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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), U n i v e r s i t y 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 t h i s t h e s i s as conforming to the r e q u i r e d  standard  THE UNIVERSITY OF BRITISH COLUMBIA May, 1969  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of  the  requirements f o r an advanced degree at the U n i v e r s i t y  of  B r i t i s h Columbia, I agree that the  L i b r a r y s h a l l make i t  f r e e l y available for reference  study.  and  I further  agree  that p e r m i s s i o n f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may  be  granted by  the  Department or by h i s r e p r e s e n t a t i v e s .  Head of  my  I t i s understood  copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be  Department of  allowed without my w r i t t e n  P/.fl<vh  <ci  The U n i v e r s i t y of B r i t i s h Vancouver 8 , Canada. Date  ^  H uy PJ  lU?  £rrtc£  Columbia  permission.  that  ABSTRACT An e c o l o g i c a l study o f g r a s s l a n d communities  sepa-  r a t e d by f e n c e l i n e s i n the Southern I n t e r i o r of B r i t i s h Columbia was conducted from s p r i n g 1968 to s p r i n g 1969. Measurements to compare p l a n t s p e c i e s composition, herbage y i e l d , growth h a b i t s and edaphic f e a t u r e s on both s i d e s of the  fences were taken i n the f i e l d .  was determined  S o i l o r g a n i c matter  i n the l a b o r a t o r y and moisture p e n e t r a t i o n  p a t t e r n s were demonstrated  i n the greenhouse.  Heavy g r a z i n g r e s u l t e d  i n the removal of the  p r i n c i p a l climax c a e s p i t o s e s p e c i e s and t h e i r by.shrubs, annuals and rhizomatous g r a s s e s . r e d u c t i o n s i n the composition, herbage the  replacement There were  y i e l d and v i g o r of  c a e s p i t o s e s p e c i e s at a l l s i t e s f o l l o w i n g heavy g r a z i n g .  The success o f the i n c r e a s e r s under heavy g r a z i n g seemed to be f a v o r e d by p o s s e s s i o n o f rhizomes, presence of unpalatable f l o w e r i n g culms and i n f l o r e s c e n c e s , shortness o f tillers  and an e l a b o r a t e means of seed d i s p e r s a l .  The  v e g e t a t i o n a l changes i n t r o d u c e d by g r a z i n g on the h e a v i l y grazed s i d e , r e s u l t e d i n a high l e v e l of o r g a n i c matter i n the  top 25 cm. of s o i l , a h i g h s o i l moisture content and  h i g h summer and low w i n t e r s o i l temperatures.  The dense  v e g e t a t i o n on the l i g h t l y grazed side m o d i f i e d both and w i n t e r s o i l  temperatures.  summer  A technique  was developed to determine the a b i l i t y  of c a e s p i t o s e 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 t h a t a e r i a l p a r t s of Agropyron spicatum collect  l i g h t r a i n s and concentrate  zone of the p l a n t . of the adaptive  This phenomenon  grasses  i s l i k e l y to be one  f e a t u r e s which enables  to dominate a r i d h a b i t a t s . susceptibility  them i n the r o o t i n g  caespitose  species  I t i s p o s s i b l e that the great  of Agropyron spicatum and other  caespitose  t o heavy g r a z i n g might be r e l a t e d to s o i l moisture  disturbances the p l a n t s .  i n t r o d u c e d by the removal of a e r i a l p a r t s of  TABLE OP CONTENTS Page INTRODUCTION  1  LITERATURE REVIEW  3  SECTION I.  The  P l a n t Community Under Grazing  The  I n d i v i d u a l P l a n t Under  Conditions The  Grazing  . . . . . . . . .  G r a z i n g and  . . .  7  the P l a n t - S o i l R e l a t i o n s h i p . .  8  P l a n t ' s Reproductive  P o t e n t i a l s and 10  the H a b i t a t F a c t o r s II. III.  LOCATION AND  DESCRIPTION OF THE  STUDY SITES.  Climate,  21  s o i l moisture  and  . temperature i n s t r u m e n t a t i o n Vegetation Laboratory  and  21 22  analysis. . Greenhouse Experiments. . .  25 27  RESULTS Floristics  13 21  METHODS F i e l d Experiments.  IV.  5  Time F a c t o r A s s o c i a t e d With the  Defoliation Effects  The  3  .  • -  27  Species Frequency, Canopy Cover, B a s a l Area and Dry Matter  Yield  37  SECTION . '  Page Species frequency  37  Canopy cover  39  B a s a l area  39  Dry matter  42  yield  43  Growth Habits Vigor  48  Phenology  50  Seed p r o d u c t i v i t y  58 61  Edaphic Features S o i l temperature  61  S o i l moisture  61  S o i l o r g a n i c matter V.  DISCUSSION  . . .  6j  .  72  Vegetation Structure  72  Growth Habits  75  Edaphic F e a t u r e s  ,  83  SUMMARY  91  BIBLIOGRAPHY  96  LIST OF TABLES TABLE I. II. III.  IV. V. VI. VII.  VIII.  IX.  X.  XI.  XII. XIII. XIV.  Page Number of s p e c i e s i n c a t e g o r i e s by s i t e s .  . .  7  The l i s t o f s p e c i e s found, i n the study a r e a  28  Species composition ( i n percentage) on f o u r s i t e s on the o p p o s i t e s i d e s of the f e n c e l i n e  36  The percentage frequency of the major species  38  Canopy percentage cover of the major species  40  B a s a l a r e a as percentage cover of the t o t a l s u r f a c e area sampled  4l  Average dry matter y i e l d i n Kgms. per Hectare of the grass herbage p r e s e n t at the end of the growing season  42  Average t i l l e r h e i g h t s of Agropyron spicatum and S t i p a columbiana measured i n J u l y 1968  49  Average l e a f b l a d e l e n g t h of Agropyron spicatum and S t i p a columbiana measured i n J u l y 1908  51  Some p h e n o l o g i c a l changes i n some p l a n t s p e c i e s at Hamilton Commonage (Upper g r a s s l a n d zone)  52  Percentage d i s t r i b u t i o n of the Bromus tectorum seeds away from the f e n c e l i n e on the T i g h t l y grazed side at Q u i l c h e n a s i t e . . . .  57  Average number of seed s t a l k s per square meter of the sampled a r e a  59  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 S t i p a columbiana  . . .  S o i l o r g a n i c matter percentage at v a r i o u s depths on both s i d e s of the fence  60 69  LIST OF FIGURES FIGURE 1.  Page ( a ) , (b) and (c) show the f e n c e l i n e a t Hamilton 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 grazed side and (L) l i g h t l y grazed side  20  A diagram of a grass t i l l e r i n d i c a t i n g the p a r t s measured f o r v i g o r d e t e r m i n a t i o n  23  (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 o f Agropyron spicatum bunches i n a l e a s t d i s t u r b e d c o n d i t i o n at Minnie Lakes and Q u i l c h e n a r e s p e c t i v e l t . The p i c t u r e r e p r e s e n t s two d i s s i m i l a r s o i l surface features  32  A mixed stand of Agropyron spicatum, F e s t u c a sp. and f o r b s i n the l i g h t l y grazed e x c l o s u r e at Hamilton Commonage s i t e  33  (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 e x c l o s u r e s r e s p e c t i v e l y at Tranquille s i t e . The p i c t u r e s were taken i n Summer, 1968  34  Bunches of Agropyron spicatum at Minnie Lakes s i t e on the l i g h t l y grazed side of the f e n c e . .  44  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  47  ( 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 v i v i p a r y i n Agropyron spicatum  53  9.  S p i k e l e t s 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) h e a v i l y grazed side and (L) l i g h t l y grazed side  56  2. 3.  4.  5.  6. 7. 8.  ix FIGURE 11.  12. 13.  Page  . S t i p a columpiana and A n t e n n a r i a dimorpha i n the h e a v i l y grazed e x c l o s u r e at Hamilton Commonage  57  S o i l temperature by depth and treatment from June 1968 through February 1969  62  S o i l moisture change by depth and treatment from J u l y to October 1968  14.  at T r a n q u i l l e  site.  .  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 . . . . . . . . . .  64  66  15.  A mist spray water-system f o r water p e n e t r a t i o n experiment  68  16.  Depth at which p e n e t r a t e d water was d e t e c t e d . I Bunches A and B i n t a c t . I I Bunches B clipped  68  17. S o i l o r g a n i c matter percentage at v a r i o u s '. ...depths and s i t e s f o r both s i d e s of the f e n c e . . 18.  Agropyron spicatum bunches w i t h the canopy spread out a f t e r mist s p r a y i n g w i t h water f o r an hour .  70  71  ACKNOWLEDGEMENT  Grateful Brink,  Professor  Division, study  work  and checking  Scientist,  are also  of the Plant-Science  Columbia  for  assistance  contribution  The Commonwealth  Technician,  British  i n the f i e l d  In addition,  always  suggesting  of the  due t o M r . A. M c L e a n ,  S t a t i o n Kamloops,  experimental  experiments  a v a i l a b l e whenever i s greatly  author  they  Research  o f the CD.A.  Columbia,  t h e members  f o r their  and p l a n t  o f the author's could  identicommittee  be o f help..  Their  appreciated.  i s also  Scholarship  providing  the scholarship  in  during  Canada  and Head  t o D r . V . C.  of the manuscript.  and Mr. L. Haupt,  fication. were  i s extended  and f o r h i s h e l p f u l d i r e c t i o n  Thanks  great  o f Agronomy  University of British  this  Research  acknowledgement  indebted  to the Canadian  and F e l l o w s h i p which  1967-1969-  enabled  Committee f o r the author  to  study  INTRODUCTION Ranges where f e n c e l i n e s have been e s t a b l i s h e d f o r many years o f t e n show s t r i k i n g physiognomic between the p l a n t communities which the Yet  i n many i n s t a n c e s  a few  differences  fences  separate.  the fence separates communities which  years e a r l i e r were comparatively homogeneous.  In many  cases i t i s obvious t h a t the f e n c e l i n e d i f f e r e n c e s are  to  a t t r i b u t e d to d i f f e r e n t g r a z i n g p a t t e r n s  the  fence s e p a r a t e s .  of the f i e l d s  I f some judgment i s used and  of g r a z i n g p r a c t i s e s i s known, such a r t i f i c i a l associated with fencelines o f f e r f o r studying  p l a n t communities  of the  obviously  the  three  differences  objective i n species  fencing,  Four study s i t e s were s e l e c t e d  to  zones known as the Lower,  zones.  One  of the  l o c a t e d at T r a n q u i l l e near Kamloops and  The  traverse.  by f e n c e s ) , where major d i f f e r -  grassland  l o c a t e d on the N i c o l a  communi-  a number of  been generated as a r e s u l t of  M i d d l e , and Upper g r a s s l a n d was  opportunity  as f e n c e l i n e s  s p r i n g term i n 1968  (separated  were chosen f o r study. represent  "ecotones"  an u n p a r a l l e l l e d  climatic conditions  At the end  ences had  some knowledge  response to g r a z i n g of as many p l a n t  t i e s , edaphic and  be  selected  three  sites  others w e r e  grassland. of the  study was  to assess  vigor, reproductive  comparative  potential,  life-  2 form, and growth h a b i t  of species  of the f e n c e l i n e  communi-  t i e s and the r e l a t i o n o f these to s o i l and some c l i m a t i c factors.  I t i s a n t i c i p a t e d that a study of t h i s nature  throw more l i g h t on the b a s i c  factors associated  will  with the  p l a n t - f e n c e - a n i m a l r e l a t i o n s h i p i n the range ecosystem.  I. The  LITERATURE REVIEW  P l a n t Community Under Stebbins  Grazing  (1950) emphasized that the  individual plant  i s a phenotype which i s the product of a given environment and  a p a r t i c u l a r g e n e t i c make-up.  In t h e i r experiments  on  the Western North American p l a n t s , Clause e_t a l . (1940) demonstrated t h a t phenotypes can be  a l t e r e d quite  profoundly  i n some c h a r a c t e r i s t i c s by environmental f a c t o r s . reported  that p l a s t i c i t y  i s o f t e n e x h i b i t e d by the amount of  stem e l o n g a t i o n , the number of branches, leaves the form of the pubescence.  The  They  i n d i v i d u a l p l a n t and  and  the nature of  a b i l i t y to adapt to a new  flowers, the  environmental  c o n d i t i o n i s more pronounced i n weedy p l a n t s .  Stebbins  (1964) concluded t h a t such a p l a s t i c i t y must r e s i d e i n c e r t a i n morphological  and p h y s i o l o g i c a l c h a r a c t e r i s t i c s of  the p l a n t concerned. Some workers on forage p l a n t s have o f t e n t h a t the  q u a l i t y of some herbage species  "moderate" g r a z i n g .  reported  "improve" under  Nelson (1934), C a n f i e l d (1948),  and  Hutchings e t a l . (1953) observed that p l a n t s when regarded as forage  respond as " f a v o r a b l y " under g r a z i n g as under  g r a z i n g " or as " f a v o r a b l y " under moderate as under grazing.  Vogel et a l . (1966) r e p o r t e d  "no  light  that four years  of  4 e i t h e r d e f e r r e d or moderate g r a z i n g on the f o o t h i l l  sheep  range, d i d not cause major changes i n the v e g e t a t i o n Instead  they observed some "improvements" i n the y i e l d ,  composition  and v i g o r of climax  such as Agropyron spicatum. et a l . (1967) have r e p o r t e d cover  cover.  of blue grama grass  dominant p e r e n n i a l  grasses  A l s o workers such as Schmutz i n c r e a s e s of composition  (Bouteloua  However, the g e n e r a l b e l i e f  g r a c i l i s ) under g r a z i n g . i s that grazing  s p e c i e s i n a community tends to handicap those to f a v o r the ungrazed s p e c i e s .  and  certain  s p e c i e s and  Since Clements (1920)  d e s c r i b e d t h i s e f f e c t o f g r a z i n g , numerous workers have proved t h a t g r a z i n g has adverse e f f e c t s on the v e g e t a t i o n . Larson e t a l . (1942), Johnson et a l . (1967), Pieper  (1956), E l l i s o n  (i960), P o t t e r  (1968) have, i n v a r i o u s ways, demon-  s t r a t e d some a p p r e c i a b l e g r a z i n g e f f e c t s even at l i g h t grazing i n t e n s i t i e s . t h a t the exact  composition  cannot be maintained of s p e c i e s other He suspected  This l e d E l l i s o n  (i960) to conclude  of a climax v e g e t a t i o n p o s s i b l y  by an i n t e n s i t y o f g r a z i n g or s e l e c t i o n  than those  exerted by p r i s t i n e  wildlife.  t h a t the r e p o r t s which c l a i m b e n e f i t to the  p l a n t s from g r a z i n g are f o r the most p a r t , e i t h e r t i v e , crude i n experimental cover  design,  specula-  inadequate i n method or  so s h o r t a time as to r e f l e c t o n l y the i n i t i a l  s t i m u l a t i o n i n herbage growth.  The s t i m u l a t i o n t h a t  occurs.  5  might be due to the s t o r e d food r e s e r v e s or to the c a r r y over e f f e c t s caused by other  stimuli.  He a l s o p o i n t e d out  that few s t u d i e s are made of " g r a z i n g per se". Most of them are made of " o v e r - g r a z i n g "  The  and/or complete p r o t e c t i o n .  I n d i v i d u a l P l a n t Under Grazing Petterson  Conditions  (1962) r e p o r t e d t h a t c e r t a i n changes i n  s t r u c t u r e and p h y s i o l o g i c a l responses induced by  prolonged  heavy g r a z i n g appeared to favor the p e r s i s t e n c e of S t i p a comata under such treatment. I n g e n e r a l a g r a z i n g animal removes p a r t s of a p l a n t and thereby to  synthesize  "food".  photosynthetic  reduces the p l a n t ' s p o t e n t i a l  I n grasses  a l s o i f the growing p o i n t s  of the t i l l e r s are e l e v a t e d to more than 2 cm. above t h e s o i l they may be removed by g r a z i n g and new leaves may not be produced t h e r e a f t e r by those shoots (Branson 1953? Booysen e t a l . 1963). s c a b r e l l a (Johnston the autumn. primordia  stage  species such as F e s t u c a  e t a l . I967) f l o r a l  i n i t i a t i o n occurs i n  This means that e a r l y removal of the shoot  i n the f o l l o w i n g s p r i n g may deny the p l a n t of t h e  opportunity reported  I n some grass  to produce seeds.  t h a t reduced t i l l e r i n g  of Harding grass  However, Laude e_t a l . (1968) a s s o c i a t e d with the f l o w e r i n g  ( P h a l a r i s tuberosa) can b e o f f s e t by  b y removal of e l o n g a t i n g f l o w e r i n g culms.  6 In a d d i t i o n to i n t e r f e r i n g w i t h p h o t o s y n t h e t i c reproductive  and  organs, g r a z i n g has profound e f f e c t s on r o o t s .  Numerous r e p o r t s have proved beyond doubt that d e f o l i a t i o n stops, r o o t growth (Weinmann 19^8, C u r t i s and C l a r k C r l d e r 1955,  Troughton 1957,  Jameson 1963)• Crider  Weaver 1958, E l l i s o n  Prom h i s extensive  1950, i960,  study on the s u b j e c t ,  (1953) r e p o r t e d t h a t removal, d u r i n g the growing  season, of at l e a s t h a l f of the f o l i a g e of grasses  both  c o o l and warm season s p e c i e s i n c l u d i n g bunch, rhizomatous, and  s t o l o n i f e r o u s types, caused r o o t growth to stop.  a l s o r e p o r t e d that w i t h  the e x c e p t i o n of orchard  He  grass  ( D a c t y l i s glomerata) stoppage occurred w i t h i n 2k hours of f o l i a g e removal and continued growth.  u n t i l recovery  of the top  A s i n g l e cut c o u l d cause 6 to 18 days of stoppage.  In h i s review, Jameson (1963) p o i n t e d out that  defoliation  does not only stop r o o t growth but i t a l s o reduces the a b i l i t y of the e x i s t i n g r o o t s to absorb n u t r i e n t s . emphasized t h a t continued  g r a z i n g reduces dry matter  v i g o r , seed y i e l d and the amount of carbohydrates underground p o r t i o n s of the herbage.  1962).  i n the  reports  i n d i c a t e that some s p e c i e s are a f f e c t e d more than Petterson  yield,  Although a l l p l a n t  s p e c i e s are a f f e c t e d by i n t e n s i v e d e f o l i a t i o n ,  (Schmutz e t a l . 1967,  He  others  7 The Time F a c t o r A s s o c i a t e d With the Defoliation  Effects  A number of r e p o r t s have i n d i c a t e d that some p l a n t s respond more c o n s p i c u o u s l y to d e f o l i a t i o n at  c e r t a i n times than a t o t h e r s .  r e p o r t e d that c l i p p i n g l i t t l e  effects  Vogel e t a l , ( 1 9 6 8 )  blue stem, b i g blue stem  and I n d i a n grass f o r three s u c c e s s i v e years at the s e e d - r i p e n i n g stage or l a t e r  i n c r e a s e d both y i e l d and  spring-initiated  But c l i p p i n g at any time  tillering.  d u r i n g summer and e s p e c i a l l y between f l o r a l and a n t h e s i s reduced  the y i e l d .  B l a l s e l e_t a l . ( 1 9 ^ 9 )  also.had. r e p o r t e d t h a t whereas Agropyron g e n e r a l l y reduced  initiation  spicatum was  i n v i g o r by c l i p p i n g any time of the  year, the g r e a t e s t damage was done l a t e i n May and e a r l y i n June. fall. exist  The e f f e c t was l e s s i n s p r i n g and l e a s t  i n the  S i m i l a r changes were r e p o r t e d by Jameson ( 1 9 6 3 ) to i n the carbohydrate  l e v e l s of some p l a n t s .  noted t h a t i n p e r e n n i a l p l a n t s there i s a decrease  He f u r t h e r i n carbo-  hydrate accumulation w i t h the onset of s p r i n g growth. D u r i n g the r e s t of the season carbohydrate  l e v e l s may  i n c r e a s e , then d e c l i n e at mid-season and r i s e again to a maximum i n the f a l l . to  He a t t r i b u t e d the e a r l y s p r i n g  u t i l i z a t i o n of carbohydrates  decline  i n the p r o d u c t i o n of new l e a v e s .  The mid-season d e c l i n e , when i t o c c u r s , might be a tempera-  8 t u r e o r m o i s t u r e response o r r e s u l t from i n d e c e d senescence  (Jameson 1963).  inflorescence-  I t i s t h e r e f o r e suspected  t h a t the poor r e g r o w t h a t mid-season might be due t o the low c a r b o h y d r a t e r e s e r v e s ( M c l l r o y 1967)• The r o l e o f c a r b o h y d r a t e s as f u n c t i o n a l r e s e r v e s w h i c h c a n be drawn on when p h o t o s y n t h e s i s i s reduced by d e f o l i a t i o n was q u e s t i o n e d by May e_t a l . (1958). Mcllroy  However,  (1967) c l a i m e d t h a t i t had been proved beyond doubt  t h a t the. c o n c e n t r a t i o n o f s o l u b l e c a r b o h y d r a t e s i n the herbage does i n f l u e n c e r e - g r o w t h a f t e r c u t t i n g .  I t may a l s o  be o f i n t e r e s t t o note t h a t Davidson e t a l . (1965) a r e of the o p i n i o n t h a t a l t h o u g h n o t as i m p o r t a n t as c a r b o h y d r a t e s , p r o t e i n s and m i n e r a l s a l t s such as phosphates  play a s i g n i f i -  cant r o l e i n the r e - g r o w t h p r o c e s s .  G r a z i n g 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 d e p r i v e s the s o i l o f i t s p r o t e c t i v e cover a g a i n s t the d i s p e r s i n g and e r o d i n g e f f e c t s of r a i n drops and r u n n i n g w a t e r , and some f r o s t and drought T r a m p l i n g may compact the s o i l  effects.  (Eaver 1956) and the veget-  a t i o n change which r e s u l t s from heavy g r 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 . (1952,53) demonstrated  I n a d e t a i l e d study Osborn  the e f f e c t i v e n e s s o f p l a n t cover i n  9 resisting running  thek i n e t i c  water.  e n e r g y o f r a i n drops and t h e speed o f  The r o o t s  of plants bind  the s o i l  l a n d s l i d e h a z a r d s and a l s o improve t h e s o i l p o r o s i t y and i n f i l t r a t i o n  and reduce  granulation,  capacity.  (1937) o b s e r v e d t h a t t h e a e r i a l p a r t s o f  Clark  herbaceous p l a n t s incoming r a i n  i n t e r c e p t e d more t h a n 50 p e r c e n t o f t h e  and a l l o w e d  s u c h i n t e r c e p t e d w a t e r t o be D a u b e n m i r e (1942)  evaporated d i r e c t l y back i n t o the a i r .  u s e d t h i s phenomenon t o e x p l a i n why t h e s o i l m o i s t u r e old  stand  area.  o f A g r o p y r o n was l o w e r t h a n o n a h e a v i l y  However, Grah and W i l s o n  p a r t o f the i n t e r c e p t e d , water The  as " s t e m f l o w " ,  p l a n t by wind. trees  grazed  (1944) d e m o n s t r a t e d t h a t  i s lost  through  r e s t o f the i n t e r c e p t e d water drains  either  i n an  drops from leaves  only  evaporation.  t o t h e ground o r i s shaken o f f the  Many i n v e s t i g a t i o n s have b e e n made o n f o r e s t  (Wood 1937,  G r a h e t a l . 1944, K i t t r e d g e  N i e d e h o f e_t a l . 1943) , g r a s s l a n d  e t a l . 1941,  shrubs and crop  plants  ( C l a r k 1937, 1940, Haynes 1940, R e i m a n n e t a l . 1946, S p e c h u t 1957).  Also  Gwynne  observed that corn  (1966) a n d G l o v e r a n d Gwynne a n d some o t h e r  Themeda t r i a n d r a u s e t h e i r  T h i s means t h a t  a spot s o i l  water than would f a l l  t r o p i c a l g r a s s e s s u c h as  aerial parts  savanna r a i n s and concentrate  (1962)  to c o l l e c t the l i g h t  them a r o u n d t h e p l a n t l o c a l i t y receives  on the open s u r f a c e .  base.  much more  Specht  rain  (1957),  10 emphasized t h a t i n t e r c e p t i o n of r a i n f a l l by v e g e t a t i o n i s a major f a c t o r i n any ecosystem. siderable  i n v e s t i g a t i o n of the water balance  Stem flow or f o l i a r  of  an  d r i p which can be of con-  importance i n a r i d p l a n t communities has  i n f l u e n c e on the d i s t r i b u t i o n of the incoming  a great  moisture.  Bharucha (1958), Shant (1966), and Daubenmire (1942) emphasized t h a t heavy g r a z i n g a f f e c t e d the p h y s i c a l s t r u c t u r e , minerals  and  o r g a n i c matter of the s o i l .  Bharucha found that  g r a z i n g a l t e r e d the mechanical composition decreased  the o r g a n i c matter and  had  a higher  than the  soil  and  the t o t a l exchangeable  b a s e s — e s p e c i a l l y exchangeable c a l c i u m . on the other hand, had  of the s o i l ,  Daubenmire  (1942),  r e p o r t e d t h a t the s o i l under g r a z i n g  l e v e l of moisture and organic matter under a p r o t e c t e d v e g e t a t i o n .  content  He a t t r i b u t e d  the higher o r g a n i c m a t t e r - l e v e l s i n the top s o i l s to the percentage of annual p l a n t s which grew on the range.  Since annuals have a short l i f e  matter i n the topmost h o r i z o n s  The  P l a n t ' s Reproductive  the H a b i t a t  shallow  organic  soil.  P o t e n t i a l and  Factors  Ellison to  of the  overgrazed  c y c l e and  r o o t systems t h e i r remains tend to increase the  high  (i960) commented t h a t a l l the evidence  i n d i c a t e that the r e l a t i o n between the p l a n t and  the  tends  11 g r a z i n g animal i s one  of p a r a s i t i s m by  the p l a n t r e c e i v e s no b e n e f i t . that i n g e n e r a l competition,  the animal, i n which  S a l i s b u r y (1°A2) p o i n t e d  out  the e f f e c t of adverse c o n d i t i o n s such as  u n l e s s of an extreme c h a r a c t e r ,  i s to cause a  r e d u c t i o n i n the number of seeds per p l a n t r a t h e r than to a f f e c t the  q u a l i t y of the seeds themselves.  that there was and  He  concluded  no c o r r e l a t i o n between the seed output c a p a c i t y  the degree of m o r t a l i t y r i s k s the progeny i s to be  sub-  j e c t e d t o , although a c e r t a i n minimum of seeds i s r e q u i r e d 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 c o n d i t i o n s seemed to possess the more meagre r e p r o d u c t i v e while  those s p e c i e s which had numerous niches  to occupy had it  equipment, or l a r g e  c a p a c i t y f o r a h i g h p o t e n t i a l progeny.  While  i s true seed output i s not d i r e c t l y p r o p o r t i o n a l • t o  m o r t a l i t y r i s k s , plants with  a short l i f e  area  the  span have a repro-  d u c t i v e p a t t e r n s u i t e d to the type of c o n d i t i o n s they stay in.  Stebbins  (1950) observed that there  are two c o r r e l a t i o n s  which h o l d r e g u l a r l y i n the p l a n t kingdom. between the l e v e l of compromise and the  i n d i v i d u a l organism.  organisms the g e n e t i c  The  first  i s that  the l e n g t h of l i f e  In s h o r t - l i v e d , r a p i d l y  of  reproducing  system i s u s u a l l y one which f a v o r s  f i t n e s s at the expense of f l e x i b i l i t y , while l e n g t h of l i f e r a i s e s the  s e l e c t i v e value  an.increasing  of genetic  systems  12 which f a v o r f l e x i b i l i t y  at the expense of immediate  fitness.  Secondly, i n organisms which are s t r u c t u r a l l y simple, l e v e l of compromise tends to f a v o r The  f a c t t h a t p l a n t s with  open h a b i t a t s while habitats  fitness. s m a l l seeds tend  heavy-seeded p l a n t s favor the  ( S a l i s b u r y 1942,  L a i g 1966)  nature of propagule w i t h  the  to dominate closed  seems to c o r r e l a t e the  the h a b i t a t f a c t o r s .  Baker (1964)  concluded t h a t i n u n d i s t r i b u t e d communities, the  native  p l a n t s which are o f t e n aliogamous, have a p p r o p r i a t e  breeding  systems to produce f i n e l y adaptive  extensive  recombinations.  On  ecotypes through  the other hand, weeds or c o l o n i z e r s 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 f o r establishment  after long-distance  i n b u i l d i n g up a l a r g e p o p u l a t i o n  q u i c k l y , would be  produce recombinants as r a p i d l y and upon " g e n e r a l purpose" genotypes.  d i s p e r s a l , or  them w i t h  and  give  and  edaphic s i t u a t i o n s .  He  defined  "general  a wide environmental  i t the a b i l i t y to grow i n a m u l t i t u d e o f Stebbins  to  t h e r e f o r e , depend more  purpose" genotypes as the k i n d of genotypes which the p l a n t b e a r i n g  unable  (1964) o b s e r v e d  provide tolerance climatic that i n  s p i t e of the f a c t t h a t weedy p l a n t s , mainly a n n u a l s , have b i g seeds which are not e a r l y chances f o r germination  and  dispersed,  t h e y have b e t t e r  establishment.  II.  LOCATION AND  The  DESCRIPTION OF  THE  STUDY SITES  f o u r s i t e s which form the study  area of  p r o j e c t are l o c a t e d i n the g r a s s l a n d v e g e t a t i o n of Southern C e n t r a l B r i t i s h Columbia, known as the These g r a s s l a n d s  occur  this the  Interior.  i n a r e g i o n l y i n g between the mountains  of the Columbian System on the e a s t , the Coast Range on west, the 53rd p a r a l l e l on the n o r t h and States  i n t e r n a t i o n a l boundary on the The  the  the  Canadian/United  south.  a r e a i s t o p o g r a p h i c a l l y rugged and r e p r e s e n t s  a n c i e n t p l a t e a u which has undergone enormous changes due uplifts  and e r o s i o n of the Late T e r t i a r y times ( T i s d a l e  B r i n k e_t a l . , Bostock 1948,  F u l t o n 1962,  1963) .  The  an to  ±9^-7,  area i s  c h a r a c t e r i z e d by numerous v a l l e y s , some of which have bottoms from 6l0 meters to n e a r l y 1524 surrounding The  the  country. c l i m a t e of the major grasslands  warm and dry w i t h  (15.5  is relatively  the average annual p r e c i p i t a t i o n v a r y i n g  from; s l i g h t l y l e s s than 18 em. to 44 cm.  meters below the l e v e l of  (7 i n s . ) i n the d r i e s t p a r t s  i n s . ) i n the wettest  parts.  The  climate i s  g r e a t l y c o n d i t i o n e d 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 ( T i s d a l e 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  run-off  i s not very e x t e n s i v e  storms and  except on extremely steep or denuded  14 The f r o s t - f r e e season ranges from 175 to 150 days  slopes.  i n areas where the experiments were conducted. The  g r a s s l a n d v e g e t a t i o n i n t h i s r e g i o n occupies the  l a r g e r and lower v a l l e y s and adjacent  slopes of the Okanagan,  N i c o l a , Thompson, F r a s e r and C h i l c o t i n watersheds. v e g e t a t i o n was f i r s t fied  This  d e s c r i b e d by T i s d a l e (1947) who c l a s s i -  i t i n t o the f o l l o w i n g g r a s s l a n d zones:  A r t errrisia or Lower Grassland  the Agropyron-  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  throughout most of the r e g i o n .  The l a t t e r  c l a s s i f i c a t i o n i s adapted i n t h i s The glacial t i l l  zones  altitudinal  account.  s o i l s of the r e g i o n are mainly sandy loam of origin.  main z o n a l types  G e n e r a l l y these  s o i l s c o n s i s t of three  d e s c r i b e d by T i s d a l e (1947) as Brown, Dark  Brown and B l a c k E a r t h Zones.  These Zones are a s s o c i a t e d  w i t h the three major d i v i s i o n s of the g r a s s l a n d  vegetation.  S o i l d e s c r i p t i o n s of t h i s g r a s s l a n d r e g i o n , i n c l u d i n g the study  area, have been p u b l i s h e d by F u l t o n (1962, 19^3, The  four s i t e s  i n v e s t i g a t e d i n the present  1967)•  study  were s e l e c t e d i n c o n j u n c t i o n w i t h Mr. A. McLean, Research S c i e n t i s t CD.A. Kamloops and Dr. V. C. B r i n k , Head o f the  15 P l a n t Science Department a t the U n i v e r s i t y of B r i t i s h Columbia,  as r e p r e s e n t a t i v e s of the three v e g e t a t i o n a l  zones o f the g r a s s l a n d s of the Nicola-Thompson area. l e a s t one s i t e was s e l e c t e d i n each zone.  Although  At these  s i t e s may not be c o n s i d e r e d by some to be t y p i c a l of the zones i n which they are l o c a t e d , t h e i r s t a t u s r e p r e s e n t s the c o l l e c t i v e appearance of some of the f e n c e l i n e v e g e t a t i o n c h a r a c t e r i s t i c s o f the area. sent a 100-kilometer  The f o u r s i t e s together r e p r e -  (approx. 62 m i l e s ) t r a n s e c t which runs  from the lower g r a s s l a n d to the upper g r a s s l a n d zone. Before the advent of the white man i n the e a r l y l800's the g r a s s l a n d s were grazed only by w i l d l i f e  possibly  mainly s m a l l p o p u l a t i o n s of deer and e l k .  ungulates  Pasture  a p p a r e n t l y d i d not e x e r t heavy g r a z i n g pressures p o s s i b l y because a b o r i g i n a l people kept t h e i r numbers at a low l e v e l . C a t t l e r a n c h i n g i n the Kamloops area s t a r t e d around but no f e n c i n g was done u n t i l the l890's. r e f e r r e d to i n t h i s account  1862  The f e n c e l i n e s  are r e l a t e d to some of these  o r i g i n a l fences which were p o s s i b l y b u i l t as the good grassland pasturage was claimed through purchase,  lease or other  means of l a n d tenure. The  s i t e s used are named a f t e r the area where they  are s i t u a t e d .  They are " T r a n q u i l l e " , "Quilchena",  Commonage" and "Minnie  Lakes".  "Hamilton  16 1.  The T r a n q u i l l e  site  ( T r a n q u i l l e Gov't Range)  l o c a t e d i n the lower g r a s s l a n d zone, i s 3 Km. (2 m i l e s ) from the Kamloops Research  Station  and 0.8 Km. from the B.C. Government Farm a t Tranquille.  The e l e v a t i o n i s 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 i n . ) and slope 6% S.E.  The v e g e t a t i o n i s c h a r a c t e r i z e d  by the p r i n c i p l e  s p e c i e s Agropyron spicatum*  and A r t e m i s i a t r i d e n t a t a N u t t . * * dominates the 2.  The former  the "ungrazed" s i d e and the l a t t e r  "grazed" s i d e of the f e n c e .  The Q u i l c h e n a s i t e on the Guichon C a t t l e Co. ranch, i s s i t u a t e d i n the middle g r a s s l a n d and about 77 Km.  zone  (48 m i l e s ) south of Kamloops  on the Kamloops-Merritt road i n N i c o l a V a l l e y . The e l e v a t i o n i s 647.7 meters sea  (2125 f t . ) above  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 i n . ) and slope i s 9$  * T h i s name i n c l u d e s both the awned type of the s p e c i e s A. spicatum (Pursch) S c r i b n . and Smith, and the awnless type A. sp i c atum v a r . inerme H e l l e r , and other p o s s i b l e i n t e r m e d i a t e v a r i e t i e s (Passey e t a l . 1963) • **The a u t h o r i t y f o r each s c i e n t i f i c name w i l l be g i v e n e i t h e r the f i r s t time the species i s mentioned or i n Table I I .  17 S.W.  The v e g e t a t i o n i s c h a r a c t e r i z e d by A.  spicatum, Poa secunda P r e s l and  Chrysothamnus  sp.  s p e c i e s on the  A. spicatum i s the dominant  "ungrazed" s i d e and Chrysothamnus dominant 3.  sp. i s the  s p e c i e s on the grazed side of the fence.  The Hamilton Commonage s i t e , on the Douglas Lake C a t t l e C. range, i s l o c a t e d i n the upper g r a s s l a n d zone.  I t i s l 6 Km.  (10 m i l e s ) east of  Q u i l c h e n a s i t e on the Minnie Lakes-Pennask road. above  The e l e v a t i o n i s 1242  meters  Lake  (4075 f t . )  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  i n . ) and slope 6fo S.S.E.  The w i n t e r - g r a z e d side of the fence i s dominated by Agropyron spicatum, F e s t u c a s c a b r e l l a T o r r . and Lupinus s e r i c e u s Pursch.  The h e a v i l y - g r a z e d  s i d e i s dominated by S t i p a columbiana Macoun and Poa p r a t e n s i s L. 4.  The Minnie Lakes S i t e , on the Douglas Lake C a t t l e Co. range, i s l o c a t e d i n the middle grassl a n d zone, about 21 Km.  (13 mi.) east of Q u i l c h e n a  s i t e on the Minnie Lakes-Pennask Lake road. e l e v a t i o n i s 1,112.5 meters level,  The  (3650 f t . ) above sea  the average annual p r e c i p i t a t i o n i s about  18 3C5  cm.  (12 i n . ) and the slope i s 5$ E. on the  l e s s grazed p l o t and 3$ N.N.W. on the grazed plot.  The  dominant p l a n t s p e c i e s on both s i d e s  of, the fence are Agropyron  spicatum and F e s t u c a  scabrella. At each s i t e an o l d f e n c e l i n e separates the  two  s i d e s which have had d i f f e r e n t g r a z i n g treatments f o r a l o n g t i m e - ( F i g . l ) . At the f i r s t  two  s i t e s , the  side  r e f e r r e d to as " l i g h t l y grazed" or " r e l i c t " had had to  little  no d i s t u r b a n c e f o r over f i f t y y e a r s , w h i l e the other  s i d e had been h e a v i l y grazed c o n t i n u o u s l y , e s p e c i a l l y i n s p r i n g and f a l l .  In the case of the l a s t two  sites,  " l i g h t l y grazed" s i d e had been o c c a s i o n a l l y very grazed i n the f a l l  lightly  and w i n t e r w h i l e the " h e a v i l y grazed" or  " d e p l e t e d " s i d e had had continuous heavy g r a z i n g . terms " l i g h t g r a z i n g " and of  the  The  "heavy g r a z i n g " r e f e r to the  the s i t e s when e x p e r i m e n t a t i o n s t a r t e d .  state  After fencing  the d e s i r e d e x c l o s u r e s on each side of the o l d f e n c e l i n e f u r t h e r g r a z i n g took p l a c e i n e i t h e r e x c l o s u r e .  For  venience  grazed"  the terms " l i g h t l y grazed" and  w i l l be used  i n t h i s t h e s i s to r e f e r to the " r e l i c t "  "depleted" e x c l o s u r e s r e s p e c t i v e l y . in  "heavily  no  con-  and  Although not i n c l u d e d  the r e p o r t e d study, g r a z i n g study areas have been set up  19  adjacent to the newly fenced area, on the assumption that the p r e s e n t continue.  g r a z i n g p r a c t i c e s i n the g e n e r a l area w i l l  ( a ) , (b) and ( c ) show t h e 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 pectively. (H) h e a v i l y g r a z e d s i d e and ( L ) lightly  grazed  side.  Ill. Field  METHODS  Experiments Exclosures  ( t o exclude ungulate users of the range)  were e s t a b l i s h e d at each of the aforementioned  sites.  For  p r a c t i c a l purposes, these e x c l o s u r e s c o n s i s t e d o f c o n t i g u ous p a i r s d i v i d e d by the range f e n c e l i n e and l o c a t e d so that both members o f the p a i r had the same s o i l a s p e c t s . Each e x c l o s u r e i s 30 by 30 meters e n c l o s e d i n a f i v e s t r a n d barbed wire fence w i t h s t e e l and wooden p o s t s , c o n s t r u c t e d on each s i d e o f the o l d f e n c e l i n e . e x c l o s u r e s a t each s i t e formed  The two  a 60 by 30 meter p l o t  d i v i d e d i n t o two s m a l l e r p l o t s by the o l d f e n c e l i n e .  In  a d d i t i o n to the barbed w i r e s , the bottom h a l f of whole e n c l o s u r e was r e i n f o r c e d w i t h a "chicken" wire n e t t i n g of about 7.5  cm. mesh.  C l i m a t e , s o i l moisture, and temperature 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  each s i t e a t the v e g e t a t i o n l e v e l . were taken weekly.  Readings  i n p a i r s at  at a l l s i t e s  At T r a n q u i l l e s i t e r e c o r d i n g was done  by means of a cumulative v i c t o r r a i n gauge. at  instru-  S o i l moisture  the other three s i t e s was monitored by the neutron  probes w h i l e a t T r a n q u i l l e where the p r e v i o u s years' r e c o r d i n g s were made, g r a v i m e t r i c means were used.  22 S o i l temperatures were measured w i t h  thermistor  probes p l a c e d i n each e x c l o s u r e at 10, 25, 50 and 100 cm. below the s o i l  surface•.  S o i l samples used f o r organic  matter a n a l y s i s 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  The  o r g a n i c matter content was determined i n the l a b o r a t o r y  at U.B.C. by the Walkley-Black Vegetation  analysis.  d e r i v e d from the s p e c i e s l i s t s cover  determinations.  identified  s u r f a c e i n each e x c l o s u r e .  method ( A l l i s o n 1965). The f l o r i s t i c compiled  l i s t s were  d u r i n g the crown  The s p e c i e s which c o u l d not be •  i n the f i e l d were tagged and brought back to the  Kamloops Research S t a t i o n f o r comparison with herbarium speciments.  The s p e c i e s composition  percentages  were  determined from the values o b t a i n e d from b a s a l area- measurements.  P h e n o l o g i c a l o b s e r v a t i o n s were made throughout the  growth p e r i o d . Culm h e i g h t s and l e a f blade on both f l o w e r i n g shoots cated i n F i g u r e 2.  lengths were measured  and v e g e t a t i v e t i l l e r s  as i n d i -  At l e a s t 30 bunches s e l e c t e d randomly  were measured on each side of the fence depending on how w e l l the s p e c i e s was r e p r e s e n t e d . 30 o c c u r r e d  I f fewer bunches  than  i n the e x c l o s u r e a l l the a v a i l a b l e bunches  were measured.  However, measurement of f l o w e r i n g culm  24 h e i g h t s was abandoned because there were very few f l o w e r i n g culms o f Agropyron a t some s i t e s .  T i l l e r h e i g h t s were  measured i n August. Counts o f the f l o w e r i n g shoots and v e g e t a t i v e t i l l e r s p e r s e l e c t e d bunch were made a t the same time the culm h e i g h t s were measured.  R a t i o s of f e r t i l e  to v e g e t a t i v e  shoots on a bunch were used to i n d i c a t e r e p r o d u c t i v e p o t e n t i a l of a bunch.  Due to shortage  of time most of the  measurements were c o n f i n e d to A. spicatum.  Seed y i e l d per  u n i t a r e a was determined by c o u n t i n g f l o w e r i n g culms i n 5 one-sqare; -meter quadrats s c a t t e r e d randomly i n each exclosure. The  b a s a l cover  means o f l i n e  of a l l p l a n t s was determined by  i n t e r c e p t method (N.A.C. - N.R.C. Pub. 890)  u s i n g 10 l i n e s o f 10 meters l o n g each p l a c e d randomly i n each e x c l o s u r e .  I n order  to keep t r a c k of the i n d i v i d u a l  p l a n t changes permanent one-square-meter-charting quadrats were e s t a b l i s h e d , two on each side of the fence N.R.C. Pub. 890).  The v e g e t a t i o n cover  (N.A.C. -  and frequency  were  determined by "the quadrat method s i m i l a r to that d e s c r i b e d by P o u l t o n The was  and T i s d a l e (1961). dry matter herbage y i e l d o f grasses  and f o r b s  determined by c l i p p i n g e i g h t randomly p l a c e d meter-  25 square permant quadrats, from each e x c l o s u r e .  Individual  s p e c i e s were c l i p p e d s e p a r a t e l y and weighed a f t e r oven drying.  C l i p p i n g was  i n October.  done at the end of the growth season .  L a b o r a t o r y and Greenhouse. Experiments An experiment  to determine the l e v e l at which  p e n e t r a t e s d i r e c t l y under was  the bunches of Agropyron  conducted i n the greenhouse  at U.B.C.  bunches were used i n the set-up i l l u s t r a t e d  water  spicatum  Transplanted i n F i g u r e 15.  .  Three s e t s of Bouyoucos moisture b l o c k s were s e t up i n the box  at the time the box was  f i l l e d with garden s o i l .  moisture b l o c k s were p l a c e d at 10, and the s o i l  was  u n i f o r m l y packed.  25,  50 and 70 cm.  (B) l e a v i n g the middle s e t of b l o c k s as a c o n t r o l One  s e t up 160 cm.  the s p r a y e r s was  trials  above the box.  (Figure  The. h e i g h t  determined beforehand i n s e v e r a l  i n which the u n i f o r m i t y of s p r a y i n g system  determined.  (A) and  month a f t e r t r a n s p l a n t i n g a non-run-off mist-  spray system was of  levels  Two bunches of A.  spicatum were p l a n t e d on the top of two b l o c k sets  15)  The  was  Watering l a s t e d one hour each time and measure-  ments were taken every two weeks. Every time measurements were done, the moisture l e v e l was  initial  determined b e f o r e w a t e r i n g and then the  26 change i n moisture l e v e l s was r e c o r d e d an hour w a t e r i n g had stopped.  after  S e v e r a l determinations were made  u s i n g both bunches and then one bunch was c l i p p e d to the ground.  F u r t h e r measurements were made u s i n g one c l i p p e d  and one u n d i p p e d  bunch.  IV.  RESULTS  Floristics There were no marked d i f f e r e n c e s i n the l i s t s o f . p l a n t s p e c i e s on the o p p o s i t e s i d e s o f the f e n c e l i n e . T r a n q u i l l e and Q u i l c h e n a s i t e s , forb  there were s l i g h t l y more  (broad-leaved) s p e c i e s on the h e a v i l y grazed s i d e s than  on the l e s s grazed ones. site  At  However, at Hamilton Commonage  the l i g h t l y grazed a r e a had more forbs' than the d e p l e t e d  area and a t Minnie Lakes  s i t e both s i d e s had e s s e n t i a l l y the  same number of s p e c i e s .  The numbers of s p e c i e s i n each  p l a n t c a t e g o r y p r e s e n t at each s i t e and- a complete  list  are shown i n Table I  of a l l s p e c i e s i s presented i n Table I I . TABLE I  NUMBER OP SPECIES IN CATEGORIES BY SITES CATEGORY  T r a n q u i l l e Quilchena  Minnie  Lakes  Hamilton C.  L  H  L  H  L  H  L  H  Porbs  4  7  11  18  18  15  28  19  Shrubs  1  1  2  3  l  l  Grasses Annuals 2 PerennijU s 3  2 3  1 3  1 5  5  5  1 8  1 7  10  13  17  27  24  21  37  29  TOTALS L  •=  L i g h t l y grazed.  H  =  H e a v i l y grazed.  2  28 TABLE I I THE LIST OF SPECIES FOUND IN THE STUDY AREA Site  SPECIES  1  Site 2  Site 3  Site J 4  L H  L H  L H  L H  P P  P P  P P  P P  GRASSES Agropyron spicatum Agropyron repens  (1) Beauv.  Bromus tectorum L.  P P P P  P P  F e s t u c a idahoenis Elmer F e s t u c a o c t o f l o r a Walt.  P P P  Festuca s c a b r e l l a Torr. Koeleria cristata (l)  P  Poa' ampla Mer. Poa compressa L.  P P  P P  P P  P P  P P  P P  P  Poa p r a t e n s i s L.  P P  Poa secunda P r e s l .  P P  Sporobolus c r y p t a n d r u s (Torr .) Gr ay  P P  P P  S t i p a columbiana Macoun Juncus b a l t i c u s  P P  P P  P P  P P  Will'd.  P  FORBS A c h i l l e a m i l l e f o l i u m L. v a r . C. L a n u l o s a (Nutt) P i p e r  P  A g o s e r i s g l a u c a Pursh. Androsace  occidentalis  P P  P P P  P  29 TABLE I I Continued Site 2  Site 3  L H  L H  L H  L H  P  P P  P P  P P  A n t e n n a r i a r o s e a 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  SPECIES  1  Site  A n t e n n a r i a dimorpha (Nutt) T. & G.  Astragalus p u r s h i i  Dougl.  A s t r a g a l u s s e r o t i n u s A.  P P  Gray  P P  Camelina m i c r o c a r p a Anderz.  P  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. Delphinium b i c o l o r  P Nutt.  Descurainia sophia  P P  P P  E p i l o b i u m paniculatum N u t t .  P  P  E r i g e r o n compositu-s Pursh.  P  P P  E r i g e r o n corymbosus Nutt.  P  E r i g e r o n l i n e a r i s (Hock) Piper. E r i g e r o n pumilus T. & G. Eriogonum  4  Site  heracleoides Nuttr  P P P  P P  P P  P  --  30 TABLE I I Continued Site 1  SPECIES  L H Geum t r i f l o r u m  Site 2 L H  Pursh.  Site 3 L H  Site 4 L H  P P  Lappula e c h i n a t a G i l .  P  P  P P  P  P  P P  P  P P  P P  P P  O x t r o p i s campestris  P  P P  Pentstemon p r o c e r u s Dougl.  P  Lithospermum r u d e r a l e Lomatiura macrocarpum (Nutt) G. & R. Lupines s e r i c e u s  Pursh.  Opuntia f r a g i l i s Haw.  Phlox  P P  P P  gracilis  Potentilla gracilis  )  P  P P Dougl.  P P  P  altissimum  Taraxacum o f f i c i n a l e  P P  P P  Senecio caus Hook.. Sisymbrium  i  P P  Weber  Tragopogon p r a t e n s i s . L.  P P  P P  P P  P P  P P  P P  V i o l a adunca Smith.  P P  Zygadenus venenosus Wats.  P P  P  SHRUBS A r t e m i s i a f r i g i d a Wall'd.  P  P  Artemisia glauca Artemisia tridentata  P  P P  P P P  P  tt. Chrysothamnus sp. ( P a l l ) B r i P P P 4. Minnie Lake s \1. T r a n q u i l l e . 2. Q u i l c h e n a . 3. Ham i l t o n C. L - L i g h t l y grazed. H-Heavily grazed. p i n d i c a t e s presence.  v  31 In g e n e r a l the number of s p e c i e s present at the s i t e i n c r e a s e d from the Lower g r a s s l a n d zone to the Upper grassl a n d zone.  T h i s c o i n c i d e d w i t h the o b s e r v a t i o n s made by  (1947).  Tisdale appeared  The d i f f e r e n c e i n the s p e c i e s number  to be more an a t t r i b u t e of the v e g e t a t i o n zone than  as a simple response  to g r a z i n g .  Out of a t o t a l of 60 s p e c i e s recorded i n the whole study a r e a (Table I I ) o n l y Agropyron spicatum, Poa secunda, A n t e n n a r i a dimorpha, Lomatium macrocarpum and A r t e m i s i a f r i g i d a were r e p r e s e n t e d a t a l l s i t e s . all  A. spicatum  dominated  the l i g h t l y grazed areas c o n t r i b u t i n g over 50$ of the  t o t a l v e g e t a t i o n cover at T r a n q u i l l e and Quilchena, and 46$  at Minnie  spicatum  Lake s i t e s .  tended  w i d e l y spaced.  Under " r e l i c t "  c o n d i t i o n s A.  t o form pure stand w i t h l a r g e bunches U s u a l l y there were l a r g e bare areas between  the bunches sometimes o n l y occupied by s m a l l s h o r t l i v e d , shallow r o o t i n g s p e c i e s such as C o l l i n s i a p a r v i f l o r a and Poa secunda ( F i g . 3)• However, a t Hamilton Commonage s i t e , the charact e r i s t i c p a t t e r n of A. spicatum bunches i n u n d i s t u r b e d s t a t e was l e s s d i s t i n c t . and w i d e l y spaced, them.  Although  the bunches were b i g  there were l i t t l e bare  areas between  The spaces between A. spicatum bunches were occupied  (a)  Fig.  3.  (a) and (b) i l l u s t r a t e t h e c h a r a c t e r i s t i c s p a c i n g of A g r o p y r o n s p i c a t u m b u n c h e s i n a l e a s t disti/nbed c o n d i t i o n a t M i n n i e Lakes and Q u i l c h e n a r e s p e c tively. 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 soil surface features.  33 by  a v a r i e t y o f o t h e r s p e c i e s o f g r a s s e s a n d f o r b s ( F i g . 4) .  Among t h e a s s o c i a t e d s p e c i e s w e r e 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 . t r i b u t e d 77$ o f t h e t o t a l was  made o f f o r b s .  Grasses  cover and t h e r e m a i n i n g  Lupinus  con-  percentage  s e r i c e u s was t h e 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 t h e t o t a l v e g e t a t i o n c o v e r . m i l l e f o l i m v a r . l a n u l o s a made up a l m o s t  Achilles  8$ o f t h e c o v e r .  and f o r b s i n t h e 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 o n b o t h  t h e 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 Tranquille growing  near  ( F i g . 5)•  and Q u i l c h e n a , t h e s m a l l bunches were and under s h r u b s  ( F i g . 5,a).  d e p l e t e d a r e a was d o m i n a t e d b y e i t h e r  At  found  At every  site  shrubs, annuals or  the  34  00 Fig. 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 e x c l o s u r e s r e s p e c t i v e l y a t Tranquille site. The p i c t u r e s were t a k e n i n summer 1 9 6 8 .  rhizomatous  grasses.  At T r a n q u i l l e A r t e m i s i a t r i d e n t a t a  c o n t r i b u t e d 76% of the t o t a l s p e c i e s cover.  At Q u i l c h e n a  Chrysothamnus sp., A r t e m i s i a f r i g i d a and Bromus tectorum together made up 76$ o f the t o t a l s p e c i e s cover. Hamilton Commonage S t i p a columbiana  At  and Poa p r a t e n s i s were  the major s p e c i e s , and a t Minnie Lakes Juneus b a l t i c u s and A r t e m i s i a f r i g i d a were the apparent The f l o r i s t i c of  increaser species.  composition expressed as percentage  the s p e c i e s b a s a l a r e a to the t o t a l v e g e t a t i o n . c o v e r i s  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 s p e c i e s on the l i g h t l y grazed s i d e and t h a t of the s p e c i e s on the h e a v i l y grazed There were marked r e d u c t i o n s i n the percentage of Agropyron  side.  composition  spicatum, F e s t u c a s c a b r e l l a and F. i d a h o e n s i s  on the h e a v i l y used side at a l l s i t e s . Bromus tectorum, S t i p a columbiana,  On the other hand  Poa p r a t e n s i s , A r t e m i s i a  t r i d e n t a n t a , Chrysothamnus sp. and A n t e n n a r i a dimorpha had significantly  g r e a t e r amounts on the d e p l e t e d s i d e than on  the l i g h t l y grazed s i d e . apparent  decrease  At a l l s i t e s  there was an  i n the composition of c a e s p i t o s e grasses  under g r a z i n g and an i n c r e a s e i n the annuals and rhizomatous s p e c i e s .  36 TABLE I I I SPECIES COMPOSITION (IN PERCENTAGE) ON FOUR SITES ON THE OPPOSITE SIDES OF FENCELINES SPECIES A.  L  65.5  spicatum  H  ** 6.3  L  H  66.3 1.3.2  Festuca scabrella  .L 46.8  3.2  H  L  H  13.8  #* 0.1  9.6  29.3  *•* 0.1  6.2  8.7 10.0  * 35.1  Festuca ideahoensis Poa  Bromus Poa  9.8* <J01 1.0  13.8  secunda tectorum  13.4 12.3  2.1  #-*  0.04 3.8  9-5 67.8 ** 6.2 0.7  S t i p a Columbians Artemisia tridentata  19.3 76.7  -  frigida  11.9  1.8  sericeus  -  1.6  3.3 11.5  Koeleria cristata OTHERS  1.4  4.6  TOTALS OF ALL SP . 100. 100. TOTAL GRASS COMPOSITION  4.6  16.6 44.4  1  Antennaria dimorpha  14.2  *•#  Chrysothamnus sp • Lupinus  10.1  <*05  pratensis  Artemisia  <.l  79.3  18.1  0.4  2.9  100.  100.  79.7 30.3  *•* 0.2  0.5  14.3  12.6 12.5  0.5  7.6- 14.7  5.7  3.0  16.8  7.5  9-5  100.  100.  11.7  100. 100. 61.8 68.7  •* 3.0  77.7 87.3  **io.dicates a s i g n i f i c a n t d i f f e r e n c e s (P<-0.01) between the l i g h t l y grazed and the h e a v i l y grazed area. •^Indicates a s i g n i f i c a n t d i f f e r e n c e (P<0.05) between the l i g h t l y grazed and h e a v i l y grazed area.  37 S p e c i e s Frequency., Canopy Cover, B a s a l Area and Dry Matter  Yield  Species frequency.  Frequency was  n o t i n g the presence or absence  determined  by  of a g i v e n s p e c i e s i n 5 0  sampling p l o t s l a i d out i n each e x c l o s u r e f o l l o w i n g the method d e s c r i b e d by P o u l t o n and T i s d a l e  (1961).  centage of the number of p l o t s i n which  the s p e c i e s o c c u r r e d  was  The per-  used as i t s percentage frequency. The frequency of Agropyron spicatum, F e s t u c a  s c a b r e l l a , F. i d a h o e n s i s , Poa ampla and Lomatium macrocarp urn was  reduced wherever g r a z i n g had been i n t e n s i f i e d  (Table I V ) .  On the other hand Poa p r a t e n s i s ,  Stipa  columbiana, Bromus tectorum, A r t e m i s i a t r i d e n t a t a ,  A.  f r i g i d a , Chrysothamnus sp. and A n t e n n a r i a dimorpha  increased  as g r a z i n g was  intensified.  Lupinus s e r i c e u s tended to  become r a r e on the d e p l e t e d s i d e on Hamilton Commonage s i t e while Poa secunda and A c h i l l e a m i l l e f o l i u m d i d not change much. The percentage of F e s t u c a s c a b r e l l a on the d e p l e t e d side of the f e n c e l i n e at Minnie Lakes, was the l i g h t l y grazed s i d e .  I t may  h i g h e r than on  be there were reasons  other than g r a z i n g which o r i g i n a l l y i n f l u e n c e d t h i s h i g h percentage.  On both s i d e s of the f e n c e , however, the  38 TABLE IV THE PERCENTAGE FREQUENCY OF THE MAJOR SPECIES  SPECIES  Tranquille  Agropyron spicatum  SITE Quilchena Minnie Hamilton C. Lakes  L  H  L  H  L  H  L  H  98  70  100  82  96  98  78  12  16  50  76  10  32  -  Festuca s c a b r e l l a Festuca idahoensis  56  72  64  48  26  10  • 5  25  6  34  ' 70  84  80  50  Poa p r a t e n s i s  14  32  S t i p a columbiana  16  82  25  -  Koeleria  cristata  Poa ampla Poa secunda  9^  94  -  millefoliun  Achillea  52  54  25  10  98  frigida  25  50  Chrysothamnus sp.  8  78  Bromus tectorum Sporobolus cryptandrus  25 _  A r t e m i s i a t r i d e n t a t a 66 Artemisia  A n t e n n a r i a dimorpha Opuntia f r a g i l i s Lupinus  36  88  -  12  10  50  18  26  25  25  Taraxacum officinale  25  25  JuncuS b a l t i c u s  14  36  20  sericeus  Lomatium macro.carpum  16  8  40  34  40  50  26  64  25  38  10  4  90  25  28  16  16  32  -  88 25  -  22 . 25  s p e c i e s was r e p r e s e n t e d b y b i g b u n c h e s whose c e n t e r s h a d died leaving thin of  the o r i g i n a l  rims of t i l l e r s  limits  With the exception of Hamilton  Commonage s i t e , t h e p e r c e n t a g e lower on the h e a v i l y used  side, at a l l sites though  the other  crowns..  Canopy c o v e r .  was  marking  (Table V ) .  canopy cover o f a l l g r a s s e s s i d e t h a n on t h e l i g h t l y  used  On H a m i l t o n Commonage,  t h e t o t a l c o v e r o f g r a s s e s was h i g h e r o n t h e  d e p l e t e d s i d e , t h e r e was a m a r k e d r e p l a c e m e n t  of caespitose  species by sod formers. Basal area. the l i n e  B a s a l a r e a m e a s u r e m e n t s w e r e made b y  i n t e r c e p t method d e s c r i b e d i n t h e "Range  B a s i c Problems  and Techniques"  The b a s a l a r e a o f e a c h percentage  p u b l i s h e d b y N.A.C.-N.R.C.  s p e c i e s was c a l c u l a t e d f r o m t h e  o f t h e sum o f a l l d i a m e t e r s , o f t h e  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 the t o t a l percentage  Research  l e n g t h of a l l t r a n s e c t s used.  transects, to  As f a r as t h e  o f t h e b a r e g r o u n d was c o n c e r n e d ,  marked change f o l l o w i n g heavy g r a z i n g .  individual  t h e r e was no  Some s p e c i e s s u c h  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 at  t h e same t i m e t h e d e c r e a s e r s w e r e r e p l a c e d b y t h e a p p a r e n t i n c r e a s e r s and i n v a d e r s . its  coverage  tage o f bare  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  on t h e d e p l e t e d s i d e ground  thus r e d u c i n g the p e r c e n -  ( T a b l e VI) a t H a m i l t o n Commonage.  4o TABLE V CANOPY PERCENTAGE COVER OF THE MAJOR SPECIES SITE SPECIES  T r a n q u i l l e •Q u i l c h e n a Minnie Hamilton Lakes Commonage  Agropyron  spicatum  L  H  L  H  65  16  59  18  Festuca s c a b r e l l a  H  L  H  48 33  4o  3  4 9  35  1  8  -  7 10  15  11  1  4  13  26  3  1'  4  1  21  13  L  Festuca idahoensis Koeleria  cristata  Poa secunda  17  23  7  12  Poa amp l a  1  Achillea millefolium  4 6  Poa p r a t e n s i s  8 20  Stipa  4  columbiana  1  6  Sporobolus cryptanarus  1  3  Artemisia tridentata  19  34  Bromus  tectorum  8 2  27  2  1  6  3  1  l  Chrysothamnus sp. Antennaria dimorpha Opuntia  fragilis  Lupinus  sericeus  Taraxacum of f i c i n ale  l  1  Artemisia f r i g i d a  3  4l  6 9  1.  2  6  l  5  l  l  47  1  . 2  1  1  2  41 TABLE VI BASAL AREA AS PERCENTAGE COVER OF THE TOTAL SURFACE AREA SAMPLED SITE T r a n q u i l l e l Q u i l c h e n a Minnie Hamilton Lakes Commonage  SPECIES  L Agropyron  spicatum  19.1  H  L  H  16  2  H  L  Festuca s c a b r e l l a  7  6  0.1  1  2  12  0.1  3  .1  2.  cristata  H  10  Festuca idahoensis Koeleria  L  3.  2  2  0.4 1  0.2 0.2  0.4 1  4  7  0.2 0, 2 2  2  Poa p r a t e n s i s  4  48  S t i p a columb i a n a  0.3 6  Poa amp l a Poa  secunda  4  Achillea millefolium  .1  .1  Bromus tectorum Sporobolus cryptanclrus  0.1  Artemisia  7  tridentata  0.3  .1  24 3 11  4  Chrysothamnus sp.  Lupinus  sericeus  l  1  A n t e n n a r i a dimorpha fragilis  0.2  3 0.2  l  l  0.2  0.1 0 l  l  -  Lomat ium macro carp urn  .1  .1  .1  O x t r o p i s campestris  .1  0.1  0.2  31  3;  24  2  0.3 0 1 6  balticus  T o t a l veget. covers  1  3  Taraxacum o f f i c i n a l e Juncus  -  1  Artemisia f r i g i d a  Opuntia  .1  7  -  1  .1 1  1  1  1  25  21  20  41  0  7;  42 Dry matter y i e l d . major  The dry herbage y i e l d of the  grass s p e c i e s sampled  a t the end of the growing  season i s g i v e n i n Table V I I . was not determined because f o r b s had d r i e d out. because  The herbage  y i e l d of forbs  at the time of measuring a l l  Shrubs, too, were not measured  they were too b i g to be measured by the c l i p p i n g  method.  A b e t t e r measure o f shrubs i s expected to be used  in future determinations. TABLE V I I AVERAGE DRY MATTER YIELD IN Kgms. PER HECTARE OF THE GRASS HERBAGE PRESENT AT THE END OF THE GROWING SEASON SITE SPECIES  Tranquille L  Agropyron Festuca  spicatun 1498  Quilchena  H  L  129  1166  scabrella  Festuca idahoensis Poa ampla  columbiana  TOTAL  L  H  196 924 393  1498  129  1166  L  H  885  35  36  66  34l  20  -*  *  130  *  6  Poa p r a t e n s i s Stipa  H  Minnie Hamilton Lakes Commonage  5  4  194  340  *  475  13  196 966 472 1555  •^Indicates presence i n the e x c l o s u r e but not i n the sampling quadrats.  874  43 Growth Habits In s e v e r a l ways an attempt  was  made to f i n d  out  whether the growth h a b i t of some major p l a n t species r e s ponded to management d i f f e r e n c e s r e p r e s e n t e d along the fences.  Owing to the shortage of time, d e t a i l e d measure-  ments were c o n f i n e d to Agropyron spicatum and other s p e c i e s were measured o n l y when comparison with A. spicatum  was  required. Agropyron spicatum, land climax  a dominant s p e c i e s i n the. grass-  ( T i s d a l e 1947), has a very high g r a z i n g value  (U.S.D.A. F o r e s t S e r v i c e 1966).  When not g r e a t l y d i s t u r b e d  on open s e m i - a r i d s i t e s , the s p e c i e s u s u a l l y produces more herbage than a l l other a s s o c i a t e d s p e c i e s combined.  It is  a p e r e n n i a l grass and g e n e r a l l y c a e s p i t o s e ( F i g . 6),  although  some rhizomatous  varieties exist  (Passey e_t a l . 19^3)  .  culms are slender and t u f t e d and i t s leaves are narrow smooth with the inner surface (upper) pubescent.  The  grooved  and  Its and  slightly  awnless v a r i e t y , sometimes c a l l e d Agropyron  spicatum v a r . inerme, was  commonest at a l l s i t e s .  However,  .a f a i r p r o p o r t i o n of the awned s t r a i n ( g e n e r a l l y c a l l e d A. spicatum) was  found at Minnie Lakes and Quilchena  sites.  Old bunches of A. spicatum l i v e f o r a number of years and  at T r a n q u i l l e and Quilchena s i t e s , where  the  44 s t a n d s h a v e n o t b e e n m a r k e d l y d i s t u r b e d f o r many no  s e e d l i n g s w e r e o b s e r v e d g r o w i n g among o l d b u n c h e s .  N o r m a l l y new p l a n t s grazing on  years,  a r e 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  i s said to f a c i l i t a t e  seed s e t t i n g .  t h e o l d b u n c h e s grow I n t h e a x i l s  New  of the o l d t i l l e r s  f l o w e r i n g c u l m s o n t h e l o w e r most n o d e s .  continue  6.  The same t i l l e r s  temperanormally  g r o w t h i n t h e s p r i n g when c o n d i t i o n s became  favorable  Fig.  subtended by  t o grow u n t i l w i n t e r  tures prevented f u r t h e r growth.  and  The new b u d s  emerged o u t o f t h e g r o u n d e a r l y i n t h e f a l l , s c a l y l e a v e s , and c o n t i n u e d  tillers  again.  Bunches o f Agropyron spicatum a t Minnie Lakes s i t e (on the l i g h t l y grazed side of the f e n c e ) . A l t h o u g h no  were t a k e n ,  i t was  h r a t e measurements o f t h e t i l l e r s d that t i l l e r s  which  finally  produced f l o w e r i n g heads grew f a s t e r tative  tillers.  than  the other  I t i s u n c e r t a i n whether these  emerged f i r s t i n the f a l l  tillers  or whether t h e i r e l o n g a t i o n r a t e  changed when they changed from b e i n g v e g e t a t i v e . t o shoots. floral  vege-  floral  In f u t u r e i t should be determined e x a c t l y when i n d u c t i o n and  initiation  take p l a c e i n t h i s  T. Lo'bb ( p e r s o n a l communication) n o t i c e d that d i f f e r e n t i a t i o n takes p l a c e l a t e r .than i n F e s t u c a The  floral  i n Agropyron spicatum -  scabrella.  s p e c i e s i s very s e n s i t i v e  management but,  species.  due  to i t s great value  to over-use and  as a forage p l a n t ,  e f f o r t s are o f t e n made to i n c r e a s e i t s abundance on ranges where i t occurs  poor  the  through good range management.  However, attempts to extend the range of t h i s s p e c i e s to other failed  area where i t does not n a t u r a l l y occur, have u s u a l l y (U.S.D.A. F o r e s t S e r v i c e 1 9 6 6 ) .  In a d d i t i o n , i t s  seed s e t t i n g h a b i t s 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 Two  spicatum  d r i e r p o r t i o n s of i t s n a t u r a l range. of the  under heavy g r a z i n g were Bromus tectorum  S t i p a columbiana. depleted was  s p e c i e s which tended to r e p l a c e  The  former was  s i d e s at T r a n q u i l l e and  w e l l represented Quilchena  abundant at Hamilton Commonage.  and  the  A. and on  the  latter  46 Bromus tectorurn i s an annual grass with able p l a s t i c i t y  i n i t s response to v a r i a t i o n s i n s i t e  ( H a r r i s 1967).  ditions  soil  moisture,  con-  At the two s i t e s where i t was found  i t produced s i n g l e culms b e a r i n g inflorescence.  a consider-  s e v e r a l s p i k e l e t s i n the  However, H a r r i s (1967) r e p o r t e d that where fertility  and l i g h t  i n t e n s i t y are not  l i m i t i n g , an i n d i v i d u a l p l a n t may produce 12 to 15 or more culms, each 50 to 75 cms. t a l l and b e a r i n g hundreds of s p i k e l e t s per culm.  Most seeds germinated e a r l y i n the  f a l l b u t s p r i n g germination Dr. V. C. B r i n k  has a l s o been observed by  (Personal communication).  The s e e d l i n g s  e s t a b l i s h e d a t the end of August were about 3 cm. t a l l i n October. in for  Normally growth stops  spring.  i n winter  and s t a r t s  again  In s p r i n g the p l a n t s do not reach g r a z i n g  heigh  c a t t l e u n t i l 2 to 3 weeks l a t e r than most a s s o c i a t e d  perennial grasses.  Once growth begins the r e p r o d u c t i o n  c y c l e i s r a p i d l y completed. June.  P l a n t s d r i e d i n the middle of  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 p l a n t i s s u c c u l e n t but as i t reaches m a t u r i t y unpalatable  the forage  becomes  and low i n n u t r i e n t s .  S t i p a columbiana i s a p e r e n n i a l grass c a l l e d Columbia needle g r a s s .  commonly  I t s t u f t s are r e l a t i v e l y  small when compared to those of A. spicatum ( F i g s . 6 &  7).  47 It  i s f i n e - l e a v e d and slender-stemmed.  I t grows on d r y  s o i l s i n canyons and on open h i l l s i d e s , mountain and p l a i n s t o s u b - a l p i n e e l e v a t i o n s . s a i d t o v a r y f r o m f a i r t o good.  peaks  Its palatability is  N o r m a l l y the s p e c i e s  o c c u r s a b u n d a n t l y on ranges where Agropyron and o t h e r b l u e g r a s s e s have been k i l l e d by o v e r g r a z i n g .  I t i s considered  a v a l u a b l e r e p l a c e m e n t 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 o f the f a i r l y good g r a s s e s t o d i s a p p e a r from t h e o v e r - u s e d range  F i g . 7.  (U.S.D.A. F o r e s t S e r v i c e 1966).  S t i p a columbiana a t Hamilton Commonage i n the h e a v i l y grazed exclosure.  The p l a n t e s t a b l i s h e d i t s e l f f r o m seed. are  awned and are produced i n l a r g e numbers.  The seeds  On H a m i l t o n  Commonage, i t was n o t i c e d t h a t the g e n i c u l a t e awn h e l p s to  48  bury the c a r y o p s i s by a r o t a t i o n motion caused by changes i n the atmospheric humidity.  More b u r i e d seeds were n o t i c e d  on bare patches on the d e p l e t e d s i d e . Vigor.  Measuring  the h e i g h t s of the f l o w e r i n g  culms o f A. spicatum was abondoned because  at some s i t e s  l a r g e enough f l o w e r i n g s t a l k s c o u l d not be o b t a i n e d .  More-  over at T r a n q u i l l e where t r i a l measurements were made, the d i f f e r e n c e between the means f o r the l i g h t l y grazed and the h e a v i l y grazed s i d e s 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 h e i g h t s 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 h e i g h t was always measured as the  d i s t a n c e from the s o i l leaf  s u r f a c e to the c o l l a r of the sheath  ( F i g . 2 ) . The mean h e i g h t s measured  of  the youngest  at  the end o f summer growth are shown i n Table V I I I . Agropyron  spicatum t i l l e r s  were s i g n i f i c a n t l y  s h o r t e r on the d e p l e t e d side o f the f e n c e l i n e than on t h e l i g h t l y grazed side a t a l l s i t e s .  Leaf blades were  c a n t l y s h o r t e r a t T r a n q u i l l e and Minnie Lakes at  Q u i l c h e n a and Hamilton Commonage.  columbiana  signifi-  s i t e s but n o t  In the case of S t i p a  n e i t h e r the t i l l e r h e i g h t s nor the l e n g t h s of  leaves i n d i c a t e d any s i g n i f i c a n t d i f f e r e n c e between the l i g h t l y and the h e a v i l y grazed areas.  R e s u l t s i n both  TABLE V I I I AVERAGE TILLER HEIGHT OF A . SPICATUM AND S. COLUMBIANA MEASURED IN AUGUST 1968 Average Height i n cm. SITE  SPECIES  L  H  S .E  L.S.D  0  Tranquille  Agropyron spicatum  28.8  24.2**  1.0  2.9 (P < .01)  Quilchena  Agropyron spicatum  30.8  27.2*  1.7  3-3 (P<0.05)  Vlinnie Lakes  Agropyron spicatum  26.8  21.4**  1.1  3-0 (P<0.01)  Hamilton Commonage Agropyron sp i c atum  31.5  26.5**  1.  2.9 (P<0.01  Stipa columb i a n a  4.8  5.3  *Indicates a s i g n i f i c a n t difference grazed and h e a v i l y grazed area.  (P-^.05) between the l i g h t l y  **Indicates a s i g n i f i c a n t difference grazed and h e a v i l y grazed area.  (P<^.01) between the l i g h t l y  4^ v  o  50 Tables V I I I and IX i n d i c a t e t h a t there was r e d u c t i o n i n the v i g o r of A. spicatum on the h e a v i l y grazed Phenology.  Phenological  observations  area. recorded  throughout the growing season are shown i n Table X.  If  what was observed a t Hamilton Commonage were true of other h a b i t a t s , then A. sp i c atum can be regarded as a p l a n t inflorescences latest.  whose  are i n boot stage e a r l i e s t and shed seeds  There was a space of a month between the boot  stage and a n t h e s i s seed r i p e n i n g .  and another -month between anthesis  and  This meant that the i n f l o r e s c e n c e s were  exposed to a two months p e r i o d when they could be destroyed by  grazing. . I t was observed that o c c a s i o n a l l y A. spicatum  "viviparous"  (Fig. §)•  Quilchena s i t e .  Further  This  turns  tendency was most common at  i n t e r e s t i n g observations  were made  when over 50$ of the i n f l o r e s c e n c e s produced on the bunches grown i n the greenhouse turned " v i v i p a r o u s " .  In a number  of cases a l l the s p i k e l e t s i n the i n f l o r e s c e n c e had t h e i r t e r m i n a l f l o r e t s turned " v i v i p a r o u s " , while the r e s t of florets  i n the same s p i k e l e t s underwent normal  D e t a i l e d account of these " p l a n t l e t s "  anthesis.  i n A. spicatum  was  f i r s t made by Marchand and McLean (1965) and the p r e s e n t observations  agreed w i t h t h e i r  description.  TABLE IX AVERAGE LEAPBLADE LENGTH OF AGROPYRON SPICATUM AND STIPA COLUMBIANA MEASURED IN JULY I968 Av. Leaf Length SITE  SPECIES  Tranquille  Agropyron  L 18.96  spicatum  i n cm. H  .15.91**  -S.E.  0.68  L.S.D. 1.9  (P<0.01) Quilchena  Agropyron  spicatum  17.5  16.35  0.67  Minnie  Agropyron  spicatum  19.8  18.09*  0.73  1.5 (p<o,05)  Agropyron  spicatum  20.5  20.29  l.o  2.0 (P<0.05)  21.. 7  21.96  Lakes  Hamilton Commonage  Stipa  columbiana  1.3  .  (p<o.05)  -  ^ I n d i c a t e s a s i g n i f i c a n t d i f f e r e n c e (P<0.05) between the l i g h t l y grazed' and the h e a v i l y grazed area. - ^ I n d i c a t e s a s i g n i f i c a n t d i f f e r e n c e (P<.0.01) between the l i g h t l y grazed and the h e a v i l y grazed area. L.S.D.  -  Least S i g n i f i c a n t D i f f e r e n c e .  r—  1  TABLE X SOME PHENO LO GlC AL CHANGES IN SOME PLANT SPECIES AT HAMILTON COMMONAGE . (UPPER GRASSLAND ZONE) Boot S t a t e MidLate June June  SPECIES  A. sp i c atum  y  B. tectorum  y  F. idahoensis P. secunda  y  y y  y  y y y  y  y  y  y  P. ampla  y  v/  y  v/  y  -  y y  L. s e r i c e u s  N.B.  Seed .Ripening MidMidLate E a r l y July July Aug. Aug.  y  S. columbiana  C. b i c o l o r  MidJuly  y  K. c r i s t a t a P. p r a t e n s i s  MidJune  Anthesis Late Early June July  y y .  y  •  y  y y  Growth i n the Upper g r a s s l a n d zone i s about two weeks behind that i n the Lower g r a s s l a n d zone. ui ro  Fig.  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 v i v i p a r y i n Agropyron spicatum.  There was  no s p e c i a l i z e d means of seed  dispersal  noted to be a s s o c i a t e d w i t h the A. spicatum seeds It  (Fig. 9).  i s most probable t h a t the d i s p e r s a l u n i t s are shaken  out of the s p i k e l e t s by wind and drop on the ground the mother p l a n t . Minnie Lakes  Germination was  around  observed i n the f a l l at  s i t e among the seeds which managed to r o l l  into s o i l cracks. As shown i n F i g u r e 6 , B. tectorum had two dispersal units.  The  topmost f e r t i l e f l o r e t  types of  remained  connected to a c l u s t e r of s t e r i l e f l o r e t s whose l o n g awns formed  parachute-like structures.  The lower f l o r e t s were  d i s p e r s e d i n d i v i d u a l l y and g e n e r a l l y they d i d not move f a r from the mother p l a n t . Hulbert  (1955)  T h i s had a l s o been r e p o r t e d by  and Klemmedson e t a l . ( 1 9 6 4 ) .  Since a t  T r a n q u i l l e and Q u i l c h e n a s i t e s , B. tectorum grew along the fence.but d i d not c r o s s i t to the l e s s grazed s i d e s (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 o f the two d i s p e r s a l u n i t s s t r a y e d f u r t h e s t from the mother p l a n t s along the f e n c e . remains  Normally when the seed germinates  the  of the d i s p e r s a l u n i t s t a y attached onto the young  s e e d l i n g f o r a w h i l e , so i f young s e e d l i n g s 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 d i s p e r s a l u n i t the s e e d l i n g s came from.  Fig.  9,  S p i k e l e t s and f l o r e t s o f A g r o p y r o n s p l o a t u m , Bromus t e c t o r u m and Stipa"""columbian.  56  Fig.  10.  A dense s t a n d of Bromus t e c t o r u m a l o n g the f e n c e a t Q u i l c h e n a . (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 grazed s i d e .  L a t e i n September B. t e c t o r u m s e e d l i n g s were sampled i n b e l t t r a n s e c t s a l o n g the f e n c e l i n e a t Q u i l c h e n a on the l i g h t l y g r a z e d s i d e and the r e s u l t s shown i n Table X I were o b t a i n e d .  The t o t a l number of s e e d l i n g s per s a m p l i n g  s t r i p e d e c r e a s e d p r o p o r t i o n a l to the d i s t a n c e f r o m the fence.  The p e r c e n t a g e of the topmost f l o r e t s i n c r e a s e d  i n p r o p o r t i o n t o d i s t a n c e away f r o m the f e n c e . On H a m i l t o n 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. t e c t o r u m at T r a n q u i l l e Quilchena.  The  s p e c i e s was  and  d e n s e l y d i s t r i b u t e d on the  d e p l e t e d s i d e of the f e n c e l i n e  ( F i g . 11)  and  lightly  r e p r e s e n t e d on the l i g h t l y grazed s i d e .  Large numbers of  seeds were produced r i g h t up t o the f e n c e l i n e b u t they appeared unable t o c r o s s to the l e s s grazed s i d e .  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 florets  52.5  64.8  74.6  85.5  82.0  % Lower florets  47.5  33-2  25.4  14.5  18.0  Fig.  11.  S t i p a columbiana and A n t e n n a r i a dimorpha In the h e a v i l y grazed e x c l o s u r e at Hamilton Commonage.  58 Seed p r o d u c t i v i t y .  Table X I I shows r e s u l t s  o b t a i n e d from s t a l k counts of the f l o w e r i n g culms of each s p e c i e s found exclosure. the f i v e  i n 5 meter-quadrats put randomly i n each  Since the p l a n t s were not u n i f o r m l y  sampling  which c o u l d o f f e r  quadrats  roughly  proved too few to give r e s u l t s  a r e l i a b l e estimate  seeds per u n i t area.  distributed  of the a v a i l a b l e  The values are shown j u s t to i n d i c a t e  the q u a n t i t y of. seed produced at each s i t e .  Since,  what was r e q u i r e d was' to determine the r e p r o d u c t i v e of the e x i s t i n g s p e c i e s another  ability  method of measurement  independent of s p e c i e s d e n s i t y was adapted.  Reproductivity  of c a e s p i t o s e s p e c i e s was r a t e d from the r a t i o of f l o w e r i n g culms to n o n - f l o w e r i n g  shoots  on each bunch or t u f t .  r a t i o s were determined from shoot  c o u r t s of at l e a s t  bunches s e l e c t e d randomly i n each e x c l o s u r e .  The thirty  R e s u l t s are  shown i n Table X I I I . The  F e r t i l e to S t e r i l e  i n d i c a t e s t h a t although  (F/S) r a t i o  i n Table  the bunches of A. spicatum  XIII on the  d e p l e t e d s i d e of the fence were s m a l l , they.had a higher c a p a c i t y to produce seeds than the b i g ones on the r e l i c t side.  G r a z i n g d i d not i n t r o d u c e any change i n the r e p r o -  d u c t i v e p o t e n t i a l of S t i p a columbiana.  TABLE XII AVERAGE NUMBER OF SEED STALKS PER SQUARE MATER OF THE SAMPLED AREA Species  Site  ;  H e a v i l y Grazed  Grazed  •• -  *  Tranquille  6  4  20  81  Agropyron spicatum  6  3  Poa  9  13  112  14  2  3  Agropyron spicatum  9  1  Poa  secunda  4  l  S t i p a columbiana  7  40  Agropyron spicatum Poa  Quilchena  Minnie Lakes  Commonage  secunda  secunda  Agropyron spicatum Poa  Hamilton  ' Lightly  secunda  Ul  vo  TABLE X I I I THE FERTINE/STERILE SHOOT RATIOS OF AGROPYRON SPICATUM AND STIPA COLUMBIANA Site  Species  Lightly  Grazed  Heavily  Grazed  Tranquille  Agropyron spicatum  1:134  1:12**  Quilchena  Agropyron spicatum  1:90  1:12**  Minnie Lakes  Agropyron spicatum  1:3  Hamilton Commonage  Agropyron spicatum  1: 24  1:75*  S t i p a columbiana  1:3  1:4  * I n d i c a t e s a s i g n i f i c a n t d i f f e r e n c e (P<0.05) grazed and the h e a v i l y grazed area.  :19  between the l i g h t l y  * * I n d i c a t e s a s i g n i f i c a n t d i f f e r e n c e ( P ^ O . O l ) between the l i g h t l y grazed and the h e a v i l y grazed area.  CA  o  61  Edaphic F e a t u r e s S o i l temperature. s o i l temperature J u l y 1968  At a l l s i t e s except Minnie  r e c o r d i n g s s t a r t e d i n mid-June and  Lakes,  early  and c o n t i n u e d through winter and. s p r i n g the  f o l l o w i n g year.  Readings were taken f o r t n i g h t l y except i n  winter when o n l y monthly r e c o r d i n g was The r e s u l t s  possible.  ( F i g . 12) show that temperatures were  higher i n s o i l s on the h e a v i l y grazed side at a l l l e v e l s i n summer.  In w i n t e r the p i c t u r e changed and the s o i l  under  heavy g r a z i n g c o n d i t i o n s became c o l d e r , while the s o i l  on  the l i g h t l y grazed s i d e remained r e l a t i v e l y warmer. S o i l moisture.  R e s u l t s of s o i l moisture c o n d i t i o n s  at a l l s i t e s throughout the growing  season would have been  very u s e f u l but s e n s i n g probes were not s e t up i n time. The only d a t a a v a i l a b l e was m e t r i c methods.  r e c o r d e d at one s i t e u s i n g g r a v i -  The r e s u l t s showed a h i g h e r moisture per-  centage on the h e a v i l y grazed side than on the grazed s i d e at a l l l e v e l s I t was  deeper  ( F i g . 13) .  noted i n the f i e l d  after a r a i n f a l l ,  the wet  lightly  that i f a t r e n c h i s dug  zone on the t r e n c h w a l l  appeared  d i r e c t l y under b i g bunches of A. spicatum than under  the i n t e r v e n i n g patches of bare ground.  No  such p e n e t r a t i o n  62  TRANQUILLE  30  S I T E •-•--•heavily grazed side  20  lightly grazed side  10  _  0  -5 LU  or  A  h 20  D  K <  10  or  2  UJ  5 CM  Depth  <L o  Z UJ  \r  20  10  5  O CM  Depth  **  16  July  June Fig.  12  (a)  10  8  6 14 5 9 Dec feb Jan Nov Soil temperature by depth and treatment from June 1968 through February 1 9 6 9 . 13 Aug  Sept  Oct  — Q U I L C H E N A  20  S I T dEe p l e t e d ^_ _ — •  side Lightly s r a zeol  s  10  2 5 CM Depth  20  Depth  5 0 CM  —  o  UJ  20  h  10  HAMILTON  CC  C 0 MM OM AGE S I T E  cc UI  a 20h  10 SO  1  L i 1. • J ' i  IS" " J5 June July  Aug.  Sept.  Oct.  —  CM  r > e  P  t h  1 Nov.  Dec.  - -  Feb  <-  q  64^  ^_ heavily grazed lightly  grazed  — h e a v i l y fcazed ^ \  lightly grazed relict  ^50 \25  12 O  10  2 July Pig,  23 July  6 Aug  20 Aug  3 Sept  17  Sept  Oct  15  Oct  29  Oct  CM  C  65 d i f f e r e n c e s were observed  on the d e p l e t e d s i d e of the  f e n c e l i n e among s m a l l bunches of A. spicatum.  I n order to  demonstrate t h i s phenomenon, an experiment was s e t up i n the greenhouse i n the f o l l o w i n g p a t t e r n .  A wooden box of  the dimensions i l l u s t r a t e d i n F i g u r e 15 was b u i l t and f i l l e d w i t h packed garden s o i l . box w i t h soil  s o i l , Bouyoucos moisture  At the time of f i l l i n g the b l o c k s were s e t i n the  i n three v e r t i c a l rows a t 70, 50, 25, and 10 cms.  below the top s u r f a c e .  Two t r a n s p l a n t e d b i g bunches  (A & B) of A. spicatum were p l a n t e d on top of two of the v e r t i c a l rows of moisture  b l o c k s as shown i n F i g u r e  l e a v i n g the middle row of b l o c k s act  as a c o n t r o l .  15,  (C) under bare ground to  A p e r i o d of one month was allowed to  pass b e f o r e t e s t i n g s t a r t e d i n order to allow the bunches to  get e s t a b l i s h e d .  was c o n s t r u c t e d  I n the meantime a mist s p r a y i n g system  ( F i g . 15),  and i t s h e i g h t adjusted so that  the a p p l i c a t o r s d i s c h a r g e d water i n a f a i r l y d i s t r i b u t i o n over  the r e q u i r e d area.  the sprayed moisture  uniform  The u n i f o r m i t y of  a t the canopy l e v e l was t e s t e d by  r e p l a c i n g the t e s t p l a n t box w i t h cans and measuring the amount of water c o l l e c t e d a f t e r a given time. system was used i n order  to prevent  tendency of o v e r - s a t u r a t i n g the s o i l the box.  A mist  spray  r u n o f f and reduce the along the w a l l s of  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 c o n t i n u e d f o r t h r e e 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  m o i s t u r e s t a t u s of the s o i l was  always measured b e f o r e  w a t e r i n g and one hour a f t e r w a t e r i n g .  Since very  small  l a t e r a l movement o f water n o r m a l l y does occur i n the i t was  soil,  assumed t h a t the m o i s t u r e d i f f e r e n c e s r e c o r d e d i n  each row of b l o c k s was t r a t i o n of water  m a i n l y due t o the downward pene-  a p p l i e d a t the top of the row.  After  t e s t i n g f o u r times i n 8 weeks w i t h b o t h bunches of A. spicatum u n d i p p e d , ( P i g . 14-)  bunch B was  c l i p p e d t o ground  level  and t e s t i n g c o n t i n u e d f o r a f u r t h e r 6 weeks  period, r  ii  11  Fig.  I/)-  The experiment f o r m o i s t u r e p e n e t r a t i o n beneath bunches of Agropyron s p i c a t u m . Bunch B clipped.  67 F i g u r e l 6 (I) r e p r e s e n t s the mean of the determinations  of the l e v e l s at which moisture  before.bunch B was  clipped.  was  sensed,  F i g u r e l 6 (II) shows the same  r e s u l t s a f t e r bunch B had been c l i p p e d . t i v e l y s m a l l e r than bunch A.  4  Bunch B was  rela-  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  i n f l u e n c e s the s o i l moisture  distribution  patterns. S o i l o r g a n i c matter.  The  r e s u l t s shown In Table  XIV  and F i g u r e 17 i n d i c a t e t h a t the o r g a n i c matter l e v e l s were higher  i n the s o i l s of the depleted areas at l e a s t  top 25 cm. latter  at T r a n q u i l l e , and Quilchena  s i t e there was  ( F i g . 17)..  At  of o r g a n i c matter than the  at Minnie  the  a r e v e r s e i n the lower h o r i z o n s  On Hamilton Commonage the l e s s grazed  higher percentages side while  sites.  i n the  s i d e had  depleted  Lakes there were no marked d i f f e r e n c e s  between the l i g h t l y and the h e a v i l y grazed s i d e s .  68  69 TABLE XIV SOIL ORGANIC MATTER PERCENTAGE AT VARIOUS DEPTHS ON BOTH SIDES OP THE FENCE Depth CM.  Site Tranquille  0-2  Quilchena Minnie Lakes Hamilton Commonage  5  Tranquille Quilchena Minnie Lakes Hamilton Commonage Tranquille  10  2.65 4.39 5.85 18.67  Tranquille Quilchena Minnie Lakes Hamilton Commonage Tranquille Quilchena  Minnie Lakes Hamilton Commonage  Lower Middle Middle  9.93 1.56  Upper Lower  2.9 2.73 8.17 1.3  Middle Upper Lower  2.64  Middle  1.07  Middle  6.99 1.8 0.91 0.413  5.9 1.26  Upper  1.13 O.49  Middle Middle  1.97 0.38 0.09 0.11 0.42  1.64 0.24  Upper Lower Middle  1.5 3.3 3.06 IO.85  1.15 2.55 9.71 1.1 2.12 1.00  Hamilton Commonage  3.33 6.36 4.18  Zone  Upper  Minnie Lakes  Quilchena  H  Grassland  12.57 2.34 3.28 3.77  2.64  Minnie Lakes  50  L  Quilchena Hamilton Commonage Tranquille  25  Organic Matter  O.65 0.10 0.92  Lower Middle Middle  Middle  Lower  Middle Upper  70  l i g h t l y grazed h e a v i l y grazed  °  1  o 0 ° l i g h t l y grazed h e a v i l y grazed  HAMILTON COMMONAGE MINNIE LAKES  U Z <  \  -I  o o  C M Fig-.  17.  S o i l organic matter percentage a t ' v a r i o u s depths and s i t e s f o r both s i d e s of t h e f e n c e .  71  Fig.  l8.  A g r o p y r o n s p i c a t u m b u n c h e s 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 w a t e r f o r an h o u r .  V. Vegetation  Structure  The if  DISCUSSION  b a s i c assumption made i n t h i s study was  a l l f a c t o r s but g r a z i n g p r e s s u r e s  that  influencing vegetation  were the same on both s i d e s of the f e n c e l i n e , then  any  d i f f e r e n c e s i n s p e c i e s and  and  s o i l c o n d i t i o n s must be The  growth h a b i t s of p l a n t s  a r e s u l t of the g r a z i n g i n f l u e n c e .  remarkable d i f f e r e n c e s i n the species  frequency,  herbage, cover  composition,  and dry matter y i e l d of the p l a n t  s p e c i e s between the l i g h t  and h e a v i l y grazed  sides  confirm  the obvious d i f f e r e n c e s i n the p l a n t communities which the f e n c e l i n e separates.  The  r e s u l t s emphasize that heavy  g r a z i n g removes the t a l l c a e s p i t o s e  species of the  climax  g r a s s l a n d such as Agropyron spicatum and F e s t u c a s c a b r e l l a and  encourages t h e i r replacement by unpalatable  grasses w i t h with 1942,  s h o r t e r l i v e s and  s m a l l s t a t u r e or  shrubs, grasses  s t r o n g v e g e t a t i v e r e p r o d u c t i v e organs (Larson et a l . Cottom e t a l . 194-5, E l l i s o n i960, Peterson  Schmutz 1967,  Pieper  1962,  1968).  At the T r a n q u i l l e s i t e ,  i n the lower  grassland  zone, Agropyron spicatum i s b e i n g r e p l a c e d under heavy g r a z i n g , by  an u n p a l a t a b l e  shrub, A r t e m i s i a t r i d e n t at .a and  Bromus tectorum, an annual g r a s s .  The percentage compo-  s i t i o n o f A. spicatum was 6.3$  on the depleted s i d e as  compared to 65.5$ on the l i g h t l y grazed  side.  The compo-  s i t i o n o f A. t r i d e n t at.a a t the same s i t e was 76.7% on the d e p l e t e d side and 19.3$  on the l i g h t l y grazed  S i m i l a r r e s u l t s were o b t a i n e d at Quilchena,  site.  a Middle  grass-  l a n d s i t e . w h i c h i s on the g r a z i n g l a n d of the Guichon C a t t l e Co.  At t h i s site. Chrysothamnus. sp., a shrub, and  Bromus tectorum  are the major i n c r e a s e r s .  When i n t e r p r e t i n g the r e s u l t s obtained on Hamilton Commonage, a s i t e  i n the Upper g r a s s l a n d zone on the Douglas  Lake C a t t l e Co. range, i t i s important i n c r e a s i n g a l t i t u d e and moisture  to remember that  and lower temperatures  might have some, i n f l u e n c e on the v e g e t a t i o n i n t h i s zone ( T i s d a l e 19^7,  S t a r r 19^7).  However, i n s p i t e of good  growing c o n d i t i o n s , the two c h a r a c t e r i s t i c climax A..spicatum and P. s c a b r e l l a are reduced the d e p l e t e d s i d e . with short t i l l e r s  Stipa  to 0.1$  species each o n  columbiana, a p e r e n n i a l grass  ( F i g . 11 and Table VIII) and Poa  p r a t e n s i s , a rhizomatous p e r e n n i a l grass, seemed to be i n c r e a s i n g almost unchecked.  R e s u l t s at t h i s s i t e  among o t h e r s , two g e n e r a l b e l i e f s :  (1)  confirm,  that p e r s i s t e n c e  under heavy g r a z i n g i s f a v o r e d by short s t a t u r e and s o d forming h a b i t s  ( P e t t e r s o n 1962, D i x 1959);  and ( 2 )  that  most o f the weedy or i n v a d i n g s p e c i e s which succeed i n  74entering n a t u r a l grasslands  and other  undisturbed  t i e s tend to do so by means of t h e i r vigorous reproductions  (Baker 1 9 6 4 ) .  communi-  vegetative  Poa p r a t e n s i s which has  increased  almost w i t h the same v i g o r on both s i d e s of the  fenceline  i s an i l l u s t r a t i o n o f the p o i n t .  c e r t a i n why Lupinus s e r i c e u s had a lower percentage on the d e p l e t e d  composition  s i d e than on the l e s s  side of the fence at t h i s s i t e . to sheep, Lupinus s e r i c e u s  I t i s not very  grazed  Although poisonous mostly,  i s not regarded as a poisonous  p l a n t to c a t t l e .  I t i s s a i d to be moderately p a l a t a b l e .  So  t h a t s p r i n g and summer g r a z i n g  i t i s possible  h e a v i l y used s i d e e l i m i n a t e d  some of the l u p i n e s .  on the Such an  i n f l u e n c e would n o t e x i s t on the l i g h t l y grazed side where grazing  takes p l a c e  shoots of l u p i n e  i n the f a l l  and winter when the a e r i a l  are d r y . I n a d d i t i o n t r a m p l i n g  to be more e f f e c t i v e on the p l a n t The  is likely  i n s p r i n g than i n the f a l l .  v e r y low dry matter herbage y i e l d s of grasses  on the d e p l e t e d  side at a l l s i t e s emphasize that whereas  s h o r t grasses and annuals may sometimes have the same or a greater  ground cover than the c a e s p i t o s e  y i e l d of herbage i s generally!-very best  low.  species,  A. spicatum was the  herbage producer at a l l s i t e s on the l i g h t l y  sides.  their  grazed  There i s no doubt th at a b e t t e r knowledge of the  r e l a t i o n s h i p of A. spicatum  to Its- micro-environment  will  75 not o n l y l e a d to i t s b e t t e r u t i l i z a t i o n but w i l l a l s o help  as a forage  plant  to r e - e s t a b l i s h i t over i t s p r i m e v a l  range.  Growth  Habits Measurements of t i l l e r h e i g h t s  and  Agropyron spicatum i n d i c a t e d t h a t there v i g o r of t h i s s p e c i e s f o l l o w i n g overuse. and  l e a f blade l e n g t h were the best  vigor.  a f t e r s t u d y i n g grass v i g o r i n two  revealed  Also the F/S  Tiller  leafy t i l l e r s .  p r a i r i e pastures  (Fertile/Sterile).shoot  ratios tended to  of f l o w e r i n g shoots i n s t e a d of  s p e c i e s as a group, i t has  some disadvantageous  i n d i v i d u a l adult plant.  A number of  workers have demonstrated t h a t i n s e v e r a l grass initiation  ing '(Lange 1956, et one  a l . 1968). can  i s associated with Sanneveld 1958,  I f such behavior  speculate  the v e g e t a t i v e  in  Whereas seed s e t t i n g i n s u r e s the s u r v i v a l  consequences on the  floral  heights  i n d i c a t o r s of p l a n t  t h a t i n c r e a s e d g r a z i n g of the species  favor a high production  of the  i s a d e c l i n e i n the  been made by H a z e l l (1967)  A s i m i l a r conclusion had  Oklahoma.  l e a f l e n g t h of  species,  a reduction in t i l l e r -  Booysen e_t a l .  Laude  e x i s t s i n A. spicatum then  t h a t i n the f i n a l a n a l y s i s , removal of  shoot by g r a z i n g 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 p l a n t , t h a t i s , r e d u c t i o n of p h o t o s y n t h e t i c and  accelerating decline i n vigor.  material  Under continuous  g r a z i n g both f a c t o r s can a c t on the p l a n t  simultaneously.  By mid-June the few f l o w e r i n g culms on the bunches of A. spicatum are up to 6 0 c m . t a l l . :  primordia  of the v e g e t a t i v e  tillers  I n a d d i t i o n , the  (which make up the  b i g g e s t p a r t of the canopy o f the b u n c h ) ( F i g . over 2 0 cm. above the ground.  6 ) are w e l l  This means that any g r a z i n g  which takes p l a c e any time from l a t e s p r i n g onwards removes both the f l o w e r i n g shoots and the a p i c a l p r i m o r d i a vegetative parts.  t i l l e r s which bear most of the p h o t o s y n t h e t i c  Removal of the a p i c a l primordium of a grass, t i l l e r  g e n e r a l l y i m p l i e s t h a t no f u r t h e r a p i c a l l e a f will  of the  take p l a c e on the t i l l e r  columbiana, w i t h  the e x c e p t i o n  concerned.  production  In S t i p a  o f the f l o w e r i n g culms  which g e n e r a l l y grow r a p i d l y to f l o w e r i n g , the r e s t 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 5 cm. above the ground ( F i g . 1 1 ) .  than  The f l o w e r i n g culms are  l e s s p a l a t a b l e due to the presence of sharp awns and c a l l u s on the caryopses. persist  The v e g e t a t i v e  shoots,  i n which  leaves  throughout summer, are too short to be g r e a t l y  affected-by  grazing.  T h e i r p r i m o r i d a remain at ground  l e v e l throughout the growing season..  Thus when compared,  S. columbiana appears to have a b e t t e r chance of a v o i d i n g  severe g r a z i n g i n f l u e n c e than A. spicatum.  Branson  (1953)  and Booysen e t a l . (19^3) p o s t u l a t e d t h a t grasses i n which the growing p o i n t s r e a c h e a r l i e s t  a h e i g h t that permits  t h e i r removal by g r a z i n g decrease under heavy g r a z i n g , while grasses whose growing p o i n t s remain at the l e v e l usually increase.  ground  This, might be one of the reasons  f o r the i n c r e a s e of S t i p a columbiana under f a i r l y heavy grazing.  Although removal of the a p i c a l p r i m o r i d a con- .  t r i b u t e s g r e a t l y towards under  the d e c l i n e of some grass s p e c i e s  g r a z i n g , other f a c t o r s connected w i t h g r a z i n g are  a l s o important. The time of f l o w e r i n g does not appear.to be a f f e c t e d by g r a z i n g pressure, on p l a n t s of the same s p e c i e s . A l l observed s p e c i e s f l o w e r e d at the same time and when v a r i a t i o n s o c c u r r e d they had no r e l a t i o n with g r a z i n g . There were marked s p e c i e s d i f f e r e n c e s as regards to the time of boot emergence, a n t h e s i s and seed r i p e n i n g .  A.  spicatum came i n t o the boot stage at the same time as i n Poa secunda and B. tectorum but a n t h e s i s d i d 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 d i s s e m i n a t i o n . r e p r o d u c t i v e organs are exposed months.  This means that the  to g r a z i n g removal f o r two  Although grazing, seemed to "improve"  p r o d u c t i v i t y of A. spicatum as the F/S r a t i o  the seed, indicates  78  and Albertsdn e t 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 e t t i n g f e r t i l e seeds (U.S.D.A. Forest Service 1966) make new p l a n t establishment u n c e r t a i n . The observations made both i n the f i e l d and i n the greenhouse agreed w i t h the r e p o r t made by Marchand and McLean (1965) that some v a r i e t i e s of A. spicatum possess some v i v i p a r y tendencies.  There are doubts whether these  b u l b i l - l i k e s t r u c t u r e s can serve as f u n c t i o n a l p r o p a g u l e s . :  However, from t h e i r s t r u c t u r e ( F i g . 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 P l a n t Physiology, as v i v i p a r o u s s t r u c t u r e s . 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 " v i v i p a r y " and "vegetative p r o l i f e r ation".  I n t h i s t h e s i s the term v i v i p a r y has been used  f o l l o w i n g Nygren (1967).  Nygren defined v i v i p a r y as the  production of vegetative propagules in addition to, flowers.  a r i s i n g instead o f , o r  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 v i v i p a r o u s p l a n t s were put i n t o three c a t e g o r i e s , namely: 1.  Those p l a n t s 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.  P l a n t s i n which b u l b i l s are formed  i n s t e a d of  f l o w e r s , e.g. Polygonum v i v i p a r u m . 3.  P l a n t s where the i n f l o r e s c e n c e s or p a r t s t h e r e o f are transformed i n t o v e g e t a t i v e shoots, e.g. Poa a l p i n a .  It i s i n this  group where most of the v i v i p a r o u s grasses occur and g e n e r a l l y the new from the lemma of the  shoot  develops  floret.  M o r p h o l o g i c a l l y , the s t r u c t u r e s observed i n A. spicatum resemble ( F i g . 18) .  those d e s c r i b e d i n category (3)  However, i t should be emphasized  apparent v i v i p a r o u s tendency  above  that  i s not widespread  this  ina l l  s t r a i n s of A. sp i c atum and even where i t o c c u r s , normal f l o w e r i n g continues to take p l a c e . both m o d i f i e d " f l o r e t s " same i n f l o r e s c e n c e .  In a number of cases  and normal f l o r e t s o c c u r r e d i n the  I t i s the o p i n i o n of the author  whereas the s t r u c t u r e s observed i n A. spicatum may able to give r i s e presence  not be  to f u n c t i o n a l v e g e t a t i v e propagules,  their  i s reason enough to suggest that some v a r i e t i e s o f  A. spicatum are n o n - o b l i g a t e v i v i p a r o u s g r a s s e s . was  that  made to i d e n t i f y the v a r i e t i e s which e x h i b i t  phenomenon.  No  attempt  this  Observations made on the greenhouse specimens  i n d i c a t e d a h i g h percentage of i n f l o r e s c e n c e whose f l o r e t s  8o turned  into b u l b i l s  ( F i g . 8 , a ) . I t i s suspected that the  r e l a t i v e l y h i g h temperature and e x t r a i l l u m i n a t i o n to which the p l a n t s were subjected increased et  the v i v i p a r o u s  a l . (1962)  tendency (Youngner i 9 6 0 ) ,  Nygren  demonstrated t h a t v a r y i n g l i g h t and tempera-  ture c o n d i t i o n s grasses.  d u r i n g winter might have  c o n t r o l v i v i p a r y i n normally  viviparous  I f i t c o u l d be proved that some s t r a i n s of A.  spicatum are v i v i p a r o u s  then one would p o s s i b l y  t h a t some of the v a r i e t i e s are p o l y p l o i d s .  suspect  However,  v i v i p a r y does not n e c e s s a r i l y prove p o l y p l o i d y since  there  are known examples of d i p l o i d grasses which are v i v i p a r o u s e.g.  Poa a l p i n a ( 2 n * 14) ( S k a l i n s k a 1 9 5 2 ) . The  r e s u l t s on the seed d i s p e r s a l mechanism i n  S t i p a columbiana suggest that the success of t h i s  species  i n the h e a v i l y used c o n d i t i o n s might a l s o be r e l a t e d to i t s a b i l i t y to s e t numerous seeds capable of b u r y i n g  themselves.  Such a mechanism may be f a v o r e d by open c o n d i t i o n s where t h e ground i s a c c e s s i b l e to the seed and where d i u r n a l variations  i n humidity and temperature are b i g enough to  facilitate  t w i s t i n g and u n t w i s t i n g  and  o f the awn.  The crowded  p o s s i b l y humid ground on the l e s s grazed side might b e  some of the reasons why S_. columbiana i s p o o r l y on that  side.  represented  81 There were very few, on the "ungrazed"  i f any, Bromus tectorum p l a n t s  s i d e at T r a n q u i l l e and Q u i l c h e n a s i t e s .  There were dense clumps of t h i s s p e c i e s on the h e a v i l y grazed s i d e , e x t e n d i n g r i g h t up to the fence barely crossed i t .  ( F i g . 10)  but  V a r i o u s reasons have been g i v e n i n  l i t e r a t u r e to e x p l a i n t h i s phenomenon and i t i s p o s s i b l e t h a t there are some other e x p l a n a t i o n s undiscovered. R e f e r r i n g to weedy p l a n t s I n . g e n e r a l , Baker (1964) t h a t although "weeds" are pre-adapted  stated  to. a wide v a r i e t y of  " d i s t u r b e d " s i t u a t i o n s , they are g e n e r a l l y unable n a t u r a l v e g e t a t i o n s w i t h -intense c o m p e t i t i o n .  to enter  H a r r i s (1967)  found t h a t Bromus tectorum s e e d l i n g s were, i n h i b i t e d more b y i n t r a - s p e c i f i c c o m p e t i t i o n than by i n t e r - s p e c i f i c i o n w i t h Agropyron  spicatum s e e d l i n g s .  the r o o t s of B. tectorum  competit-  He e x p l a i n e d that  s e e d l i n g s grew f a s t e r than those  of A. spicatum s e e d l i n g s , and continued to grow even i n winter.  T h i s enabled B. tectorum to r e s i s t more the.,  shortage of moisture if  i n s p r i n g and e a r l y summer. .However,  the young Agropyron  spicatum s u r v i v e the hazards  s e e d l i n g stage they become more t o l e r a n t to droughts competition. wider  and  T h e i r r o o t s are t h i c k e r and. grow e x t e n s i v e l y  and deeper  annual.  i n the  than those of Bromus tectorum which i s an  Thus i t may  be that the s e e d l i n g s of B.  get e s t a b l i s h e d on the bare ground patches  tectorum  i n the stand of  82 A. spicatum (Table X I ) , but never grow to m a t u r i t y . H a r r i s (1967) i s of the o p i n i o n t h a t mature Agropyron p l a n t s may  spicatum  compete w i t h Bromus tectorum f o r other f a c t o r s  i n a d d i t i o n to moisture.  He s u s p e c t s - t h a t reduced amounts  of a v a i l a b l e n i t r a t e s might be one of the other unknown factors. R e s u l t s r e p o r t e d i n t h i s t h e s i s on the a b i l i t y of the canopy of A. spicatum to i n t e r c e p t and rainfall,  redistribute  seem to have a b e a r i n g on the c a p a b i l i t y of mature  A. spicatum p l a n t s to e x e r c i s e c o n t r o l over B... tectorum. Harris  (1967) p o i n t e d out that B. tectorum tends to be a weak  competitor i n p l a c e s where there i s summer p r e c i p i t a t i o n . I f t h i s i s true then one can s p e c u l a t e t h a t , i t may  be  that  the e x t e n s i v e r o o t s of mature A. spicatum (Coupland e_t a l . 1965)  u t i l i z e s a l l the s p r i n g moisture i n top s o i l s  early  i n s p r i n g and then i f there are any recharges i n form of r a i n most of the r e c e i v e d moisture i s c o n c e n t r a t e d d i r e c t l y under the bunches.  This w i l l keep patches of hare ground  too dry f o r B. tectorum to c o l o n i z e and at the same time m a i n t a i n the supremacy of A. spicatum. In the stand. However, when the canopy of A. spicatum i s removed by g r a z i n g 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 i s of i n t e r e s t to note that g e n e r a l l y i n  83 n a t u r a l g r a s s l a n d s , c a e s p i t o s e s p e c i e s tend to dominate the dry h a b i t a t s . A. spicatum  T h i s tendency  (Passey 1963)  i s not only conspicuous i n  i n which c a e s p i t o s e v a r i e t i e s  dominate the dry s i t e s but a l s o i n other, .species i n c l u d i n g some t r o p i c a l grasses such as Sporobolus p y r a m i d a l i s , Cymbopo/gon afronardus and Cftnchrus c i l i a r i s .  I t i s hard  to g e n e r a l i z e i n a case such as t h i s but i t may be c a e s p i tose s p e c i e s have some adaptive f e a t u r e s , some of which remain u n d i s c o v e r e d , which makes them s p e c i a l l y f o r dry h a b i t a t s .  adapted  One o f these f e a t u r e s may be-the  of the canopy to i n t e r c e p t the incoming  ability  rain.  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 l e v e l s i n the s o i l s on the h e a v i l y used s i d e . can be suggested  There are a number of reasons which  to e x p l a i n the phenomenon:  First,  i t is  important to p o i n t out that determinations were s t a r t e d at the b e g i n n i n g of J u l y when most o f the annuals on the d e p l e t e d s i d e were j u s t completing t h e i r growth.  Secondly,  the b i g bunches of A. spicatum w i t h e x t e n s i v e r o o t systems on the l i g h t l y grazed side absorb  and t r a n s p i r e more water  than the s m a l l shallow-rooted annuals on the d e p l e t e d s i d e . T h i r d l y , the annuals and s m a l l p e r e n n i a l s such as Poa  secunda on the d e p l e t e d side spend  the main p a r t of t h e i r  growth e a r l y when evapo t r a n s p i r a t i o n r a t e s are r e l a t i v e l y . low.  By c o n t r a s t r a p i d growth and p r o d u c t i o n of Agropyron  spicatum occurs d u r i n g the heat of summer when evapot r a n s p i r a t i o n r a t e s are h i g h e s t .  F i n a l l y b i g bunches of  A. spicatum on the l i g h t l y grazed s i d e "concentrate" the water r e c e i v e d i n summer under t h e i r crowns.  Such a  behaviour does not only c o n f i n e the r e c e i v e d water i n the zone where t r a n s p i r a t i o n l o s s e s are g r e a t e s t , but i t a l s o makes some c o n v e n t i o n a l means'of moisture d e t e r m i n a t i o n l e s s meaningful s i n c e 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 f a v o r higher moisture  i n the s o i l on the d e p l e t e d side than on the l e s s grazed side. B a s i n g t h e i r e x p l a n a t i o n s on the o b s e r v a t i o n made by C l a r k (1937), Daubenmire e_t a l . (19^2) suggested s i n c e herbaceous  that  p l a n t s i n t e r c e p t over 50$ of the r a i n f a l l  and allow t h a t i n t e r c e p t e d water to evaporate back i n the air  ( C l a r k 1937)  then t h i s might be one of the reasons why  there was l e s s moisture i n the s o i l s of the ungrazed than the grazed.  However, Grah and Wilson  three forms of I n t e r c e p t i o n :  side  (1944) d e f i n e d  85 1.  " T r a n s i t o r y storage",, the water will air  2.  d r a i n from a p l a n t under  that  still  condition.  " C o n d i t i o n a l storage",  the a d d i t i o n a l  water that can be removed by wind or by f o r c e f u l 3.  "Residual  shaking.  storage",  or the water  can be removed only by The  t r a n s i t o r y storage  that  evaporation.  component of the i n t e r c e p t e d  rain-  f a l l e i t h e r f a l l s d i r e c t l y to the ground from the f o l i a g e or runs along  the leaves  suspected t h a t r a i n f a l l  and stems to the ground.  It is  i n t e r c e p t i o n by grasslands and  crops may be even higher  than t h a t of the f o r e s t s  (Specht  1957). In the l i g h t o f 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 r e p o r t e d observations  i n t h i s t h e s i s together  w i t h the  made by Glover and Gwynne (1962) and Gwynne  (1966), i t i s c l e a r that the f r a c t i o n of water l o s t the a i r a f t e r i n t e r c e p t i o n may not be l a r g e . of c a e s p i t o s e "funneled"  grasses,  into  In the case  most of the i n t e r c e p t e d water i s  down i n t o the crown of the bunch by the a e r i a l  shoots and then "channeled" down Into the r o o t i n g zone by  86 the p l a n t s . the  The p e r c o l a t i o n of the i n t e r c e p t e d water i n t o  s o i l under the bunch i s a c c e l e r a t e d by the high  infil-  t r a t i o n c a p a c i t y of the s o i l  i n t h i s zone created by the  e f f e c t s o f r o o t s on the s o i l  (Baver 1956).  When wet, the  canopy of A. spicatum spreads out ( F i g . 18). not only  increase'the  This does  water i n t e r c e p t i n g c a p a c i t y of the  canopy b u t i t a l s o i n c r e a s e s  the area of ground  from the incoming moisture.  The f a c t that  sheltered  transplanted  bunches were used i n the greenhouse experiment, makes the explanation  that the d i f f e r e n c e s i n water p e n e t r a t i o n i n  the A. spicatum mature stand completely u n l i k e l y .  i s mainly due to r o o t  influence  The r o o t s of the bunches^ used had no  chance to penetrate beyond 25 cm. when the t e s t i n g s t a r t e d . Assuming t h a t the r e s u l t s r e p o r t e d  are true and  t h a t A. spicatum uses i t s canopy to monopolize the incoming moisture then i t would be p o s s i b l e to answer some of the questions  connected w i t h the l o s s of v i g o r of t h i s  under g r a z i n g .  One can speculate  species  that the removal o f the  canopy of A. spicatum takes the species from i t s p l a c e where i t can out-compete i t s annual invaders. s i n c e the p l a n t i s a deeply-rooted al.  species  Secondly,  (Daubenmire _et  1942, Coupland e t a l . 1965, H a r r i s 1967)  the o n l y way  i t can d i r e c t enough water i n t o i t s r o o t i n g zone i s by means of I t s canopy.  I f the canopy I s removed the deep  87 r o o t s stop g e t t i n g the moisture ability  they need thus r e d u c i n g t h e  to regrow e s p e c i a l l y d u r i n g summer.  removal of the canopy allows the moisture  Thirdly,  to be d i s t r i b u t e d  evenly which encourages the growth of shallow-rooted c o l o n i z e r s which i n t u r n out-compete the already weakened A.  spicatum. S o i l temperature r e s u l t s  on the h e a v i l y grazed in winter.  i n d i c a t e t h a t the s o i l s  side are warmer i n summer and c o l d e r  A d i f f e r e n c e of up to 3°C. i n summer were  recorded  a t l e v e l s of 2 5 , and 50 cm. at T r a n q u i l l e and a t  Hamilton  Commonage.  100  D i f f e r e n c e s c o u l d be detected even a t  cm. below the s o i l s u r f a c e a t 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' s h e l t e r e d the s o i l from the extreme summer heat a n d the winter The  coldness. s o i l organic matter determinations  indicated  that there were higher l e v e l s of organic matter i n t h e s o i l s on the l i g h t l y grazed  sides.  the r e v e r s e o c c u r r e d and a t Minnie  At Hamilton  Commonage  Lakes there was no  marked d i f f e r e n c e between 'the values obtained o n t h e two sides.  The higher values on the d e p l e t e d side are d i f f i -  c u l t to e x p l a i n since most r e p o r t s i n the l i t e r a t u r e  have  r e p o r t e d h i g h s o i l organic matter l e v e l s on t h e u n g r a d e d  BB side  (Bharu'cha e t a l . 1958,  1969).  Sant 1966,  Schuster  e_t a l .  However, i t appears p o s s i b l e t h a t the annuals and  shrubs found  i n h i g h c o n c e n t r a t i o n s on the grazed  side a t  T r a n q u i l l e and Q u i l c h e n a c o n t r i b u t e d towards the u n u s u a l l y h i g h l e v e l s ' of organic matter.  At Hamilton Commonage,  where the i n v a d i n g s p e c i e s on the depleted side are perenn 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  d i f f e r e n c e s , on both  Lakes where there were no species  s i d e s the l e v e l s of s o i l  organic  matter were more pr l e s s the same on both s i d e s .  It is  t h e r e f o r e p o s s i b l e t h a t the annuals with short l i f e and  cycles  the shrubs which shed p l e n t y of dead leaves help to  raise  the l e v e l s of the o r g a n i c matter i n the top s o i l on  the d e p l e t e d s i d e of the f e n c e l i n e . g r a z i n g animals  Also trampling by the  i s l i k e l y to break and bury the a e r i a l p a r t s  of the annuals on the depleted s i d e . (1942) made s i m i l a r o b s e r v a t i o n s p r a i r i e of south-eastern  Daubenmire e_t a l .  i n the Agropyron-Foa  Washington.  I t would be a b i t presumptuous to draw very c o n c l u s i o n s u s i n g one year's o b s e r v a t i o n s .  firm  Nevertheless,  some of the r e s u l t s r e p o r t e d i n t h i s t h e s i s appear to shed l i g h t on more i n t e r e s t i n g p o i n t s which f u t u r e i n v e s t i g a t i o n s may develop.  Besides  r e a f f i r m i n g the w e l l documented  e f f e c t s of o v e r g r a z i n g on p l a n t s and s o i l  ( E l l i s o n 196)0) ,  89  a f e w new o b s e r v a t i o n s  h a v e b e e n made.  o u t above o t h e r s  One p o i n t w h i c h  has  tended t o stand  i s that over-use  not  only deprive  Agropyron spicatum  and  reproductive  organs b u t i t a l s o m o d i f i e s  does  of i t s photosynthetic the micro-  e n v i r o n m e n t i n s u c h a way t h a t i t i n t e r f e r e s w i t h some o f the  adaptive  f e a t u r e s which enable the species  own i n i t s d r y n a t u r a l , h a b i t a t . such adaptive  features  intercept light directed  into  One o u t s t a n d i n g  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  zones where i t i s b e s t used by t h e p l a n t  annual invaders  and e v a p o r a t i o n .  Indirectly,  that a r t i f i c i a l  I t n e e d s no  "ecotones"  associated with the f e n c e l i n e offer unparalleled for  studying  fence  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 . to i l l u s t r a t e  o  the study has  o b j e c t s u c h as a  t o c r e a t e , a new s e t o f e n v i r o n m e n t a l  further.proof  with  i s least available t o  t o demonstrate t h a t a passive  can h e l p  example o f  i s the a b i l i t y of a e r i a l p a r t s to  deep r o o t s a n d w h e r e s u c h m o i s t u r e  tried  to hold i t s  opportunity  the response o f i n d i v i d u a l range s p e c i e s t o  grazing. Suggestions But  f o r f u r t h e r w o r k a r e many and o b v i o u s .  t h e most i m p o r t a n t  ones a r e : t h a t t h e p r e s e n t  t h i s B.C. I n t e r i o r  grassland  that i n connection  with this,  tance  to the r e s u l t s reported  study of  t r a n s e c t be c o n t i n u e d , and i t w o u l d be o f g r e a t  impor-  i n t h i s a c c o u n t and t o f u t u r e  90 i n v e s t i g a t i o n to f i n d out as much as p o s s i b l e about the h i s t o r y of the g r a z i n g patterns i n the area of study.  The  author f e e l s s t r o n g l y 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 t h i s type of study.  Also- i t would be of i n t e r e s t to conduct  p i l o t i n v e s t i g a t i o n s on the water i n t e r c e p t i o n behavior of A. spicatum i n order to determine the l e a s t amount of '. canopy necessary, to maintain the moisture balance of the r o o t i n g zone.  Further studies on the "viviparous" tenden-  c i e s 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 v i v i p a r y but w i l l also c l a r i f y when normal f l o r a l i n d u c t i o n and i n i t i a t i o n take place and what environmental f a c t o r s 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 n a t u r a l and a r t i f i c i a l reseeding p o t e n t i a l s of t h e species on the range.  SUMMARY  1.  The  f i r s t phase of the e c o l o g i c a l study of  p l a n t communities separated b y . f e n c e l i n e s four grassland  s i t e s i n the  Columbia from, s p r i n g 1968  to s p r i n g 1969.  fenced e x c l o s u r e rainfall,  was  built  s o i l moisture and  3.  The  At'each  site  some s o i l  investigated.-  and  study s i t e s a permanently . instrumentation  temperature!were  apparent d i f f e r e n c e s  t i e s ; separated by  f o r measuring installed.  i n the p l a n t  communi-  the f e n c e l i h e s were q u a n t i t a t i v e l y  Although g e n e r a l l y  the  "major"  species  on both sides of the f e n c e , there were marked  differences vegetation 4.  i n herbage y i e l d , composition,frequency cover between the opposite The  columbiana was  determined by measuring t i l l e r There was  a l o s s of v i g o r  growing on the h e a v i l y grazed s i d e . the v i g o r of S t i p a columbiana was measurements were the best  and  communities.  v i g o r of Agropyron spicatum and  l e a f blade l e n g t h .  species.  on  on both s i d e s of the fence were compared. 2. " At each of the four  occurred  conducted  Southern I n t e r i o r of B r i t i s h .  p l a n t growth h a b i t s , c l i m a t i c f a c t o r s and features  was  Stipa  "height" i n A.  and  spicatum  No marked change i n  recorded.  i n d i c a t o r of v i g o r  Tiller in  "height"  caespitose  92 5.  P h e n o l o g i c a l o b s e r v a t i o n s were recorded through-  out the growing  season.  V a r i a t i o n s i n the time of f l o w e r i n g  i n a g i v e n s p e c i e s seemed not to be d i r e c t l y r e l a t e d to grazing pressure. 6.  I n Agropyron  spicatum f l o w e r i n g shoots seemed  to grow f a s t e r than t i l l e r s .  They got i n t o the boot  stage  e a r l y i n summer b u t a n t h e s i s was not recorded u n t i l a month later.  Seeds r i p e n e d approximately two months a f t e r the  boot stage.  The amount of f e r t i l e  seeds produced  i n this  s p e c i e s on both, s i d e s of the fence was very low a t a l l s i t e s except Minnie J..  Lakes.  There were i n d i c a t i o n s that " f a i r l y "  g r a z i n g tended to i n c r e a s e the r a t i o of f e r t i l e shoots on.the bunches of Agropyron 8.  heavy to s t e r i l e  spicatum.  " V i v i p a r y " or v e g e t a t i v e 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 -  a t i o n i n c r e a s e d when p l a n t s were s u b j e c t to high and supplement l i g h t i n g  temperature  i n the greenhouse i n w i n t e r .  No  s p e c i f i c measurements were made on l i g h t l e v e l s and temperature 9.  variations. I t was noted that caryopses of S t i p a  are " d r i l l e d "  columb-iana  i n t o the ground by the humidity c o n t r o l l e d .  t w i s t i n g and u n t w i s t i n g of the twice g e n i c u l a t e awns. Bromus tectorum had two types of d i s p e r s e d u n i t s .  The  topmost f e r t i l e f l o r e t was d i s p e r s e d attached to a c l u s t e r 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 d i s p e r s e d individually.  The topmost f l o r e t s are e a s i l y c a r r i e d by  wind. 10.  Although Bromus tectorum seeds can penetrate  to over 5 meters i n t o the e s t a b l i s h e d stand of Agropyron spicatum from the h e a v i l y used s i d e , there were very few mature Bromus tectorum p l a n t s on the l i g h t l y grazed  side.  I t i s p o s s i b l e A. spicatum e x e r t s c o m p e t i t i o n p r e s s u r e on the s e e d l i n g s of B. tectorum.. 11.  The a e r i a l p a r t s of Agropyron  spicatum were  shown to i n t e r c e p t water and d i r e c t i t under the crown of the p l a n t .  C l i p p i n g the a e r i a l p a r t s to ground  level  prevented the p l a n t from c o l l e c t i n g e x t r a water and the depth o f moisture p e n e t r a t i o n under the c l i p p e d bunch was the same as t h a t o f the bare ground  control.  Concentratin  the l i g h t r a i n s w i t h i n the r o o t i n g zone of the p l a n t  con-  cerned, seems to be an important adaptive f e a t u r e of deepr o o t e d c a e s p i t o s e s p e c i e s growing 12.  i n dry p l a c e s .  Higher s o i l moisture was recorded i n the s o i l  on the h e a v i l y grazed side than on the l i g h t l y grazed side This was a t t r i b u t e d t o :  (i)  a high composition  of p e r e n n i a l 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 h e a v i l y grazed  s i d e complete t h e i r growth e a r l y i n the year when e v a p o t r a n s p i r a t i o n  l o s s e s of  moisture are r e l a t i v e l y low; (ii)  the extensive  r o o t systems- of c a e s p i t o s e  s p e c i e s which e x t r a c t more moisture from the  s o i l than the shallow  r o o t systems  of annuals; (iii)  the a e r i a l p a r t s of c a e s p i t o s e which c o n f i n e  species  the i n c i d e n t moisture w i t h i n  t h e i r r o o t i n g zone, where i t . i s most l i k e l y to be l o s t through t r a n s p i r a t i o n and  l e s s l i k e l y to be detected by some  conventional  13.  means of moisture measurement.  S o i l s on the h e a v i l y grazed side were  i n summer and c o l d e r i n winter grazed s i d e .  than those.on the l i g h t l y  Dense v e g e t a t i o n on the l i g h t l y grazed c i d  might be r e s p o n s i b l e f o r the m o d i f i c a t i o n of s o i l ture .  warmo  temper  . . 14. higher  Determinations  •  95  of s o i l organic matter, i n d i c a t e d  organic matter l e v e l s i n the top 2 5 cm. of the s o i l  under heavy g r a z i n g than t h a t under l i g h t g r a z i n g . s h o r t - l i v e d shallow-rooted  annuals together with  The  shrubs  which shed dead leaves every year might be r e s p o n s i b l e f o r the high organic matter l e v e l s i n the top s o i l s on the h e a v i l y grazed 15.  side.  I t i s . s u s p e c t e d that the "supremacy" of the  c a e s p i t o s e v a r i e t i e s of Agropyron spicatum.in with  light  deep r o o t s .  dry places  summer r a i n s i s f a c i l i t a t e d by i t s canopy and Removal of the canopy e i t h e r by c l i p p i n g or  heavy g r a z i n g makes the p l a n t unable to d i r e c t the moisture i n t o i t s deep r o o t i n g zone. canopy of a c a e s p i t o s e  In a d d i t i o n removal of the  species withdraws the uneven moisture  d i s t r i b u t i o n on the s o i l s u r f a c e thus encouraging the growth of the shallow-rooted  annual  invaders.  BIBLIOGRAPHY A l b e r t s o n , P.W. R e i g e l , A, and L. Launch bauch J r . 1953. E f f e c t s of d i f f e r e n t i n t e n s i t i e s of c l i p p i n g on short grasses i n West-Central Kansas. E c o l . 34:  1-20.  A l l i s o n , L.E. 1965 i n the "Methods of s o i l a n a l y s i s Part 2" P u b l i s h e d by the American S o c i e t y of Agronomy.  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