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A study of manganese (III) oxidation of hindered phenols Poh, Bo Long 1972

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)3253  HYDROLOGIC  PROPERTIES AND  WATER  • BALANCE OF THE FOREST FLOOR OF A CANADIAN WEST COAST WATERSHED  by  ANDRE P. PLAMONDON  B.S.F., U n i v e r s i t e  L a v a l , 1968  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS  FOR THE DEGREE OF  DOCTOR OF PHILOSOPHY (Forest  Hydrology  - Biometeorology)  i n the Department of Forestry We a c c e p t t h i s required  THE  t h e s i s as c o n f o r m i n g t o t h e  standard  UNIVERSITY OF BRITISH June,  -po^d  does ^ 4 * id  1972  COLUMBIA  In p r e s e n t i n g  this thesis in p a r t i a l  f u l f i l m e n t of  requirements f o r an advanced degree at the  the  University  o f B r i t i s h Columbia, I agree t h a t the  L i b r a r y s h a l l make  it  study. I f u r t h e r  f r e e l y a v a i l a b l e f o r reference  and  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may o f my  granted by  Department or* by h i s r e p r e s e n t a t i v e s .  stood t h a t  the  s h a l l not  be  allowed without my  permission.  Department o f University  Forestry of B r i t i s h  Vancouver 8, Canada  Columbia  Head  I t i s under-  copying o r p u b l i c a t i o n o f t h i s t h e s i s  f i n a n c i a l gain  The  be  for  written  i  ABSTRACT  The  importance of the  o f e r o s i o n has  f o r e s t f l o o r i n the  prevention  been w e l l e s t a b l i s h e d ; however, i t s r o l e i n  the c o n t r o l o f the amount and p l a n t growth has  t i m i n g o f water y i e l d  and  been o n l y p a r t i a l l y i n v e s t i g a t e d . The  in need  to determine the r o l e o f the f o r e s t f l o o r i n watershed hydrol o g y i s e s p e c i a l l y important where i t i s s e v e r a l  centimeters  t h i c k as i n the humid, s t e e p l y s l o p i n g f o r e s t s of Canadian West Coast. The  the  o b j e c t i v e o f t h i s study was  q u a n t i t a t i v e l y d e s c r i b e the processes  to  c o n t r o l l i n g the amount  o f water absorbed by the f o r e s t f l o o r d u r i n g p r e c i p i t a t i o n and  the amount of water l o s t by d r a i n a g e ,  evaporation,  and  t r a n s p i r a t i o n . In a d d i t i o n , a survey of the s p a t i a l v a r i a t i o n o f the depth and  the p h y s i c a l and h y d r o l o g i c p r o p e r t i e s of  the f o r e s t f l o o r was Chapter aspect,  and  I.  undertaken.  Depth o f f o r e s t f l o o r and  altitude,  slope,  f o r e s t b a s a l area were s y s t e m a t i c a l l y measured  over f o u r r e p r e s e n t a t i v e areas w i t h i n a Coast Mountain watershed. M u l t i p l e r e g r e s s i o n was  used to develop an  equation  t h a t p r e d i c t s the average f o r e s t f l o o r depth o f a s m a l l p l o t from p h y s i o g r a p h i c and  f a c t o r s . Bulk d e n s i t y , s a t u r a t i o n c a p a c i t y  f i e l d moisture c a p a c i t y were determined i n the  from samples c o l l e c t e d i n the f i e l d .  laboratory  Bulk d e n s i t y was  r e l a t e d to depth o r to the p h y s i o g r a p h i c  not  factors. Saturation  ii  and  f i e l d moisture c a p a c i t i e s were l i n e a r l y r e l a t e d t o t h e  forest floor Chapter  depth. II.  E s t i m a t e s o f t h e e v a p o r a t i o n from t h e  f o r e s t f l o o r u s i n g the energy  balance method were compared  w i t h measurements made by a s m a l l , s e n s i t i v e  weighing  l y s i m e t e r . E v a p o r a t i o n was w e l l e s t i m a t e d by the net r a d i a t i o n minus the s o i l heat f l u x , i n d i c a t i n g a s m a l l , downward,sensible heat f l u x . R e s u l t s suggest  t h a t the  s i m i l a r i t y p r i n c i p l e was not a p p l i c a b l e under the canopy. For much o f the time, e v a p o r a t i o n from the f o r e s t was  floor  a c a p i l l a r y flow l i m i t e d , r a t h e r than an energy  limited,  process. Chapter  III.  The r o l e o f the f o r e s t f l o o r i n water-  shed hydrology was i n v e s t i g a t e d by measuring the components of  i t s water balance on a 30° s l o p e and by determining i t s  water r e t e n t i o n and h y d r a u l i c c o n d u c t i v i t y c h a r a c t e r i s t i c s i n the l a b o r a t o r y . The h y d r a u l i c c o n d u c t i v i t y v a r i e d by about three o r d e r s o f magnitude over a range o f m a t r i c p o t e n t i a l s between -0.01 and -0.1 b a r s . When the f o r e s t f l o o r had reached rainfall, for  i t s maximum water content d u r i n g  the drainage r a t e through  approximately  the m a t r i x  0.5% o f the r a i n f a l l  r a t e . The amount  of  water absorbed  of  t h e i n i t i a l water content and h y d r a u l i c c o n d u c t i v i t y .  I t appears  during r a i n f a l l  accounted  was l a r g e l y a f u n c t i o n  t h a t t h e f o r e s t f l o o r c o n t r i b u t e s t o delayed  storm-  iii  flow,  stores  plants, or  a significant  does not  significantly  a f f e c t streamflow Chapter  measure the  IV.  The  conductivity  are  state  measuring  undisturbed  laboratory  briefly  sample o f  i s described.  are  that  top  of  the  water content w i t h i n  the  hanging plate  the  at the  the  gradient  be  can  length  of  the  hydraulic  The  simple  at  steady-  a constant  of  in the  rate  the  sample  method at  maintained  is controlled  w a t e r column from a forest floor a small  i n the  hanging water  core. matric  s a m p l e by  column.  of  the  a c h r o m a t o g r a p h y micropump the  to  conductivity  main f e a t u r e s  method i s t h a t  the  flow,  used  forest floor material  - length  bottom of  advantage o f  the  by  a variable  t o base  for  c h a r a c t e r i s t i c s of  reviewed. A  water i s a p p l i e d  sample  contribute  procedures p r e v i o u s l y  porous m a t e r i a l  an  a v a i l a b l e water  peaks.  hydraulic  method o f  amount o f  the while  by  porous  An potential  adjusting  iv TABLE OF CONTENTS  Page ABSTRACT  i  LIST OF TABLES  viii  LIST OF FIGURES  -  ix  ACKNOWLEDGEMENTS  xlii  Introduction  1  Literature Cited  3  CHAPTER I - GENERAL SURVEY OF SOME PHYSICAL AND HYDROLOGIC CHARACTERISTICS OF THE FOREST FLOOR  6  Introduction  6  F i e l d Design and Procedures  7  L a b o r a t o r y Procedures  12  Results  1*+  and D i s c u s s i o n  a) P h y s i c a l c h a r a c t e r i s t i c s  14  F o r e s t f l o o r depth and i n f l u e n c i n g parameters  15  F o r e s t f l o o r depth, weight, and bulk d e n s i t y r e l a t i o n s h i p s  19  D i s t r i b u t i o n o f f o r e s t f l o o r depth.. 22 b) H y d r o l o g i c  characteristics  25  Saturation capacity  30  F i e l d moisture c a p a c i t y  33  V  Page Conclusion... Literature  Cited...  CHAPTER I I - ENERGY BALANCE METHOD FOR ESTIMATING EVAPORATION FROM THE FOREST FLOOR  38  Introduction  39  Theory  HO  E x p e r i m e n t a l S i t e and Measurements  42  Results  45  and D i s c u s s i o n  Energy balance  45  Bowen r a t i o and s i m i l a r i t y  47  Aerodynamic method  52  Turbulence under the canopy  54  Evaporation  59  and s o i l moisture  Conclusion Literature  59 Cited  60  CHAPTER I I I - THE ROLE OF HYDROLOGIC PROPERTIES OF THE FOREST FLOOR IN WATERSHED HYDROLOGY  63  Introduction  64  Theory  65  E x p e r i m e n t a l S i t e and Methods  69  Results  76  and D i s c u s s i o n  Water r e t e n t i o n c h a r a c t e r i s t i c s .  76  Hydraulic  78  conductivity characteristics..  Water balance o f the f o r e s t precipitation  floor  during 80  vi Page Water balance o f the f o r e s t  f l o o r during  drying periods  85  Seasonal d i s t r i b u t i o n o f water content i n the f o r e s t  floor  88  Implications f o r plant  growth  94  I m p l i c a t i o n s f o r watershed hydrology  94  Conclusion Literature  96 Cited  98  CHAPTER IV - LABORATORY MEASUREMENTS OF HYDRAULIC CONDUCTIVITY CHARACTERISTICS OF THE FOREST FLOOR  ..  Introduction  99 99  Review o f Procedures Used P r e v i o u s l y  100  Methods and R e s u l t s  105  Literature  10 8  Cited  APPENDIX I - L i s t o f the p l o t numbers i n Chapter I by  area  I l l  APPENDIX I I - T a b u l a t i o n by p l o t s  o f the average depths  o f humus and t o t a l f o r e s t  f l o o r with  r e s p e c t i v e standard d e v i a t i o n s , biophysical  characteristics  their  and o f the  (Chapter I ) . . . 112  APPENDIX I I I - L i s t i n g o f sample c h a r a c t e r i s t i c s  by p l o t  f o r Chapter I . Four samples were c o l l e c t e d i n each p l o t  115  vii Page APPENDIX IV - Time trends o f t o t a l water p o t e n t i a l profiles  f o r the f o r e s t f l o o r  during  three drying periods APPENDIX V  - Drainage, and  evaporation,  120 transpiration,  t o t a l water d e p l e t i o n r a t e s f o r -  the f o r e s t f l o o r f o r a d r y i n g p e r i o d APPENDIX vi.  -  Volumetric  water contents  of n e g l i g i b l e drainage p o t e n t i a l o f -15 bars  124  a t the time  and a t a m a t r i c 126  viii LIST OF TABLES Table Chapter  Page I  1  P l o t frequency biophysical  d i s t r i b u t i o n by c l a s s e s o f  features  11  2  Forest f l o o r physical  characteristics  3  Ground cover by study areas  4  Coefficients  16  o f c o r r e l a t i o n between f o r e s t  f l o o r depth and i n f l u e n c i n g 5  15  parameters  18  Average and c o n f i d e n c e l i m i t s o f f i e l d moisture  and s a t u r a t i o n  capacities  30  CHAPTER I I 3 1  -3  V o l u m e t r i c water content cm cm  and  e v a p o r a t i o n r a t e s f o r the f o r e s t  floor  (mm d a y )  49  - 1  2  A n a l y s i s o f temperature and wind speed data under the canopy by 30 sec mean v a l u e s over s i x 26-min p e r i o d s on 10 August 1971  57  CHAPTER I I I 1  Water balance The  components d u r i n g  d a t a a r e f o r p e r i o d s d u r i n g which the  p r e c i p i t a t i o n i n t e n s i t y , matric and  rainfall.  total potential  l y constant  potential,  g r a d i e n t were r e l a t i v e 84  ix LIST OF FIGURES Figure  Page  Chapter I 1  L o c a t i o n o f the p l o t s w i t h i n Seymour Watershed  2  9  Relation of forest  f l o o r depth t o  influencing  parameters 3  Relation of forest forest  4  20 f l o o r oven-dry weight to  f l o o r depth  21  R e l a t i o n between b u l k d e n s i t y and  forest  f l o o r depth 5  23  Frequency d i s t r i b u t i o n s o f humus and  forest  f l o o r depths i n A r e a s 1, 2, 3 and 4 6  D e t a i l e d map o f f o r e s t  24  f l o o r depth i n P l o t A  (Seymour Watershed) 7  D e t a i l e d map o f f o r e s t  26 f l o o r depth i n P l o t B  (Seymour Watershed) 8  27  Frequency d i s t r i b u t i o n s o f humus and  forest  f l o o r depths w i t h i n P l o t s A and B 9  29  R e l a t i o n between s a t u r a t i o n c a p a c i t y , e x p r e s s ed i n c e n t i m e t e r s o f w a t e r , a n d f o r e s t  floor  depth 10  R e l a t i o n between f i e l d  31 moisture capacity  e x p r e s s e d i n c e n t i m e t e r s o f w a t e r and f l o o r depth  forest 34  X  Figure  Page  Chapter I I 1  Measured and c a l c u l a t e d energy  balance  components f o r a wet (1 August, 19 70) and 2  a dry (9 August, 1971) day  Temperature and vapour p r e s s u r e  46 differ-  ences between 20 and 110 cm above the forest floor 3  48  Mean temperature d i f f e r e n c e s f o r p e r i o d s of  2 min between 2 0 and 110 cm above the  f o r e s t f l o o r measured with a s p i r a t e d and u n a s p i r a t e d thermocouples 4  H a l f h o u r l y v a l u e s o f eddy d i f f u s i v i t y for at  5  51  water vapour versus mean wind speed 110 cm above the f o r e s t f l o o r  D a i l y lysimeter evaporation rate  53 versus  v o l u m e t r i c water content o f s o i l between 0 and 5 cm  60  Chapter I I I 1  C r o s s - s e c t i o n o f s o i l on land with angle  a, showing two-dimensional  slope  coordinate  system and flow v e c t o r s 2  Typical forest floor profile  67 and bulk  d e n s i t i e s o f the L, F, and H h o r i z o n s  70  xi  Figure 3  Page Water  retention  forest  floor  c h a r a c t e r i s t i c s of the  a t 1,  2, 6,  10, and  14-cm  depths 4  . 77  Hydraulic of  conductivity  the matric  (0 t o 8-cm  d e p t h ) and H  hydraulic  0.01  cm  day  ± 0.07,  and  function  p o t e n t i a l f o r the F  depth) h o r i z o n s . in  as a  The  (8 t o  17-cm  measurement  errors  c o n d u c t i v i t i e s o f 100, are approximately  1  + 0.003 cm d a y  +  1,  1.0,  respective-  - 1  !y 5  79  Changes time  of 7  8  9  16-cm  ...  water content d e p t h s and  the f o r e s t f l o o r  a t t h e 2, 6,  t o t a l water during  Drainage, evaporation,  rates  floor  during  period  Drainage, evaporation,  rates  floor  during  period  horizons  water  .86  f o r the f o r e s t i n October  c o n t e n t o f t h e F and  as a f u n c t i o n o f t i m e . The  content  plotted  i n September...  t r a n s p i r a t i o n , and  water d e p l e t i o n  Volumetric  83  f o r the f o r e s t  total  a drying  content  t r a n s p i r a t i o n , and  water d e p l e t i o n a drying  81  9,  rainfall  total  water  floor  rainfall  Volumetric and  water p o t e n t i a l with  and d e p t h f o r t h e f o r e s t  during 6  of total  and r a i n f a l l  are  87  H  total  also 89  xii  Figure  Page R e l a t i o n s h i p between the minimum water  10  content b e f o r e r a i n f a l l and the maximum i n c r e a s e o f water content d u r i n g r a i n fall  f o r a 17-cm  a 30°slope. The  thick forest floor  v o l u m e t r i c water content 3  a t s a t u r a t i o n was Chapter 1  IV  1:1  l i n e was  on  0.8 8 cm  fitted  -3 cm  . The  93  by eye t o the d a t a . .  Diagram o f the apparatus  used t o measure  h y d r a u l i c c o n d u c t i v i t y c h a r a c t e r i s t i c s of the f o r e s t f l o o r m a t e r i a l i n the  laboratory.106  ACKNOWLEDGEMENTS  The  author i s indebted  t o Dr. B.C. G o o d e l l ,  Professor  o f F o r e s t Hydrology, F a c u l t y o f F o r e s t r y and t o Dr. T.A. B l a c k , A s s i s t a n t P r o f e s s o r o f Biometeorology, Department o f S o i l Science all  f o r t h e i r guidance and encouragement d u r i n g  phases o f t h i s  study.  S p e c i a l thanks are due t o Mr. J . W a l t e r s , the U.B.C. Research F o r e s t and t o the G r e a t e r Board f o r t h e i r c o o p e r a t i o n  Director of  Vancouver Water  d u r i n g the f i e l d phase o f t h i s  study. S i n c e r e thanks goes t o Dr. J . DeVries cooperation  forhis willing  d u r i n g the l a b o r a t o r y phase o f t h i s  research.  I wish t o extend my thanks to Drs. T. B a l l a r d , P. Haddock, and A. Kozak f o r t h e i r h e l p f u l l c r i t i c i s m s the w r i t i n g phase o f t h i s  during  thesis.  Many thanks t o the S o i l Science  and F o r e s t r y s t a f f f o r  their assistance. The  r e q u i r e d funds were made a v a i l a b l e through  grants  from the N a t i o n a l Research C o u n c i l o f Canada and the Canada Department o f the Environment Je r e m e r c i e mis  (NCWRR).  t r e s specialement  mon epouse pour a v o i r  s a competence de s e c r e t a i r e a ma d i s p o s i t i o n et p l u s  encore pour sa p a t i e n c e carriere  d'etudiant.  e t son support  moral durant  ma  INTRODUCTION The has  r o l e o f the f o r e s t f l o o r i n watershed  hydrology  l o n g been a c o n t r o v e r s i a l s u b j e c t o f study.  t h i s century, water by  Henri  (1904) i n v e s t i g a t e d the a b s o r p t i o n  leaf l i t t e r .  n o t a b l y one  by  Early i n  S t u d i e s of broader scope  followed,  Lowdermilk (1930) i n which the e f f e c t s  f o r e s t l i t t e r on e r o s i o n , r u n o f f and  by f o r e s t l i t t e r .  qualitative. Stickel  The  of  p e r c o l a t i o n were  examined through comparison between p l o t s covered covered  of  and  not  r e s u l t s were, however, o n l y  (1931), as r e p o r t e d by K i t t r e d g e  (1948)  u s i n g c o r r e l a t i o n a n a l y s i s found t h a t the e v a p o r a t i o n  rate  }  from the f o r e s t f l o o r was  the s i n g l e most  f a c t o r i n f l u e n c i n g i t s moisture  important  content.  In more r e c e n t y e a r s , s e v e r a l q u a n t i t a t i v e s t u d i e s o f water r e l a t i o n s h i p s o f the f o r e s t f l o o r have been undertaken but none have attempted the comprehensive  and  q u a n t i t a t i v e e v a l u a t i o n o f the processes  the  controlling  amount o f water absorbed d u r i n g p r e c i p i t a t i o n and amount o f water l o s t by d r a i n a g e , transpiration Broadfoot, and  ( B a l c i , 1964;  1953;  P a t r i c , 1965;  Metz, 1958;  R u t t e r , 1966;  Bernard, 1963;  C u r t i s , 1960; Helvey, 1964;  Molchanov, 1963; Semago and  evaporation,  and  Blow,  K i t t r e d g e , 1948; Mader and  P l a c e , 1950;  Nash, 1962;  the  1955; Helvey  Lull,  1968;  Rowe,  1955;  Trimble  and  Lull,1956).  Such a comprehensive study o f the h y d r o l o g i c r o l e  of  a t h i c k f o r e s t f l o o r on s t e e p l y s l o p i n g land i s the o b j e c t -  i v e o f t h i s study. The study was comprised o f f o u r parts: (i)  a survey o f the s p a t i a l v a r i a b i l i t y o f some hydrol o g i c and p h y s i c a l p r o p e r t i e s o f the f o r e s t  floor  over a mountainous watershed, near Vancouver, Depth, b u l k d e n s i t y , and water r e t e n t i o n  B.C.  capacity  o f the f o r e s t f l o o r were determined f o r b i o p h y e i c a l l y d i f f e r e n t areas o f the watershed. The are r e p o r t e d (ii)  results  i n Chapt. 1.  the development and t e s t i n g o f methods o f e s t i m a t i n g e v a p o r a t i o n from the f o r e s t f l o o r . The study was c a r r i e d out i n a Douglas f i r p l a n t a t i o n on the U n i v e r s i t y o f B r i t i s h Columbia Research F o r e s t a t Haney, B.C. under w e l l d e f i n e boundary  conditions.  Values o f the e v a p o r a t i o n c a l c u l a t e d by the energy b a l a n c e and aerodynamic methods were compared w i t h t h a t measured  by a small, weighing  l y s i m e t e r . These r e s u l t s are r e p o r t e d i n Chapt. 2. ( i i i ) the measurement o f the water b a l a n c e components  of  the f o r e s t f l o o r on a 30° s l o p e i n Seymour Watershed d u r i n g n a t u r a l w e t t i n g and d r y i n g p e r i o d s . I t was attempted t o e x p l a i n the magnitude o f the water s t o r a g e , d r a i n a g e , and e v a p o r a t i o n components water b a l a n c e by a b e t t e r knowledge  o f the  o f the water  r e t e n t i o n and c o n d u c t i v i t y p r o p e r t i e s o f the f o r e s t  - 3 f l o o r . The r e s u l t s o f t h i s study  are r e p o r t e d i n  Chapt. 3. (iv)  the l a b o r a t o r y measurement o f the c o n d u c t i v i t y c h a r a c t e r i s t i c s o f the f o r e s t f l o o r . These c h a r a c t e r i s t i c s are p a r t i c u l a r l y d i f f i c u l t  to  determine f o r the f o r e s t f l o o r m a t e r i a l . The method o f measurement i s d e s c r i b e d i n Chapt. 4.  Literature Cited BALCI, A.N.  ,  1964.  P h y s i c a l , chemical,  and h y d r o l o g i c a l  p r o p e r t i e s o f c e r t a i n Western Washington f o r e s t  floor  t y p e s . Unpub. PhD. T h e s i s . Wash. S t a t e Univ. BERNARD, J.M.  196 3.  F o r e s t f l o o r moisture c a p a c i t y o f  the New J e r s e y pine b a r r e n s . BLOW, F.E.  1955.  Quantity  o f l i t t e r upon upland  Ecology  44: 574-576.  and h y d r o l o g i c  characteristics  oak f o r e s t s i n e a s t e r n  Tennessee.  J o u r . F o r e s t r y 53: 190-195. BR0ADF00T, W.M.  195 3.  U.S. F o r e s t Serv. CURTIS, W.R.  1960.  U.S. F o r e s t Serv. KITTREDGE, J . Hill,  194 8.  Moisture  i n hardwood f o r e s t  floor.  S.E. F o r e s t r y Note 85, l p . Moisture  storage by l e a f  litter.  Lake S t a t e Tech. Note 577, 2pp. Forest i n f l u e n c e s .  349pp. MacGraw-  N.Y.  HELVEY, J.D., and J.H. PATRIC.  Canopy and  litter  i n t e r c e p t i o n o f r a i n f a l l by hardwoods o f e a s t e r n  United  States.  196 5.  Water Resources Res. 1: 19 3^206.  - 4 HELVEY, J.D.  1964.  forest l i t t e r Forest  R a i n f a l l i n t e r c e p t i o n by hardwood  i n t h e southern A p p a l a c h i a n .  Serv, Res. Paper SE-8, 9pp.  HENRI, E. morte.  19 04.  F a c u l t e d ' i m b i b i t i o n de l a c o u v e r t u r e  Revue des Eaux e t F o r e t s  LOWDERMILK, W.C.  19 30.  Influence  r u n - o f f , p e r c o l a t i o n , and s o i l 28:  U.S.  43: 353-361. o f f o r e s t l i t t e r on  erosion.  J . Forestry  474-491.  MADER, D.L. and H.W. LULL. water storage  196 8.  Depth, weight, and  o f t h e f o r e s t f l o o r i n white p i n e  i n Massachusetts.  stands  U.S. F o r e s t Serv. Res. Paper NE-109,  35pp. METZ, L . J .  1958.  Forestry  56: 36.  MOLCHANOV, A.A. Translated  M o i s t u r e h e l d i n pine  196 3.  litter.  J.  The h y d r o l o g i c a l r o l e o f f o r e s t s .  from R u s s i a n I s r a e l program f o r  scientific  t r a n s l a t i o n 400pp. PLACE, I . C M .  1950.  Comparative moisture regimes o f  humus and r o t t e n wood. Res.  Div. S i l v .  ROWE, P.B.  Can Dept. Res. Develop.  L e a f 1 . 37.  1955.  E f f e c t s o f the f o r e s t f l o o r on  d i s p o s i t i o n o f r a i n f a l l i n pine 53:  Forest  stands.  Jour.  Forestry  342-348.  RUTTER, A . J .  1966.  Studies  on the water r e l a t i o n o f  Pinus s y l v e s t r i s i n p l a n t a t i o n c o n d i t i o n s .  IV D i r e c t  - 5 observations  on the r a t e s o f t r a n s p i r a t i o n ,  o f i n t e r c e p t e d water, and e v a p o r a t i o n surface.  J . Appl.  evaporation  from the s o i l  E c o l . 3: 393-405.  SEMAGO, W.T. and A . J . NASH.  1962.  Interception of  p r e c i p i t a t i o n by a hardwood f o r e s t f l o o r i n the M i s s o u r i Ozarks. Bull.  Univ. M i s s o u r i Agr. Expt. S t a . Res.  796, 31pp.  TRIMBLE, G.R., J r . , and H.W.  LULL.  1956.  The r o l e o f  f o r e s t humus i n watershed management i n New England. U.S. F o r e s t  Serv. NE. S t a . Paper 85, 34pp.  -  6  -  GENERAL SURVEY OF SOME PHYSICAL AND HYDROLOGIC.  CHARACTERISTICS  OF THE FOREST FLOOR Abstract. aspect,  Depth o f f o r e s t f l o o r and a l t i t u d e ,  and f o r e s t b a s a l  slope,  a r e a were s y s t e m a t i c a l l y  measured o v e r f o u r r e p r e s e n t a t i v e  areas w i t h i n a Coast  M o u n t a i n w a t e r s h e d . M u l t i p l e r e g r e s s i o n was u s e d t o d e v e l o p an  equation  t h a t p r e d i c t s t h e average f o r e s t f l o o r  of a s m a l l p l o t from physiographic saturation capacity in  the laboratory  density factors. ly  and f i e l d  f a c t o r s . Bulk  depth  density,  m o i s t u r e c a p a c i t y were d e t e r m i n e d  from samples c o l l e c t e d i n t h e f i e l d .  was n o t r e l a t e d t o d e p t h o r t o t h e Saturation  and f i e l d  physiographic  m o i s t u r e c a p a c i t i e s were  related to the forest floor  Bulk  linear-  depth.  Introduction The f o r e s t f l o o r c o m p o n e n t o f t h e f o r e s t e c o s y s t e m serves important functions regeneration, logic  and s o i l  i n nutrient c y c l i n g , tree  biology,  and i n f l u e n c e s many h y d r o -  c h a r a c t e r i s t i c s of forest lands.  mineral  soil  I t insulates the  f r o m extremes o f t e m p e r a t u r e and o f f e r s  mechanical p r o t e c t i o n from e r o s i o n a l f o r c e s . I t s water c a p a c i t y may be i m p o r t a n t i n d e l a y i n g  peak  holding  flow.  Knowledge o f t h e d e p t h , s p a t i a l d i s t r i b u t i o n , and p h y s i c a l and h y d r o l o g i c  properties  of the forest floor i s  n e c e s s a r y f o r the sound management o f f o r e s t e d It  i s impossible to f u l l y  understand  watersheds.  the h y d r o l o g i c changes  a s s o c i a t e d w i t h l a n d management without knowledge o f the r o l e of the f o r e s t f l o o r l a y e r i n the s o i l atmosphere The  - plant -  system. f i r s t s e t of o b j e c t i v e s of t h i s  survey was:  reconnaissance  t o measure the depth and the bulk d e n s i t y of  the f o r e s t f l o o r ; to e x p l o r e the s p a t i a l v a r i a t i o n of i t s depth; and t o determine  the c o r r e l a t i o n of depth w i t h some  easily recognizable, influencing The  second  parameters.  s e t of o b j e c t i v e s was:  e f f e c t s of environmental  t o determine  the  f a c t o r s on the amounts of water  h e l d at f i e l d moisture c a p a c i t y and s a t u r a t i o n c a p a c i t y , and t o f i n d out i f these amounts c o u l d be p r e d i c t e d from knowledge of the f o r e s t  f l o o r depth. An e q u a t i o n p r e d i c t i n g  the amount o f water h e l d by the f o r e s t f l o o r would make p o s s i b l e e x t r a p o l a t i o n from a d e t a i l e d p l o t study t o a l a r g e r area. Field The  Design and  survey was  Procedures  c a r r i e d out w i t h i n the Seymour R i v e r Basin  which s t r e t c h e s northward  20 m i l e s (32.2  km)  from i t s mouth  i n B u r r a r d I n l e t . The catchment i s a t y p i c a l U-shaped v a l l e y 2 mi  2  of  the Coast Mountain Range. I t s area i s 69.5  (18 0 km  of  which 30% i s covered by mature timber, 10% by immature  timber, 27% by s c r u b , 18% by a l p i n e v e g e t a t i o n , and s l i d e s , r o c k s , water, and  swamps.  15%  by  )  - 8 The  survey was  not s t a t i s t i c a l l y designed to  e s t i m a t e the v a r i a n c e o f the p h y s i c a l characteristics  o f the f o r e s t  determine what subsequent f o r assessment  or hydrologic  f l o o r , but t o  investigations  o f the r o l e o f the f o r e s t  l o g y o f a Coast Mountain  watershed.  w i l l be necessary f l o o r i n the hydro-  I f knowledge from  detailed,  plot  be s a f e l y  e x t r a p o l a t e d , t h i s type o f approach would be  highly  studies of forest  quickly  floor characteristics  can  e f f i c i e n t . On the o t h e r hand, i f the h y d r o l o g i c  characteristics  o f the f o r e s t  sampling o f a c t u a l  f l o o r vary too much s p a t i a l l y ,  moisture content over a watershed  n e c e s s a r y to supplement d e t a i l e d Two  s t u d i e s on sample  may  be  plots.  sampling areas were p i c k e d on each s i d e o f the  v a l l e y , a t d i f f e r e n t d i s t a n c e s from the I n l e t , f o r systema t i c study o f f o r e s t  f l o o r depth under overmature  timber stands  ( F i g . 1 ) . A l l areas were w i t h i n the C o a s t a l , Western Hemlock, B i o g e o c l i m a t i c Zone o f B r i t i s h Columbia  (Krajina,  1965). T h i s  zone corresponds to the South P a c i f i c Coast Region d e s c r i b e d by Rowe (1959). In each area a t r a n s e c t  (C.2) l i n e was  more o r l e s s p e r p e n d i c u l a r l y to the r i v e r from the bottom to the 2,500 f e e t bottom a p l o t was  valley  (762 m) contour l e v e l . On the  established  every 200  feet  established  more i n t e n s i v e  a t every 400  feet  a plot  (121.9 m) o f a l t i t u d e . For  study o f Area 1, f o u r supplementary  were r u n up to an a l t i t u d e of 1,000  valley  (61 m) o f h o r i z o n -  t a l d i s t a n c e , whereas on the steep s i d e s o f the v a l l e y was  run  feet  (304.8  m).  transects  -  F i g u r e 1.  9  -  L o c a t i o n o f the p l o t s w i t h i n Seymour watershed.  - 10 -  A t o t a l o f 60 p l o t s were thus e s t a b l i s h e d i n d i f f e r e n t a r e a s , and over ranges o f a l t i t u d e s and exposures. Table 1 shows the number o f p l o t s by study areas and f a c t o r s assumed t o i n f l u e n c e f o r e s t f l o o r depth. W i t h i n each p l o t the f o r e s t f l o o r depth was  system-  a t i c a l l y measured along a l i n e p a s s i n g through the p l o t c e n t e r and r u n n i n g a t 4 5° t o the main t r a n s e c t  line.  Twenty depth measurements were taken a t one f o o t on each s i d e o f the c e n t e r . Any measurable on l o g s and stones was  intervals  l a y e r o f humus  included.  The f o r e s t f l o o r was not s e p a r a t e d i n t o L, F , and H h o r i z o n s as the s e p a r a t i o n between F and H would have been a r b i t r a r y . The t o t a l depth o f o r g a n i c m a t e r i a l  exclusive  of  humus. The  i d e n t i f i a b l e r o t t e n wood was c l a s s i f i e d as  t h i c k n e s s o f r o t t e n wood was r e c o r d e d s e p a r a t e l y . Three parameters o f depth were thus o b t a i n e d : depth o f humus, depth o f r o t t e n wood, and t o t a l depth o f f o r e s t  floor  (humus p l u s r o t t e n wood). Logs and undecomposed  branches  l y i n g on the top o f the l i t t e r were not i n c l u d e d i n the depth measurements. C a l c u l a t i o n o f average depth and volume of  each component, and a l s o c a l c u l a t i o n o f the percentage  of  total  f o r e s t f l o o r volume t h a t r o t t e n wood r e p r e s e n t s  were thus p o s s i b l e . Four types o f s o i l  c o v e r were r e c o g n i z e d : humus,  r o t t e n wood, undecomposed l o g s and branches, and s t o n e s .  - 11 -  T a b l e 1. P l o t frequency d i s t r i b u t i o n by c l a s s e s o f biophysical Influencing parameters AREA  ALTITUDE  SLOPE  ORIENTATION  BASAL AREA of f o r e s t  RADIATION INDEX  features. Classes  Frequency (No. o f p l o t s i n each c l a s s )  1 2 3 4 7 01 1001 1301 1601 1901 2201  38 7 8 7 -  10 00 1300 1600 1900 2200 2500  0-10 11 - 20 21 - 30 31 - 40 HI - 50  ft ft ft ft ft ft degree degree degree degree degree  N NE E SE S SW S  0.4092 0.5301 0.5860 -  14 15 15 10 6 2 5 33 4 5 3 8  1-80 81 - 160 161 - 240 241 - 320 321 - 400 401 - 480 0.2561 -  26 15 5 . 5 5. 4  sq.ft/acre sq.ft/acre sq.ft/acre sq.ft/acre sq.ft/acre sq.ft/acre  0.186 2 0.2893 0.3713 0.4185 0.4690 0.5447 0.5912  2 19 18 10 6 5 2 4 1 41 1 7 4  - 12 The  -  f r a c t i o n a l a r e a covered by each type was  estimated o  i n each p l o t by means o f f o u r 10  square f o o t  (0.9 29 m  g r i d s . A c i r c u l a r sample o f f o r e s t f l o o r 15 cm was  c o l l e c t e d from each of f o u r p o i n t s  l o c a t e d about the p l o t To  20 f e e t  of t h e s e , t o be  and  (6.1  m)  p r o p e r t i e s , two  i n s i z e were e s t a b l i s h e d .  c a l l e d P l o t A, was  located  One  i n Area 1,  l a t e r used to map  the  the  t h e s e , depths o f humus  the p o s i t i o n o f each t r e e was  was  of  plots,  r o t t e n wood were measured at i n t e r s e c t i o n s of a  information  one  recorded.  This  f o r e s t f l o o r depth  t r e e l o c a t i o n s . Twenty-five samples were a l s o c o l l e c t e d  from each p l o t at the for v a r i a b i l i t y  confusion  i n the  t o as P l o t A and from the  Laboratory  i n t e r s e c t i o n s o f a 5 square f o o t g r i d  s t u d i e s o f oven-dry weight, b u l k  saturation capacity,  be  hydrologic  P l o t B, i n Area 3 ( F i g . 1 ) . On  f o o t g r i d and  and  systematically  center.  f o r e s t f l o o r depth and  other,  i n diameter  i n v e s t i g a t e more i n t e n s i v e l y the v a r i a b i l i t y  each 20 by  )  and  f i e l d moisture c a p a c i t y .  t e x t , these two  To  avoid  referred plots  will  transects. Procedures brought to  the  f o r d e t e r m i n a t i o n of the b u l k d e n s i t y ,  the  m o i s t u r e c a p a c i t y , and d e n s i t y was  p l o t s w i l l be  P l o t B whereas the n o n - s p e c i f i e d  Each sample c o l l e c t e d i n the laboratory  density,  the  f i e l d was  saturation capacity.  The  field  bulk  o b t a i n e d by d i v i d i n g the oven-dry weight o f  sample by volume at the  f i e l d moisture content.  the  - 13  -  F i e l d moisture c a p a c i t y has amount o f m o i s t u r e h e l d by i n the f i e l d ,  soil  been d e f i n e d  a f t e r i t has  been  covered to prevent e v a p o r a t i o n ,  t o d r a i n f o r 24 h r s . A more r e a l i s t i c  as  and  the  saturated allowed  d e f i n i t i o n of  field  m o i s t u r e c a p a c i t y i s the amount o f m o i s t u r e h e l d a f t e r the r a t e o f d r a i n a g e has  m a t e r i a l l y decreased. T h i s i s a f u n c t i o n  o f the u n s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y o f the which i n t u r n i s a f u n c t i o n o f the m a t r i c conformance w i t h B a l c i o f water was  (1964), a m a t r i c  a p p l i e d , and  e q u i l i b r i u m was  to be the  c a p a c i t y . Since the t h i c k n e s s  as r e f e r e n c e The was  p o t e n t i a l . In  p o t e n t i a l o f -100  the water content measured at  considered  ranged from 1 t o 30 cm  o f the  field  moisture  forest floor  zero g r a v i m e t r i c u o t a n t i a l ) .  procedure f o r d e t e r m i n i n g s a t u r a t i o n  the bottom end  samples  the centers o f the samples were used  levels ( i . e .  to support the  material  capacity  sample on a l a y e r of c h e e s e c l o t h  over  o f an open c y l i n d e r , completely immerse i t  i n water f o r 4 8 h r s , then suspend i t i n a i r f o r 10 min allow  f r e e drainage b e f o r e  weighing.  Another v a r i a b l e r e p o r t e d  i n the l i t e r a t u r e i s the  e f f e c t i v e s a t u r a t i o n c a p a c i t y which has Balci  been d e f i n e d  (1964) as the maximum amount o f water h e l d  rainfall.  holding  by  during  B a l c i determined the e f f e c t i v e s a t u r a t i o n  c a p a c i t y i n the l a b o r a t o r y  to  under simulated " r a i n f a l l  by  a f o r e s t - f l o o r sample on a porous p l a t e under a  cm  - I n constant  matric  p o t e n t i a l o f -100 cm o f water. With such  a system, the r e s i s t a n c e o f the p l a t e t o water flow  causes  the p a t r i c p o t e n t i a l a t the bottom o f the sample t o be somewhat h i g h e r natural r a i n f a l l mineral -100  than -100 cm o f water. In the f i e l d , under c o n d i t i o n s , the m a t r i c  p o t e n t i a l a t the  s o i l - f o r e s t f l o o r i n t e r f a c e would be h i g h e r  cm o f water and would a l s o d i f f e r  i n t e n s i t y . Since  f i e l d conditions  a b l e i n the l a b o r a t o r y  with  rainfall  are not r e a d i l y reproduce-  the author b e l i e v e s t h a t  recognition  o f e f f e c t i v e s a t u r a t i o n c a p a c i t y as a s p e c i f i c s o i l istic  should  than  not be encouraged. The water h e l d  character-  i s i n fact  a f u n c t i o n o f the average h y d r a u l i c c o n d u c t i v i t y o f the m a t e r i a l which i s a more exact and  c h a r a c t e r i s t i c . The importance  a p p l i c a t i o n o f h y d r a u l i c c o n d u c t i v i t y , as w e l l as the  f i e l d measurements o f f o r e s t f l o o r water content under high  i n t e n s i t i e s o f r a i n f a l l , w i l l be r e p o r t e d  Results  i n Chapter 3.  and D i s c u s s i o n  a) P h y s i c a l c h a r a c t e r i s t i c s Humus and t o t a l f o r e s t f l o o r depth f o r each p l o t o f the t r a n s e c t s o f Areas 1 t o 4 are r e p o r t e d  i n Appendix I I .  Averages o f p h y s i c a l c h a r a c t e r i s t i c s o f the f o r e s t f l o o r , as based on t r a n s e c t d a t a , r e s p e c t i v e confidence  a r e p r e s e n t e d i n Table 2 w i t h  limits  Over the surveyed a r e a s ,  their  (95%). the p l o t averages o f f o r e s t  f l o o r depth ranged from 3 cm t o 4 5 cm. S i x t y - t h r e e  percent  o f f o r e s t f l o o r volume was humus; the remaining volume, 37% was r o t t e n wood. The  a r e a l extent  o f each o f f o u r types o f ground cover  - 15 Table 2. F o r e s t f l o o r p h y s i c a l CHARACTERISTICS  AREA  characteristics N  AVERAGES and 95-percent Confidence limits  1  Humus depth (cm)  6,6 + 0.35  2  F o r e s t f l o o r depth (cm)  Bulk d e n s i t y (g cm  ± 1.20  280  8.3 + 0.76  320  11.6  3  1520  4  17.8  + 2.09  280  1  11.9  ± 0.65  1520  2  16.3  + 1.62  280  3  12.7  + 1.26  320  4  25.5  ± 2.55  280  All  (1-4)  0.147 ± 0.007  240  )  N= Number o f o b s e r v a t i o n s  i s p r e s e n t e d i n Table 3. I t can be seen t h a t the a r e a l extent  o f the ground s u r f a c e , i n t o which water cannot  infiltrate  (e.g. l o g and stone) i s v e r y l i m i t e d . Forest  floor  depth  and influencing  parameters.  Simple  r e g r e s s i o n e q u a t i o n s were c a l c u l a t e d r e l a t i n g t h e t o t a l f o r e s t f l o o r depth (DF), and the humus depth (DH) t o  - 16 -  a l t i t u d e , s l o p e , b a s a l a r e a , r a d i a t i o n index, and the d i s t a n c e northward from Burrard I n l e t  (Table 4 ) . These  v a r i a b l e s were assumed to be the most important, r e a d i l y measurable, b i o p h y s i c a l parameters w i t h f o r e s t f l o o r depth i n mountainous  Table 3. Ground  watersheds.  cover by study a r e a s .  Ground Area  correlated  cover  (%)  Humus  Rotten wood  Log  1  83.3  6.4  4.9  5.4  2  87.7  3.9  1.9  6.4  3  94.1  2.5  0.4  3.0  4  86.9  5.3  7.3  0.6  1  Stone  1  No o v e r - l a y e r o f humus.  The a l t i t u d e i s an index o f temperature which decomposition o f l i t t e r ,  and may  also affect  p r o d u c t i o n . The angle o f the s l o p e may  affects litter  a f f e c t the  decomposi-  t i o n r a t e by i n f l u e n c i n g th© amount o f energy a v a i l a b l e the  and  water regime o f a s i t e . The b a s a l area i s r e l a t e d t o the  age and s t o c k i n g o f the s t a n d which a f f e c t the amount o f  litter  - 17 falling  each y e a r . B a s a l a r e a i s a l s o r e l a t e d t o canopy  d e n s i t y which i n f l u e n c e s the r a d i a t i o n i n p u t t o the f o r e s t floor.  ( I n overmature  independent  stands l i t t e r f a l l  i s perhaps more  o f the b a s a l a r e a ) . The d i s t a n c e from the  I n l e t p r o b a b l y serves as an index o f sunshine d u r a t i o n , rainfall  i n t e n s i t y , and temperature,  s i n c e i t was  observed t h a t c l o u d s and r a i n occured more o f t e n towards the head o f the catchment.  The r a d i a t i o n index parameter  i s an e f f i c i e n t and convenient  f o r e x p r e s s i n g t h e combined e f f e c t s o f the  s l o p e and a s p e c t o f a s i t e on the p o t e n t i a l s o l a r i n p u t t o the s i t e .  energy  In turn, i t should be an index t o the  r a t e o f o r g a n i c matter decay and thus t o the depth o f f o r e s t f l o o r . I t i s the r a t i o o f the annual s o l a r beam r a d i a t i o n  (atmosphere  potential  a t t e n u a t i o n = 0) on the  s u r f a c e t o the annual p o t e n t i a l s o l a r beam i r r a d i a t i o n on a s u r f a c e always  normal  t o the s o l a r beam (Frank  et at.,  1966). The l a t t e r i s simply the s o l a r constant times the d u r a t i o n o f sunshine f o r the y e a r . The annual  potential  r a d i a t i o n t o t a l on a s u r f a c e i s equal t o the s o l a r constant times the c o s i n e o f the angle o f i n c i d e n c e times t h e p o t e n t i a l d u r a t i o n o f sunshine on the s u r f a c e . The  i n c i d e n c e angle f o r a t e r r e s t r i a l s u r f a c e depends  i n t u r n on f i v e independent  variables; terrestrial  latitude,  time o f day, time o f y e a r , s u r f a c e s l o p e , and s u r f a c e  - 18 o r i e n t a t i o n . T h e r e f o r e the r a d i a t i o n index  includes  e f f e c t s o f the parameters o f both s l o p e and a s p e c t .  Table 4. C o e f f i c i e n t s o f c o r r e l a t i o n between f o r e s t f l o o r depth and i n f l u e n c i n g  parameters.  Correlation coefficient Independent  variables  ALT ( A l t i t u d e SLP  feet)  (Slope degree)  BAR ( B a s a l  2 area feet )  DIS ( D i s t a n c e m i l e s ) RAD ( R a d i a t i o n N = 60  index)  Excluding  Including  r o t t e n wood DH  r o t t e n wood DF  0.538**  0.253*  0 .591**  0.128 ns  0.318*  0.244 ns  0.505**  0 .454**  -0.488**  -0.557**  ns = non s i g n i f i c a n t  *  S i g n i f i c a n t a t the 5% l e v e l  **  S i g n i f i c a n t a t the 1% l e v e l .  R a d i a t i o n index, the best s i n g l e v a r i a b l e ,  explains  about 30% o f f o r e s t f l o o r depth v a r i a t i o n . The n e g a t i v e c o r r e l a t i o n w i t h t h i s v a r i a b l e r e f l e c t s i t s e f f e c t on decomposition r a t e o f the o r g a n i c m a t t e r . The  relationships  f a c t o r s were c a l c u l a t e d  between depth and s e v e r a l by m u l t i p l e  t h a t were b e s t w i t h r e s p e c t  regression.  influencing  The equations  t o both ease o f measurement o f  - 19 the independent  -  v a r i a b l e s and the  s i g n i f i c a n c e o f the  c o r r e l a t i o n c o e f f i c i e n t s were: DH  = 13.19  - 21.7  * RAD  + 0.000339 * DIS  * ALT  R =  .751  DF = 26.31  - 38.3  * RAD  + 0.000282 * DIS  * ALT  R =  .661  In  these equations the r a d i a t i o n index i s as g i v e n  by Frank et a i . ( 1 9 6 6 ) . The d i s t a n c e and a l t i t u d e were r e s p e c t i v e l y i n m i l e s and i n f e e t . The two account  equations  f o r 56 and 44% of the v a r i a b i l i t i e s of DH and  DF  r e s p e c t i v e l y . F i g u r e 2 shows the p r e d i c t i n g s u r f a c e w i t h the 95% c o n f i d e n c e The  limits.  low percentage  of v a r i a t i o n accounted f o r  i n d i c a t e s t h a t some important f a c t o r s have not been i n c l u d e d i n the model. Past events such as f l o o d , w i n d f a l l , and may  have much e f f e c t on f o r e s t f l o o r depth but such  fire  effects  c o u l d not be measured. Rotten wood depth, which i s i n c l u d e d i n DF,  i s p r o b a b l y i n f l u e n c e d by past w i n d f a l l e v e n t s . That  f i r e may  have been i n f l u e n t i a l i s i n d i c a t e d by the  presence  of c h a r c o a l on Areas  f l o o r t h i c k n e s s on these two  1, and  observed  3. The average  areas i s l e s s . The  forest  predictive  e q u a t i o n s must be used w i t h c a u t i o n as the b a s i c data were not c o l l e c t e d at random. Forest  floor  depth,  weight,  R e g r e s s i o n a n a l y s i s was of  and  bulk  density  relationships.  used t o p r e d i c t the oven-dry  weight  the f o r e s t f l o o r i n grams per square c e n t i m e t e r (W)  i t s depth  from  ( F i g . 3). The c o n f i d e n c e l i m i t s were not computed  s i n c e the v a r i a n c e o f W about homogeneous.  the r e g r e s s i o n l i n e i s not  - 20  •  Figure  2.  Relation  ~  o f f o r e s t , f l o o r depth  . influencing  parameters.  (DF)  to  - 21 -  Figure  3.  Relation forest  of  f l o o r  forest depth.  f l o o r  oven-dry  weight  to  -  22  -  As based on sampling a l o n g t r a n s e c t s , bulk d e n s i t y i s n o t c o r r e l a t e d w i t h depth  ( F i g . 4 ) . I t was a l s o  found  t h a t b u l k d e n s i t y was n o t s i g n i f i c a n t l y c o r r e l a t e d w i t h any o f the environmental parameters measured. The v a r i a t i o n o f the b u l k d e n s i t y around  the mean i s l a r g e because  roots,  r o t t e n wood, o r m i n e r a l matter may be i n c l u d e d i n t h e sample.  These  i n c l u s i o n s cause g r e a t e r v a r i a t i o n s a t  s h a l l o w e r depths as they then r e p r e s e n t a h i g h percentage o f the t o t a l  weight.  The i n s e r t o f Figure 4 shows the r e l a t i o n s h i p between t h e b u l k d e n s i t y and depth o f samples  taken  w i t h i n the two r e l a t i v e l y u n i f o r m P l o t s A and B. I t i n d i c a t e s t h a t t h e average b u l k d e n s i t y o f the f o r e s t f l o o r was independent o f the depth i n P l o t B, whereas i t significantly  ( 9 5 % l e v e l ) decreased w i t h depth i n P l o t A.  T h i s i s e x p l a i n e d by the f a c t t h a t on P l o t A s e v e r a l were taken from the t h i c k and l o o s e l i t t e r l a y e r  samples  around  t r e e bases. Distribution  of forest  floor  depth.  o f humus and t o t a l f o r e s t f l o o r depths  The f r e q u e n c y d i s t r i b u t i o n  (humus p l u s r o t t e n  wood) a r e p r e s e n t e d by study areas i n F i g u r e 5 . In t h i s f i g u r e each c r o s s o r dot r e p r e s e n t s t h e r e l a t i v e frequency o f each c l a s s o f 2 cm depth. Zero depth i s a s e p a r a t e c l a s s . The cumulative f r e q u e n c i e s a r e a l s o p l o t t e d i n the same f i g u r e . F o r example the percentage o f t h e a r e a covered by f o r e s t  - 2 3 -  fx UJ  5  0-4  o o  Ul  rx o < HO 2 Iu. o  SD  « 01 ui a TRANSECT OO  DATA  N = 240  I  8  12  16  20  24  28  32  FOREST FLOOR DEPTH (cm)  Figure  4. R e l a t i o n between b u l k d e n s i t y and f o r e s t floor  depth.  - 24 i  1  1  1  20  1  1  1  1  1  SEYMOUR WATERSHED 1969  .  CUMULATIVE.\  I \ ' \  1  r  ;-  8  100  x— 75 AVERAGE DEPTH  i«  HUMUS  .V  10  (cm)  If— x,x"-~  90  FOREST FLOOR  « — « 140  y\  5 Are0  \.-''<?  3  CUMULATIVE^^  S20  o  o £ 100 >  -  - 75  k  \  ,•'  AVERAGE DEPTH (cm)  / / * \ . \  FOREST FLOOR « — * 120  / \ x «  / \  HUMUS  *  " 0  I 4  —I  < ! t  1  I  V...--. \ « x^ |_ i ~ i 16 20 24 DEPTH (cm)  1  AVERAGE DEPTH (cm) HUMUS • 170  50  N = I520  ,  12  1  6-5  »^- v.  Areo I I I 8  UJ  / UJ  > '^~'  15 -  25  s  o  .?>.X—«—"*  x  5 o  5  N = 300  ••v..\  o  50  1  25  x / -i.''— --r-»—.i-432 36 40 >  28  i  1  SEYMOUR WATERSHED  FOREST FLOOR x—x25-5  1  1  r 100  1969 " " "  75  N = 300 !  £  \  ^CUMULATIVE  5  o  i  -''\-''"  Area 4  ^/  ^-«-^  0  2  50  -  25  S  0  a.  75  => S  2 0  CUMULATIVE  AVERAGE DEPTH (cm) HUMUS 11-5  10  >  /T-?*^  5 -  j'J>^ 0  F i g u r e 5.  Area 2 4  ,  ,  8  * 12  FOREST FLOOR » — x 160  A  \ I \  u  H50  N'280  ^'^Ni?  16 20 24 D E P T H (cm)  28  Frequency d i s t r i b u t i o n s  25  '~"~?--^« 32  36  40  o f humus and f o r e s t  f l o o r depths i n Areas 1, 2, 3 and 4.  - 25 f l o o r l e s s than 3 cm t h i c k of f o r e s t  i n Area 1 i s 25%.  f l o o r i s r e c o g n i z e d as a f f e c t i n g  s i t e hydrology, or f o r e s t distributions  tree  regeneration,  f u e l s u p p l y , such frequency  provide useful  having a c r i t i c a l  I f a s p e c i f i c depth  estimates o f the s u r f a c e a r e a  depth o f f o r e s t  floor (Ffolliott  et al.,  1968). F o r e s t f l o o r depths were examined i n d e t a i l over P l o t s A and B ( F i g . 6 and 7 ) . In g e n e r a l the depth o f the forest  f l o o r i n c r e a s e s s h a r p l y a t the base o f each  tree.  However, the accumulation o f d e b r i s i s very v a r i a b l e any  one t r e e  around  and the o r g a n i c l a y e r depth does not smoothly  decrease w i t h d i s t a n c e away from the trunk t o i n c r e a s e a g a i n midway between 2 t r e e s . i s as much i n f l u e n c e d The  The depth i s very u n p r e d i c t a b l e and  by t e r r a i n d e p r e s s i o n s as by the t r e e s .  h e t e r o g e n e i t y o f the f o r e s t  f l o o r depth i s f u r t h e r  ed by decaying wood which i s randomly The  frequency d i s t r i b u t i o n s  depths f o r P l o t s on  distributed.  o f humus and f o r e s t  (Fig. 5). Similarly  from t h a t  floor  A and B are shown i n F i g u r e 8. The d i s t r i b u t i o n  P l o t A, Area 1 i s a p p r e c i a b l y d i f f e r e n t  itself  affect-  from t h a t  on Area 1  the d i s t r i b u t i o n on P l o t B d i f f e r s  on Area 3. T h i s e x e m p l i f i e s the h e t e r o g e n e i t y o f  these f o r e s t b) H y d r o l o g i c  floor  characteristics,  characteristics  Saturation capacities,  and f i e l d  moisture c a p a c i t i e s  determined  -  26  -  DISTANCE Cm)  Figure 6  D e t a i l e d map  of forest  (Seymour V/atershed)  f l o o r depth i n P l o t A  -  27  -  DISTANCE (m)  Figure 7 .  Detailed  map  of forest  (Seymour Watershed)  f l o o r depth i n P l o t B .  - 29 -  i 20 -  1  1 i i 1 SEYMOUR WATERSHED 1969  —i  r  r 100  CUMULATIVE •  75 AVERAGE DEPTH (cm) HUMUS 9-6  50  FOREST FLOOR i — * 14 4 N = 388 -  25  5  o z  Ul  o z  Ul  o  0  0  o 20-  VI--"'"'  ^i-""""*  1  " ^ C U M U  jjj  IOO  LATIVE  75  15 HUMUS  //// w  .'/ //  • '  F i g u r e 8.  /  . » Plot A (within 8 area12I)  FOREST FLOOR  81  O 50  «—*II0 N = 4I5  25  Vv  X/\«—-»  16 20 OEPTH (cm)  24  28  32  36  J  S  AVERAGE DEPTH (cm) 10 •  £  40  Frequency d i s t r i b u t i o n s o f humus and f o r e s t f l o o r depths w i t h i n P l o t s A and B .  - 30 from the f o r e s t f l o o r samples c o l l e c t e d i n the t r a n s e c t are l i s t e d  plots  i n Appendix I I I . Table 5 p r e s e n t s f o r a l l t r a n s e c t s the  averages and t h e c o n f i d e n c e l i m i t s o f f i e l d  moisture and  s a t u r a t i o n c a p a c i t i e s . The samples c o l l e c t e d i n the f i e l d excluded r o t t e n wood as much as p o s s i b l e , the l a t t e r b e i n g the o b j e c t  o f another  study.  Table 5. Average and c o n f i d e n c e l i m i t s o f f i e l d  moisture  and s a t u r a t i o n c a p a c i t i e s .  N = 24 0  WATER CONTENT % o f dry  Characteristics Field  weight  cm o f  % of  water  volume  moisture  capacity  214 ± 8  2.2+0.2  31+3  Saturation  453 +17  4.5+0.3  67+5  capacity  Saturation  capacity.  Simple r e g r e s s i o n  o f the s a t u r a t i o n  capacity  i n c e n t i m e t e r s o f water on f o r e s t f l o o r  explains  79% o f the v a r i a t i o n ( F i g . 9a). The l e a s t squares  l i n e intercepts the y-axis  a t 0.76 cm. B a l c i (1964),  the same method t o determine reported  depth  the s a t u r a t i o n  using  capacity,  an i n t e r c e p t a t 0.70 cm. The author b e l i e v e s  that  these p o s i t i v e i n t e r c e p t s were mainly due t o the t e c h n i q u e used.  - 31 -  Figure  9.  R e l a t i o n between s a t u r a t i o n c a p a c i t y , e x p r e s s e d i n c e n t i m e t e r s o f w a t e r and forest  floor  depth.  -  Two  systematic  32  -  e r r o r s are a s s o c i a t e d w i t h  t e c h n i q u e . At e q u i l i b r i u m the average m a t r i c  this  potential  o f a sample suspended i n a i r approximates h a l f  (negative)  i t s t o t a l depth, assuming t h a t t h e r e i s no water w i t h i n the sample and  entrapped  t h a t the m a t r i c p o t e n t i a l at the  bottom o f the sample i s z e r o . Thus the e q u i l i b r i u m m a t r i c p o t e n t i a l o f a sample i n c r e a s e s ( n e g a t i v e l y ) with i t s depth and  consequently  would tend to decrease  i t s average v o l u m e t r i c water w i t h an i n c r e a s e i n depth.  content  The  amount o f water d r a i n i n g out i s a f u n c t i o n o f the shape o f the water r e t e n t i o n c h a r a c t e r i s t i c s o f the f o r e s t m a t e r i a l . The  d a t a show t h a t the v o l u m e t r i c water  at s a t u r a t i o n c a p a c i t y decreased  significantly  w i t h an i n c r e a s e o f f o r e s t f l o o r depth. The r e g r e s s i o n l i n e i s then  floor  content  (95%level)  s l o p e o f the  s m a l l e r than i t should be. A second  source o f e r r o r i s the adherence of water to the w a l l s the c o n t a i n e r . E r r o r from t h i s source  should a l s o  depress  the s l o p e o f the r e g r e s s i o n by c a u s i n g a r e l a t i v e l y over-estimate  greater  o f s a t u r a t i o n c a p a c i t i e s o f the t h i n n e r samples.  A c o n d i t i o n e d r e g r e s s i o n p a s s i n g through the o r i g i n found  of  statistically significantly  (95% level)  was  different  from the o r i g i n a l model ( F i g . 9 a ) . I l l u s t r a t i o n o f the s p a t i a l u n i f o r m i t y o f the s a t u r a t i o n c a p a c i t y as a f u n c t i o n o f depth i s g i v e n comparison o f F i g . 9a w i t h F i g , 9b. There i s no  by  statistic-  -  ally and  significant  33  -  (95% l e v e l ) d i f f e r e n c e between the  the l e v e l s o f those two  slopes  r e g r e s s i o n l i n e s . Thus t h e r e  i s no i n d i c a t i o n t h a t s a t u r a t i o n c a p a c i t y i s i n f l u e n c e d by environmental  f a c t o r s . The  r e s i d u a l v a r i a n c e about  t r a n s e c t data l i n e i s s i g n i f i c a n t l y  the  (95% l e v e l ) g r e a t e r  than the r e s i d u a l v a r i a n c e about the P l o t B l i n e . T h i s i s p r i n c i p a l l y due t r a n s e c t data  to the s c a t t e r i n the upper p a r t o f  the  line.  S a t u r a t i o n c a p a c i t y , determined as d e s c r i b e d  earlier,  i s not a h y d r o l o g i c a l l y u s e f u l parameter on s l o p i n g l a n d . As 3 w i l l be shown i n Chapt. 3, I t exceeds by about 0.20  cm  cm  the v o l u m e t r i c water content o f the f o r e s t f l o o r d u r i n g intensity r a i n f a l l  -3  high  (0.5 cm/hr f o r 5 h r s ) . However, s a t u r a t i o n  c a p a c i t y i s very easy to measure and may comparison o f d i f f e r e n t a r e a s . The  be u s e f u l i n the  v o l u m e t r i c water  content  o f i n d i v i d u a l samples can be c a l c u l a t e d from F i g . 9 by d i v i d i n g i t s water content  at s a t u r a t i o n by i t s t o t a l  Field  The water content  moisture  capacity.  at a m a t r i c p o t e n t i a l f o r e s t f l o o r depths  -100  cm of water was  ( F i g . 10a).  v a r i a b i l i t y as compared with s a t u r a t i o n c a p a c i t y . The curves  in  depth.  centimeters  regressed  against  Depth e x p l a i n s 84% o f  79% o f the v a r i a b i l i t y  r e s i d u a l v a r i a n c e s o f the  are s i g n i f i c a n t l y d i f f e r e n t  (95% l e v e l ) .  parameters were e v a l u a t e d on the same samples.  of two  Both The  the  \  34  -  1  1  I  SEYMOUR - 6  -  1 1 F .-0-19I + 0 301 1 OF  - 4 _r>0949  I  —  1  i  1—  1  1969  WATERSHEO 1  r -09OO  -  ."^  2  N'25 (o) Tronjacl dolo - 2  )  /  I  (b) Plot 8 i 8  4  i 12  -  *  16  95-percent confidence limit*  " t OF-20"  6  0  4  ,  0  1  8  F , '0-48S0I2 - 4 •1-97 tO 08 D F  *.  2  -  r  N • 240  .  . S E-£ * 0-634  ....\r^-' . ;•:-•§• I*.: •.. : .• '• O  > 4  i 8  f '-O 137 + 0309 X DF r»0 9l7 i 12  i 16  -  r »OB4l 2  1 20  » 24  ! 2B  I 32  FOREST FLOOR DEPTH (cm)  F i g u r e 1 0 . R e l a t i o n between f i e l d m o i s t u r e expressed floor  capacity^  i n centimeters o f water and f o r e s t  depth.  }  - 35 -  d i f f e r e n c e i n the c o e f f i c i e n t s of d e t e r m i n a t i o n a t t r i b u t e d to the more r i g o r o u s technique measurements o f f i e l d  F i g u r e 10b  used i n  capacity.  shows the v a r i a t i o n of the  c a p a c i t y w i t h depth w i t h i n P l o t B .  moisture of  moisture  the v a r i a t i o n of f i e l d  is  moisture  field About  c a p a c i t y with  10% depth  i s not e x p l a i n e d even though the samples were c o l l e c t e d the same day w i t h i n a 100 differences The  square f e e t a r e a . No  significant  (95% l e v e l ) were found between curves  v o l u m e t r i c water content  of i n d i v i d u a l  a and  b.  samples  can be c a l c u l a t e d from F i g . 10 by d i v i d i n g i t s water content  at f i e l d moisture  U s e f u l i n f o r m a t i o n was  c a p a c i t y by i t s t o t a l  depth.  p r o v i d e d by u s i n g t r a n s e c t data  r e g r e s s the v o l u m e t r i c water content  at f i e l d  to  moisture  capacity  on the f o r e s t f l o o r depth. I t was  found  t h e r e was  no s i g n i f i c a n t c o r r e l a t i o n between the  that two  v a r i a b l e s . T h i s i n d i c a t e s the p o s s i b i l i t y o f e x t r a p o l a t i n g the d a t a from a p l o t to a l a r g e a r e a . From the above f i n d i n g , which says t h a t the f i e l d f o r e s t f l o o r was expected  t h a t one  moisture  c a p a c i t y o f the  the same a l l over the study a r e a , i t i s r e t e n t i o n curve w i l l be r e p r e s e n t a t i v e o f  the whole a r e a . Samples from t h r e e s i t e s were used to determine the v o l u m e t r i c water content 80 and  100  at t e n s i o n s o f  60,  cm o f water. Among the t h r e e s i t e s , the d i f f e r e n c e  - 36 d i d not  exceed the  -  experimental  error.  Conclusion On  the  watershed s t u d i e d , the  o f a s m a l l p l o t can 30%  (95%  be  average f o r e s t  p r e d i c t e d w i t h an  l e v e l ) through use  f l o o r depth  accuracy of  of i n f l u e n c i n g  factors  e v a l u a t e d from a t o p o g r a p h i c map.  Knowing the  the  saturation  forest  f l o o r at one  p o i n t , the  c a p a c i t y a t t h i s p o i n t can water (95% o f any (95%  be  forest  f l o o r sample can  be  depth  from 0 to forest  30 cm.  Since the  f l o o r are  f l o o r on  the  Literature BALCI, A.N.  estimated w i t h i n + 1.2  hydrologic characteristics  to e s t i m a t e the  FRANK, E.C.  observ-  e f f e c t s of the  of  forest  Cited Physical,  c h e m i c a l , and  Unpub. PhD.  hydrological  and  i r r a d i a t i o n on Paper RM-18.  R.  floor  T h e s i s Wash. S t a t e Univ.  LEE.  slopes.  1966.  Potential  s o l a r beam  U.S.D.A. F o r e s t Serv.  Res.  the  features  h y d r o l o g i c response of t h i s watershed.  1964.  cm  f l o o r thickness ranging  p r o p e r t i e s o f c e r t a i n Western Washington f o r e s t types.  of  f i e l d moisture c a p a c i t y  s i m i l a r over d i f f e r e n t p h y s i o g r a p h i c  appears p o s s i b l e  of  cm  l e v e l ) . These c o n f i d e n c e i n t e r v a l s o f i n d i v i d u a l  a t i o n s were determined f o r f o r e s t  it  readily  e s t i m a t e d w i t h i n ± 2.2  l e v e l ) . S i m i l a r l y , the  about  - 37 KRAJINA, V . J .  1965.  Biogeoclimatic  zones and  a t i o n o f B r i t i s h Columbia E c o l . o f Western N.A. ROWE, J.S.  1959.  Northern A f f a i r s  Bull.  123.  Forest and  regions  National  o f Canada.  classific1:  1-17.  Dept.  Resources, F o r e s t r y  Branch,  - 38 ENERGY BALANCE METHOD FOR ESTIMATING EVAPORATION FROM THE FOREST FLOOR  Abstract.  1  Estimates o f the e v a p o r a t i o n from the f o r e s t  f l o o r u s i n g the energy  balance method were compared w i t h  measurements made by a s m a l l , s e n s i t i v e , w e i g h i n g l y s i meter. E v a p o r a t i o n was w e l l estimated by the net r a d i a t i o n minus the s o i l heat f l u x , i n d i c a t i n g a small, downward, s e n s i b l e heat  f l u x . R e s u l t s suggest  t h a t the s i m i l a r i t y  p r i n c i p l e was not a p p l i c a b l e under the canopy. For much o f the time, e v a p o r a t i o n from the f o r e s t f l o o r was a capillary  flow l i m i t e d , r a t h e r than an energy  limited,  process.  T h i s c h a p t e r was submitted of Forest  Research.  as a paper t o Canadian J o u r n a l  -  -  39  Introduction F o r e s t h y d r o l o g i s t s s p e c u l a t e about the i n f l u e n c e o f the s u r f a c e o r g a n i c l a y e r o f the f o r e s t on the amount and t i m i n g o f water y i e l d , e s p e c i a l l y where t h i s  l a y e r may  s e v e r a l c e n t i m e t e r s t h i c k , as i n the c o o l , humid o f the west c o a s t o f B r i t i s h water b a l a n c e  Columbia.  forests  Knowledge o f the  of the f o r e s t f l o o r i s e s s e n t i a l t o a  s o l u t i o n o f t h i s problem, and index models  be  ( T u r n e r , 1966)  i s also r e q u i r e d i n moisture  used  f o r p r e s c r i b e d burning  programs. U n t i l now  the e v a p o r a t i o n from the f o r e s t  floor  has  been commonly e s t i m a t e d e i t h e r by p e r i o d i c g r a v i m e t r i c sampling  (Helvey, 1964;  p e r i o d i c a l l y weighing bottomed box et al. , 1962, simple and e r r o r and  Mader et a l . , 1968)  o r by  a sample c o n t a i n e d i n a s c r e e n -  (Helvey et al. , 1965) R u t t e r , 1966).  or i n a tray  These methods, a l t h o u g h  i n e x p e n s i v e , are s u b j e c t t o s e r i o u s are not a c c u r a t e enough t o y i e l d  estimates of evaporation.  (Semago  sampling  short period  L a r g e , s e n s i t i v e weighing  l y s i m e t e r s have p r o v i d e d a c c u r a t e e v a p o r a t i o n r a t e s under most a g r i c u l t u r a l c o n d i t i o n s ( F r i t s c h e n , 1966) they..are i m p r a c t i c a l The  but  .  i n mountainous, f o r e s t e d a r e a s .  m i c r o m e t e o r o l o g i c a l methods, on the o t h e r hand  have the advantages o f measuring e v a p o r a t i o n over s h o r t i n t e r v a l s without  time  d i s t u r b i n g the environment and p r o v i d i n g  i n f o r m a t i o n on the n a t u r e of the p r o c e s s e s  (Tanner,  1967).  - 40 Very  few  m i c r o m e t e o r o l o g i c a l measurements o f  e v a p o r a t i o n under a canopy have been r e p o r t e d i n the literature.  3aumgartner (1956), u s i n g the energy  technique,estimated  the e v a p o r a t i o n  f l o o r t o be somewhat s m a l l e r than  from the  0.5  forest  mm/day.  Denmead  (1964) r e p o r t e d t h a t the e v a p o r a t i o n r a t e one  meter  above the ground under a p i n e p l a n t a t i o n a t 1145 May, 1963, was  0.014  (1970) e s t i m a t e d  mrrt/hr (see h i s f i g . 2).  balance  AEST i n  Black et al.  the e v a p o r a t i o n under a snap bean canopy by  u s i n g the l i m i t i n g v a l u e o f e i t h e r the a b i l i t y o f the to for  conduct  water to the s u r f a c e o r the energy  evaporation.  can be e s t i m a t e d  The  evaporation  by  e i t h e r one  m i c r o m e t e o r o l o g i c a l methods and  eddy c o r r e l a t i o n .  The  of the  the energy b a l a n c e  evaporation  soil  available  from a s o i l  surface  three  energy b a l a n c e ,  aerodynamic,  r e s e a r c h d e s c r i b e d here  undertaken to assess the u s e f u l n e s s o f the and  }  was  aerodynamic  approaches to e s t i m a t i n g  from the f o r e s t  floor.  In  addition,  e v a p o r a t i o n measurements were made d u r i n g d r y i n g p e r i o d s to  determine t o what degree the e v a p o r a t i o n  from the  f o r e s t f l o o r i s an energy o r c a p i l l a r y flow l i m i t e d p r o c e s s .  Theory The  energy b a l a n c e  uniform,  a t the f o r e s t  f l o o r surface of a  c l o s e d canopy f o r e s t o f i n f i n i t e - e x t e n t i s  -  R where R  n  n  Ul  -  (1)  = LE + H + G  i s the net r a d i a t i o n  f l u x at the f o r e s t  floor  s u r f a c e , LE i s the l a t e n t heat f l u x , H i s the s e n s i b l e heat f l u x , and G i s the s o i l heat f l u x . t h a t h o r i z o n t a l l y advected heat i s zero. are  relatively  easy t o measure.  (1) t o e s t i m a t e LE i s how simplifying first,  T h i s assumes 3oth R  n The problem i n u s i n g  to measure K.  One  assumptions can be made at t h i s  t h a t the d i f f u s i v i t i e s  o f two point:  f o r l a t e n t and  heat t r a n s f e r w i t h i n the biomass  and G  sensible  are equal (K v  H  or  second, t h a t s e n s i b l e heat t r a n s f e r from the  to  the f o r e s t  = K, ) h canopy  f l o o r s u r f a c e i s n e g l i g i b l e because o f the  o c c u r r e n c e o f a s t r o n g temperature i n v e r s i o n d u r i n g most of  the day.  With the f i r s t  assumption  (1) becomes the  f a m i l i a r energy balance/Bowen r a t i o e q u a t i o n LE = (R - G ) / ( l + B) n where B i s the Bowen r a t i o  (B = yAT/Ae), y i s the  p s y c h r o m e t r i c c o n s t a n t , AT dry  (2)  and Ae are r e s p e c t i v e l y the  b u l b temperature d i f f e r e n c e and the vapour p r e s s u r e  d i f f e r e n c e between two h e i g h t s .  With the second  assumption  (1) becomes LE ' ~  -  R  n  - G  (3)  The f o r m a l t r a n s p o r t e q u a t i o n f o r water  expressed i n f i n i t e  vapour  form i s LE = (pc /y)K Ae/Az v  (4)  _ 42 _  where K  v  i s the eddy d i f f u s i v i t y  f o r water vapour,. Ae/Az  i s the vapour p r e s s u r e g r a d i e n t , p i s the d e n s i t y o f a i r , and c  i s the s p e c i f i c heat o f a i r .  P  A more p r a c t i c a l  o f e q u a t i o n (4) i s the simple aerodynamic  form  expression:  LE = CUAe  (5)  where, U i s the wind speed measured  at a s i n g l e  height,  Ae i s the vapour p r e s s u r e d i f f e r e n c e between two h e i g h t s , and C i s a c o n s t a n t which i s a f u n c t i o n o f the s i t e  geometry  (Tanner, 1967). The f i r s t  o b j e c t i v e o f t h i s study was  to determine  the v a l i d i t y o f the above assumptions by use of a small, weighing l v s i m e t e r .  The second o b j e c t i v e was  to  a s s e s s the u s e f u l n e s s o f the aerodynamic method i n e s t i m a t i n g e v a p o r a t i o n under the canopy.  E x p e r i m e n t a l S i t e and Measurements The study was  c a r r i e d out i n the summers o f 1970  a t the U n i v e r s i t y o f B r i t i s h 4 8 km is  e a s t o f Vancouver.  25.4  1971  Columbia Research F o r e s t ,  The average summer p r e c i p i t a t i o n  cm which i s 11% o f the annual p r e c i p i t a t i o n  ( G r i f f i t h , 1963).  The s i t e was  an 11-year o l d Douglas f i r  p l a n t a t i o n with a 2 m x 2 m tree spacing. 8.2  and  m high;  the .canopy was  2.5 m above the f o r e s t vegetation.  The t r e e s were  c l o s e d and had a w e l l d e f i n e d  floor.  The topography was  There was flat  no u n d e r s t o r y  to gently  rolling.  base  -  43  -  S u n f l e c k i n g o f the f l o o r was r e l a t i v e l y u n i f o r m . forest  f l o o r was a 1.5  The  cm t h i c k , l i t t e r l a y e r w i t h an - 3  average b u l k d e n s i t y o f 0.036 gm cm beneath the f o r e s t  .  The m i n e r a l s o i l  f l o o r was C a p i l a n o g r a v e l l y  sandy  loam c o n t a i n i n g 14% o r g a n i c n a t t e r by w e i g h t i n t h e  top  7 cm. Net r a d i a t i o n was measured c o n t i n u o u s l y w i t h a S w i s s t e c o l i n e a r net r a d i o m e t e r 1 m l o n g t o o b t a i n s p a t i a l l y and t e m p o r a l l y i n t e g r a t e d v a l u e . Four s o i l flux plates  c o n n e c t e d i n s e r i e s were l o c a t e d d i a g o n a l l y  a c r o s s one t r e e i n t e r s p a c e a t surface.  5 cm below the f o r e s t  floor  S o i l h e a t f l u x i n the t o p 5 cm was d e t e r m i n e d  by c a l o r i m e t r y ; the t e m p e r a t u r e i n t e g r a t i n g diode-thermometers.  was measured w i t h 2 The h e a t c a p a c i t y was  c a l c u l a t e d from t w i c e d a i l y measurements content  heat  i n t h e 0-5 cm d e p t h .  temperatures  of s o i l  water  S o i l heat f l u x and  were sampled t w i c e h o u r l y .  I n 1971 the  n e t r a d i o m e t e r and the h e a t f l u x p l a t e s were i n s t a l l e d 2 meters away from the 1970 l o c a t i o n . E v a p o r a t i o n was measured w i t h a s i m p l e w e i g h i n g l y s i m e t e r c o n s i s t i n g of", a 7.5 cm deep by 14.6 cm d i a m e t e r , i n s u l a t e d , a c r y l i c cylinder containing a s o i l carefully  core.  A c o r e .was  c u t each morning between 0500 and 0700 h r s .  The l y s i m e t e r was p l a c e d i n a h o l e w i t h t h e c o r e ' s f l u s h w i t h the f o r e s t  floor.  surface  Weights were r e c o r d e d e v e r y  _ 44 4 hours  w i t h a r e s o l u t i o n e q u i v a l e n t t o a 0.00G mm  o f water.  depth  The s u n f l e c k i n g p a t t e r n on t h e l y s i m e t e r  s u r f a c e was not n o t i c e a b l y d i f f e r e n t adjacent f l o o r .  from  t h a t on the  The l y s i m e t e r was made deep enough t o  p r e v e n t water shortage w i t h i n the core and consequent underestimates  of evaporation.  the s o i l . c o r e  a t t h e end o f 24 hours  profiles virtually The  sampling o f  showed  moisture  the same as those o f t h e a d j a c e n t  anemometers.  f l o o r w i t h Thornthwaite, s e n s i t i v e , cup  V.'et and d r y b u l b g r a d i e n t s between 20 and  cm above t h e f o r e s t  f l o o r were measured w i t h s h i e l d e d ,  a s p i r a t e d , 26-gauge thermocouples, apparatus  mounted on a r o t a t i n g  which i n t e r c h a n g e d top and bottom sensors  15 minutes  (Sargeant  and Tanner, 1967).  dry and wet b u l b g r a d i e n t s were c o n t i n u a l l y F u r t h e r measurements o f h o r i z o n t a l temperature  g r a d i e n t s , and temperature  and v e r t i c a l fluctuations  Suggested  0.001-  and c o n s f a n f a n wires- and were p a i n t e d w i t h  h i g h r e f l e c t a n c e paint^'. 2  under  thermocouples.  thermocouple j u n c t i o n s were made by b u t t w e l d i n g copper  Both  recorded.  the canopy were made w i t h f i n e wire, u n a s p i r a t e d  diameter  every  V/et and d r y b u l b  d i f f e r e n c e measurements had an a c c u r a c y o f 0.01 C.  The  soil.  wind v e l o c i t y was measured a t 20 and 110 cm  above t h e f o r e s t  110  Moisture  The a i r temperature  fluctuations  by-G..W. • T h u r t e l l i n a p e r s o n n a l  communication.  -  -  4 5  were measured w i t h the f i n e w i r e thermocouples of which one  junction  sensed the a c t u a l a i r temperature and the-  o t h e r the temperature o f a s h i e l d e d b r a s s b l o c k .  :  The b l o c k had a thermal time c o n s t a n t o f 2 minutes c o n t a i n e d a diode thermometer. r e c o r d e d on a s t r i p  R e s u l t s and  chart  v7ere  recorder.  c o n d i t i o n s o f south western  Columbia p r e v a i l e d d u r i n g the measurement p e r i o d s .  Only 2.5%  o f the d a i l y shortwave  reached the f o r e s t f l o o r . f l o o r was  r a d i a t i o n above the  to 0.18  canopy  The d a i l y net r a d i a t i o n at the  5% o f i t s c o u n t e r p a r t above the canopy.  volumetric s o i l 0.28  signals  Discussion  The t y p i c a l dry weather British  Thermocouple  and  The  moisture c o n t e n t o f the top 5 cm ranged from  cm', era" 3  3  i n 1970. and from 0.08  to 0.06  cm  -  3  _3  cm  . i n 1971.  Energy the  balance.  energy b a l a n c e components f o r 2 c l e a r days.  s e n s i b l e heat was (1).  F i g . 1 p r e s e n t s the d i u r n a l t r e n d s o f  calculated  The l a r g e f l u c t u a t i o n s  combined  e r r o r s i n measuring  The  as the r e s i d u a l i n e q u a t i o n i n H are the r e s u l t o f the R , G and LE.  The  upper  and lower p a r t s o f the f i g u r e compare the e v a p o r a t i o n r a t e s under the same net r a d i a t i o n f l u x but d i f f e r e n t moisture c o n d i t i o n s .  I t shows t h a t under d r i e r  soil  c o n d i t i o n s the energy not used t o evaporate water  was  soil  -  F i g u r e 1.  Measured  ns  -  and c a l c u l a t e d  components f o r a wet  energy balance  (1 August, 1970)  a d r y (9 August, 1971)  day.  and  - 47 c o n d u c t e d i n t o the s o i l . 3 cal cm  day  - 2  The s o i l h e a t f l u x changed  i n 1970 t o 13 c a l c m  - 1  Air  temperatures  5°C  h i g h e r i n 1971 than i n 1970. The  is  day  - 1  i n 1971.  under the canopy were on t h e  average  l a g i n t h e e v a p o r a t i o n measured by the  attributable  to the s l i g h t l y d i f f e r e n t  between i t and t h e u n d i s t u r b e d s o i l The  - 2  results  lysimeter  t h e r m a l regime  ( B l a c k et al. , 1 9 6 8 ) .  o f F i g . 1 were r e p r o d u c e d on s e v e r a l  with different  soil  Temperature  c o r e s i n the  occasions  lysimeter.  and v a p o u r p r e s s u r e  20 and 110 cm are shown i n F i g . 2.  differences Temperature  between inversions  d u r i n g the p e r i o d s o f s t u d y o c c u r r e d d u r i n g b o t h t h e and n i g h t t i m e . gradients  The l a r g e p o s i t i v e d a y t i m e  suggest  The s m a l l  i n p u t o f s e n s i b l e h e a t from the canopy t o the f o r e s t expected.  daytime  temperature  conditions of strong s t a b i l i t y .  indicated i n F i g . 1 i s therefore  from  This  floor  lends  support to the assumption o f n e g l i g i b l e s e n s i b l e heat t o the f o r e s t  f l o o r as e x p r e s s e d i n e q u a t i o n  n e g a t i v e vapour pressure o c c u r r e d at a l l t i m e s .  gradients  show t h a t  (3).  The  evaporation  Although nighttime condensation d i d  n o t o c c u r under t h e canopy i t was o b s e r v e d w i t h i n t h e Bowen ratio  in  and  similarity.  flux  H a l f h o u r l y Bowen r a t i o s  canopy. used  e q u a t i o n (2) were c a l c u l a t e d from the d a t a shown i n F i g . 2 . In  T a b l e 1, e v a p o r a t i o n r a t e s c a l c u l a t e d from  (2) and (3) are compared w i t h those measured by the  equations lysimeter.  -  i  i  '  1  1  i  48  -  •  i  1  •12  1  1  i  1  r  -16 -  0  •  4  •  1  6  HOURS  F i g u r e 2.  i  16  ;  i  i  20  >  •  24  POT  Temperature and vapour p r e s s u r e  differences  between 20 and 110 cm above the f o r e s t  floor.  - 49  TABLE 1.  Volumetric  and  evaporation  (mm  day ^ ) .  water  rates  Volumetric water content  Date  -  content  cm  f o r the f o r e s t  Lysimeter  cm floor  Energy balance estimates E q . (2) Eq.. (3)  1  August  1970  0.28  0.31  0.48  0.25  10  August  1970  0.18  0.26  0.43  0.21  9 August  1971  0.08  0.14  0.25  0.12. 0.10  10  August  1971  0.07  0.ll  --  11  August  1971  0.07  0.14  --  0.  H  -  50  -  E q u a t i o n (3) s l i g h t l y u n d e r e s t i m a t e s r a t e whereas  equation  1.5 t o 2 . 5 .  These r e s u l t s  the  (2) o v e r e s t i m a t e s  evaporation by a f a c t o r o f  s t r o n g l y suggest  that  s i m i l a r i t y a s s u m p t i o n (K = K, ) does n o t a p p l y v n ~ the canopy. estimated  Eddy d i f f u s i v i t i e s  the  beneath C^ )  f o r w a t e r vapour  v  from t h e l y s i m e t e r e v a p o r a t i o n r a t e s and  the  v a p o u r p r e s s u r e g r a d i e n t s f o r the a f t e r n o o n h o u r s ranged 2 - 1 2 from 30 t o 60 cm sec i n 1970, and from 18 t o 50 cm sec  1  i n 1971.  From the c a l c u l a t e d s e n s i b l e heat f l u x e s  of. F i g . 1 and t h e t e m p e r a t u r e  gradients, estimates  a f t e r n o o n v a l u e s o f the eddy d i f f u s i v i t y (K,n ) v a r i e d between 5 and 5 0 cm2 sec -1 .  f o r s e n s i b l e heat S i n c e rl was  u s u a l l y v e r y s m a l l , and had h i g h p e r c e n t a g e s these"values  of  of  Of e r r o r ,  'cannot be c o n s i d e r e d h i g h l y  reliable. C a l c u l a t i o n s i n d i c a t e d t h a t a d v e c t i o n was n e g l i g i b l y s m a l l compared t o t h e v e r t i c a l energy f l u x e s used i n equations  (2) and ( 3 ) .  thermocouple sensors vapour p r e s s u r e  The p o s s i b i l i t y o f t h e  d i s t u r b i n g the t e m p e r a t u r e  structure  Temperature d i f f e r e n c e s  thermocouple  measured by the unaspir-ated, f i n e  d i f f e r e n c e s measured by the ( F i g . 3).  and the  under the canopy was i n v e s t i g a t e d .  w i r e thermocouples were i n good agreement temperature  aspirated  with  the  aspirated  This i n d i c a t e s t h a t the  aspirated  t h e r m o c o u p l e p r o v i d e d a good e s t i m a t e o f AT under  the  -  51 -  1  1  1  T  1  1  o o o  to o z 0.6 r> III  EN  o  U _l 0.  Y  /  o o  / 0  Ul  THE  AT  cc  o 0.3  o  0  <  EM UNAS PIR  /o  ° ^  /  /  /  0.2  »-  1=1 LINE  o 0  cc UJ UJ 1CL  o  o  /  ~3  0.5 tr o UJ o u. o u. o o s 0.4 rr =>  1 0  U.B.C RESEARCH FOREST HANEY, B.C. o.e • DOUGLAS FIR 2M * 2M SPACING 6 2 M HIGH to 0.7 PLANTED 1959 z o  o  0 0  o  12 AUGUST 1971 (1038 - 1144 )  0.1 •  1  /  -  °  I  1  1  _i  I  i  i  I.I  0.2 0.3 0.4 0.5 0.6 0.7 TEMPERATURE DIFFERENCE (C) (ASPIRATED THERMOCOUPLE JUNCTIONS)  Figure  3.  Mean temperature d i f f e r e n c e s f o r p e r i o d s o f 2 min between 2 0 and 1 1 0 cm above t h e f o r e s t f l o o r measured w i t h a s p i r a t e d and u n a s p i r a t e d thermocouples.  - 52 canopy.  However, l a r g e r e l a t i v e e r r o r s o c c u r i n t h e  c a l c u l a t i o n o f LE from  (2) (Fuchs  and Tanner, 1970).  During the a f t e r n o o n the Bowen r a t i o s , which ranged - 0 . 6 t o -0.9,could 17 t o 4 5%.  from  p o s s i b l y have been i n e r r o r by  The r e l a t i v e e r r o r o f t h e Bowen r a t i o  i n c r e a s e s as i t s v a l u e s approach -1.0. of the Bowen r a t i o method causes  estimate  The i n a c c u r a c y  a maximum e r r o r o f about  30 t o 59% i n e s t i m a t i n g a f t e r n o o n v a l u e s o f LE,assuming t h a t R and G are a c c u r a t e t o 5%. n Aerodynamic  Method.  calculated  Values o f C i n e q u a t i o n  (5) were  from the l y s i m e t e r e v a p o r a t i o n r a t e and the  vapour p r e s s u r e d i f f e r e n c e between 20 and 110 cm above the forest  floor.  Considerable v a r i a b i l i t y  which i n d i c a t e d  i n C were  found  t h a t the t r a n s p o r t process was not a simple  f u n c t i o n o f U and Ae.  In o r d e r t h a t e q u a t i o n  (5) be used,  C must be e s t a b l i s h e d t o be o n l y a f u n c t i o n o f s i t e i.e.  independent  o f wind speed.  In o t h e r 'words, f o r C t o  be a c o n s t a n t , the eddy d i f f u s i v i t y must be a l i n e a r f u n c t i o n o f U. diffusivities  geometry  f o r water vapour  K  y  In F i g . 4 the eddy  f o r water vapour C ^ ) c a l c u l a t e d from t h e v  l y s i m e t e r e v a p o r a t i o n r a t e s and t h e vapour p r e s s u r e g r a d i e n t s are p l o t t e d  a g a i n s t the wind v e l o c i t y measured a t 110 cm  above t h e s u r f a c e .  No simple r e l a t i o n s h i p e x i s t s between  the two v a r i a b l e s , t h e r e f o r e the simple aerodynamic method appears floor.  t o be u n r e l i a b l e i n e s t i m a t i n g LE from t h e f o r e s t  - 53 -  U.B.C. RESEARCH FOREST HANEY, B.C. DOUGLAS FIR 211 I 2 M SPACING  9  AUGUST 1971 HOURS 0 - 4 4-8 8-12 12 - 16 16 - 2 0 20-23  8.2 M HIGH PLANTED  60  1959  O O o  oo o  50  e u O  < >-  o I  G  e  40 •  x  30  o >  20  10  0  20 EDDY  ure  4 .  Half  40  DIFFUSIVITY  60 FOR  80  100  WATER  hourly values  water vapour versus above t h e f o r e s t  120  VAPOUR  160  MO  (cm* sec" )  o f eddy  1  diffusivity for  mean w i n d  floor.  s p e e d a t 1 1 0 cm  - 54. Turbulence  under  degree of  the  stability  were c a l c u l a t e d . while  Canopy. under the  Afternoon  at night, although  difficult range  turbulent  1 to  20.  mixing  ranging  turbulence  (Oke,  1970).  from  theoretically 1965;  Oke,  0.1  starts  to  0.5  et  under corn  surface these  as  as  gravity  Our  study  the  atmosphere  of  the  deals with  above t h e  Ri =  (1970) t h a t  turbulence  numbers  = 0.3  the  size  of the  can  entirely forest  be  (Uebb ,  does n o t  small  occur,  at Ri  i n these  =  0.3.  studies  the  asperities.  due  to  such  (V/iin-Nielsen,  different  0.10  mixing  Oke  turbulence  an  found  r e p o r t e d by  waves o r k a t a b a t i c d r i f t  day.  been  c o n d i t i o n s - e x t e n d i n g high.above  c o n d i t i o n s the  high  Ri  Richardson  compared w i t h  m  and  t r a n s p o r t remains n e g l i g i b l y  were f o r s t a b l e  to  some  = 0.2  vertical  of the  2.2  decay o f t u r b u l e n c e  c e s s a t i o n of  5,  (1971).  complete  magnitudes  to  Richardson  at approximately  between R i  I t was  0.02  that  s t u d i e s i t has  to decay  numbers  g r a d i e n t s were  canopy.  although  The  from  the  numbers were e s t i m a t e d  al.  field  complete  occurs  1970).  speed  under the  Druilhet  The  ranged  Smoke s t u d i e s i n d i c a t e d  From l a b o r a t o r y and that  values  the wind  occurred  were r e p o r t e d by  to d e s c r i b e  canopy, Richardson  t o measure, R i c h a r d s o n  from  numbers  In o r d e r  processes 1965).  situation  i s turbulent during  Under  i n which most  - 55 -  • E d d i e s o f t u r b u l e n t motion are caused by the e f f e c t s o f e i t h e r t h e r m a l buoyancy or both. resulted  o r mean wind s h e a r ,  In o r d e r to f i n d out i f t u r b u l e n t  motion  from the r i s i n g o f a i r c e l l s warmed by  s u n f l e c k s on the f o r e s t  f l o o r , temperature  differences  between s u n f l e c k s and shaded areas v;ere measured near the s u r f a c e w i t h f i n e w i r e thermocouples. ranged from 10 t o 30 cm i n d i a m e t e r . j u n c t i o n was  One  sunflecks thermocouple  kept w i t h i n the c e n t e r t h i r d o f a p a r t i c u l a r  s u n f l e c k w h i l e the o t h e r thermocouple was  The  kept i n shade.  At 0.5  junction  cm above the l i t t e r  (50 cm away) s u r f a c e the  average h o r i z o n t a l temperature d i f f e r e n c e s were l e s s than 0.5  C f o r any one minute p e r i o d .  D i f f e r e n c e s of 1 C f o r  s h o r t e r time i n t e r v a l s were r e c o r d e d .  At 2 cm above the  s u r f a c e the temperature d i f f e r e n c e s were s m a l l e r than 0.2 w h i l e the 15 minute than 0.05  C.  average temperature d i f f e r e n c e s were l e s s  I t would  appear t h a t because the s u n f l e c k s  moved r a p i d l y a c r o s s the s u r f ace, t h e r e "was-not enough time f o r l o c a l h e a t i n g o f the a i r near the f o r e s t I t i s c o n c l u d e d t h a t the e f f e c t o f buoyancy f l o o r was  C  ••  floor.  near the  forest  not the f a c t o r c a u s i n g t u r b u l e n t motion under the  canopy. In view o f the observed t u r b u l e n c e under the canopy shown by the smoke r e l e a s e s , other-mechanisms"of must be c o n s i d e r e d .  turbulent  transfer  I t has been suggested t h a t the m i x i n g  - 56 under the canopy i s p r i m a r i l y caused by the t u r b u l e n t a i r c u r r e n t s above the f o r e s t (1964).  (Denmead, 1964;  Valendik,  A n a l y s e s o f t u r b u l e n c e s p e c t r a by A l l e n  (1968)  show t h a t t u r b u l e n c e under the canopy i s a s s o c i a t e d w i t h large scale eddies.  He a l s o r e p o r t e d t h a t the p e r i o d  between l a r g e gusts was o f 100 cm sec""  1  about 21 seconds f o r wind speeds  under a l a r c h  canopy.  I f t u r b u l e n t t r a n s p o r t w i t h i n and beneath the canopy i s due t o p e n e t r a t i o n o f wind gusts from above the canopy, then two r e s u l t i n g e f f e c t s can be h y p o t h e s i z e d . if  First,  t h e s e gusts t r a n s p o r t warm a i r from the canopy t o the  forest  f l o o r , t h e r e should be a p o s i t i v e c o r r e l a t i o n between  wind speed and a i r temperature.  Second, i f an i n c r e a s e i n  wind speed below the canopy r e s u l t s and c o n s e q u e n t l y , d e c r e a s e d v e r t i c a l then  i n increased  turbulence  temperature g r a d i e n t s ,  t h e r e s h o u l d be a n e g a t i v e c o r r e l a t i o n between wind  speed and temperature g r a d i e n t . H o r i z o n t a l wind speed, a i r temperature, and  vertical  temperature g r a d i e n t s beneath the canopy were measured  on  s e v e r a l c l e a r days i n o r d e r t o t e s t t h e s e two h y p o t h e s e s . The means, s t a n d a r d d e v i a t i o n s ,  s, and c o r r e l a t i o n  coefficients,  r , f o r an a f t e r n o o n p e r i o d are shown i n Table 2. In two o f the s i x p e r i o d s a s i g n i f i c a n t c o r r e l a t i o n between the wind speed and the a i r temperature i n d i c a t e s t h a t wind gusts  transported  - 57 -  TABLE 2.  A n a l y s i s o f temperature and wind  d a t a under the canopy  using  speed  30 sec mean v a l u e s  o v e r s i x 26-min p e r i o d s on 10 August  1971.  The  bar denotes the 26-min time average.  Periods U (cm sec""'")  (C)  T  AT  S  r  r  (C  AT u , u,T  AT  m"") 1  1336 -1400  1418 -1442  1442 -1506  38.9  40.9  43.3  40 . 5  36.2  32 . 6  10.6  13.1  13.3  12.5  11.6  11. 8  27. 23  27.89  28.15  28.48  28 .16  28. 31  0. 35  0.57  0.65  0 . 59  0.47  0.68  0.60 '  0.68  0.60  0 . 81  0.65  0 . 89  0.25  0 . 39  0. 32  0.42  0 .25  0 . 36  0. 33*  -0 . 20  0.04  0.16  -0 . 3 8*  0. 33*  0.03  -0 .18  0.21  * Significant  a t 95% l e v e l  1518 -1542  1542 -1606  0.06  1946 -2010  0.25 0 . 38--  some s e n s i b l e h e a t f r o m t h e c a n o p y t o t h e The  correlation  coefficients  temperature gradients In order  to f u l l y  and  is limited  surface  show any  systematic  trend.  t u r b u l e n t t r a n s p o r t under  frequency,  o r by  Soil  and  Moisture.  e i t h e r by  the  the  s i z e of turbulent  f l o o r , the  Evaporation  the  capillary  d e t e r m i n e w h i c h -of t h e s e  eddies  against  the  of s o i l  ( F i g . 5).  f l o w of w a t e r t o the  limited  evaporation  These r e s u l t s  there  s e v e r a l days d u r i n g which the  forest  5%  of the  suggest that  i n south  even though o n l y  surface,To  from- t h e  volumetric water content  drying periods  evaporation  soil  forest  r a t e s f o r sunny days were  extensive are  from  energy a v a i l a b l e at the  lysimeter evaporation  plotted  the  and  known.  Evaporation soil  floor.  between wind speed  not  describe  canopy,the o r i g i n , m u s t be  do  forest  of the net  5  cm  during  western 3 r i t i s h soil  top  water  Columbia, limits  r a d i a t i o n reaches  floor.  Conclusions The  energy balance  b e t w e e n wet  and  of the  dry  soil  moisture  content  r a t e and  an  estimate  of evaporation  forest floor differed conditions.  The  reduction of  r e s u l t e d i n a decrease i n the  increase  i n the  soil  heat f l u x .  i s g i v e n by  temperature inversions p r e v a i l i n g  (R  considerably  under the  evaporation  A simple  - G).  soil  The  canopy  hourly  strong appeared  - 59. -  1  1  1  U.B.C RESEARCH FOREST HANEY, B.C. DOUGLAS FIR 2M x 2M SPACING 8.2 M HIGH PLANTED 1959  0.3  0  fc 0.2 • o  1970  • 1971  <  or o o. < >  0.1 or ui  NET RADIATION AT THE FOREST FLOOR  >_i  doy"  • 0.3 mm 0  (WATER EQUIVALENT)  0.1  VOLUMETRIC WATER  F i g u r e 5.  1  0.2 CONTENT  0.3  (cm cm" ) -3  3  D a i l y l y s i m e t e r e v a p o r a t i o n r a t e versus v o l u m e t r i c water content o f s o i l between 0 and 5 cm.  -  to l i m i t  60 -  t h e downward movement o f s e n s i b l e h e a t .  b e t t e r estimate o f evaporation  v/ould be g i v e n  A  by (R  - G - H).  t h i s would n e c e s s i t a t e the d i r e c t measurement o f the s e n s i b l e heat. the  A b e t t e r understanding o f turbulent  canopy r e q u i r e s h i g h  three  3  0.35 the  cm  under  r e s o l u t i o n measurements o f t h e  dimensional turbulence  c o n t e n t s o f the s o i l  transport  surface  spectra.  At v o l u m e t r i c  (0-5 cm) s m a l l e r  water  than about"  -3  cm  i t would appear t h a t the e v a p o r a t i o n  rate  from  f o r e s t f l o o r s u r f a c e was l i m i t e d by the a b i l i t y o f the  s o i l t.o conduct water t o the s u r f a c e . Literature  Cited  BAUMGARTNER, A.  1956. I n v e s t i g a t i o n s o f t h e h e a t - and  water-economy o f a young f o r e s t . Melbourne  T r a n s l a t i o n No. 3760.  (1953).  BLACK, T.A., G. W. THURTELL and C.B. TANNER. 1 9 6 8 . Hydraulic and  load-cell  tests.  Soil  lysimeter, construction,  calibration  S c i . Soc. Am. Proc. 3 2 ( 5 ) : 623-629.  BLACK, T.A., C.B. TANNER and W.R. GARDNER. 1 9 7 0 . Evapotranspiration 62:  Agron. J .  66-69.  DENMEAD, O.T. diffusivities 3:  from a snap bean c r o p .  383-389.  196U. E v a p o r a t i o n  s o u r c e s and apparent  i n a f o r e s t canopy.  J . of Appl.  Meteorol.  - 61 DRUILHET, A., A. PERRIER, J . FONTAN and J . L . LAURENT. 1971. use  Analysis of turbulent t r a n s f e r s i n vegetation:  o f thoron  f o r measuring the d i f f u s i v i t y  profiles.  Boundary-Layer Meteorology 2: 17 3-187. FRITSCHEN, L . J . crops  1966.  Evapotranspiration  rates of f i e l d  determined by the Bowen r a t i o method.  Agron. J .  58: 339-342. GRIFFITH, B.G.  1968.  cone p r o d u c t i o n  Phenology, growth, and flower and  of 154 Douglas f i r t r e e s on the  U n i v e r s i t y F o r e s t as i n f l u e n c e d by c l i m a t e and fertilizer,  1957-1967.  U.B.C. F a c u l t y o f F o r e s t r y ,  B u l l . No. 6, 7 0 pp. HELVEY, J.D. and J.H. PATRIC.  1965.  Canopy and  litter  i n t e r c e p t i o n o f r a i n f a l l by hardwoods o f e a s t e r n United  States.  HELVEY, J.D.  Water Resources Res. 1: 193-206.  1964.  R a i n f a l l i n t e r c e p t i o n by hardwood  f o r e s t l i t t e r i n the southern A p p a l a c h i a n .  U.S.  F o r e s t Serv. Res. Paper SE-8. MADER, D.L. and LULL, H.W. water storage  196 8.  Depth, weight, and  o f the f o r e s t f l o o r i n white  stands i n Massachusetts.  pine  U.S.D.A. F o r . Serv. Res.  Paper NE-109. OKE, T.R. in  19 70.  Turbulent  stable conditions.  t r a n s p o r t near the ground  J . Appl. Meteorol.  9: 778-786.  -  RUTTER, A . J . Pinus  1966.  sylvestvis  62  S t u d i e s on the water r e l a t i o n s o f  i n plantation conditions.  IV.  D i r e c t o b s e r v a t i o n s on the r a t e s o f t r a n s p i r a t i o n , e v a p o r a t i o n o f i n t e r c e p t e d water, and e v a p o r a t i o n from the s o i l  surface.  J . Appl. Ecol.  SARGEANT, D.H. and C.B. TANNER.  1957.  3: 393-405. A simple  apparatus  f o r Bowen r a t i o d e t e r m i n a t i o n s .  Meteorol.  6: 414-413.  SEMAGO, W.T. and A . J . NASH.  1962.  J . Appl.  Interception of  p r e c i p i t a t i o n by a hardwood f o r e s t f l o o r i n the M i s s o u r i Ozarks. Res.  B u l l . 796.  TANNER, C.B. In  196 7.  R.M. Hagan  Agronomy  Measurement o f e v a p o t r a n s p i r a t i o n .  (ed.) I r r i g a t i o n o f A g r i c u l t u r a l  Lands.  11: 534-555.  TURNER, J.A. to  Univ. M i s s o u r i Agr. Expt. S t a .  1966.  slash burning.  The s t o r e d moisture  index/A  guide  B.C. F o r e s t S e r v i c e , P r o t e c t i o n  D i v i s i o n , V i c t o r i a , B.C. VALENDIK, E.N. of  1964.  The p e n e t r a t i o n and t r a n s f o r m a t i o n  wind i n p i n e f o r e s t s .  Can. Dept. F o r . T r a n s l a t i o n  71F. WEBB, E.K.  1965.  A e r i a l microclimate.  Meteorol.  Monographs 6: 27-53. WIIN-NIELSEN, A.  1965.  On t h e p r o p a g a t i o n o f g r a v i t y  waves i n a h y d r o s t a t i c c o m p r e s s i b l e wind s h e a r .  T e l l u s 17: 306-320.  fluid  with  vertical  -  THE  ROLE OF  63  -  OF HYDROLOGIC PROPERTIES THE  FOREST FLOOR  IN WATERSHED HYDROLOGY  1  Abstract.  The  h y d r o l o g y was  r o l e o f the  f o r e s t f l o o r i n watershed  i n v e s t i g a t e d by measuring the  o f i t s water balance on a 30° s l o p e and i t s water r e t e n t i o n and characteristics  i n the  hydraulic laboratory.  by  components determining  conductivity The  hydraulic  c o n d u c t i v i t y v a r i e d by about f o u r o r d e r s of magnitude over a range o f m a t r i c -0.08  bars.  When the  p o t e n t i a l s between -0.003  f o r e s t f l o o r had  maximum water content d u r i n g  T h i s c h a p t e r was  and  reached i t s  r a i n f a l l , the  drainage  presented as a paper at the  National  Symposium on Watersheds i n T r a n s i t i o n sponsored by American Water Resources A s s o c i a t i o n  and  Colorado  the State  U n i v e r s i t y at F o r t C o l l i n s , Colorado, on June 19-21, 1972 .  -  rate  6»* -  through the m a t r i x accounted f o r a p p r o x i m a t e l y  0.5% o f t h e r a i n f a l l during r a i n f a l l  rate.  was l a r g e l y a f u n c t i o n  water c o n t e n t and h y d r a u l i c floor.  The amount o f water absorbed  I t appears t h a t  o f the i n i t i a l  conductivity  the f o r e s t  floor  o f the f o r e s t contributes  t o d e l a y e d stormflow, s t o r e s a s i g n i f i c a n t amount o f available  water f o r p l a n t s ,  does not s i g n i f i c a n t l y  c o n t r i b u t e t o base flow o r a f f e c t  steamflow peaks.  Introduction  The  forest  sloping  f l o o r p l a y s a major r o l e i n the h y d r o l o g y o f  forest  lands.  One o f i t s more important  functions  i s t o s h i e l d the m i n e r a l s o i l from r a i n d r o p impacts which d i s l o d g e s o i l p a r t i c l e s t o cause the c l o g g i n g o f s o i l and  r e d u c t i o n o f water i n f i l t r a t i o n  It also retains the  rainfall  exceeds the i n f i l t r a t i o n  capacity  soil.  These two a s p e c t s o f the r o l e o f the f o r e s t are  soil.  c o n s i d e r a b l e water and d e t a i n s water when  intensity  o f the m i n e r a l  i n t o the m i n e r a l  pores  b e n e f i c i a l t o the w e l l  floor  regulated y i e l d o f high  quality  water.  They a r e p a r t i c u l a r l y important i n the West Coast  forests  o f B r i t i s h Columbia where the f o r e s t  f l o o r may  - 65 -  be many c e n t i m e t e r s t h i c k , where f a l l  and w i n t e r r a i n s  are p r o l o n g e d , and summers a r e d r y . Q u a l i t a t i v e l y the r o l e o f the f o r e s t f l o o r recognized  was  as e a r l y as 1930 (Lowdermilk, 1930) but  quantitative  information  on f o r e s t f l o o r s such as those  o f the Canadian West Coast i s s t i l l  l a c k i n g , as i s  knowledge o f the water c o n d u c t i n g c h a r a c t e r i s t i c s o f these o r g a n i c  profiles.  T y p i c a l f o r e s t f l o o r s on the  West Coast a r e on s l o p i n g , r a t h e r  than on f l a t ,  T h i s adds c o m p l e x i t y t o t h e i r h y d r o l o g i c The  purpose of the r e s e a r c h  reported  paper was t o e l u c i d a t e t h e h y d r o l o g i c f l o o r by a l a b o r a t o r y conductivity  role. in this  r o l e o f the f o r e s t  study o f i t s water r e t e n t i o n and  properties  b a l a n c e under c o n d i t i o n s c y c l e s o f w e t t i n g and  land.  and a f i e l d  study o f i t s water  of s l o p i n g land  and n a t u r a l  drying.  Theory The  flow o f water through an i s o t r o p i c porous medium can  be c a l c u l a t e d by the t h r e e - d i m e n s i o n a l form o f t h e Darcy e q u a t i o n : -*•  Q = -kViJ.  (1)  -*•  where Q i s t h e volume flow o f water per u n i t  cross-sectional  -  are  -  p e r u n i t time; k i s the h y d r a u l i c  which i s a f u n c t i o n the  66  potential  conductivity,  o f s o i l water c o n t e n t ; and 7^ i s  gradient  vector.  In s o i l s w i t h n e g l i g i b l e  the p o t e n t i a l i s g i v e n by i|» = ip + 4< , ^ g m where 4» i s t h e g r a v i t a t i o n a l p o t e n t i a l and u> i s t h e g " m . osmotic D o t e n t i a l ,  matric p o t e n t i a l .  In a n i s o t r o p i c  considered a tensor rather  s o i l s , k must be  than a s c a l a r as i n (1)  ( L i a k o p o u l o s , 1965; Z a s l a v s k i  and Rogowski, 1969).  c o o r d i n a t e system used i n the f o l l o w i n g shown i n F i g . 1. axis) can  I f cross-slope  The  discussion i s  flow (along  the y'.  i s n e g l i g i b l e , the flow o f water i n s l o p i n g  soil  be c o n s i d e r e d t o be two-dimensional ( F i g . 1 ) .  more, assuming t h a t  Further-  the p r i n c i p a l axes ( d i r e c t i o n s i n  which t h e flow and the p o t e n t i a l g r a d i e n t  coincide,  C h i l d s , 1969) a r e p a r a l l e l t o the x' and z' axes, (1) can  be r e w r i t t e n -  *  •  -  as: »  -  -*-  Q = - ( k ,34//8x'i + k ,3ip/3z' k) where k , and k the  x  1  r  a r e the h y d r a u l i c  (2)  conductivities for  and z' d i r e c t i o n s r e s p e c t i v e l y  and are d i f f e r e n t  i n a n i s o t r o p i c s o i l s , 3^/3x' and 34>/Sz' a r e the h y d r a u l i c g r a d i e n t s i n the x' and z' d i r e c t i o n s r e s p e c t i v e l y , and -»• -*• i  and k are the u n i t v e c t o r s i n the x  respectively.  and z' d i r e c t i o n s  f  With the f u r t h e r assumption t h a t  there are  n e g l i g i b l e m a t r i c g r a d i e n t s i n the x' d i r e c t i o n , 3i|» /3x'-0 and Q . = k . s i n a, where Q . i s t h e flow m x' x' x' r  x  -  Figure  1.  67  -  C r o s s - s e c t i o n o f s o i l on l a n d w i t h angle a,  showing two-dimensional  system and  flow  vectors.  slope coordinate  - 68 -  component i n t h e x ' d i r e c t i o n and a i s t h e s l o p e a n g l e . I f k , i s assumed c o n s t a n t , is,  t h e n 9Q , / 3 x ' = 0;  that  t h e r e i s no d i v e r g e n c e o f f l o w i n the x ' d i r e c t i o n and  the flow o f water through the surface A i s equal to t h r o u g h B i n F i g . 1. the f o r e s t  From ( 2 ) , t h e f l o w o f w a t e r t h r o u g h  f l o o r m a t r i x to the m i n e r a l s o i l  i s given by:  Q . = - k . 34»/9z' z z  (3)  where k , and 3<|'/9z' a r e e v a l u a t e d f o r the f o r e s t matrix adjacent  that  floor  t o t h e i n t e r f a c e between the f o r e s t  floor  and t h e m i n e r a l s o i l . The w a t e r b a l a n c e f o r a p e r i o d o f t i m e o f a volume element o f a s l o p i n g f o r e s t  f l o o r c o n t a i n i n g r o o t s and  i n w h i c h t h e r e i s no d i v e r g e n c e o f f l o w i n e i t h e r the y ' or x ' d i r e c t i o n s i s : (4)  P r E + T + A W + R + D + M  where P i s the p r e c i p i t a t i o n ; E i s the e v a p o r a t i o n the f o r e s t  floor:  from  T i s the t r a n s p i r a t i o n ( r e m o v a l o f w a t e r  by r o o t s ) ; AW i s t h e change o f s t o r e d w a t e r (AW = W - W . where W and W are t h e i n i t i a l o  and f i n a l w a t e r  contents, '  r e s p e c t i v e l y ) ; R i s the surface r u n o f f ; D i s the from t h e f o r e s t surface  drainage  f l o o r m a t r i x normal t o t h e f o r e s t  and i s c a l c u l a t e d from ( 3 ) ;  floor  (D = Q , ) ; and M i s "2*  the s a t u r a t e d  flow through only macropores.  (The t e r m  macropore i s used h e r e t o i n c l u d e a l a r g e p o r e , passageway, c h a n n e l , t u n n e l , o r v o i d i n t h e s o i l ,  cavity, through  - 69 -  which water- u s u a l l y d r a i n s by g r a v i t y , A u b e r t i n , 19 71). S i n c e t u r b u l e n t flow through macropores (Whipkey,  has been observed  1969), the Darcy e q u a t i o n cannot be used t o  c a l c u l a t e the t o t a l  flow through the f o r e s t  floor  (Childs,  1969).  E x p e r i m e n t a l S i t e and Methods The e x p e r i m e n t a l s i t e was  l o c a t e d at an a l t i t u d e o f  460 m i n the Seymour Watershed B.C.  32 km n o r t h o f Vancouver,  w i t h i n the w e t t e r subzone o f the c o a s t a l western  hemlock b i o g e o c l i m a t i c zone  ( K r a j i n a , 1965).  The o v e r -  s t o r y v e g e t a t i o n i n the v i c i n i t y o f the s i t e was o l d growth western hemlock (Tsuga and western r e d c e d a r (Thuja A non-uniform canopy  (Raf.) Sarg.)  hetevophylla  Conn) 59 meters  plioata  caused l a r g e s p a t i a l v a r i a t i o n o f  p r e c i p i t a t i o n and s o l a r r a d i a t i o n on the f o r e s t The u n d e r s t o r y was The f o r e s t  mainly Vaacinium  1 cm o f r e l a t i v e l y undecomposed l i t t e r s t r u c t u r e s were e a s i l y d i s c e r n i b l e  17 cm t h i c k , w i t h i n which  original  (L h o r i z o n ) ; 7 cm o f  p a r t l y decomposed o r g a n i c m a t t e r i n which discernible  floor.  spp.  f l o o r a t the s i t e was  s t r u c t u r e s were s t i l l  tall.  original  (F h o r i z o n ) ; and 9 cm  o f h i g h l y decomposed o r g a n i c m a t t e r (H h o r i z o n ) .  A  nearby p r o f i l e and the b u l k d e n s i t y o f each h o r i z o n are shown i n F i g . 2.  There were no sharp t r a n s i t i o n s i n  -  70  -  FOREST FLOOR PROFILE LAYER  DEPTH  BULK DENSITY  Figure  2.  T y p i c a l f o r e s t f l o o r p r o f i l e i n Seymour Watershed study a r e a showing the b u l k d e n s i t i e s o f the L, F, and H h o r i z o n s .  - 71 -  the degree o f decomposition horizons.  In the. v i c i n i t y  between the t h r e e  o f t h e s i t e , bulk d e n s i t i e s  were s i m i l a r among: for-'e^f f l o o r s r a n g i n g 50 cm i n t h i c k n e s s . -  Beneath the f o r e s t  e l u v i a t e d mineral;, h o r i z o n  organic  from 10 t o f l o o r was an  (Ae). 3 t o 5 cm t h i c k c o n t a i n i n g  many d i s c o n t i n u i t i e s - caused by r o o t s , stones , o r o r g a n i c matter. till.  The s o i l : p r o f i l e developed. on compacted  Tree r o o t s were p r e v a l e n t i n the f o r e s t " f l o o r . The  water.retention' c h a r a c t e r i s t i c s o f the f o r e s t  f l o o r were determined '.in- the l a b o r a t o r y . p o t e n t i a l s ranging  Standard  For m a t r i c  from 0 t o -325 cm o f water, a f r i t t e d  glass funnel^connected used.  glacial  t o a hanging water column was  p r e s s u r e -membrane apparatus was used t o  determine v o l u m e t r i c water c o n t e n t o f -1, -4 , and -14 b a r s . between the f o r e s t  at matric p o t e n t i a l s  To ensure a good;'rcr>n".tact-  f l o o r m a t e r i a l and t h e porous p l a t e  o r membrane, t h e samples were p r e s s e d  against a s l u r r y  o f ground o r g a n i c matter ( B o e l t e r , 1964).  The samples  were s a t u r a t e d p r i o r t o d r a i n i n g . Hydraulic c o n d u c t i v i t y , f o r matric p o t e n t i a l s ranging from 0 t o -100 cm o f water was determined by a  steady-  s t a t e method s i m i l a r i n p r i n c i p l e t o the one used by Richards  (1931).  R i c h a r d s mounted the s o i l  v e r t i c a l l y between two porous p l a t e s .  sample  A differential  - 72 manometer measured  the p o t e n t i a l  gradient  porous cups p o s i t i o n e d i n the sample.  between  A vacuum b o t t l e  connected t o the top and bottom p l a t e s c o n t r o l l e d water c o n t e n t o f the s o i l  column.  G r a v i t y and the  h y d r o s t a t i c p r e s s u r e o f a water column e x t e n d i n g the  the  above  upper p l a t e caused water movement through t h e sample.  The i n f l o w and outflov; o f water, t h e m a t r i c and the p o t e n t i a l g r a d i e n t were  potential,  measured.  S a t i s f a c t o r y c o n t a c t can be ensured between  the  h i g h l y decomposed H h o r i z o n o f the f o r e s t f l o o r and a bottom porous p l a t e such as used by R i c h a r d s ,  whereas  good c o n t a c t between  the F h o r i z o n and a top porous  plate i s d i f f i c u l t .  Thus changes i n R i c h a r d ' s apparatus  were n e c e s s a r y . A 10-cm  t h i c k , f o r e s t f l o o r sample was supported  by a commercial, porous alundum bottom end o f an 11-cm  I.D.,  c y l i n d e r ; w h i l e no p l a t e was sample  (Plamondon,  1972).  p l a t e f a s t e n e d to the  30 cm l o n g ,  plexiglas  used a t the t o p end o f the  A chromatography micropump  a p p l i e d p r e s e l e c t e d , c o n s t a n t water f l u x e s 110 ml hr '*') t o the top o f the column. -  F o r flow r a t e s  lower than 9 ml h r ^, a cam t i m e r r e g u l a t e d c y c l e o f the pump. ( 0 . 2 5 - 0 . 5 mm)  A 10-cm  (of 9 to  the d u t y -  t h i c k l a y e r o f c o a r s e sand  added on t o p o f the sample  evenly  -  distributed  73  -  the a p p l i e d water and  a l s o allowed a i r  penetration that simulated n a t u r a l c o n d i t i o n s . c o n t e n t w i t h i n the sample was  Water  a d j u s t e d by hanging  v a r i a b l e water column on the bottom p l a t e .  It  a  was  found p o s s i b l e t o a d j u s t the l e n g t h of t h i s column so t h a t the m a t r i c p o t e n t i a l g r a d i e n t was  approximately  zero and  thus the imposed flow l a r g e l y  gravitational.  impedance porous cups a t 2 and  8 cm above the  Two  low  alundum p l a t e and  connected  to water manometers  measured the m a t r i c p o t e n t i a l . system was  minimized  E v a p o r a t i o n from  by i n s e r t i n g a vented  the  rubber  s t o p p e r i n the top o f both the p l e x i g l a s c y l i n d e r the b u r e t t e used  to c o l l e c t  the o u t f l o w .  c o n d u c t i v i t y o f the Ae h o r i z o n was  and  The h y d r a u l i c  determined  by  the  same t e c h n i q u e . S e v e r a l components o f the h y d r o l o g i c b a l a n c e a f f e c t i n g the w e t t i n g and d r y i n g of the f o r e s t measured on the e x p e r i m e n t a l October  26, 1971.  s i t e from September 7 t o  P r e c i p i t a t i o n i n t e n s i t y was  under the canopy by a t i p p i n g bucket standard r a i n average  gauges were used  o f the p r e c i p i t a t i o n .  Two  to o b t a i n a s p a t i a l Water flow on the top  measurable d u r i n g most  events.  f o l d e d a t a r i g h t angle  sheet  recorded  r a i n gauge.  o f the humus l a y e r was A metal  f l o o r were  rainfall was  i n s t a l l e d a t a depth o f 2 cm t o c a t c h t h i s r u n o f f . s i d e o f the angle was pushed 4 cm i n t o the f o r e s t  One floor  t o l e a v e t h e o t h e r s i d e normal t o t h e s u r f a c e and t o channel  the water t o a b o t t l e .  The  e v a p o r a t i o n was measured by a s m a l l ,  lysimeter containing a f o r e s t f l o o r core. c y l i n d e r o f t h e l y s i m e t e r was i n s u l a t e d heat  weighing  The a c r y l i c  from  lateral  f l u x by a 2.5-cm t h i c k s h e l l o f styrofoam.  c o r e ' s s u r f a c e was s e t f l u s h w i t h the a d j a c e n t floor.  The forest  In the absence o f l y s i m e t e r d a t a , the e v a p o r a t i o n  was approximated from energy b a l a n c e  measurements  (Plamondon and B l a c k , 1972). In o r d e r t o c a l c u l a t e the v o l u m e t r i c water and  the d r a i n a g e  content  from the o r g a n i c l a y e r , the water  p o t e n t i a l a t s e v e r a l depths had t o be r e c o r d e d .  To  ensure minimum d i s t u r b a n c e o f the n a t u r a l water flow tern.;, th.e . p o t e n t i a l .was measured by a tensiometer having  s m a l l , water d i s p l a c e m e n t .  A ceramic  pat-  system  cup, 2-cm  l o n g by 1-cm O.D., h a v i n g an a i r e n t r y v a l v e o f 800 cm o f water, was b u r i e d a t each o f the depths o f 2, 6, 9, 16,  18 and 20 cm below and normal t o the f o r e s t  surface.  floor  The cups a t the 18 and 20-cm depths were i n  the Ae and the B h o r i z o n s r e s p e c t i v e l y . l o c a t e d on a u n i f o r m  The cups were  30° s l o p e about 3 meters downslope  -  75  -  from a break i n the microtopography. not permit  upslope  T h i s break d i d  water t o flow through  f l o o r a t the s i t e .  The  the  s i x cups were connected  s t r a i n - g a u g e , p r e s s u r e t r a n s d u c e r s by b r a s s and  0.32-cm I.D.  distilled  A detailed  transducer, tensiometer  to s i x  fittings  nylon h y d r a u l i c l i n e s f i l l e d  water.  with  d e s c r i p t i o n o f the  system and  pressure-  i t s characteristics  has been g i v e n by W i l l i n g t o n (1971).  Wet  b a t t e r i e s were used to power the system. connected  forest  storage These were  t o an i n v e r t e r , which powered a D.C.  power  s u p p l y c a p a b l e o f a c c e p t i n g a v o l t a g e between 90  and  130  to  v o l t s A.C.  0.03%  and h a v i n g  o f the output  a time  setting.  stability  The  equal  electrical  signals  from the p r e s s u r e t r a n s d u c e r s were r e c o r d e d by means o f an automatic  s t e p p i n g s w i t c h and  strip  chart  recorder. F o r e s t f l o o r d r a i n a g e was equation  (3).  tensiometer  The  v o l u m e t r i c water content  l e v e l was  p o t e n t i a l s and  determined  by  at each  from the m a t r i c  the water r e t e n t i o n c h a r a c t e r i s t i c s .  T h e t o t a l water c o n t e n t , expressed o b t a i n e d by  calculated  i n cm o f water,  was  summing the water c o n t e n t o f each depth  increment. The c m was  v o l u m e t r i c water content o f the top 1  r e g u l a r l y measured by g r a v i m e t r i c sampling.  This  was  necessary  s i n c e the water content  of t h i s layer  c o u l d not be measured with a t e n s i o m e t e r poor c o n t a c t between i t and The  the h i g h l y porous  v o l u m e t r i c water content  o f the r e s t o f  f o r e s t f l o o r and Ae h o r i z o n was at  i r r e g u l a r time  R e s u l t s and Water  was  sampled g r a v i m e t r i c a l l y  intervals.  Characteristics.  The  the c o r r e s p o n d i n g  the m a t e r i a l ( F i g . 3).  The  forest  floor  degree o f  decomposition  p o r o s i t y o f the  litter  l a r g e l y composed o f macropores which d r a i n e d at a  m a t r i c p o t e n t i a l g r e a t e r than potentials  l e s s than  -1 cm o f water.  T h i s was  At  of  other l a y e r .  a p p a r e n t l y because o f the g r e a t e r p r o p o r t i o n  micropores  present.  A v e r y s m a l l amount o f water d r a i n e d from depth when the m a t r i c p o t e n t i a l was b a r t o -15 of  matric  -9 cm o f water, the lower h a l f  the H h o r i z o n r e t a i n e d more water than any  of  the  water r e t e n t i o n c h a r a c t e r i s t i c s t h a t v a r i e d  w i t h depth and of  litter.  Discussion  Retention  p r o f i l e had  because o f  bars.  the water was  decreased  any from  -1  W i t h i n t h i s range o f p o t e n t i a l most probably  r e t a i n e d by the f i b r o u s  m a t e r i a l o r i n the h i g h l y decomposed bottom l a y e r , by decomposed f i b r o u s substance c o l l o i d a l organic matter.  and  i n t e r s t i c e s of  the  F i g u r e 3.  Water r e t e n t i o n forest depths.  characteristics  f l o o r at 1,  2,  6,  10  and  of  the  14-cm  -  Hydraulic water  conductivity  r e t e n t i o n  v/ith  the  large  of F  differences were  matric  the  the  the  H h o r i z o n  be  and  layer  surface At  between At smaller  i n  the  layer  as  f l o o r ,  between  a  function  the  were  measured. up  the  Anisotropy  h y d r a u l i c  normal  made  for  4).  both  organic  widely  forest  (Fig.  so  the  vary  separately  horizons  predominantly  greater range  matric was  and  of  p a r a l l e l Since  highly  matter  i t  was  to  surface  de-  assumed  p a r a l l e l  than 0  that  to  probably  perpendicular cm  -12  potentials  the  less  the  of  matric  difference  than  the  i n  to  the  the  p o t e n t i a l . between  the  v a r i a b i l i t y  samples. high i n  and  matric  the  potentials  H horizon  than  of  water  content  the  lower  porosity  a b i l i t y  lower  this  to  conductivity  hypothesized  c o l l o i d a l  the  range  pores i t s  was  curves  t h i s  was  of  determined cm)  conductivity  lower  two  was  of  found  Conductivity  was  (8-17  Since  i s o t r o p i c . The  F  h y d r a u l i c  c h a r a c t e r i s t i c s  surface  composed to  H  horizon  F  conductivity to  i n  expected.  and  were  decomposition  p o t e n t i a l  cm)  (1-8  of  of  -  characteristics.  properties  degree  horizons  78  matric  to  conduct  potentials  i n  the of  water. the  the  conductivity  the  h o r i z o n .  F  smaller the On  size  of  H horizon  the  micropores  was  other of  In the  reduced  hand,  the  H  at  79 -  E i g u r e 4.  Hydraulic conductivity  as a f u n c t i o n o f  the m a t r i c p o t e n t i a l f o r the F (0 t o 8-cm depth) and H (8 t o 17-cm depth) h o r i z o n s . The measurement e r r o r s conductivities are  i n hydraulic  o f 100, 1, and 0.01 cm day  approximately ± 1.0, ± 0.07, and  ± 0.003 cm d a y  - 1  respectively.  -  80 -  h o r i z o n remained r e l a t i v e l y w a t e r f i l l e d  so t h a t  the  c o n d u c t i v i t y was g r e a t e r t h a n t h a t o f the F h o r i z o n . The  most s t r i k i n g f e a t u r e  o f the f o r e s t  floor  m a t e r i a l was t h a t a t a m a t r i c p o t e n t i a l o f -3 cm o f w a t e r the average h y d r a u l i c c o n d u c t i v i t y o f the whole -1  2  p r o f i l e was about 10  cm day  , w h i l e at a m a t r i c  p o t e n t i a l o f -80 cm i t had d e c r e a s e d by f o u r of  magnitude.  orders  Very s i m i l a r c h a r a c t e r i s t i c s were  r e p o r t e d f o r p e a t s o i l s by W i l s o n and R i c h a r d s ( 1 9 3 8 ) . They a l s o showed t h a t f o r m a t r i c p o t e n t i a l s  between  -4 0 and -2 0 0 cm o f w a t e r the h y d r a u l i c c o n d u c t i v i t y of  a p e a t s o i l was l o w e r t h a n t h a t o f a sandy s o i l  h i g h e r than t h a t o f a c l a y .  In our study the  f l o o r had a l o w e r c o n d u c t i v i t y t h a n t h a t o f  but  forest  the  e l u v i a t e d sandy h o r i z o n (Ae) a t m a t r i c p o t e n t i a l s l o w e r t h a n -30 cm o f w a t e r . of  t h e Ae was not measured a t h i g h e r m a t r i c p o t e n t i a l s .  Water  If  The h y d r a u l i c c o n d u c t i v i t y  balance  of  the forest  floor  during  E and T a r e n e g l i g i b l e d u r i n g r a i n f a l l ,  precipitation.  (4) becomes:  P = A W + R + D + M  (5)  S i n c e , P , AW and R a r e m e a s u r a b l e , and D can be c a l c u l a t e d from ( 3 ) , M i s o b t a i n e d as t h e r e s i d u a l i n ( 5 ) .  The  changes o f w a t e r p o t e n t i a l w i t h t i m e and d e p t h d u r i n g t h e r a i n s t o r m o f O c t o b e r 12 are p r e s e n t e d  in Fig. 5  w h i c h shows t h e d e p t h o f w e t t i n g and t h e g r a d i e n t s o f  - 81 -  TOTAL  POTENTIAL  (cm  of water)  F i g u r e 5. Changes o f t o t a l water p o t e n t i a l depth f o r the f o r e s t  f l o o r during  w i t h time and rainfall.  - 82 -  the t o t a l p o t e n t i a l normal t o the s u r f a c e . water c o n t e n t s water c o n t e n t  a t depths o f 2, 6, 9 and 16 cm and the t o t a l o f t h e 17-cm t h i c k f o r e s t  above storm as d e r i v e d i n F i g . 6.  The v o l u m e t r i c  from use o f F i g s . 3 and 5, a r e shown  Half-hourly r a i n f a l l  a l s o shown i n t h i s  f l o o r d u r i n g the  figure.  i n t e n s i t i e s i n cm hr " ' a r e -  1  Because o f the c o n s i d e r a b l e  s p a t i a l v a r i a t i o n of r a i n f a l l  i n t e n s i t y beneath the canopy,  errors i n estimating r a i n f a l l  above the t e n s i o m e t e r s  expected.  D i f f e r e n c e s between r a i n f a l l  were  measured on both  s i d e s o f the p l o t were as l a r g e as 50% o f t h e mean. The  slow r a t e o f movement o f the w e t t i n g  through the s o i l m a t r i x the b e g i n n i n g  i s shown by the time l a g between  o f the storm and the appearance o f the w e t t i n g  f r o n t a t any depth. o f depth.  The time l a g was a n o n - l i n e a r f u n c t i o n  T h i s was q u i t e l i k e l y  h y d r a u l i c c o n d u c t i v i t y with  due t o the change i n  depth and t o water movement  through macropores ( A u b e r t i n , 1971).  A f t e r reaching a  maximum a t 2000 h r , the t o t a l water content while the r a i n f a l l o f 0.5 cm hr"" '. 1  continued  decreased  f o r M h r a t an average r a t e  An i n c r e a s e o f s a t u r a t e d flow  through  macropores may be r e s p o n s i b l e f o r t h i s b e h a v i o u r . drainage  front  The  r a t e c a l c u l a t e d between 2000 and 2400 by (3)  was 0.8% o f the p r e c i p i t a t i o n normal t o t h e s l o p e t h i s same p e r i o d  (Table 1 ) .  during  -  F i g u r e 6.  83 -  V o l u m e t r i c water content a t the 2 , 6 , 9 16-cm forest  and  depths and t o t a l water content o f the f l o o r during  rainfall.  Table 1.  Water balance components d u r i n g r a i n f a l l . The data are f o r p e r i o d s d u r i n g which t h e p r e c i p i t a t i o n i n t e n s i t y , matric p o t e n t i a l and t o t a l p o t e n t i a l g r a d i e n t were r e l a t i v e l y constant.  9<J//3z' Date  Time  m  z'  (cm) (cm/day)  P  R  1  (cm) (cm)  M (cm)  D  R/P  M/P  D/P  D/M  (cm)  (%)  (%)  (%)  (%)  10/09/71  1700-1900  2.4  70  0.025  1.6  0.4  1.2  0.005  25  75  0.3  0.4  28/09/71  2000-2400  0.4  80  0.018  0.5  0.1  0.4  0.001  20  80  0.3  0.3 i CO  1400-1700  1.7  55  0.043  1.1  '0.4  0.7  0.009  35  65  0.8  1.3  1700-2100  1.5  55  0.043  1.0  0.3  0.7  0.012  30  70  1.2  1.7  2100-2300  1.5  55  0.043  0.8  0.3  0.5  0.006  30  70  0.7  1.2  12/10/71  2000-2400  2.4  61  0.034  1.8  0.6  1.2  0.014  35  65  0.8  1.2  22/10/71  0000-1000  1.6  59  0.036  4.7  1.6  3.1  0.006  35  65  0.1  0.2  25/10/71  1300-1900  1.8  63  0.032  2.6  1.3  1.3  0.001  50  50  0.05  0.1  03/10/71  Runoff ( l a t e r a l flow through the l i t t e r ) was only observed f o r s h o r t d i s t a n c e s (50 t o 100 cm) over the smoothly s l o p i n g s i t e . Water running o f f was i n t e r c e p t e d by any microtopographic change i n the s l o p e and c h a n n e l l e d through the f o r e s t f l o o r .  * i  - 85 -  T a b l e 1 c o n t a i n s the e s t i m a t e s o f the water balance  components for* 8 p e r i o d s d u r i n g which the m a t r i c  p o t e n t i a l , the t o t a l were r e l a t i v e l y  p o t e n t i a l g r a d i e n t , and  constant.  Drainage  through  the the  rainfall forest  f l o o r m a t r i x e v a l u a t e d a t the 13 cm depth ranged 0.1 to  t o 1.2%  range from  through of  o f the p r e c i p i t a t i o n . ,  macropores from  i n the s o i l m a t r i x . accuracy o f ±25%. moved through  50 to 80%.  Runoff was  the f o r e s t  Approximately  of  estimated with  f l o o r by way  the  forest  also  from (6).  floor  during  drying  periods.  and  (4) becomes:  AW  + D = 0  are measured, and  (6)  D can be  calculated  ( 3 ) , then T can be c a l c u l a t e d as the r e s i d u a l i n The  r a t e s o f t o t a l water d e p l e t i o n , d r a i n a g e ,  e v a p o r a t i o n , and  t r a n s p i r a t i o n f o r two  September and October The  observed  A u b e r t i n , 1971).  T + E + AW S i n c e E and  an  o f macropores  D u r i n g d r y i n g p e r i o d s R and M can be n e g l e c t e d consequently  0.8%  the f o r e s t f l o o r o c c u r r e d  a p p r e c i a b l y w e t t i n g the m a t r i x was  balance  flov;  That a l a r g e q u a n t i t y o f water  by o t h e r s (Whipkey, 1969; Water  estimated  20 t o 50% o f the p r e c i p i t a t i o n w h i l e  the t o t a l water flow through  without  Runoff was  from  19 71 a r e p l o t t e d  d r a i n a g e r a t e s were c a l c u l a t e d by  h y d r a u l i c c o n d u c t i v i t y and  periods during i n F i g s . 7 and (3) i n which  p o t e n t i a l g r a d i e n t were  8.  86  -  T  1  1  SEPTEM8ER  Figure  7.  -  1  1  r  1971  Drainage, e v a p o r a t i o n ,  t r a n s p i r a t i o n , and  t o t a l water d e p l e t i o n r a t e s f o r the f o r e s t f l o o r during  a d r y i n g p e r i o d i n September.  - 87  Figure  Drainage,  -  e v a p o r a t i o n , t r a n s p i r a t i o n , and  t o t a l water d e p l e t i o n r a t e s f o r the f o r e s t f l o o r during  a  drying period  i n October.  - 88 e v a l u a t e d a t t h e 13-cm depth. decreased rainfall.  The d r a i n a g e  rate  r a p i d l y w i t h time a f t e r the c e s s a t i o n o f S i n c e the t r a n s p i r a t i o n r a t e s were c a l c u l a t e d  as r e s i d u a l s i n ( 6 ) , t h e i r v a l u e s c o n t a i n e d the e r r o r s i n measurement o f t h e o t h e r components. drainage  r a t e was lower  The average  i n September than  i n October  because o f t h e lower water c o n t e n t o f the f o r e s t The  floor.  amount o f t r a n s p i r a t i o n was n o t i c e a b l y lower i n  October than Seasonal  September.  distribution  of water content  in  the  forest  floor.  The  t o t a l water c o n t e n t and the v o l u m e t r i c water  for  the 0-8 cm and 8-17 cm depth i n t e r v a l s , as o b t a i n e d  from t e n s i o m e t e r extending  content  d a t a , shown i n F i g . 9 f o r t h e p e r i o d  from September 7 t o October 25.  averages o f r a i n f a l l  intensities  Half-daily  i n cm h r ~ ^ and storm  t o t a l s a r e a l s o shown.  V o l u m e t r i c a l l y t h e r e was l e s s  water i n the upper h a l f  (0-8 cm) than i n t h e lower  (8-17  f l o o r d u r i n g t h e measurement  cm) o f the f o r e s t  period.  half  F o r d r y i n g p e r i o d s t h i s can be e x p l a i n e d by  t h e h i g h e r water r e t e n t i o n c a p a c i t y o f t h e H h o r i z o n . On  t h e o t h e r hand, d u r i n g r a i n f a l l  the matric  potential  would have t o be h i g h e r than about -4 cm o f water f o r the F h o r i z o n t o c o n t a i n more water than t h e H h o r i z o n (Fig.  3). This l e v e l o f matric p o t e n t i a l i s not  reached  on a s l o p e s i n c e t h e h y d r a u l i c c o n d u c t i v i t y  - 89 -  F i g u r e 9.  Volumetric water content  o f the F and H h o r i z o n s  as a f u n c t i o n o f t i m e . The t o t a l w a t e r and r a i n f a l l  are a l s o  plotted.  content  - 90 -  of the f o r e s t  f l o o r ( F i g . 4) a t a m a t r i c p o t e n t i a l o f  -4 cm o f water exceeds the r e c o r d e d maximum  rainfall  intensity. The AW  as a r e s u l t o f r a i n f a l l  max  the  maximum i n c r e a s e o f f o r e s t  difference  rainfall, W . mm  was c a l c u l a t e d  by t a k i n g to  between t h e minimum water c o n t e n t and t h e maximum water c o n t e n t  rainfall, W . ' max  before  during ^  Thus, '  AW  = W max  The  f l o o r water c o n t e n t ,  max  - W .( mm  7  )  r a t i o s o f the maximum i n c r e a s e i n t h e water  content o f f o r e s t  f l o o r to the t o t a l r a i n f a l l  (normal  to the s l o p e ) were computed f o r nine storms d u r i n g t h e p e r i o d o f measurement. from 0.0 3 t o 0.44.  E i g h t out o f nine r a t i o s  ranged  F o r t h e storm on September 23, a l l  o f t h e 0.77 cm r a i n f a l l was absorbed by t h e f o r e s t floor.  This i s attributed  t o the small s i z e o f the  storm and t o t h e low i n i t i a l water c o n t e n t o f t h e organic The  layer. relationships  between the maximum i n c r e a s e o f  water c o n t e n t , i n t e n s i t y , s l o p e , and the water and  conductivity  complex. rate  p r o p e r t i e s o f the f o r e s t  I t can be p o s t u l a t e d t h a t  affects  retention  f l o o r are  the p r e c i p i t a t i o n  the p a r t i t i o n i n g o f t h e flow between R,  M and D and t h a t  this partitioning varies  s l o p e a n g l e and t h e f o r e s t  with the  f l o o r water c o n t e n t .  This  - 91 r e l a t i o n s h i p can be expressed by r e w r i t i n g  (5) as  follows: W = W  + P - R (P,o,W) - M (P,a,W) - D (P,a,W)  (8)  When W = W , then max P = R (P,ct,W ) + M (P,ct,W ) + D (P,ct,W ) ' ' max max ' ' max This  (9)  s i m p l e a n a l y s i s i n d i c a t e s t h a t the water c o n t e n t  o f the f o r e s t f l o o r w i l l hydraulic conductivity  increase  the slope  and t h e  a r e such t h a t the r a t e o f water  output from the f o r e s t f l o o r r a t e o f water i n p u t  until  (P).  (R + M + D) e q u a l s t h e  In t h i s  study t h e maximum  water c o n t e n t o f the 17-cm t h i c k , f o r e s t f l o o r was found •to range from 7.4 t o 8.1 cm r e s p e c t i v e l y , c o r r e s p o n d i n g to h y d r a u l i c  c o n d u c t i v i t i e s o f 0.06 and 1.4 cm day "*" -  i n the F h o r i z o n .  Since  the h y d r a u l i c  exhibits a large increase  conductivity  as a r e s u l t o f a s m a l l  increase  o f water c o n t e n t , the i n t e n s i t y o f r a i n f a l l p r o b a b l y has a n e g l i g i b l e e f f e c t on the maximum water c o n t e n t o f t h e forest  floor.  T h i s may e x p l a i n why no c l e a r r e l a t i o n s h i p  was found between t h e maximum i n c r e a s e and  rainfall  intensity.  o f water c o n t e n t  In a d d i t i o n , t h e p a r t i t i o n i n g  o f t h e r a i n f a l l between R, M and D i s p o s s i b l y more complex than  (9) suggests s i n c e each term may be a  function of other f a c t o r s . action" runoff  F o r example,  (Whipkey, 1969) o f d r y l i t t e r than wet l i t t e r ,  regardless  "shingle  can cause more  o f the slope  angle  - 92 o r the t o t a l  f o r e s t f l o o r water  content.  S i n c e the v a l u e s o f W reached d u r i n g the p e r i o d max study can be c o n s i d e r e d almost c o n s t a n t , t h e r e should 5  of  v  be a s i m D l e r e l a t i o n s h i p between AW and V/ • . I f the max mm s a t u r a t i o n water content was reached d u r i n g r a i n f a l l , t h e r e l a t i o n s h i p between AV/ and 17 . would be a s t r a i g h t max mm l i n e ( i n s e r t o f F i g . 1 0 ) . In F i g . 10, t h e observed v a l u e s o f AW are p l o t t e d against W . max mm J  storms.  The r e s u l t s  i s not r e a c h e d ,  f o r nine  rain-  show t h a t as l o n g as s a t u r a t i o n  the r e l a t i o n between the two v a r i a b l e s  may not be l i n e a r .  Point  (a) i s o f f the l i n e  because  the t o t a l r a i n f a l l o f the September 2 3 storm was o n l y 0.77  cm.  Points  o f water content respectively  (b) and ( c ) a r e the maximum i n c r e a s e s f o r t h e October 2 0 and 2 2 storms  ( F i g . 9b).  Because t h e r e was o n l y a  s h o r t p e r i o d o f time between those  storms and t h a t o f  October 18, o n l y a f r a c t i o n o f the r e t a i n e d water from the p r e v i o u s  storm d r a i n e d  away.  In these two cases  t h e r e l a t i o n s h i D between AW and 17 . appears t o be max mm * different. On a s i t e with l e s s s l o p e , W would max v  probably  be l a r g e r because o f l e s s r u n o f f .  though not c o n s i d e r e d the relationship.  Hysteresis,  i n t h i s paper, may a l s o a f f e c t  F o r p r a c t i c a l purposes a l i n e a r  r e l a t i o n s h i p , as i n F i g . 10, can b e used t o e s t i m a t e  - 93 -  F i g u r e 10.  R e l a t i o n s h i p between  the minimum water  content  b e f o r e r a i n f a l l and the maximum i n c r e a s e o f water content  during r a i n f a l l  for a  17-cm  t h i c k f o r e s t f l o o r on a 30° s l o p e . The v o l u m e t r i c water content 0.8 8 cm  3  cm~ . 3  The 1:1  eye t o the d a t a .  at s a t u r a t i o n was  line  was  fitted  by  - 94  -  the maximum i n c r e a s e o f water content o f the minimum water content a  before  from knov/ledge  the o c c u r r e n c e of  rainstorm.  Implications  for  plant  growth.  It  i s reasonable  to  assume t h a t the d i f f e r e n c e between the water content the f o r e s t f l o o r . a t the time o f n e g l i g i b l e d r a i n a g e the water c o n t e n t  at -15  bars m a t r i c  available for evapotranspiration.  The  average  and  at -15  bars,  cm  and  day  1  .  and  2.7  To the l a t t e r amount we  can  add  the water  the d r a i n i n g p e r i o d  therefore, provide  an  (0.4  cm).  cm r e s p e c t i v e l y .  The  evapotranspired forest floor  8-day water supply  t r a n s p i r a t i o n i f a reasonable  summer  r a t e o f 4 mm  McNaughton, 1972)  day  - 1  The  the a v a i l a b l e water f o r evapo4.2  can,  was  at the time o f n e g l i g i b l e d r a i n a g e  t r a n s p i r a t i o n were 6.9,  during  matric  T h i s corresponded to a  h y d r a u l i c c o n d u c t i v i t y o f about 0.015 •total water content  and  potential i s  p o t e n t i a l at the time o f n e g l i g i b l e d r a i n a g e a p p r o x i m a t e l y -9 0 cm o f water.  of  (Black and  f o r evapo-  evapotranspiration is  assumed. Implications  in  watershed  hydrology.  On  sloping  land  the p o t e n t i a l c a p a c i t y o f the f o r e s t f l o o r to r e t a i n flood-producing because t h e r e r e t a i n e d by  r u n o f f and  snowmelt i s r a t h e r meagre  i s an upper l i m i t  it.  t o the amount o f water  High i n t e n s i t y r a i n f a l l s t h a t  often  - 95 -  r e s u l t i n f l o o d s on the west c o a s t o f B r i t i s h Columbia o c c u r d u r i n g the r a i n y season when the f o r e s t a l r e a d y wet. the f o r e s t l.U  The  floor is  maximum amount o f water absorbed  f l o o r d u r i n g the p e r i o d o f measurement  was  cm o r about 7% o f the r a i n s t o r m amounts known to  have caused  flood  the average  l e n g t h o f time e l a p s e d between the  of  by  a r a i n s t o r m and  o f the f o r e s t  damage i n the l o c a l a r e a .  Furthermore, beginning  the time o f the maximum water c o n t e n t  f l o o r was  12 hours.  I f the t o t a l  p r e c i p i t a t i o n d u r i n g these 12 h r s i s s u f f i c i e n t t o i n c r e a s e the f o r e s t  f l o o r water content t o i t s maximum o f  approximately  8 cm o f water, the water r e t e n t i v e c a p a c i t y o f the  forest  floor will  time.  have no e f f e c t on peak flows  By a b s o r b i n g some water the f o r e s t reduce  peak flows caused  was  f l o o r may  not have any  by storms o f l o n g e r d u r a t i o n .  and  12-hours  e f f e c t on  Forest f l o o r  those drainage  measurable f o r 3 t o 6 days f o l l o w i n g r a i n f a l l , t h e r e f o r e  c o n t r i b u t i n g t o d e l a y e d stormflow.  A f t e r t h i s p e r i o d the  d r a i n a g e became very s m a l l , i n d i c a t i n g contributed  t h a t the f o r e s t  retain different  has observed o f the f o r e s t rainfall  floor  n e g l i g i b l y t o base f l o w .  F o r e s t f l o o r s on h o r i z o n t a l areas and may  delay  by storms of l e s s than  d u r a t i o n but a p p a r e n t l y w i l l caused  after this  amounts of water.  water accumulating  The  depressions s e n i o r author  up t o 10 cm deep on  f l o o r i n some d e p r e s s i o n s d u r i n g h i g h  (0.5 cm hr " ' f o r 5 h r s ) . -  1  The  s o i l had  been  top intensity wetted  - 96 -  by t o t a l antecedent p r e c i p i t a t i o n f l o o r on h o r i z o n t a l significant effects  o f 4 cm.  S i n c e the  areas and i n d e p r e s s i o n s r e p r e s e n t s a  f r a c t i o n o f the t o t a l watershed  of the f o r e s t  stormflow may  forest  a r e a , the  f l o o r on peak flow and d e l a y e d  be more important than t h i s study  indicates.  Conclusion The r o l e o f the f o r e s t better  f l o o r i n watershed  understood w i t h knowledge o f i t s water  and c o n d u c t i v i t y  characteristics.  were found t o be l a r g e l y decomposition conductivity  These  determined  o f the o r g a n i c matter. o f the f o r e s t  After  the f o r e s t  0.5%  The  o f -3 and -100 cm of i t s maximum  rate  and  about  floor.  During  The  by the f o r e s t  largely  forest  floor.  drying  controlled  by the i n i t i a l  The water r e t e n t i v e  AW  depths.  f l o o r during water  c o n t e n t , the a n g l e o f the s l o p e and the h y d r a u l i c o f the f o r e s t  of  to r e l i a b l y calculate measured at s e v e r a l  r a i n f a l l was  was  0.8%  and D from m a t r i c p o t e n t i a l s amount o f water absorbed  4 orders  matrix drainage rate  the t o t a l flow through the f o r e s t found p o s s i b l e  of  hydraulic  f l o o r had reached  o f the p r e c i p i t a t i o n  p e r i o d s i t was  characteristics  f l o o r changed by about  water c o n t e n t the c a l c u l a t e d about  retention  by the degree  o f magnitude between m a t r i c p o t e n t i a l s water.  hydrology i s  conductivity  c a p a c i t y o f the  f l o o r can have an e f f e c t on peak f l o w s caused  by  - 97 -  r a i n f a l l of limited to delayed flow.  duration.  The f o r e s t  stormflow but has a n e g l i g i b l e  floor effect  The r e t e n t i o n p r o p e r t i e s o f the f o r e s t  have a s i g n i f i c a n t  effect  on p l a n t growth  contributes on base  floor  may  particularly  i n south western B r i t i s h Columbia where t h e summers a r e dry.  The most important c o n t r i b u t i o n s o f the f o r e s t  to watershed h y d r o l o g y a r e p r o t e c t i o n o f the m i n e r a l against raindrop  floor soil  impact and p r e s e r v a t i o n o f the numerous  surface depressions  which t e m p o r a r i l y  s t o r e water.  Literature Cited AUBERTIN, G.M.  19 71.  in forest soils  Nature and e x t e n t  o f macropores  and t h e i r i n f l u e n c e on  water movement.  subsurface  U.S.D.A. F o r e s t Serv. Res. Paper  NE-192. BLACK, T.A. and K.G. McNAUGHTON.  19 72.  Average  Bowen-  r a t i o methods o f c a l c u l a t i n g e v a p o t r a n s p i r a t i o n a p p l i e d t o a Douglas f i r f o r e s t . Meteorol.  Boundary-Layer  ( i n press).  BOELTER, D.H.  1964.  water s t o r a g e  techniques  properties o f organic  Soc. Amer. Proc. CHILDS, E.C.  Laboratory  f o r measuring  soils.  Soil Sci.  28: 823-824.  1969. An i n t r o d u c t i o n t o the p h y s i c a l b a s i s  o f s o i l water phenomena.  Wiley-Interscience,  John  Wiley and Sons L t d . , T o r o n t o . KRAJINA, V . J . of B r i t i s h  1965.  Biogeoclimatic  Columbia.  LIAKOPOULOS, A.C.  1965.  zones and c l a s s i f i c a t i o n  E c o l . o f Western N.A.  Darcy s c o e f f i c i e n t of permeability 1  as symmetric t e n s o r o f second rank. Hydrol.  1: 1-17.  I n t . Assoc. S c i .  X: 41-4 8.  LOWDERMILK, W.C.  1930.  Influence  o f f o r e s t l i t t e r on  r u n - o f f , p e r c o l a t i o n , and s o i l e r o s i o n . 28: 474-491.  J . Forestry  PLAMONDON, P.A.  1972. H y d r o l o g i c p r o p e r t i e s and  water b a l a n c e o f t h e f o r e s t f l o o r o f a Canadian West Coast watershed. of  Brit.  Unpub. Ph.D. T h e s i s U n i v .  C o l . pp  PLAMONDON, P.A. and T.A. BLACK.  1972. Energy  balance  method f o r e s t i m a t i n g e v a p o r a t i o n from the f o r e s t floor.  Can. J . F o r . Res. (submitted)  WHIPXEY, R.Z. catchments  1969. Storm r u n o f f from by s u b s u r f a c e r o u t e s .  t h e i r computation. Leningrad  I n f l o o d s and  I n t . Assoc. S c i . Hydrol.  Symp. P r o c . 1967: 773-779.  WILLINGTON, R.P. of  forested  19 71.  Development and a p p l i c a t i o n  a technique f o r evaluating root  zone d r a i n a g e .  Unpub. Ph.D. T h e s i s , U n i v . o f B r i t . ' C o l . 42 pp. WILSON, B.D. and S.J. RICHARDS. c o n d u c t i v i t y o f peat s o i l s tensions.  19 38.  at d i f f e r e n t  J . Amer. Soc. Agron.  ZASLAVKSY, D. and A.S. ROGOWSKI. and m o r p h o l o g i c infiltration  Capillary capillary  30: 583-588. 1969. H y d r o l o g i c  i m p l i c a t i o n s o f a n i s o t r o p y and  i n s o i l p r o f i l e development.  -Soc. Amer. P r o c . 33: 594-599.  Soil Sci.  -  99  -  LABORATORY MEASUREMENT OF HYDRAULIC CONDUCTIVITY CHARACTERISTICS OF THE FOREST FLOOR Abstract.  The procedures p r e v i o u s l y used t o measure t h e  h y d r a u l i c c o n d u c t i v i t y c h a r a c t e r i s t i c s o f porous m a t e r i a l are b r i e f l y reviewed. A simple s t e a d y - s t a t e  method o f  measuring the h y d r a u l i c c o n d u c t i v i t y o f an  undisturbed  sample o f f o r e s t f l o o r m a t e r i a l described.  i n the laboratory i s  The main f e a t u r e s o f t h e method a r e t h a t the  water i s a p p l i e d a t a constant  r a t e a t the top o f t h e  sample u s i n g a chromatography micropump w h i l e t h e water content w i t h i n t h e sample i s c o n t r o l l e d by hanging a v a r i a b l e - l e n g t h water column from a porous p l a t e a t the bottom o f the f o r e s t f l o o r c o r e . An advantage o f the method i s t h a t a s m a l l m a t r i c  p o t e n t i a l gradient  can be  maintained i n the sample by a d j u s t i n g the l e n g t h o f t h e hanging water  column.  Introduction The water r e t e n t i o n and c o n d u c t i v i t y c h a r a c t e r i s t i c s o f a s o i l have a c o n s i d e r a b l e  e f f e c t on the h y d r o l o g i c response  o f a watershed and on p l a n t growth. Because o f the d i f f i c u l t y of measurement, there  i s a s e r i o u s look o f knowledge o f  h y d r a u l i c c o n d u c t i v i t y c h a r a c t e r i s t i c s o f many s o i l s . The forest organic  l a y e r forming the top o f f o r e s t s o i l  isa  h i g h l y porous and l a y e r e d m a t e r i a l . The composition o f t h i s  - 100 layer  -  ( f o r e s t f l o o r ) v a r i e s - from the r e l a t i v e l y  unaltered  v e g e t a l d e b r i s near the s u r f a c e t o the h i g h l y decomposed organic  matter at depth. S p e c i a l care must be  p r e s e r v e the  taken to  f o r e s t f l o o r s t r u c t u r e while determining i t s  h y d r a u l i c c o n d u c t i v i t y . The  o b j e c t i v e s o f t h i s paper are  to b r i e f l y review the procedures p r e v i o u s l y used to measure the h y d r a u l i c c o n d u c t i v i t y c h a r a c t e r i s t i c s o f porous and  to describe  a simple method o f measuring the  c o n d u c t i v i t y c h a r a c t e r i s t i c s of an u n d i s t u r b e d f o r e s t f l o o r m a t e r i a l i n the l a b o r a t o r y . The here can be used t o determine the h y d r a u l i c c h a r a c t e r i s t i c s o f the c o n t e n t s between the  materials  hydraulic  sample o f  method  discussed  conductivity  f o r e s t f l o o r over the range o f water  c o n d i t i o n s o f s a t u r a t i o n and of n e g l i g i b l e  d r a i n a g e . For most f o r e s t f l o o r m a t e r i a l around Vancouver, B.C., t h i s i m p l i e s 0 and  -100 The  a range of m a t r i c  to -150  p o t e n t i a l s between  cm o f water.  hydraulic conductivity, k i s defined  by the  Darcy  equation q = - k 3473Z where q i s the water f l u x d e n s i t y , p o t e n t i a l gradient, and  Bf/aZ i s the  4* i s the sum  total  o f matric, g r a v i t a t i o n a l ,  osmotic p o t e n t i a l s .  Review o f The  and  (1)  Procedures Used  Previously  procedures used to e s t i m a t e the h y d r a u l i c  conductivity  c h a r a c t e r i s t i c s o f porous m a t e r i a l s have been r e c e i v e d  by  - 101  -  R i c h a r d s and Moore (1952), E l r i c k  (1953), and  Klute  (1965). The h y d r a u l i c c o n d u c t i v i t y of u n s a t u r a t e d m a t e r i a l may  be determined  non-steady-state  e i t h e r by s t e a d y - s t a t e o r  t e c h n i q u e s . During s t e a d y - s t a t e c o n d i t i o n s  the m o i s t u r e c o n t e n t , m a t r i c p o t e n t i a l , p o t e n t i a l g r a d i e n t and  f l u x are c o n s t a n t w i t h time. In the l a t t e r  t h e s e q u a n t i t i e s change w i t h Elrick  technique  time.  (196 3) found t h a t the h y d r a u l i c c o n d u c t i v i t y  measured by both techniques agreed w e l l a t low water c o n t e n t , but a t h i g h water content the n o n - s t e a d y - s t a t e found u n r e l i a b l e . The  e x p e r i m e n t a l c o n d i t i o n s which  the n e c e s s a r y mathematical s t a t e case are d i f f i c u l t  based  was  fulfill  assumptions f o r the non-steady-  to a t t a i n  T h e o r e t i c a l methods ( C h i l d s and 1958)  method  ( N i e l s e n and  B i g g a r , 1961).  C o l l i s George, 1950;  on s o i l water r e t e n t i o n d a t a cannot  be used  c a l c u l a t e the h y d r a u l i c c o n d u c t i v i t y o f the f o r e s t s i n c e the l a t t e r s h r i n k s and  sweels  Marshall, to  floor  and has a heterogeneous  structure. S e v e r a l s i m i l a r forms o f apparatus  to determine  the  c o n d u c t i v i t y ' b y the s t e a d y - s t a t e method have been r e p o r t e d i n the l i t e r a t u r e . Richards to  (1931) was  probably the  measure u n s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y by  c o n s t a n t f l u x method.  the  He mounted the sample t o be  a n a l y z e d i n a r e c t a n g u l a r frame between two set  first  porous p l a t e s  about 4 cm a p a r t . Porous cups p o s i t i o n e d i n the sample  - 102 and connected  t o a d i f f e r e n t i a l manometer measured the  potential  g r a d i e n t a c r o s s the sample. A vacuum b o t t l e  connected  t o the top and bottom p l a t e s c o n t r o l l e d the  water content o f the s o i l column. The p r e s s u r e o f a h y d r o s t a t i c column extending above the upper c e l l and the g r a v i t a t i o n a l  g r a d i e n t a c r o s s the sample  the water t o move through  caused  the sample. The i n f l o w and  o u t f l o w o f water, and the p o t e n t i a l g r a d i e n t were measured. A few years l a t e r , Richards and Wilson a s i m i l a r apparatus  t o determine  (19 36)  used  the u n s a t u r a t e d h y d r a u l i c  c o n d u c t i v i t y o f peat s o i l s . T h i s time the sample was s e t h o r i z o n t a l l y between two porous p l a t e s t o g i v e zero g r a v i t a t i o n a l g r a d i e n t a c r o s s the sample. D i f f e r e n t t e n s i o n s were a p p l i e d at the ends o f the s o i l to  cause the water t o move through  column  the s o i l .  The vacuum b o t t l e used by Richards t o c o n t r o l s o i l water content may be r e p l a c e d by hanging  water  columns from.both p l a t e s , o r t h e sample may be e n c l o s e d w i t h i n a p r e s s u r e chamber. Elrick used  (1964) s e t the s o i l  core h o r i z o n t a l l y and  low impedance, c e l l u l o s e a c e t a t e f i l t e r s t o e l i m i n a t e  the need f o r t e n s i o m e t e r s . At h i g h water c o n t e n t , flow a l o n g the lower s i d e o f the sample may o c c u r . I t has been found  i n t h i s l a b o r a t o r y t h a t c l o g g i n g o f these  filters  - 103 can l e a d t o erroneous unless c o r r e c t i o n Richards to  p o t e n t i a l gradient determination,  f o r membrane impedance i s a p p l i e d .  (1965) found  t h a t t h i s impedance, i s d i f f i c u l t  measure and the c o n t a c t impedance cannot  be determined  experimentally. Methods  in  which one end o f the s o i l  core i s i n  c o n t a c t w i t h a porous p l a t e , w h i l e the o t h e r end i s f r e e l y exposed t o e v a p o r a t i o n have been used  (Gardner and  M i k l i c h , 1962; N i e l s e n et al. , 1960). The e v a p o r a t i v e f l u x i s maintained  by water s u p p l i e d through  the porous p l a t e .  Methods r e q u i r i n g porous p l a t e s a t both ends o f the sample must have p r o v i s i o n made f o r a i r t o e n t e r o r escape as t h e water content o f the sample changes. When u s i n g any o f these apparatus,  the m a t r i c p o t e n t i a l  g r a d i e n t should be kept as s m a l l as p o s s i b l e i n o r d e r t o r e l a t e the average  h y d r a u l i c c o n d u c t i v i t y to a p a r t i c u l a r  m a t r i c p o t e n t i a l o r water content  ( C h i l d s , 1969). F o r t h i s  r e a s o n , t h e d e t e r m i n a t i o n o f u n s a t u r a t e d h y d r a u l i c conductivity  on h o r i z o n t a l samples cannot  be recommended. Zero  m a t r i c p o t e n t i a l g r a d i e n t i s a l s o very d i f f i c u l t  to obtain  i n the e v a p o r a t i v e - t y p e o f apparatus. C h i l d s and C o l l i s - G e o r g e (1950) achieved a zero m a t r i c p o t e n t i a l g r a d i e n t by u s i n g a long s o i l end to  immersed i n water. The s o i l generate  column w i t h the lower  column was s u f f i c i e n t l y  a zone o f uniform water content  long  (the t r a n s m i s s i o n  - 104  -  zone) i n which the h y d r a u l i c c o n d u c t i v i t y was  approximately  equal to the c o n t r o l l e d r a t e o f water i n p u t a t the t o p . moisture  content a d j u s t s i t s e l f to p r o v i d e the  p e r m e a b i l i t y t o conduct  necessary  the imposed flow w i t h the  a l gradient of p o t e n t i a l "  ( C h i l d s and  As p o i n t e d out by these a u t h o r s  ;  gravitation-  C o l l i s - G e o r g e , 1950).  t h i s method i s l i m i t e d  s t r u c t u r e l e s s m a t e r i a l s such as sands. T h i s technique been used 1969)  "The  s u c c e s s f u l l y w i t h P l a i n f i e l d sand  and w i t h C a p i l a n o g r a v e l l y sandy loam  ( B l a c k et  to  has al.  3  (Willington,  1971). An a l t e r n a t i v e method i s t o measure the flow o f i n f i l t r a t i n g water i n t o a s o i l column i n i t i a l l y kept a t a u n i f o r m low water c o n t e n t . The water i s s u p p l i e d through  a  membrane i n o r d e r t o m a i n t a i n the s u r f a c e m a t e r i a l at  a g i v e n s u c t i o n and  than s a t u r a t i o n .  "The  a t a constant water content  less  s u c t i o n g r a d i e n t at the s u r f a c e  approaches zero and the moisture p r o f i l e moves downwards at  a c o n s t a n t v e l o c i t y w i t h a c o n s t a n t shape a f t e r a l o n g  time"  (Youngs,1964). In the zone o f zero m a t r i c p o t e n t i a l  g r a d i e n t the c o n d u c t i v i t y equals the f l u x . T h i s method i s simple and r e l a t i v e l y s h o r t samples can be used. The  matric  p o t e n t i a l , however, at the top of the porous m a t e r i a l d i f f e r s from the porous p l a t e ' s t e n s i o n s i n c e the p l a t e o f f e r s r e s i s t a n c e t o the flow o f i n f i l t r a t i n g water. Thus, a f t e r each c o n d u c t i v i t y d e t e r m i n a t i o n a d i f f e r e n t  sample  - 105 must be used because the s o i l water content must be measured  destructively.  Methods and R e s u l t s The apparatus d e s c r i b e d f i r s t by Richards  (1931) seemed  s u i t e d to measurement o f h y d r a u l i c c o n d u c t i v i t y c h a r a c t e r i s t i c s o f an u n d i s t u r b e d f o r e s t f l o o r sample i f the need and means o f a p p l y i n g a p o s i t i v e head t o the sample c o u l d be e l i m i n a t e d . With f o r e s t f l o o r m a t e r i a l , a good c o n t a c t between  the top p l a t e and the r e l a t i v e l y undecomposed F  h o r i z o n i s very d i f f i c u l t t o a c h i e v e . On the o t h e r a good c o n t a c t between  the bottom p l a t e and the more  decomposed H h o r i z o n i s e a s i l y a c h i e v e d . To the d i f f i c u l t y top p l a t e was water f l u x was  overcome  at the upper s u r f a c e of the sample, the e l i m i n a t e d and a constant and a d j u s t a b l e a p p l i e d a t the top o f the column by a  chromatography micropump. The micropump was 3 to  hand,  p r o v i d e flow r a t e s from 9 t o 110 cm 3 -1  r a t e s lower than  9 cm  hr  adjustable  -1 hr  . For flow  , a cam t i m e r was  r e g u l a t e the duty c y c l e o f the pump. A 11-cm  used t o I.D.,  l o n g , a c r y l i c c y l i n d e r with a commercial porous  30 cm  alundum  p l a t e a t t a c h e d t o the bottom formed the c o n t a i n e r f o r undisturbed  samples o f the f o r e s t f l o o r ,  ( F i g . 1). A  10 cm t h i c k l a y e r o f coarse sand (0.2 5-0.5  mm)  was put on  the sample i n o r d e r t o e v e n l y d i s t r i b u t e the water over the top o f the f o r e s t  floor.  -  106  -  MICROPUMP WATER RESERVOIR  TIMER—j STOPPER  WATER MANOMETERS SANO-  TENSIOMETER C U P  CY::.:  FOREST FLOOR  -  c:.v ALUMINUM FUNNEL-*  1  POROUS  PLATE  _ TYGON  .  TUBING  —l  OUTFLOW BURETTE  10  •-STAND ONLY THE SOIL C O L U M N IS D R A W N  F i g u r e 1.  Diagram o f the a p p a r a t u s used t o measure  ;  - h y d r a u l i c c o n d u c t i v i t y c h a r a c t e r i s t i c s o f the forest  f l o o r material  i n the l a b o r a t o r y .  - 107 The t o p p l a t e e l i m i n a t i o n and the pump a p p l i c a t i o n o f w a t e r had o t h e r b e n e f i t s b e s i d e s the one noted above. A i r c o u l d r e a d i l y p e n e t r a t e the top o f the sample t o s i m u l a t e n a t u r a l c o n d i t i o n s a n d , a l s o , the w a t e r i n p u t r a t e c o u l d be preselected.  E v a p o r a t i o n from the system was m i n i m i z e d by  i n s e r t i n g a r u b b e r s t o p p e r i n the top o f the  acrylic  c y l i n d e r . A s t o p p e r a l s o p r e v e n t e d e v a p o r a t i o n from  the  b u r e t t e used t o c o l l e c t the o u t f l o w . The n e c e s s a r y s m a l l g r a d i e n t s o f m a t r i c p o t e n t i a l were k e p t s m a l l by i n c r e a s i n g the t e n s i o n on the bottom p l a t e as the w a t e r i n p u t r a t e was d e c r e a s e d .  I t was  t h e o r e t i c a l l y i m p o s s i b l e under c o n s t a n t w a t e r f l u x c o n d i t i o n s t o o b t a i n zero m a t r i c p o t e n t i a l s , s i n c e the h y d r a u l i c c o n d u c t i v i t y of forest  f l o o r m a t e r i a l s l o w l y changes w i t h depth  and the m a t r i c p o t e n t i a l g r a d i e n t changes s i m i l a r l y . To m i n i m i z e the e f f e c t s  of nonlinear, t o t a l potential  and t o keep the e r r o r s i n manometer r e a d i n g  gradients  below an  a c c e p t a b l e l e v e l , t h e t e n s i o m e t e r s were p o s i t i o n e d v e r t i c a l l y 6 cm a p a r t . The t h i c k n e s s o f the f o r e s t  floor,  and thus o f  s a m p l e s , was b o t h t r o u b l e s o m e and advantageous measurements.  its  to c o n d u c t i v i t y  A d i s a d v a n t a g e was t h a t a c o n s i d e r a b l e p e r i o d o f  t i m e was r e q u i r e d t o p r o c e e d from one s t e a d y - s t a t e t o  another.  F o r example, w i t h a 10 cm t h i c k s a m p l e , 4 days were r e q u i r e d t o r e a c h s t e a d y - s t a t e a t a m a t r i c p o t e n t i a l o f -30 cm o f w a t e r . On t h e o t h e r h a n d , s t r u c t u r a l d i s t u r b a n c e s caused by c u t t i n g t h e ends o f the t h i c k samples were r e l a t i v e l y s m a l l .  - 108 The m o d i f i e d R i c h a r d s  1  method was used t o determine  the h y d r a u l i c c o n d u c t i v i t y c h a r a c t e r i s t i c s o f the F and H h o r i z o n s o f the f o r e s t f l o o r o f a mountainous watershed near Vancouver, B r i t i s h Columbia. were each approximately 10-cm  The F and H h o r i z o n s  t h i c k . H y d r a u l i c conduct-  i v i t i e s normal and p a r a l l e l t o the f o r e s t f l o o r s u r f a c e were determined  f o r the F h o r i z o n . The r e s u l t s are shown  i n F i g . 4 (Chapter 3 ) .  P r o v i d e d t h a t e v a p o r a t i o n i s prevented,  the method i s r e l i a b l e from s a t u r a t i o n t o m a t r i c p o t e n t i a l s o f approximately  -100  cm o f water and appears  for research i n forest  Literature  practical  hydrology.  Cited  BLACK, T.A., W.R.  GARDNER, and G.W.  THURTELL.  1969.  The  p r e d i c t i o n o f e v a p o r a t i o n , d r a i n a g e , and s o i l water s t o r a g e f o r a bare s o i l . BOELTER, D.H.  S o i l S c i . Soc. Amer. Proc. 33: 655-660.  1964.  L a b o r a t o r y techniques f o r measuring  water s t o r a g e p r o p e r t i e s o f o r g a n i c s o i l s .  Soil S c i .  Soc. Amer. P r o c . 28: 823-824. CHILDS, E.C.  1969.  An i n t r o d u c t i o n t o the p h y s i c a l b a s i s  o f s o i l water phenomena.  W i l e y - I n t e r s c i e n c e John Wiley  g Sons L t d . Toronto. CHILDS, E.C. and N. COLLIS-GOERGE. o f porous m a t e r i a l s . ELRICK, D.E.  1963.  19 50.  The p e r m e a b i l i t y  Proc. Roy. Soc. A. 201: 392-405.  Unsaturated  A u s t . J . S o i l . Res. 1: 1-8.  flow p r o p e r t i e s o f s o i l s .  ELRICK, D.E., and D.H. BOWMAN. apparatus  f o r s o i l moisture  1964.  Note on an improved  flow measurements.  Soil  S c i . Soc. Amer. Proc. 28: 450-453. GARDNER, W.R., and F . J . MIKLICH.  1962.  Unsaturated  c o n d u c t i v i t y and d i f f u s i v i t y measurements by a c o n s t a n t flux  method.  KLUTE, A.  S o i l S c i . 93: 271-274.  1965.  L a b o r a t o r y measurement o f h y d r a u l i c  c o n d u c t i v i t y of unsaturated s o i l .  In Methods o f s o i l  a n a l y s i s P a r t I , E d i t e d by C A . Black Agronomy MARSHALL, T . J . and  size  1958.  distribution  A relation o f pores.  NIELSEN, D.R., and J.W. BIGGAR. capillary  conductivity.  between p e r m e a b i l i t y J . S o i l S c i . 9: 1-8.  1961.  Soil  Measuring  S c i . 92: 192-193.  NIELSEN, D.R., and D. KIRKHAM, and E.R. PERRIER. Soil capillary  1960.  c o n d u c t i v i t y : Comparison o f measured and  calculated values. RICHARDS, B.G.  9. 253-272.  1965.  S o i l S c i . Soc. Amer. Proc. 24: 157-160 D e t e r m i n a t i o n o f the u n s a t u r a t e d  p e r m e a b i l i t y and d i f f u s i v i t y  f u n c t i o n s from  pressure  p l a t e o u t f l o w d a t a w i t h n o n - n e g l i g i b l e membrane impedance. C.S.I.R.O.  S.M.S. Res. Paper No. 57.  RICHARDS, L.A.  19 31.  C a p i l l a r y conduction o f l i q u i d s  through porous mediums.  P h y s i c s 1: 318-333.  RICHARDS, L.A., and D.C. MOORE. capillary  1952.  Influence of  c o n d u c t i v i t y and depth o f w e t t i n g on moisture  r e t e n t i o n i n soil..  T r a n s . Amer. Geophys. Union 33:  531-5  - 110 RICHARDS, L.A., and B.D. WILSON.  19 36.  Capillary  c o n d u c t i v i t y measurements i n peat s o i l s .  Jour.  Amer. Soc. Agron. 28: 42 7-4 31. RICHARDS, S . J . , and L.V. WEEKS.  1953.  Capillary  c o n d u c t i v i t y v a l u e s from moisture y i e l d and t e n s i o n measurements on s o i l columns.  S o i l S c i . Soc. Amer.  Proc. 17: 206-209. WILLINGTON, R.P.  19 71.  Development and a p p l i c a t i o n o f  a technique f o r evaluating PhD. T h e s i s  root  zone d r a i n a g e . Unpub.  Univ. o f B r i t . C o l . 42 pp.  WILSON, B.D., and S.J. RICHARDS.  1938.  C a p i l l a r y conduct-  i v i t y o f peat s o i l s a t d i f f e r e n t c a p i l l a r y  tensions.  J . Amer. Soc. Agron. 30: 583-5 88. YOUNGS, E.G.  1964.  the h y d r a u l i c  An i n f i l t r a t i o n method o f measuring  c o n d u c t i v i t y o f u n s a t u r a t e d porous  S o i l S c i . 92: 307-311.  materials.  - Ill APPENDIX I  L i s t o f the P l o t numbers by a r e a  AREA 1  PLOT NUMBER 1 to  24  inclusively  32 to 45  inclusively  2  25  to  31  inclusively  3  46  to  53  inclusively  4  54 to  60  inclusively  - 112 -  APPENDIX I I  T a b u l a t i o n by p l o t s o f the average depths o f humus and t o t a l f o r e s t f l o o r w i t h t h e i r r e s p e c t i v e standard deviations,  and o f the b i o p h y s i c a l  c h a r a c t e r i s t i c s . Each  depth f i g u r e i s the average o f 40 measurements.  Plot No  Humus Depth  SD  (cm)  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30  i i  5.9 2.7 4.3 7.3 6.3 5.5 11.7 5.6 6.0 4.6 3.2 5. 3 3.8 11.9 9.4 3.3 11.4 6.2 7.0 6.6 5.4 11.7 17.6 6.1 11.5 9.0 13.0 13.9 8.1 10.7  Forest  floor  Depth  SD  (cm)  4.60 1.89 3.78 8.92 5.56 5.85 11.13 5 .46 3.68 5.47 3.06 4.54 4 . 34 5.51 6.59 5.52 8.19 5.51 3.28 5.89 8.40 8.98 13.11 8.97 10 .06 7.33 10.47 11.95 9.23 10.24  11.1 7.3 7.0 14.7 16.4 15.0 24.5 13.8 7.5 19.2 5.3 9.0 3.9 12.1 11.0 3.7 11.4 6.1 13.2 11.1 7.0 16.2 22.3 15.0 24.1 19.3 15.7 16 .8 8.9 13.0  Altitude  Aspect  Basal area  (feet)  6.79 6.28 6.18 12.31 16.37 13.76 14.11 14 .06 5.39 20.81 5.03 9.77 4 . 36 5.45 8.10 6.27 8.19 5.56 13.73 12.00 11.22 10.65 15.87 30 .41 15.72 17.61 14.05 12.37 9.42 10.90  Slope  730 760 800 850 890 910 950 1050 1100 1170 1230 1280 1360 1440 1680 1790 2100 2430 720 760 890 920 1090 1130 910 1050 1190 1390 1850 2080  Index  (ft )  (degree)  9 18 7 15 18 20 20 20 16 21 23 26 30 46 41 40 46 39 9 13 27 26 22 30 25 30 30 27 36 45  Radiation  2  E E E E E E E E E E S SE SE E E E S SE E E E E E E W W W W W W  200 200 200 220 190 130 40 170 240 150 220 140 310 160 240 120 260 180 160 210 120 110 210 270 250 120 290 160 210 170  0.4181 0.4185 0.4182 0.4185 0.4185 0.4185 0 .4185 0 .4185 0.4185 0.4185 0.5430 0.5203 0.5301 0 .4092 0 .4092 0.4092 0.5912 0 .5414 0 .4181 0 .4182 0 .4181 0.4181 0.4181 0.4172 0.4172 0 .4172 0.4172 0.4172 0.4172 0.4092  (continued) Plot No  Humus Depth  SD  (cm)  31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 . 56 57 58 59 60  15.1 4.1 5.2 7.7 4.6 4.0 7.0 8.0 9.9 5.5 5.7 6.3 4.7 3.0 8.4 2.9 8.1 7.7 8.9 12.8 8.7 11.9 5.2 12.2 13.8 8.2 22.0 34.5 21.8 12.1  Forest f l o o r Depth  16.0 6.9 11.3 24.1 10.4 9.5 18.0 13.5 18.0 7.2 15.4 11.6 5.0 8.7 10.4 3.0 10.4 9.9 16.8 17.1 15.4 16.6 12 .2 23.4 27.3 13.2 26.1 45.3 28.6 14.7  Slope  Aspect  SD  (cm)  10.15 2.81 3.31 5.48 5.30 3.27 5.47 9.04 7.61 4.47 4.24 4.77 5.18 2.70 8.86 1.65 7 .17 5.92 5.21 6.19 5.43 9.33 6.72 10.96 10.74 8.33 10.65 27.82 20.73 11.66  Altitude  area (feet)  9.95 6.08 11.14 16.54 11.58 11.07 14 .04 13.34 12.88 6.89 10.68 11.12 5.33 11.31 8.87 1.72 8 .32 6.68 10.10 9.47 9.14 10.87 19.78 12 .88 19.85 10.71 11.34 29 .01 28.67 13.44  Basal  2430 740 790 810 880 .950 1060 1080 720 740 760 830 870 910 960 880 1100 1300 1400 1800 2100 2500 880 1030 1250 1400 1830 2180 2430 1950  (degree)  33 9 10 15 18 20 18 15 5 8 7 10 9 10 15 10 34 42 13 38 40 44 1 9 2.8 25 28 33 36 36  Radiation Index  (ft ) 2  W E E E E E E E E E E E E E E SW SW SW W S  s s s  NE NE NE. NE N N NE  160 240 240 200 100 40 160 120 440 160 160 160 160 160 280 280 480 400 320 360 440 440 360 440 400 280 320 360 240 400  0.4165 0.4181 0.4182 0.4182 0.4185 0.4185 0.4185 0.4185 0.4179 0.4179 0.4179 0.4182 0.4182 0.4182 0.4185 0.4690 0.5370 0.5447 0.5414 0.5860 0.5860 0.5860 0.4178 0.3713 0.2800 0.2893 0.2800 0.1862 0.1862 0.2561  - 115 APPENDIX  HI  LISTING OF SAMPLE CHARACTER!STIIS FOUR SAMPLES WERE CCLLECTED IN EACH PLOT PLOT ND 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 3 5 5 5 6  6  6 6  7 7 7 7 8 8 8 8 9 9 9 9 10 10 10 10 11 11 11 11 12 12 12 12  DEPTH (CM) 8.4 7 . 6  9.4 5. 1 14.0 3.8 1.8 10. 2 3.6 4.3 2.8 3.8 9.7 2.5 5.6 4.3 5.1 7. 6 5.3 5.6 5. 1 9.7 5.6 10.2 3.3 14. 2 4.8 5. 1 12.4 2.3 20.1 1.3 2.3 4.3 2 .3 4.3 8.4 7.6 2.8 4.3 1.0 1.8 4. 1 2.5 3.6 2.5 2.3 2.0  WEIGHT (G/M2) 0.951 0.600 1.426 0.758 1.692 0.617 0. 379 1. 839 0.538 0.538 0.379 0.600 1.109 0.509 0.826 0.442 0.600 0. 758 0.668 0.696 0.668 1.075 0. 730 1.172 0.539 1.681 0.600 0.758 1.109 0.317 3.865 0.193 0. 442 0.600 0.351 0.475 1.392 0.888 0.696 0.572 0.379 0.475 0.600 0.351 0.413 0. 379 0.634 0.351  B . DENS (O/CMi) 0.110 0.076 0.147 0.145 0. 117 0.157 0.207 0. 175 0.146 0.121 0.131 0. 153 0.111 0.194 0.143 0.099 0.114 0.C96 0.121 0.115 0. 127 0.100 0. 127 0.112 0.149 0.114 0.120 0.145 0.086 0.134 0.187 0.147 0. 187 0.135 0.149 0.107 0. 161 0.113 0.241 0.128 0.362 0.259 0. 143 0.134 0.113 0. 145 0.269 0.167  SAT CPTY F.M.C U OF WEIGHT) 445. 457. 378. 4 37. 282. 40 9. 467. 305 . 39 5. 289. 564. 424. 441. 43 3 . 386. 464. 466. 553 . 459. 498. 455 . 4 50. 443 . 475. 400 . 464 . 513. 381 . 551 . 463 . 224. 576. 368. 475. 513. 471 . 335. 400. 441 . 450. 407. 33 5. 518. 755. 599. 482 . 320. 594.  230. 249. 243. 262. 189. 194. 206. 154. 184. 153. 205. 2 07. 229. 194. 225. 240. 216. 243. 235. 2H2. 214*. 224. 24 9 . . 207. 194. 301. 282. 240. 300. 195. 114. 179. 137. 207. 198. 227. 203. 222. 201. 232. 115. 150. 295 . 327. 236. 169. 101. 134.  SAT CPTY F.M.C (CM OF WATER) 4.?3 2 .74 5.39 3.31 4.77 2.52 1. 77 5.61 2.12 1.55 2. 14 2 .54 4.89 2.21 3.19 2. 05 2.80 4.19 3. 06 3. 4 7 3.04 4. 84 3.23 5. 57 2. 04 7.80 3. 08 2. £9 6.11 1 .47 8. 66 I. 1 I 1 .62 2. t)5 1. BO 2.24 4.66 3.55 3 .07 2.57 1. 54 1.59 3.11 2. 65 2.47 1.83 2. 03 2.08  2. 19 1. 49 3.47 1.99 3.23 1.23 0. 78 2.83 0.99 0. 8? 0.78 1.24 2. 54 0.9 9 1.86 1.0 6 1. 30 1.84 1 . 57 1.96 1. 43 2. 41 1.82 2.43 0. 99 5.06 1 . 69 1.8 2 3. 33 0.62 4. 41 0. 34 0.63 1.24 0. 69 1.38 2. 83 1.97 1. 43 1.33 0. 44 0. 71 1.78 1.15 0. 97 0.64 0. 64 0.47  - 116 APPENDIX I I I L I S T I N G OF SAMPLE CHARACTERISTICS FOUR SAMPLES WERE COLLECTED IN EACH PLOT IT NO  13 13 13 13 14 14 14 14 15 15 15 15 16 16 16 16 17 17 17 17 18 18 18 18 19 19 19 19 20 20 20 20 21 21 21 21 22 22 22 22 23 23 23 23 24 24 24 24  DEPTH (CM )  WEIGHT (G/M2)  B . DENS (G/CM3)  4.1 6. 1 4.6 4.1 6. 1 3.8 8.9 9.4 12.4 6.6 8.6 5.3 3.8 6.3 6. 1 3.0 14.5 4. 1 10.4 9.4 3.0 1.0 2.5 7.4 6.9 9.7 2.0 9.9 12.7  0.475 0. 600 0.730 0.379 0. 679 0. 300 1.743 0.985 2.111 1.953 0.940 0. 849 0.990 0.934 0. 691 0.434 2.224 0. 504 1.228 1.290 0. 538 0. 164 0. 328 0.996 0. 758 1. 109 0.7 30 1.805 2.77 3 0.481 1 .868 0. 566 0. 594 0.566 0. 226 0.368 0.396 0.764 0.368 0.821 4.075 0. 905 1.070 2.0 49 0. 888 0.747 1.862 1.070  0.113 0. 095 0. 155 0.090 0. 108 0. 076 0. 190 0.10 1 0. 164 0. 286 0. 105 0. 154 0.252 0.142 0.110 0. 131 0. 149 0. 120 0. 114 0. 133 0.171 0. 157 0.125 0.131 0. 107 0.111 0. 348 0. 177 0. 212 0.080 0.21S 0. 103 0. 103 0 .080 0. 086 0. 117 0.1 16 0.139 0. 1 17 0. 209 0. 129 0. 099 0. 146 0.182 0. 125 0. 075 0. 142 0.080  5.8 8.4 5.3 5.6 6.9 2.5 3.0 3.3 5.3 3.0  3.8 30.5 8. 9 7.1 10.9 6. 9 9.7 12.7 13.0  F.M.C SAT CPTY {% OF WE IGHT) 519. 560. 396. 564. 423 . 413. 233. 50 5. 355. 278. 328 . 311 . 280. 427. 53 8. 482. 398. 516. 532. 427. 50 7. 54 5. 569. 50 7. 508. 439. 210. 309. 255. 635. 271. 465. 619. 60 5. 613 . 608. 564. 400 . 546. 307. 39 4. 449. 348. 300. 52 5. 52 7. 308. 511.  163. 263. 175. 213. 102. 158. 84. 189. 187. 80. 165. 61. 160. 215. 111. 167. 140. 221. 235. 198. 218. 252. 233. 220. 243. 242. 63. 181. 117. 282. 271. 233. 267. 295. 225. 369. 250. 207. 233. 143. 247. 213. 102. 150. 217. 186. 145. 229.  SAT CPTY F.M.C (CM OF WATER) 2.47 3.36 2.89 2. 14 2 .87 1.24 4.06 4.97 7.49 5.43 3.08 2.64 2. 77 3. 99 3.72 2.09 8. 85 2.60 6.53 5.51 2. 73 0.89 1. 87 5. 05 3.85 5.42 1.53 5.58 7.07 3.05 5. 06 2 .75 3.68 3.42 1.39 2.24 2.23 3 .06 2.01 2.52 16.05 4 .07 3.72 6. 15 4.66 3.94 5.73 5.47  0.30 1 .61 1.28 0.81 0.69 0.47 1.46 1.86 3.9 5 1. 56 1. 55 0. 52 1 . 58 2. 01 0.77 0.72 3. 11 1.11 2.89 2. 56 1.17 0.41 0. 77 2. 19 1.84 2. 68 0. 46 3. 27 3.24 •1.36 5.06 1. 3D 1. 59 1.67 0. 51 1.36 0.99 1. 58 0.88 1.21 10.06 1.93 1.09 3. 07 1.93 1. 39 2.70 2.45  - 117 APPENDIX I I I L I S T I N G OF S A M P L E C H A R A C T E R I S T I C S F O U R S A M P L E S WERE C O L L E C T E D I N E A C H P L O T  >r  NO  25 25 25 25 26 26 26 26 27 27 27 27 28 28 28 28 29 29 29 29 30 30 30 30 3i 31 31 31 32 32 32 32 33 33 33 33 34 34 34 34 35 35 35 35 36 36 36 36  DEPTH  (CM) 9.4 4.6 10.4 14.0 8.6 9.1 4.8 17.0 2.3 6. 1 10. 2 2.8 14.2 5. 6 4.8 20.1 3.8 4.1 4.1 4. 1 6.9 2.8 11.2 2.5 12.7 21.8 6. 9 6.9 4.6 2.3 3.3 2 .3 4.1 1.5 4.6 3.6 3.6 7.6 4.1 5.6 2.5 3 .3 5. 1 2.8 7.9 4.3 4. 1 5.1  WEIGHT  B.  (G/M2)  (0/CM 3 )  1. 143 0.651 1.019 2. 643 0.990 1.273 0.481 2.479 0.340 1.613 2. 63 3 0.311 2.039 0. 707 0.679 2.156 0. 538 0.894 0.787 0. 985 0.753 0.335 1.154 0.243 1.822 3.181 1. 862 2.411 0.539 0. 198 0.453 0.990 0. 424 0.283 0.707 0.566 0. 368 1. 370 0.594 0. 623 0. 283 0.226 0.877 0.340 1.426 0.464 0. 470 0. 566  DENS  0. 118 0. 138 0.095 0.183 0. I l l 0. 135 0. 097 0. 14 1 0. 144 0.256 0. 256 0. 108 0. 137 0. 123 0. 136 0. 104 0. 137 0.2 13 0.187 0.235 0. 106 0. 106 0. 100 0. 093 0. 139 0. 141 0. 26 3 0.341 0. 108 0. 084 0. 133 0.378 0. 101 0. 180 0.150 0. 154 0. C99 0. 174 0.142 0. 108 0.108 , 0.066 0.167 0. 118 0. 175 0.104 0. 112 0. 108  SAT C P T Y F.M.C {% U F W E I G H T )  41 9. 478. 574. 245 . 469. 387. 600 . 340. 550. 277. 22 7. 707. 343. 476. 467. 490 . 404. 359. 455. 249. 484. 654 . 40 5. 858. 510. 411 . 2 63 . 181 . 617 . 757. 53 8. 143. 633 . 580. 456. 510 . 73 3. 336. 543. 53 6. 630. 913. 374. 600. 362. 571 . 599. 543.  211. 222. 254. 123. 223. 222. 288. 216. 267. 184. 154. 255. 161. 243. 242. 268. 73. 79. 150. 71. 133. 117. 230. 300. 347. 303. 102. 96. 317. 242. 136. 80. 240. 230. 224. 260. 263. 183. 462. 277. 240. 275. 232. 225. 226. 262. 329. 280.  SAT C P T Y F.M.C ( C M OF WATER)  4.79 3. 11 5. 85 6.48 4. 64 4.93 2.89 8.43 1. 87 4.4 7 6.09 2.20 6. 89 3.3 7 3.17 10.57 2.17 3.21 3. 58 2.45 3 .64 2.00 4.68 2.09 9. 29 13.07 4.90 4.36 3. 14 1.50 2.44 l.<t2 2.69 1.64 3. 23 2. 89 2.71 4.60 3.23 3.34 - 1.78 2.07 3.28 2.04 5. 16 2.65 2.81 3. 07  2.41 1. 44 2. 59 3.25 2.21 2.83 1. 39 5.35 0.91 2.97 4.13 0.7 9 3. 23 1.70 1. 64 5. 78 0. 39 0.71 1.13 0.73 1.04 0. 36 2.66 0.73 6.32 9. 64 1 .93 2. 31 1.61 0. 48 0.62 0. 79 1.0 2 0.65 1. 58 1. 47 0.97 2. 51 2. 75 1.72 0. 68 0.62 2.3 4 0. 76 3.22 1.22 1. 55 1.58  -  118  -  APPENDIX  III  L I S T I N 3 OF S A M P L E CHARACTERISTICS F O U R S A M P L E S WERE C O L L E C T E D I N E A C H P L O T PLOT  37 37 37 37 38 38 38 38 39 39 39 39 AO 40 40 40 41 41 41 41 42 42 42 42 43 43 43 43 44 44 44 44 45 45 45 45 46 46 46 46 47 47 47 47 48 48 48 48  NO  DEPTH (CM)  WEIGHT (G/M2)  6 . DENS (G/CM3)  2 .8 5. 1 17.0 5.1 15.7 14. 2 6.1 11.9 7.9 6.6 3.8 3.3 6.6 3.6 6. 1 8. 6 3.0 7.1 3.0 7. 1 8.6 6. 1 4.6 6.1 4.1 3.0 3.0 3.8 2.0 2.0 1.0 2.8 3.0 3.8 1.3 6. 6 2.0 5.1 3.6 1.8 4 .6 2.8 5.1 3.8 12.4 5. 1 4.1 4.1  0.311 0.538 3.305 0.526 2.586 3.616 0.730 2 . 8 52 1.137 1.205 0.560 0.639 1.681 0.504 0.563 1.734 0.515 1.160 0.668 1.058 0.872 0.589 0.453 0.504 0.390 0. 402 0.583 0.526 0.226 0.334 0.153 0.458 0.436 0.526 0.232 0. 849 0.238 0.277 0. 464 0.226 0.521 0.305 0.707 0.611 1.771 0.679 0.753 0.758  0.108 0.103 0.188 0.100 0.159 0 . 246 0.116 0.231 0.140 0.177 0.142 0.183 0.247 0.137 0.093 0.191 0.164 0.158 0.212 0.144 0.098 0.094 0.096 0.080 0.093 0 . 128 0.185 0.135 0.108 0.159 0.146 0.159 0.138 0.134 0.177 0 . 125 0.113 0.053 0 . 126 0.123 0.110 0.106 0.135 0.155 0.136 0.129 0.179 0.181  SAT  (Z  CPTY F.M.C OF W E I G H T )  724. 485. 304. 504. 359. 215. 427. 221 . 458. 318. 508. 354. 244. 520. 600. 276. 466. 335. 345 . 421. 521. 556 . 614. 494. 533 . 62 6 . 329. 508. 63 9 . 531. 41 8 . 522 . 510. 558. 61 7 . 513 . 733. 757. 518. 970. 549. 63 5 . 463. 409. 380. 503. 346. 343.  291. 304. 249. 329. 216. 103. 225. 115. 234. 194. 301. 145. 152. 255. 239. 155. 267. 176. 213. 29 1 . 251. 227. 215. 209. 291. 300. 200. 245. 313. 18 1 . 293. 293. 153. 225. 198. 239 . 3 38. 251. 209. 323. 324. 239. 226. 200. 255. 273. 189. 181.  SAT C P T Y ( C M OF 2.25 2.61 10.05 2 . 65 9.28 7.78 3 . 12 6.3 0 5.21 3 .83 2.85 2.26 4.10 2 . 62 3.5 0 4.70 2.40 3 . 89 2.30 4.4 6 4.54 3 .27 2.78 2.49 2 . 03 2.51 1 . 92 2.67 1.45 1.77 0.64 2.39 2.22 2 . 94 1.43 4.35 I. 74 2 . 10 2.40 2.20 2.86 2 .09 3.28 2.50 6.73 3.42 2.60 2.60  F.M.C WATER) 0.91 1.63 8.23 1.73 5 . 59 3.91 1. 64 3. 28 2. 66 2 . 34 1 . 69 0.93 2.55 1.28 1 . 39 2. 64 1.37 2. 04 1. 46 3.08 2.19 1. 34 0.97 1.05 1 . 14 1.21 1.17 1. 29 0 . 70 0 . 60 0.45 1 . 34 0.67 1.18 0.46 2.0 3 0 . 80 0. 70 0.97 0.73 1.69 0.73 1 .60 1.22 4 . 52 1.85 1 . 42 1 . 37  -  1 1 9  -  APPENDIX L I S T I N G FOUR  )T  OF  S A M P L E S  SAMPLE WERE  III C H A R A C T E R I S T I C S  C O L L E C T E D  IN  EACH  PLOT  DEPTH  WEIGHT  B .  (CM)  (G/M2)  (G/CM3)  4 9  1 4 . 7  3 . 4 0 9  0 . 2 2 3  241  144.  8 . 2 2  4 . 9 1  49  9 . 1  1 . 5 5 6  0 .  3 3 9 .  1 7 9 .  5 . 2 8  2 . 7 9  49  1 2 . 4  1 . 5 2 8  0 . 1 1 9  3 6 4 .  2 1 4 .  5 .  3 . 2 7  4 9  6 . 6  1 . 0 9 8  0 .  3 5 6 .  2 0 6 .  3 . 9 1  2 . 2 6  50  1 7 . 8  1 . 7 0 4  0. 0 9 3  52 3 .  3 7 9 .  8 . 9 1  6 .  46  50  1 6 . 8  1 . 5 1 1  0.  5 6 4 .  3 1 6 .  8 . 5 2  4.  77  5 0  1 1 . 2  1 . 2 6 2  0 . 1 0 9  442  69  5 0  6.  0. 6 9 1  0. 1 0 1  5 7 5 .  NO  6  DENS  1 6 5 16 1 0 8 7  SAT  CPTY  U  OF .  .  F . M . C WEIGHT)  SAT  CPTY  (CM  OF  5 6  F . M . C WATER)  2 1 3 .  5 . 5 8  2.  2 3 6 .  3 . 9 7  1 . 6 3  51  5 . 3  0 . 7 5 3  0.  4 8 1 .  2 2 4 .  3 . 6 2  1. 69  51  5 . 6  0 . 3 4 0  0 . 0 5 9  6 5 7 .  2 3 8 .  2 . 2 3  0 . 8 1  51  6.  0. 8 6 6  0 .  1 3 8  3 8 7 .  1 9 3 .  3 . 3 5  1 . 6 7  51  6 . 3  1.1  0 . 1 7 6  3 6 0 .  150.  4.  1 . 7 3  52  5  0 . 8 9 4  0 . 1 5 5  4 0 3 .  185.  3 . 6 0  1 . 6 5  52  9 .  1. 2 5 6  0 . 1 2 3  3 64 .  1 5 1 .  4 . 5  1 . 9 0  0 . 9 3 4  0 .  1 3 7  4 7 8 .  2 5 4 .  4 . 4 6  2 . 3 7  2 . 1 1 1  0 .  1 6 4  3 8 6 .  1 4 3 .  8 . 1 5  3 . 0 2  52 52  1  1 3 7  . 6 9  6 . 6 12  . 4  54  16 7  53  2 . 5  0 . 9 1 1  0 . 3 4 7  2 1 9 .  114.  2 . 0 0  1 . 0 4  53  1 . 3  0 . 4 3 0  0 . 3 2 8  2 8 8 .  126.  I . 2 4  0 .  54  53  2 . 5  0 . 2 8 9  0 . 1 1 0  52 4 .  180.  1 . 5 1  0 .  52  53  1 . 5  0 . 3 0 5  0 .  1 9 4  50 6 .  137.  1 . 5 5  0 . 4 2  54  5. 1  0. 5 6 0  0.  107  565  .  2 5 3 .  3 . 1 7  1 . 4 5  54  7 . 1  0 . 8 3 8  0 . 1 1 4  49 9 .  178.  4.  1 8  1 . 4 9  54  8 . 4  0 . 7 1 3  0 . 0 8 3  6 6 5 .  2 5 4 .  4 .  7 4  54  8 . 4  1. 0 4 7  0 . 1 2 1  5 1 0 .  2 6 3 .  5 . 3 4  2 . 7 5  2 7 5 .  2 . 7 5  1. 79  9 1 .  6 . 7 2  3 . 0 4  1 . 8 1  55  3 . 8  0 . 6 5 1  0.  55  1 3 . 2  3 . 3 4 5  0 . 2 4 5  201  55  5 . 6  0. 5 8 9  0 .  1 0 2  1 8 6 .  9 7 .  1 . 0 9  0 .  5 5  3 . 0  0 . 6 0 0  0 . 1 9 1  3 8 2 .  1 9 9 .  2 . 2 9  1 . 1 9  56  1 . 5  0 . 2 4 9  0 . 1 5 8  5 9 8 .  2 1 1 .  1 .  0.  53  56  9 . 1  1 . 7 0 9  0 . 16 1  3 7 0 .  146.  6 . 3 2  2.  50  1 . 6 8 7  0 . 1 1 5  441  3 6 7 .  7 . 4 4  6 . 1 9 1 . 3 1  56  1 4 .  2  56  4 . 1  57  1 1 . 2  57  8 . 9  165  4 2 3 . .  .  4 9  57  0 . 5 4 3  0 . 1 2 9  5 2 4 .  2 4 1 .  2 .  1 . 4 8 8  0 . 1 2 9  4 2 1 .  2 7 0 .  6 . 2 7  4.  1. 5 6 8  0 .  3 2 6 .  1 9 7 .  5 . 1 1  3 . 0 9 8 . 2 2  171  85  02  57  2 6 . 2  2. 5 1 3  0. 0 9 3  471  3 2 7 .  1 1 . 8 4  57  1 4 . 5  2 . 3 0 3  0 .  1 5 4  3 3 5 .  1 5 2 .  7 . 7 2  58  7 . 4  1 . 2 2 2  0 . 16 1  3 7 3 .  180.  4 . 5 6  2 . 2 0  58  1 6 . 8  2 . 2 2 4  0 . 1 2 9  4 1 2 .  2 7 2 .  9 .  6 . 0 5  58  1 6 . 8  2 . 1 9 0  0 . 1 2 7  4 3 7 .  58  2 4 . 1  3 . 4 1 3  0 . 1 3 7  444  59  1 0 .  2. 6 0 9  0 . 2 4 9  2 4 5 .  1 3 7 .  6 . 3 9  3 . 5 7  2  .  3 1 1 . .  3 0 3 .  16  9 . 5 7 1 5 .  15  3 . 50  6. 81 10.  3 4  59  5 . 1  0 . 9 9 6  0 .  3 3 8 .  2 0 5 .  3 . 3 7  2 . 0 4  59  1 5 . 0  2 . 9 4 3  0 . 1 9 0  3 0 1 .  1 7 5 .  8.  5.  1 5  59  9 . 9  1. 6 9 2  0 . 1 6 5  3 0 4 .  1 9 9 .  5 . 1 4  3.  37  1 9 0  86  6 0  7 . 9  1 . 6 0 2  0 .  197  3 7 6 .  2 2 8 .  6 . 0 2  3 . 6 5  6 0  8 . 9  1 . 4 9 4  0 . 1 6 3  4 1 3 .  2 9 2 .  6 . 1 7  4 . 3 6  6 0  1 4 . 5  3 . 0 1 7  0 . 2 0 2  2 7 8 .  1 3 8 .  8 . 3 9  4 . 1 6  6 0  6 . 9  1 . 5 5 6  0 . 2 2 0  1 9 1 .  1 1 1 .  2 . 9 7  1 . 7 3  - 120 -  APPENDIX IV  Time t r e n d s o f t o t a l w a t e r p o t e n t i a l p r o f i l e s f o r t h forest  f l o o r d u r i n g t h r e e d r y i n g p e r i o d s . The g r a v i t  a t i o n a l p o t e n t i a l i s z e r o a t the f o r e s t  floor  These d a t a were used t o c a l c u l a t e the w a t e r presented  surfac  balances  i n F i g u r e s 7 and 8 i n C h a p t e r I I I and i n  Appendix V .  - 121 -  T  1  i  1  SEYMOUR  TOTAL  POTENTIAL  1  r—  WATERSHED  (cm ©< »ol«r)  - 122 -  SEYMOUR  WATERSHED  0800 I2O0I8O0, 0200  TIME  o O  FOREST Ae -220  FLOOR  HORIZON  -180 TOTAL  -140 POTENTIAL (cm of  -too water)  -60  -20  - 123 -  SEYMOUR WATERSHED  TIME  0600 1200  1200/0800 '1800 0200  P "  '/ ' I / " DATE 18 '17  16'15 14 13 13  o o o o  <  UJ  m  < O ror O  u. o o o z  o oo FOREST FLOOR Ae HORIZON i  i  -100  TOTAL  LU  -60  POTENTIAL (cm of woter)  -20  - 124  _  APPENDIX V  Drainage, e v a p o r a t i o n ,  t r a n s p i r a t i o n , and  t o t a l water  d e p l e t i o n r a t e s f o r the f o r e s t f l o o r d u r i n g a d r y i n g p e r i o d i n October. T h i s i s a f u r t h e r example of a water balance during  a drying period discussed  i n Chapter I I I .  - 125 -  T  1  1  1  1  1  1  r  - 126  APPENDIX VI  T a b l e o f measured v o l u m e t r i c water contents at the time o f n e g l i g i b l e drainage  and at a m a t r i c p o t e n t i a l o f -15  bars f o r s e v e r a l d r y i n g p e r i o d s Drying period  (Seymour Watershed).  V o l u m e t r i c water content at time of  1971  , 3 (cm  n e g l i g i b l e drainage f o r 4 depth: cm  -3 ). N  16 cm  2 cm  6 cm  9 cm  Sept.  0 . 30  0. 39  0.43  0 .49  Oct.  0 .28  0 . 39  0.42  0 .49  13 - 18 Oct.  0 .30  0.40  0.43  0 .49  0 .29  0.39  0.43  0 .49  -84  -92  -105  -90  11-23 4-12  Average water content Average m a t r i c potential T o t a l water  content a t time o f n e g l i g i b l e  T o t a l water  content at -15 bars  A v a i l a b l e water f o r e v a p o t r a n s p i r a t i o n  drainage  6 . 9 cm 4 . 2 cm 2.7  cm  

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