i l l e r s were t a k e n , i t was d t h a t t i l l e r s w h i c h f i n a l l y produced flowering heads grew faster than the other vege-tative t i l l e r s . I t i s uncertain whether these t i l l e r s emerged f i r s t i n the f a l l or whether their elongation rate changed when they changed from being vegetative.to f l o r a l shoots. In future i t should be determined exactly when f l o r a l induction and i n i t i a t i o n take place i n this species. T. Lo'bb (personal communication) noticed that f l o r a l d i f f e r e n t i a t i o n takes place l a t e r i n Agropyron spicatum -.than i n Festuca s c a b r e l l a . The species i s very sensitive to over-use and poor management but, due to i t s great value as a forage plant, e f f o r t s are often made to increase i t s abundance on the ranges where i t occurs through good range management. However, attempts to extend the range of this species to other area where i t does not n a t u r a l l y occur, have usually f a i l e d (U.S.D.A. Forest Service 1 9 6 6 ) . In addition, i t s seed s e t t i n g habits are very i r r e g u l a r , e s p e c i a l l y i n higher and dri e r portions of i t s natural range. Two of the species which tended to replace A. spicatum under heavy grazing were Bromus tectorum and Stipa columbiana. The former was well represented on the depleted sides at Tranquille and Quilchena and the l a t t e r was abundant at Hamilton Commonage. 46 Bromus tectorurn i s an annual grass with a consider-able p l a s t i c i t y i n i t s response to variations i n site con-diti o n s (Harris 1967). At the two sit e s where i t was found i t produced single culms bearing several spikelets i n the inflorescence. However, Harris (1967) reported that where s o i l moisture, f e r t i l i t y and l i g h t i ntensity are not l i m i t i n g , an i n d i v i d u a l plant may produce 12 to 15 or more culms, each 50 to 75 cms. t a l l and bearing hundreds of spikelets per culm. Most seeds germinated early i n the f a l l but spring germination has also been observed by Dr. V. C. Brink (Personal communication). The seedlings established at the end of August were about 3 cm. t a l l i n October. Normally growth stops i n winter and starts again in spring. In spring the plants do not reach grazing heigh for c a t t l e u n t i l 2 to 3 weeks l a t e r than most associated perennial grasses. Once growth begins the reproduction cycle i s r a p i d l y completed. Plants dried i n the middle of June. Where B. tectorurn grows to a reasonably large size, the forage produced i s n u t r i t i v e as long as the plant i s succulent but as i t reaches maturity the forage becomes unpalatable and low i n nutrients. Stipa columbiana i s a perennial grass commonly c a l l e d Columbia needle grass. Its tufts are r e l a t i v e l y small when compared to those of A. spicatum (Figs. 6 & 7 ) . 47 I t i s f i n e - l e a v e d and slender-stemmed. I t grows on dry s o i l s i n canyons and on open h i l l s i d e s , mountain peaks and p l a i n s to sub-alpine e l e v a t i o n s . I t s p a l a t a b i l i t y i s sa i d to vary from f a i r to good. Normally the species occurs abundantly on ranges where Agropyron and other blue-grasses have been k i l l e d by overgrazing. I t i s considered a valuable replacement p l a n t under such c o n d i t i o n s and I t i s among the l a s t of the f a i r l y good grasses to disappear from the over-used range (U.S.D.A. Fo r e s t Service 1966). F i g . 7. S t i p a columbiana at Hamilton Commonage i n the h e a v i l y grazed e x c l o s u r e . The p l a n t e s t a b l i s h e d i t s e l f from seed. The seeds are awned and are produced i n la r g e numbers. On Hamilton Commonage, i t was n o t i c e d that the geni c u l a t e awn helps to 4 8 bury the caryopsis by a ro t a t i o n motion caused by changes in the atmospheric humidity. More buried seeds were noticed on bare patches on the depleted side. Vigor. Measuring the heights of the flowering culms of A. spicatum was abondoned because at some sit e s large enough flowering stalks could not be obtained. More-over at Tranquille where t r i a l measurements were made, the difference between the means for the l i g h t l y grazed and the heavily grazed sides were not s i g n i f i c a n t l y d i f f e r e n t . The mean heights were 2 8 . 3 and 2 5 . 4 +_ 2 . 2 cm. L.S.D. 3 . 8 (P< 0 . 0 5 ) respectively. The t i l l e r height was always measured as the distance from the s o i l surface to the c o l l a r of the sheath of the youngest leaf (Fig. 2 ) . The mean heights measured at the end of summer growth are shown i n Table VIII. Agropyron spicatum t i l l e r s were s i g n i f i c a n t l y shorter on the depleted side of the fenceline than on t h e l i g h t l y grazed side at a l l s i t e s . Leaf blades were s i g n i f i -cantly shorter at Tranquille and Minnie Lakes si t e s but n o t at Quilchena and Hamilton Commonage. In the case of Stipa  columbiana neither the t i l l e r heights nor the lengths of leaves indicated any s i g n i f i c a n t difference between the l i g h t l y and the heavily grazed areas. Results in both TABLE VIII AVERAGE TILLER HEIGHT OF A . SPICATUM AND S. COLUMBIANA MEASURED IN AUGUST 1968 SITE SPECIES Average Height in cm. L H S .E 0 L.S.D Tranquille Agropyron 2.9 spicatum 28.8 24.2** 1.0 (P < .01) Quilchena Agropyron 3-3 spicatum 30.8 27.2* 1.7 (P<0.05) Vlinnie Lakes Agropyron 26.8 3-0 spicatum 21.4** 1.1 (P<0.01) Hamilton Commonage Agropyron 2.9 sp ic atum 31.5 26.5** 1. (P<0.01 Stipa 4.8 columb iana 5.3 *Indicates a s i g n i f i c a n t difference (P-^.05) between the l i g h t l y grazed and heavily grazed area. **Indicates a s i g n i f i c a n t difference (P<^.01) between the l i g h t l y grazed and heavily grazed area. 4^ v o 50 Tables VIII and IX indicate that there was reduction in the vigor of A. spicatum on the heavily grazed area. Phenology. Phenological observations recorded throughout the growing season are shown i n Table X. I f what was observed at Hamilton Commonage were true of other habitats, then A. sp ic atum can be regarded as a plant whose inflorescences are i n boot stage e a r l i e s t and shed seeds l a t e s t . There was a space of a month between the boot stage and anthesis and another -month between anthesis and seed ripening. This meant that the inflorescences were exposed to a two months period when they could be destroyed by grazing. . It was observed that occasionally A. spicatum turns "viviparous" (Fig. §)• This tendency was most common at Quilchena s i t e . Further i n t e r e s t i n g observations were made when over 50$ of the inflorescences produced on the bunches grown i n the greenhouse turned "viviparous". In a number of cases a l l the spikelets i n the inflorescence had their terminal f l o r e t s turned "viviparous", while the rest of f l o r e t s i n the same spikelets underwent normal anthesis. Detailed account of these "p l a n t l e t s " i n A. spicatum was f i r s t made by Marchand and McLean (1965) and the present observations agreed with their description. TABLE IX AVERAGE LEAPBLADE LENGTH OF AGROPYRON SPICATUM AND STIPA COLUMBIANA MEASURED IN JULY I968 Av. Leaf Length i n cm. SITE SPECIES L H - S . E . L.S.D. Tranquille Agropyron spicatum 18.96 .15.91** 0.68 1 . 9 (P<0.01) Quilchena Agropyron spicatum 17.5 16.35 0.67 1 . 3 . ( p < o . 0 5 ) Minnie Lakes Agropyron spicatum 19.8 18.09* 0.73 1.5 ( p < o , 0 5 ) Hamilton Commonage Agropyron spicatum Stipa columbiana 20.5 21.. 7 -20.29 21.96 l . o 2.0 (P<0.05) ^Indicates a s i g n i f i c a n t difference (P<0.05) between the l i g h t l y grazed' and the heavily grazed area. -^Indicates a s i g n i f i c a n t difference (P<.0.01) between the l i g h t l y grazed and the heavily grazed area. L.S.D. - Least S i g n i f i c a n t Difference. r—1 TABLE X SOME PHENO LO GlC AL CHANGES IN SOME PLANT SPECIES AT HAMILTON COMMONAGE . (UPPER GRASSLAND ZONE) Boot State Anthesis Seed . Ripening SPECIES Mid- Late Mid- Late Early Mid- Mid- Late Early Mid-June June June June July July July July Aug. Aug. A. sp ic atum y y y B. tectorum y y y F. idahoensis y y P. secunda y y y K. c r i s t a t a y y y v / P. pratensis y v / y -S. columbiana y y P. ampla y y y L. sericeus y y • y C. bicolor y . y N.B. Growth in the Upper grassland zone i s about two weeks behind that i n the Lower grassland zone. ui r o F i g . 3 , ( a ) , ( b ) , and ( c ) , are i l l u s t r a t i o n s of v e g e t a t i v e p r o l i f e r a t i o n or vivipary i n Agropyron spicatum. There was no spec i a l i z e d means of seed dispersal noted to be associated with the A. spicatum seeds (Fig. 9 ) . I t i s most probable that the dispersal units are shaken out of the spikelets by wind and drop on the ground around the mother plant. Germination was observed i n the f a l l at Minnie Lakes s i t e among the seeds which managed to r o l l into s o i l cracks. As shown i n Figure 6 , B. tectorum had two types of dispersal u n i t s . The topmost f e r t i l e f l o r e t remained connected to a cluster of s t e r i l e f l o r e t s whose long awns formed parachute-like structures. The lower f l o r e t s were dispersed i n d i v i d u a l l y and generally they did not move f a r from the mother plant. This had also been reported by Hulbert (1955) and Klemmedson et a l . ( 1 9 6 4 ) . Since at Tranquille and Quilchena s i t e s , B. tectorum grew along the fence.but did not cross i t to the less grazed sides (Fig. 1 0 ) , an attempt was made to f i n d out how f a r the seeds moved on the l i g h t l y grazed side and which of the two d i s p e r s a l units strayed furthest from the mother plants along the fence. Normally when the seed germinates the remains of the dispersal unit stay attached onto the young seedling for a while, so i f young seedlings are c a r e f u l l y dug out of the s o i l i t i s easy to t e l l which type of dispersal unit the seedlings came from. F i g . 9, S p i k e l e t s and f l o r e t s of Agropyron sploatum, Bromus tectorum and Stipa"""columbian. 56 F i g . 1 0 . A dense stand of Bromus tectorum along the fence at Quilchena. (H) h e a v i l y grazed side and (L) l i g h t l y grazed s i d e . Late i n September B. tectorum seedlings were sampled i n b e l t t r a n s e c t s along the f e n c e l i n e at Quilchena on the l i g h t l y grazed side and the r e s u l t s shown i n Table XI were obtained. The t o t a l number of seedlings per sampling s t r i p e decreased p r o p o r t i o n a l to the distance from the fence. The percentage of the topmost f l o r e t s increased i n p r o p o r t i o n to distance away from the fence. On Hamilton Commonage S. columbiana had the same d i s t r i b u t i o n p a t t e r n as B. tectorum at T r a n q u i l l e and Quilchena. The species was densely d i s t r i b u t e d on the depleted side of the f e n c e l i n e ( F i g . 11) and l i g h t l y represented on the l i g h t l y grazed side. Large numbers seeds were produced r i g h t up to the fenceline but they appeared unable to cross to the less grazed side. of TABLE XI PERCENTAGE DISTRIBUTION OF THE BROMUS TECTORUM SEEDS AWAY FROM THE FENCELINE ON THE LIGHTLY GRAZED SIDE AT QUILCHENA SITE Distance from fence 0 1 meter 2 meters 4 meters 4.5 meters % Topmost f l o r e t s 52.5 64.8 74 . 6 85.5 82.0 % Lower f l o r e t s 47.5 33-2 25 .4 14.5 18.0 F i g . 11. Stipa columbiana and Antennaria dimorpha In the heavily grazed exclosure at Hamilton Commonage. 58 Seed pr o d u c t i v i t y . Table XII shows results obtained from stalk counts of the flowering culms of each species found i n 5 meter-quadrats put randomly i n each exclosure. Since the plants were not uniformly d i s t r i b u t e d the f i v e sampling quadrats proved too few to give r e s u l t s which could o f f e r a r e l i a b l e estimate of the available seeds per unit area. The values are shown just to indicate roughly the quantity of. seed produced at each s i t e . Since, what was required was' to determine the reproductive a b i l i t y of the e x i s t i n g species another method of measurement independent of species density was adapted. Reproductivity of caespitose species was rated from the r a t i o of flowering culms to non-flowering shoots on each bunch or t u f t . The r a t i o s were determined from shoot courts of at lea s t t h i r t y bunches selected randomly i n each exclosure. Results are shown i n Table XIII. The F e r t i l e to S t e r i l e (F/S) r a t i o i n Table XIII indicates that although the bunches of A. spicatum on the depleted side of the fence were small, they.had a higher capacity to produce seeds than the b i g ones on the r e l i c t side. Grazing did not introduce any change in the repro-ductive p o t e n t i a l of Stipa columbiana. TABLE XII AVERAGE NUMBER OF SEED STALKS PER SQUARE MATER OF THE SAMPLED AREA Site Species '; L i g h t l y Grazed Heavily Grazed * •• -Tranquille Agropyron spicatum 6 4 Poa secunda 20 81 Quilchena Agropyron spicatum 6 3 Poa secunda 9 13 Minnie Lakes Agropyron spicatum 112 14 Poa secunda 2 3 Hamilton Commonage Agropyron spicatum 9 1 Poa secunda 4 l S tipa columbiana 7 40 Ul vo TABLE XIII THE FERTINE/STERILE SHOOT RATIOS OF AGROPYRON SPICATUM AND STIPA COLUMBIANA Site Species L i g h t l y Grazed Heavily Grazed Tranquille Agropyron spicatum 1:134 1:12** Quilchena Agropyron spicatum 1:90 1:12** Minnie Lakes Agropyron spicatum 1:3 :19 Hamilton Commonage Agropyron spicatum 1: 24 1:75* Stipa columbiana 1:3 1:4 *Indicates a s i g n i f i c a n t difference (P<0.05) between the l i g h t l y grazed and the heavily grazed area. **Indicates a s i g n i f i c a n t difference (P^O.Ol) between the l i g h t l y grazed and the heavily grazed area. CA o 61 Edaphic Features S o i l temperature. At a l l si t e s except Minnie Lakes, s o i l temperature recordings started i n mid-June and early July 1968 and continued through winter and. spring the following year. Readings were taken f o r t n i g h t l y except in winter when only monthly recording was possible. The r e s u l t s (Fig. 12) show that temperatures were higher i n s o i l s on the heavily grazed side at a l l levels in summer. In winter the picture changed and the s o i l under heavy grazing conditions became colder, while the s o i l on the l i g h t l y grazed side remained r e l a t i v e l y warmer. S o i l moisture. Results of s o i l moisture conditions at a l l s i t e s throughout the growing season would have been very useful but sensing probes were not set up i n time. The only data available was recorded at one s i t e using gravi-metric methods. The r e s u l t s showed a higher moisture per-centage on the heavily grazed side than on the l i g h t l y grazed side at a l l lev e l s (Fig. 13) . I t was noted i n the f i e l d that i f a trench is dug after a r a i n f a l l , the wet zone on the trench wall appeared deeper d i r e c t l y under b i g bunches of A. spicatum than under the intervening patches of bare ground. No such penetration 6 2 30 20 •-•--•heavily grazed side lightly grazed side 10 _ 0 -5 T R A N Q U I L L E S I T E LU h A 20 or D K < 10 or UJ <L o Z UJ \r 20 10 2 5 C M Depth 5 O C M Depth ** 16 July June Fig. 1 2 (a) 13 Aug 10 Sept 8 Oct 5 Nov 6 Dec 9 Jan 14 feb Soil temperature by depth and treatment from June 1968 through February 1 9 6 9 . 2 0 10 — Q U I L C H E N A S I T E depleted ^ _ _ s — • side L i g h t l y s r a zeol 2 5 CM Depth 20 — o 5 0 CM Depth UJ CC h cc UI a 20 10 H A M I L T O N C 0 MM OM AGE S I T E 20h 10 S O C M r > e P t h 1 L i 1. • J ' i 1 IS" " J5 June July Aug. Sept. — - - <-q Oct . Nov. Dec. Feb 64-^ ^_ heavily grazed l i g h t l y grazed O 12 10 — h e a v i l y fcazed ligh t l y ^ grazed \ r e l i c t ^50 C M \ 2 5 C M Pig, 2 23 6 20 3 1 7 1 5 29 July July Aug Aug Sept Sept Oct Oct Oct 65 differences were observed on the depleted side of the fenceline among small bunches of A. spicatum. In order to demonstrate this phenomenon, an experiment was set up i n the greenhouse i n the following pattern. A wooden box of the dimensions i l l u s t r a t e d i n Figure 15 was b u i l t and f i l l e d with packed garden s o i l . At the time of f i l l i n g the box with s o i l , Bouyoucos moisture blocks were set i n the s o i l i n three v e r t i c a l rows at 70, 50, 25, and 10 cms. below the top surface. Two transplanted b ig bunches (A & B) of A. spicatum were planted on top of two of the v e r t i c a l rows of moisture blocks as shown in Figure 15, leaving the middle row of blocks (C) under bare ground to act as a contr o l . A period of one month was allowed to pass before t e s t i n g started i n order to allow the bunches to get established. In the meantime a mist spraying system was constructed (Fig. 15), and i t s height adjusted so that the applicators discharged water i n a f a i r l y uniform d i s t r i b u t i o n over the required area. The uniformity of the sprayed moisture at the canopy l e v e l was tested by replacing the test plant box with cans and measuring the amount of water col l e c t e d after a given time. A mist spray system was used i n order to prevent run off and reduce the tendency of over-saturating the s o i l along the walls of the box. T e s t i n g w i t h the a c t u a l p l a n t s s t a r t e d a month a f t e r t r a n s p l a n t i n g and continued f o r three and one h a l f months. Water was a p p l i e d f o r one hour each time and the moisture st a t u s of the s o i l was always measured before watering and one hour a f t e r watering. Since very small l a t e r a l movement of water normally does occur i n the s o i l , i t was assumed that the moisture d i f f e r e n c e s recorded i n each row of b l o c k s was mainly due to the downward pene-t r a t i o n of water a p p l i e d at the top of the row. A f t e r t e s t i n g four times i n 8 weeks w i t h both bunches of A. spicatum u n d i p p e d , bunch B was c l i p p e d to ground l e v e l ( P i g . 14-) and t e s t i n g continued f o r a f u r t h e r 6 weeks p e r i o d , r ii 11 F i g . I/)- The experiment f o r moisture p e n e t r a t i o n beneath bunches of Agropyron spicatum. Bunch B c l i p p e d . 67 Figure l6 (I) represents the mean of the 4 determinations of the lev e l s at which moisture was sensed, before.bunch B was clipped. Figure l6 (II) shows the same re s u l t s after bunch B had been clipped. Bunch B was r e l a -t i v e l y smaller than bunch A. The r e s u l t s demonstrate c l e a r l y the degree to which the canopy of the bunch o'f A. spicatum influences the s o i l moisture d i s t r i b u t i o n patterns. S o i l organic matter. The r e s u l t s shown In Table XIV and Figure 17 indicate that the organic matter l e v e l s were higher i n the s o i l s of the depleted areas at least i n the top 25 cm. at Tranquille, and Quilchena s i t e s . At the l a t t e r s i t e there was a reverse i n the lower horizons (Fig. 17).. On Hamilton Commonage the less grazed side had higher percentages of organic matter than the depleted side while at Minnie Lakes there were no marked differences between the l i g h t l y and the heavily grazed sides. 68 69 TABLE XIV SOIL ORGANIC MATTER PERCENTAGE AT VARIOUS DEPTHS ON BOTH SIDES OP THE FENCE Depth Site Organic Matter Grassland CM. L H Zone Tranquille 2.65 3.33 Lower 0-2 Quilchena 4.39 6.36 Middle Minnie Lakes 5.85 4.18 Middle Hamilton Commonage 18.67 12.57 Upper Tranquille 1.5 2.34 Lower 5 Quilchena 3.3 3.28 Middle Minnie Lakes 3.06 3.77 Middle Hamilton Commonage IO.85 9.93 Upper Tranquille 1.15 1.56 Lower 10 Quilchena 2 .64 2.9 Middle Minnie Lakes 2.55 2.73 Middle Hamilton Commonage 9.71 8.17 Upper Tranquille 1.1 1.3 Lower 25 Quilchena 2.12 2 .64 Middle Minnie Lakes 1.00 1.07 Middle Hamilton Commonage 6.99 5.9 Upper Tranquille 1.8 1.26 Lower 50 Quilchena 0.91 1.13 Middle Minnie Lakes 0.413 O.49 Middle Hamilton Commonage 1.97 1 .64 Upper Tranquille 0.38 0 .24 Lower Quilchena 0.09 O.65 Middle Minnie Lakes 0.11 0.10 Middle Hamilton Commonage 0.42 0.92 Upper ° 1 o 0 ° l i g h t l y grazed heavily grazed 70 l i g h t l y grazed heavily grazed U HAMILTON COMMONAGE MINNIE LAKES Z < o o \ -I C M Fig-. 17. S o i l organic matter percentage at'various depths and si t e s for both sides of t h e fence. 71 F i g . l 8 . A g r o p y r o n s p i c a t u m bunches w i t h the canopy s p r e a d out a f t e r m i s t spraying w i t h water f o r an hour. V. DISCUSSION Vegetation Structure The basic assumption made in this study was that i f a l l factors but grazing pressures influencing vegetation were the same on both sides of the fenceline, then any differences i n species and growth habits of plants and s o i l conditions must be a r e s u l t of the grazing influence. The remarkable differences i n the species composition, frequency, herbage, cover and dry matter y i e l d of the plant species between the l i g h t and heavily grazed sides confirm the obvious differences i n the plant communities which the fenceline separates. The r e s u l t s emphasize that heavy grazing removes the t a l l caespitose species of the climax grassland such as Agropyron spicatum and Festuca scabrella and encourages th e i r replacement by unpalatable shrubs, grasses with shorter l i v e s and small stature or grasses with strong vegetative reproductive organs (Larson et a l . 1942, Cottom et a l . 194-5, E l l i s o n i960, Peterson 1962, Schmutz 1967, Pieper 1 9 6 8 ) . At the Tranquille s i t e , i n the lower grassland zone, Agropyron spicatum i s being replaced under heavy grazing, by an unpalatable shrub, Artemisia trident at .a and Bromus tectorum, an annual grass. The percentage compo-s i t i o n of A. spicatum was 6.3$ on the depleted side as compared to 65.5$ on the l i g h t l y grazed side. The compo-s i t i o n of A. t r i d e n t at.a at the same s i t e was 76.7% on the depleted side and 19.3$ on the l i g h t l y grazed s i t e . Similar r e s u l t s were obtained at Quilchena, a Middle grass-land site.which i s on the grazing land of the Guichon Cattle Co. At t h i s site. Chrysothamnus. sp., a shrub, and Bromus tectorum are the major increasers. When inte r p r e t i n g the re s u l t s obtained on Hamilton Commonage, a s i t e i n the Upper grassland zone on the Douglas Lake Cattle Co. range, i t i s important to remember that increasing a l t i t u d e and moisture and lower temperatures might have some, influence on the vegetation i n th i s zone (Tisdale 19^7, Starr 19^7). However, i n spite of good growing conditions, the two c h a r a c t e r i s t i c climax species A..spicatum and P. sca b r e l l a are reduced to 0.1$ each on the depleted side. S t i p a columbiana, a perennial grass with short t i l l e r s (Fig. 11 and Table VIII) and Poa pratensis, a rhizomatous perennial grass, seemed to be increasing almost unchecked. Results at this s i t e confirm, among others, two general b e l i e f s : (1) that persistence under heavy grazing i s favored by short stature and sod forming habits (Petterson 1962, Dix 1959); and (2 ) that most of the weedy or invading species which succeed i n 74-entering natural grasslands and other undisturbed communi-t i e s tend to do so by means of their vigorous vegetative reproductions (Baker 1964). Poa pratensis which has increased almost with the same vigor on both sides of the fenceline i s an i l l u s t r a t i o n of the point. It is not very c e r t a i n why Lupinus sericeus had a lower composition percentage on the depleted side than on the less grazed side of the fence at thi s s i t e . Although poisonous mostly, to sheep, Lupinus sericeus i s not regarded as a poisonous plant to c a t t l e . I t is said to be moderately palatable. So i t i s possible that spring and summer grazing on the heavily used side eliminated some of the lupines. Such an influence would not ex i s t on the l i g h t l y grazed side where grazing takes place i n the f a l l and winter when the a e r i a l shoots of lupine are dry. In addition trampling i s l i k e l y to be more e f f e c t i v e on the plant in spring than i n the f a l l . The very low dry matter herbage yields of grasses on the depleted side at a l l s i t e s emphasize that whereas short grasses and annuals may sometimes have the same or a greater ground cover than the caespitose species, their y i e l d of herbage i s generally!-very low. A. spicatum was the best herbage producer at a l l s i t e s on the l i g h t l y grazed sides. There i s no doubt th at a better knowledge of the rela t i o n s h i p of A. spicatum to Its- micro-environment w i l l 75 not only lead to i t s better u t i l i z a t i o n as a forage plant but w i l l also help to r e - e s t a b l i s h i t over i t s primeval range. Growth Habits Measurements of t i l l e r heights and leaf length of Agropyron spicatum indicated that there i s a decline i n the vigor of this species following overuse. T i l l e r heights and leaf blade length were the best indicators of plant vigor. A similar conclusion had been made by Hazell (1967) after studying grass vigor i n two p r a i r i e pastures i n Oklahoma. Also the F/S ( F e r t i l e / S t e r i l e ) . s h o o t r a t i o s revealed that increased grazing of the species tended to favor a high production of flowering shoots instead of l e a f y t i l l e r s . Whereas seed setting insures the s u r v i v a l of the species as a group, i t has some disadvantageous consequences on the i n d i v i d u a l adult plant. A number of workers have demonstrated that i n several grass species, f l o r a l i n i t i a t i o n i s associated with a reduction i n t i l l e r -ing '(Lange 1956, Sanneveld 1958, Booysen e_t a l . Laude et a l . 1968). If such behavior exists i n A. spicatum then one can speculate that i n the f i n a l analysis, removal of the vegetative shoot by grazing and'depression of t i l l e r i n g by f l o r a l i n i t i a t i o n haVe e s s e n t i a l l y the same e f f e c t on the plant, that i s , reduction of photosynthetic material and accelerating decline i n vigor. Under continuous grazing both factors can act on the plant simultaneously. By mid-June the few flowering culms on the bunches of A. spicatum are up to 6 0 c m . : t a l l . In addition, the primordia of the vegetative t i l l e r s (which make up the biggest part of the canopy of the bunch)(Fig. 6) are well over 2 0 cm. above the ground. This means that any grazing which takes place any time from late spring onwards removes both the flowering shoots and the a p i c a l primordia of the vegetative t i l l e r s which bear most of the photosynthetic parts. Removal of the apical primordium of a grass, t i l l e r generally implies that no further apical leaf production w i l l take place on the t i l l e r concerned. In Stipa  columbiana, with the exception of the flowering culms which generally grow r a p i d l y to flowering, the rest of the shoots are v e g e t a t i v e , t i l l e r s and do not grow t a l l e r than 5 cm. above the ground (Fig. 1 1 ) . The flowering culms are less palatable due to the presence of sharp awns and ca l l u s on the caryopses. The vegetative shoots, i n which leaves p e r s i s t throughout summer, are too short to be greatly affected-by grazing. Their primorida remain at ground l e v e l throughout the growing season.. Thus when compared, S. columbiana appears to have a better chance of avoiding severe grazing influence than A. spicatum. Branson (1953) and Booysen et a l . (19^3) postulated that grasses i n which the growing points reach e a r l i e s t a height that permits their removal by grazing decrease under heavy grazing, while grasses whose growing points remain at the ground l e v e l usually increase. This, might be one of the reasons for the increase of Stipa columbiana under f a i r l y heavy grazing. Although removal of the a p i c a l primorida con- . tributes greatly towards the decline of some grass species under grazing, other factors connected with grazing are also important. The time of flowering does not appear.to be affected by grazing pressure, on plants of the same species. A l l observed species flowered at the same time and when variations occurred they had no r e l a t i o n with grazing. There were marked species differences as regards to the time of boot emergence, anthesis and seed ripening. A. spicatum came into the boot stage at the same time as i n Poa secunda and B. tectorum but anthesis did not occur u n t i l a month l a t e r . There was a space of two months from boot emergence to seed dissemination. This means that the reproductive organs are exposed to grazing removal for two months. Although grazing, seemed to "improve" the seed, productivity of A. spicatum as the F/S r a t i o indicates 78 and Albertsdn et a l . (1953) had stated e a r l i e r , the small bunches on the depleted side and the species' u n r e l i a b i l i t y i n s etting f e r t i l e seeds (U.S.D.A. Forest Service 1966) make new plant establishment uncertain. The observations made both i n the f i e l d and i n the greenhouse agreed with the report made by Marchand and McLean (1965) that some v a r i e t i e s of A. spicatum possess some vivip a r y tendencies. There are doubts whether these b u l b i l - l i k e structures can serve as functional :propagules. However, from t h e i r structure (Fig. 8), they resemble the apomictic propagules described by Marchand e_t a l . (1965) as vegetative p r o l i f e r a t i o n s and by Nygren (1967) i n the Encyclopedia of Plant Physiology, as viviparous structures. There i s considerable v a r i a t i o n i n the l i t e r a t u r e concerning the usage of the term "vivipary" and "vegetative p r o l i f e r -ation". In t h i s thesis the term vivipary has been used following Nygren (1967). Nygren defined vivipary as the production of vegetative propagules a r i s i n g instead o f , o r i n addition to, flowers. He adopted the c l a s s i f i c a t i o n out-l i n e d by Braun (1857) i n which viviparous plants were put into three categories, namely: 1. Those plants i n which b u l b i l accessory formations i n the f l o r a l a x i l s or f l o r a l branches, prevent f r u i t and seed development, e.g. Agave sp. 79 2. Plants i n which b u l b i l s are formed instead of flowers, e.g. Polygonum viviparum. 3. Plants where the inflorescences or parts thereof are transformed into vegetative shoots, e.g. Poa alpina. It i s i n this group where most of the viviparous grasses occur and generally the new shoot develops from the lemma of the f l o r e t . Morphologically, the structures observed i n A. spicatum resemble those described i n category (3) above (Fig. 18) . However, i t should be emphasized that this apparent viviparous tendency i s not widespread in a l l strains of A. sp ic atum and even where i t occurs, normal flowering continues to take place. In a number of cases both modified " f l o r e t s " and normal f l o r e t s occurred i n the same inflorescence. I t is the opinion of the author that whereas the structures observed i n A. spicatum may not be able to give r i s e to functional vegetative propagules, their presence i s reason enough to suggest that some v a r i e t i e s o f A. spicatum are non-obligate viviparous grasses. No attempt was made to i d e n t i f y the v a r i e t i e s which exhibit this phenomenon. Observations made on the greenhouse specimens indicated a high percentage of inflorescence whose f l o r e t s 8o turned into b u l b i l s (Fig. 8 , a). I t i s suspected that the r e l a t i v e l y high temperature and extra illumination to which the plants were subjected during winter might have increased the viviparous tendency (Youngner i 9 6 0 ) , Nygren et a l . (1962) demonstrated that varying l i g h t and tempera-ture conditions control vivipary i n normally viviparous grasses. I f i t could be proved that some strains of A. spicatum are viviparous then one would possibly suspect that some of the v a r i e t i e s are polyploids. However, vivi p a r y does not necessarily prove polyploidy since there are known examples of d i p l o i d grasses which are viviparous e.g. Poa alpina (2n * 14) (Skalinska 1 9 5 2 ) . The r e s u l t s on the seed dispersal mechanism i n Stip a columbiana suggest that the success of this species i n the heavily used conditions might also be rel a t e d to i t s a b i l i t y to set numerous seeds capable of burying themselves. Such a mechanism may be favored by open conditions where t h e ground i s accessible to the seed and where diurnal variations i n humidity and temperature are big enough to f a c i l i t a t e twisting and untwisting of the awn. The crowded and possibly humid ground on the less grazed side might be some of the reasons why S_. columbiana is poorly represented on that side. 81 There were very few, i f any, Bromus tectorum plants on the "ungrazed" side at Tranquille and Quilchena s i t e s . There were dense clumps of t h i s species on the heavily grazed side, extending r i g h t up to the fence (Fig. 10) but barely crossed i t . Various reasons have been given i n l i t e r a t u r e to explain t h i s phenomenon and i t i s possible that there are some other explanations undiscovered. Referring to weedy plants In.general, Baker (1964) stated that although "weeds" are pre-adapted to. a wide variety of "disturbed" s i t u a t i o n s , they are generally unable to enter natural vegetations with -intense competition. Harris (1967) found that Bromus tectorum seedlings were, in h i b i t e d more by i n t r a - s p e c i f i c competition than by i n t e r - s p e c i f i c competit-ion with Agropyron spicatum seedlings. He explained that the roots of B. tectorum seedlings grew faster than those of A. spicatum seedlings, and continued to grow even i n winter. This enabled B. tectorum to r e s i s t more the., shortage of moisture i n spring and early summer. .However, i f the young Agropyron spicatum survive the hazards i n the seedling stage they become more tolerant to droughts and competition. Their roots are thicker and. grow extensively wider and deeper than those of Bromus tectorum which is an annual. Thus i t may be that the seedlings of B. tectorum get established on the bare ground patches i n the stand of 82 A. spicatum (Table XI), but never grow to maturity. Harris (1967) is of the opinion that mature Agropyron spicatum plants may compete with Bromus tectorum for other factors in addition to moisture. He suspects-that reduced amounts of available n i t r a t e s might be one of the other unknown fac t o r s . Results reported i n this thesis on the a b i l i t y of the canopy of A. spicatum to intercept and re d i s t r i b u t e r a i n f a l l , seem to have a bearing on the c a p a b i l i t y of mature A. spicatum plants to exercise control over B... tectorum. Harris (1967) pointed out that B. tectorum tends to be a weak competitor i n places where there is summer p r e c i p i t a t i o n . If t h i s i s true then one can speculate t h a t , i t may be that the extensive roots of mature A. spicatum (Coupland e_t a l . 1965) u t i l i z e s a l l the spring moisture i n top s o i l s early in spring and then i f there are any recharges i n form of r a i n most of the received moisture is concentrated d i r e c t l y under the bunches. This w i l l keep patches of hare ground too dry for B. tectorum to colonize and at the same time maintain the supremacy of A. spicatum. In the stand. However, when the canopy of A. spicatum i s removed by grazing the unequal d i s t r i b u t i o n moisture i s removed and B. tectorum and other invaders get a chance to enter the stand A. spicatum. I t is of interest to note that generally in 83 natural grasslands, caespitose species tend to dominate the dry habitats. This tendency i s not only conspicuous in A. spicatum (Passey 1963) i n which caespitose v a r i e t i e s dominate the dry sit e s but also i n other, .species including some t r o p i c a l grasses such as Sporobolus pyramidalis, Cymbopo/gon afronardus and Cftnchrus c i l i a r i s . I t i s hard to generalize i n a case such as this but i t may be caespi-tose species have some adaptive features, some of which remain undiscovered, which makes them s p e c i a l l y adapted for dry habitats. One of these features may be-the a b i l i t y of the canopy to intercept the incoming r a i n . Edaphic Features The s o i l moisture r e s u l t s obtained from Tranquille showed r e l a t i v e l y higher moisture lev e l s i n the s o i l s on the heavily used side. There are a number of reasons which can be suggested to explain the phenomenon: F i r s t , i t i s important to point out that determinations were started at the beginning of July when most of the annuals on the depleted side were just completing their growth. Secondly, the b i g bunches of A. spicatum with extensive root systems on the l i g h t l y grazed side absorb and transpire more water than the small shallow-rooted annuals on the depleted side. Thirdly, the annuals and small perennials such as Poa secunda on the depleted side spend the main part of their growth early when evapo transpiration rates are r e l a t i v e l y . low. By contrast rapid growth and production of Agropyron  spicatum occurs during the heat of summer when evapo-tra n s p i r a t i o n rates are highest. F i n a l l y b i g bunches of A. spicatum on the l i g h t l y grazed side "concentrate" the water received i n summer under their crowns. Such a behaviour does not only confine the received water i n the zone where tran s p i r a t i o n losses are greatest, but i t also makes some conventional means'of moisture determination less meaningful since measurements are taken on the bare ground patches between the bunches. Such a r e d i s t r i b u t i o n of -the incoming moisture i s not l i k e l y to be pronounced on the "depleted side where there are no b i g bunches of A. spicatum. So a l l these reasons seem to favor higher moisture i n the s o i l on the depleted side than on the less grazed side. Basing their explanations on the observation made by Clark (1937), Daubenmire e_t a l . (19^2) suggested that since herbaceous plants intercept over 50$ of the r a i n f a l l and allow that intercepted water to evaporate back in the ai r (Clark 1937) then this might be one of the reasons why there was less moisture i n the s o i l s of the ungrazed side than the grazed. However, Grah and Wilson (1944) defined three forms of Interception: 85 1. "Transitory storage",, the water that w i l l drain from a plant under s t i l l a i r condition. 2. "Conditional storage", the additional water that can be removed by wind or by f o r c e f u l shaking. 3. "Residual storage", or the water that can be removed only by evaporation. The t r a n s i t o r y storage component of the intercepted r a i n -f a l l either f a l l s d i r e c t l y to the ground from the fol i a g e or runs along the leaves and stems to the ground. I t i s suspected that r a i n f a l l interception by grasslands and crops may be even higher than that of the forests (Specht 1957). In the l i g h t of the above c l a s s i f i c a t i o n and from the r e s u l t s reported i n this thesis together with the observations made by Glover and Gwynne (1962) and Gwynne (1966), i t i s clear that the f r a c t i o n of water l o s t into the a i r after interception may not be large. In the case of caespitose grasses, most of the intercepted water is "funneled" down into the crown of the bunch by the a e r i a l shoots and then "channeled" down Into the rooting zone by 86 the plants. The percolation of the intercepted water into the s o i l under the bunch i s accelerated by the high i n f i l -t r a t i o n capacity of the s o i l i n this zone created by the eff e c t s of roots on the s o i l (Baver 1956). When wet, the canopy of A. spicatum spreads out (Fig. 18). This does not only increase'the water intercepting capacity of the canopy but i t also increases the area of ground sheltered from the incoming moisture. The fac t that transplanted bunches were used i n the greenhouse experiment, makes the explanation that the differences i n water penetration i n the A. spicatum mature stand is mainly due to root influence completely u n l i k e l y . The roots of the bunches^ used had no chance to penetrate beyond 25 cm. when the testing started. Assuming that the res u l t s reported are true and that A. spicatum uses i t s canopy to monopolize the incoming moisture then i t would be possible to answer some of the questions connected with the loss of vigor of thi s species under grazing. One can speculate that the removal of the canopy of A. spicatum takes the species from i t s place where i t can out-compete i t s annual invaders. Secondly, since the plant i s a deeply-rooted species (Daubenmire _et a l . 1942, Coupland et a l . 1965, Harris 1967) the only way i t can di r e c t enough water into i t s rooting zone is by means of I t s canopy. I f the canopy Is removed the deep 87 roots stop getting the moisture they need thus reducing the a b i l i t y to regrow e s p e c i a l l y during summer. Thirdly, removal of the canopy allows the moisture to be distributed evenly which encourages the growth of shallow-rooted colonizers which i n turn out-compete the already weakened A. spicatum. S o i l temperature results indicate that the s o i l s on the heavily grazed side are warmer i n summer and colder in winter. A difference of up to 3°C. in summer were recorded at le v e l s of 2 5 , and 50 cm. at Tranquille and at Hamilton Commonage. Differences could be detected even a t 100 cm. below the s o i l surface at Hamilton Commonage. I t i s most l i k e l y the dense forage cover on the l i g h t l y grazed side' sheltered the s o i l from the extreme summer heat and the winter coldness. The s o i l organic matter determinations indicated that there were higher l e v e l s of organic matter in the s o i l s on the l i g h t l y grazed sides. At Hamilton Commonage the reverse occurred and at Minnie Lakes there was no marked difference between 'the values obtained on the two sides. The higher values on the depleted side are d i f f i -c u l t to explain since most reports in the l i t e r a t u r e have reported high s o i l organic matter levels on the ungraded BB side (Bharu'cha et a l . 1958, Sant 1966, Schuster e_t a l . 1969). However, i t appears possible that the annuals and shrubs found i n high concentrations on the grazed side at Tranquille and Quilchena contributed towards the unusually high levels' of organic matter. At Hamilton Commonage, where the invading species on the depleted side are peren-n i a l s , l e v e l s of organic matter were higher on the l i g h t l y grazed side. At Minnie Lakes where there were no species differences, on both sides the leve l s of s o i l organic matter were more pr less the same on both sides. It is therefore possible that the annuals with short l i f e cycles and the shrubs which shed plenty of dead leaves help to raise the le v e l s of the organic matter in the top s o i l on the depleted side of the fenceline. Also trampling by the grazing animals i s l i k e l y to break and bury the a e r i a l parts of the annuals on the depleted side. Daubenmire e_t a l . (1942) made similar observations i n the Agropyron-Foa p r a i r i e of south-eastern Washington. It would be a b i t presumptuous to draw very firm conclusions using one year's observations. Nevertheless, some of the r e s u l t s reported i n this thesis appear to shed l i g h t on more int e r e s t i n g points which future investigations may develop. Besides reaffirming the well documented ef f e c t s of overgrazing on plants and s o i l ( E l l i s o n 196)0) , 89 a few new o b s e r v a t i o n s have been made. One p o i n t which has tended t o s t a n d out above o t h e r s i s t h a t over-use does not o n l y d e p r i v e Agropyron s p i c a t u m o f i t s p h o t o s y n t h e t i c and r e p r o d u c t i v e organs b u t i t a l s o m o d i f i e s the m i c r o -environment i n such a way t h a t i t i n t e r f e r e s w i t h some of the a d a p t i v e f e a t u r e s w h i c h enable the s p e c i e s t o h o l d i t s own i n i t s d r y n a t u r a l , h a b i t a t . One o u t s t a n d i n g example of such a d a p t i v e f e a t u r e s i s the a b i l i t y of a e r i a l p a r t s t o i n t e r c e p t l i g h t summer r a i n s . The " c o l l e c t e d " m o i s t u r e i s d i r e c t e d i n t o zones where i t i s b e s t used by the p l a n t w i t h deep r o o t s and where such m o i s t u r e i s l e a s t a v a i l a b l e t o o a n n u a l i n v a d e r s and e v a p o r a t i o n . I n d i r e c t l y , the s t u d y has t r i e d t o demonstrate t h a t a p a s s i v e o b j e c t such as a fen c e can h e l p t o create, a new s e t o f e n v i r o n m e n t a l f a c t o r s which can e f f e c t p r o f o u n d changes i n the v e g e t a t i o n . I t needs no f u r t h e r . p r o o f t o i l l u s t r a t e t h a t a r t i f i c i a l " e cotones" a s s o c i a t e d w i t h the f e n c e l i n e o f f e r u n p a r a l l e l e d o p p o r t u n i t y f o r s t u d y i n g the response o f i n d i v i d u a l range s p e c i e s t o g r a z i n g . S u g g e s t i o n s f o r f u r t h e r work are many and o b v i o u s . But the most i m p o r t a n t ones a r e : t h a t the p r e s e n t s t u d y of t h i s B.C. I n t e r i o r g r a s s l a n d t r a n s e c t be c o n t i n u e d , and t h a t i n c o n n e c t i o n w i t h t h i s , i t would be of g r e a t impor-tance t o the r e s u l t s r e p o r t e d i n t h i s account and to f u t u r e 90 investigation to f i n d out as much as possible about the hist o r y of the grazing patterns i n the area of study. The author f e e l s strongly that lack of documented h i s t o r i c a l background .of the area of study, i s a weakness i n this type of study. Also- i t would be of interest to conduct p i l o t investigations on the water interception behavior of A. spicatum i n order to determine the least amount of '. canopy necessary, to maintain the moisture balance of the rooting zone. Further studies on the "viviparous" tenden-cies of A. spicatum. w i l l not only help to point out when during the f l o r a l Induction phase temperature and-lightly promote vivip a r y but w i l l also c l a r i f y when normal f l o r a l induction and i n i t i a t i o n take place and what environmental factors are. necessary. There i s no doubt such information w i l l throw more l i g h t on the p o s s i b i l i t y of improving t h e natural and a r t i f i c i a l reseeding potentials of t h e species on the range. SUMMARY 1. The f i r s t phase of the ecological study of plant communities separated by.fencelines was conducted on four grassland s i t e s i n the Southern Interior of B r i t i s h . Columbia from, spring 1968 to spring 1969. At'each s i t e plant growth habits, climatic factors and some s o i l features on both sides of the fence were compared. 2. " At each of the four study si t e s a permanently . fenced exclosure was b u i l t and instrumentation for measuring r a i n f a l l , s o i l moisture and temperature!were i n s t a l l e d . 3. The apparent differences in the plant communi-ties; separated by the fencelihes were quantitatively investigated.- Although generally the "major" species occurred on both sides of the fence, there were marked differences i n herbage y i e l d , composition,frequency and vegetation cover between the opposite communities. 4. The vigor of Agropyron spicatum and Stipa columbiana was determined by measuring t i l l e r "height" and leaf blade length. There was a loss of vigor i n A. spicatum growing on the heavily grazed side. No marked change in the vigor of Stipa columbiana was recorded. T i l l e r "height" measurements were the best indicator of vigor in caespitose species. 92 5. Phenological observations were recorded through-out the growing season. Variations i n the time of flowering i n a given species seemed not to be d i r e c t l y related to grazing pressure. 6. In Agropyron spicatum flowering shoots seemed to grow faster than t i l l e r s . They got into the boot stage early i n summer but anthesis was not recorded u n t i l a month l a t e r . Seeds ripened approximately two months after the boot stage. The amount of f e r t i l e seeds produced i n this species on both, sides of the fence was very low at a l l s i t e s except Minnie Lakes. J.. There were indications that " f a i r l y " heavy grazing tended to increase the r a t i o of f e r t i l e to s t e r i l e shoots on.the bunches of Agropyron spicatum. 8. "Vivipary" or vegetative p r o l i f e r a t i o n was observed on Agropyron spicatum. The magnitude of p r o l i f e r -ation increased when plants were subject to high temperature and supplement l i g h t i n g in the greenhouse i n winter. No s p e c i f i c measurements were made on l i g h t levels and temperature va r i a t i o n s . 9. I t was noted that caryopses of Stipa columb-iana are " d r i l l e d " into the ground by the humidity controlled. twisting and untwisting of the twice geniculate awns. Bromus tectorum had two types of dispersed units. The topmost f e r t i l e f l o r e t was dispersed attached to a cluster of i n f e r t i l e f l o r e t s and the lower f l o r e t s were dispersed i n d i v i d u a l l y . The topmost f l o r e t s are e a s i l y carried by wind. 10. Although Bromus tectorum seeds can penetrate to over 5 meters into the established stand of Agropyron spicatum from the heavily used side, there were very few mature Bromus tectorum plants on the l i g h t l y grazed side. I t i s possible A. spicatum exerts competition pressure on the seedlings of B. tectorum.. 1 1 . The a e r i a l parts of Agropyron spicatum were shown to intercept water and di r e c t i t under the crown of the plant. Clipping the a e r i a l parts to ground l e v e l prevented the plant from c o l l e c t i n g extra water and the depth of moisture penetration under the clipped bunch was the same as that of the bare ground control. Concentratin the l i g h t rains within the rooting zone of the plant con-cerned, seems to be an important adaptive feature of deep-rooted caespitose species growing i n dry places. 12. Higher s o i l moisture was recorded in the s o i l on the heavily grazed side than on the l i g h t l y grazed side This was attributed to: (i) a high composition of perennial grasses on the. l i g h t l y grazed side which continue growing during summer and exhaust the s o i l moisture. Annuals on the heavily grazed side complete their growth early in the year when evapotranspiration losses of moisture are r e l a t i v e l y low; ( i i ) the extensive root systems- of caespitose species which extract more moisture from the s o i l than the shallow root systems of annuals; ( i i i ) the a e r i a l parts of caespitose species which confine the incident moisture within their rooting zone, where i t . i s most l i k e l y to be l o s t through transpiration and less l i k e l y to be detected by some conventional means of moisture measurement. 13. S o i l s on the heavily grazed side were warm o in summer and colder i n winter than those.on the l i g h t l y grazed side. Dense vegetation on the l i g h t l y grazed c i d might be responsible for the modification of s o i l temper ture . . • 95 . 1 4 . Determinations of s o i l organic matter, indicated higher organic matter leve l s i n the top 2 5 cm. of the s o i l under heavy grazing than that under l i g h t grazing. The sho r t - l i v e d shallow-rooted annuals together with shrubs which shed dead leaves every year might be responsible for the high organic matter leve l s i n the top s o i l s on the heavily grazed side. 1 5 . I t is.suspected that the "supremacy" of the caespitose v a r i e t i e s of Agropyron spicatum.in dry places with l i g h t summer rains i s f a c i l i t a t e d by i t s canopy and deep roots. Removal of the canopy either by c l i p p i n g or heavy grazing makes the plant unable to di r e c t the moisture into i t s deep rooting zone. In addition removal of the canopy of a caespitose species withdraws the uneven moisture d i s t r i b u t i o n on the s o i l surface thus encouraging the growth of the shallow-rooted annual invaders. BIBLIOGRAPHY Albertson, P.W. Reigel, A, and L. 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