UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Evapotranspiration from a dry Douglas fir forest Curtis, John Reeves 1975

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1975_A6_7 C87_7.pdf [ 1.97MB ]
Metadata
JSON: 831-1.0093176.json
JSON-LD: 831-1.0093176-ld.json
RDF/XML (Pretty): 831-1.0093176-rdf.xml
RDF/JSON: 831-1.0093176-rdf.json
Turtle: 831-1.0093176-turtle.txt
N-Triples: 831-1.0093176-rdf-ntriples.txt
Original Record: 831-1.0093176-source.json
Full Text
831-1.0093176-fulltext.txt
Citation
831-1.0093176.ris

Full Text

EVAPOTRANSPIRATION FROM A DRY DOUGLAS F I R FOREST by JOHN REEVES CURTIS B.Sc,  McGill University,  1972  A THESIS SUBMITTED I N PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n t h e Department of Soil  We a c c e p t t h i s required  Science  thesis  as c o n f o r m i n g  to the  standard  THE UNIVERSITY OF B R I T I S H COLUMBIA A p r i l 1975  In  presenting  an  advanced  the I  Library  further  for  degree shall  agree  scholarly  by  his  of  this  written  this  thesis  in  at  University  the  make  that  it  purposes  for  freely  permission may  representatives. thesis  partial  be  It  financial  for  gain  permission.  University  of  British  2075 W e s b r o o k P l a c e V a n c o u v e r , Canada V6T 1W5  Date  Aon/  1^7^  of  Columbia,  British  Columbia  for  extensive by  the  understood  Depa rtment  The  of  available  granted  is  fulfilment  shall  Head  be  requirements  reference copying  that  not  the  of  agree  and  of my  I  this  or  allowed  without  that  study. thesis  Department  copying  for  or  publication my  - i iABSTRACT Evapotranspiration ratio/energy  balance technique  Douglas f i r f o r e s t . the  m e a s u r e m e n t s u s i n g t h e Bowen were, made o v e r a d r y  S o i l water matric  potential  over  p e r i o d o f measurement v a r i e d f r o m 0 t o -10.5 b a r s .  With the premise that the e q u i l i b r i u m evaporation a s s o c i a t e d w i t h adequate water supply expresses evapotranspiration net  rate  essentially  as a f r a c t i o n o f d a i l y  r a d i a t i o n , the r a t i o o f l a t e n t heat f l u x t o net  radiation  f o r 24-hour p e r i o d s  of s o i l water matric to approximately potential site.  half  i s examined as a f u n c t i o n  potential.  This r a t i o , i s reduced  i t s maximum v a l u e  a p p r o a c h e s -10 b a r s f o r t h e  The r e d u c t i o n  experimental  i s n o t as g r e a t - a s  changes i n s o i l w a t e r s t o r a g e , transpiration  as t h e m a t r i c  t h a t i m p l i e d by  indicating that  o f water not o r i g i n a t i n g  zone i s c a r r i e d o n d u r i n g p e r i o d s  evapo-  i n the root  of considerable  water  stress.  W h i l e some w a t e r may be f l o w i n g upward f r o m b e l o w  the r o o t  zone, i t i s f e l t  evapotranspired  that over h a l f  water i s released  stems d u r i n g t h e most s e v e r e  of the d a i l y  from storage  period.  i n tree  - iii  -  TABLE OF CONTENTS Page ABSTRACT  i  L I S T OF FIGURES  i  iv'  ACKNOWLEDGEMENTS  v i  L I S T OF SYMBOLS  v i i  INTRODUCTION  1  EXPERIMENTAL PROCEDURE  4  A.  Experimental  Site  4  B.  Experimental  Methods  6  RESULTS AND DISCUSSION  10  A.  Soil Water Potential  Content  and  B.  Daytime Course of Net and Latent Heat Flux  C.  The Relationship LE/R and i> n m  Matric Radiation  between  r  D.  Evapotranspiration Using R and i> data ° n m  Estimates  r  E.  Water  Balance  of the. Forest  10 13 24 32 34  CONCLUSIONS  40  REFERENCES '  43  APPENDIX I  45  APPENDIX I I  47  - iv L I S T OF  FIGURES  Figure  1.  W a t e r r e t e n t i o n c u r v e f o r Dashwood s e r i e s . g r a v e l l y sandy loam. Each p o i n t i s the a v e r a g e w a t e r c o n t e n t 0 o f t h e 15, 30., 45 and 60 cm d e p t h s a m p l e s a t a s i n g l e . v a l u e of s o i l water matric p o t e n t i a l Bars• i n d i c a t e range of water .contents.  Figure  2.  S o i l water matric p o t e n t i a l ^ f o r June;.17A u g u s t 19, 19 74. Each p o i n t i s the average v a l u e o f t h e m a t r i c p o t e n t i a l s a t t h e 15, 30 and 4 5 cm d e p t h s .  Figure  3.  A v e r a g e v o l u m e t r i c w a t e r c o n t e n t f o r J u n e 20A u g u s t 20 o f t h e 0-60 cm d e p t h o f s o i l f r o m g r a v i m e t r i c sampling.  Figure  4.  D i u r n a l t r e n d i n wet- and d r y - b u l b temperature d i f f e r e n c e s AT and AT r e s p e c t i v e l y o v e r 1. m h e i g h t a b o v e t h e c a n o p y f o r J u n e - 1 8 , 1974. Note the r e v e r s i n g o f t h e g r a d i e n t s a r o u n d 0800 PST. W  Figure  5.  Daytime course o f s u r f a c e r e s i s t a n c e r (from energy balance measurements)and stomatal resistance r (projected leaf a r e a b a s i s ) f o r J u n e 18 and J u l y 25, 1974. The ' d i s a g r e e m e n t o f t h e two v a l u e s i s l a r g e on a p e r c e n t a g e b a s i s i n t h e m o r n i n g . C  s  Figure  6a.  Diurnal trend i n R and LE f o r J u n e 18, 1974. S o l i d dots are energy b a l a n c e measurements o f L E , w h i l e c i r c l e s show LE e s t i m a t e d f r o m s t o m a t a l r e s i s t a n c e measurements. The s o l i d l i n e f o r LE was drawn by e y e .  Figure  6b.  Diurnal trend i n R and LE f o r J u l y 25, 1974. S o l i d dots are energy b a l a n c e measurements o f L E , w h i l e c i r c l e s show LE e s t i m a t e d f r o m s t o m a t a l r e s i s t a n c e measurements. The s o l i d l i n e f o r LE was drawn by e y e .  Figure  7.  F i g u r e s 6a and 6b t o g e t h e r t o i l l u s t r a t e t h e e f f e c t s of decreased s o i l water matric p o t e n t i a l ijj on LE. Note t h a t R i s h i g h e r on J u n e 18.  n  n  m  Figure  8.  n  R and LE on J u l y 19, t h e . ' f i r s t c l e a r day a f t e r the r a i n y p e r i o d i n mid-July. The m i d - a f t e r n o o n peak i n LE i s p r e s e n t , b u t n o t p r o n o u n c e d . n  -  Figure  9.  V  -  R a n d LE on J u l y 8, t h e l a s t day o f t h e f i r s t d r y i n g p e r i o d , a n d t h e most s e v e r e o b s e r v e d day f r o m t h e a s p e c t o f w a t e r stress. L E / R was o n l y 0.26. n  Figure  10.  LE/R as a f u n c t i o n o f 'soil water m a t r i c p o t e n t i a l ^ f o r t e n s e l e c t e d f i n e days. The number a d j a c e n t t o e a c h p o i n t i s t h e date. n  m  Figure  11.  L E / L E q - a s a f u n c t i o n o f i j j , where L E q represents the d a i l y e q u i l i b r i u m evaporation rate. D i f f e r e n c e s i n t h i s curve and F i g u r e 10 a r e due o n l y t o d i f f e r e n c e s i n d a i l y mean t e m p e r a t u r e s .  Figure  12.  LE/LE as a f u n c t i o n o f > (logarithmic s c a l e ) "for v a r i o u s authors (taken from van B a v e l , 1 9 6 7 ) . N o t e t h a t t h e maximum evapo.transpiration rate L E i s determined d i f f e r e n t l y f o r d i f f e r e n t a u t h o r s , and i n t h i s study i s t a k e n as t h e e q u i l i b r i u m r a t e .  e  e  m  m a  m  m a x  Figure  13.  LE/R as a f u n c t i o n o f v o l u m e t r i c water content. T h i s a n d F i g u r e 10 a r e r e l a t e d through t h e water r e t e n t i o n curve f o r t h e s o i l , and a l l o w e v a p o t r a n s p i r a t i o n e s t i m a t e s f r o m w a t e r c o n t e n t m e a s u r e m e n t s . t o be made.  Figure  14.  D a i l y t o t a l s o f R a n d LE f o r J u n e 1 7 A u g u s t 1 4 , 1974 . P o i n t s u s e d t o . - o b t a i n F i g u r e 10 a r e shown a s t r i a n g l e s .  Figure  15.  W a t e r b a l a n c e o f t h e 0-60 cm d e p t h o f s o i l f o r J u n e 1 7 - A u g u s t 1 4 , 1974. V a l u e s a r e ' d a i l y a v e r a g e s i n mm o f w a t e r . The r e s i d u a l term i s discussed i n the t e x t .  Figure  n  R  S o i l w a t e r m a t r i c p o t e n t i a l a t "four d e p t h s f o r June 17-August 19, 1974, i n d i c a t i n g direction of gradients i n the v e r t i c a l axis.  - vi ACKNOWLEDGEMENTS I c a n n o t hope t o f u l l y of  e x p r e s s my  appreciation  t h e guidance,:. i n s i g h t , and e n t h u s i a s m o f  s u p e r v i s o r , D r . T.A. Master's  studies.  my  B l a c k , i n a l l phases o f  my  I s i n c e r e l y f e e l that the accomplish-  ments r e p r e s e n t e d i n t h i s w o r k a r e e v e r y b i t as much h i s as m i n e . A p a r t i c u l a r d e b t o f g r a t i t u d e i s owed t o Mr. in  J o e Nnyamah, whose m e t i c u l o u s and r e l i a b l e the ' f i e l d  of s o i l  m o i s t u r e measurements formed  indispensable cornerstone of t h i s I w i s h t o t h a n k Mr. for  t h e i r key r o l e s  t h a n k s t o Mr.  Tan  especially  and  and c r i t i c i s m i n t h e  office.  for their friendship,  discussion,  a l s o i n d e b t e d t o t h o s e who  s e r v e d on my  Rowles,  Oke  T h a n k s a r e due to  l i k e to express  and M i s s R u t h H a r d y f o r t h e i r  support i n the f i e l d  D r s . C.A.  study.  i n the success of the i n s t r u m e n t a t i o n I would  I am  type t h i s  T.M.  t o Mrs.  B a l l a r d , T.R. Retha  Gerstmar,  and R.A.  who  committee; Freeze.  took the  time  thesis.  Funds f o r t h i s r e s e a r c h w e r e made a v a i l a b l e g r a n t s f r o m Canada Department o f t h e Environment NCWRR), and  an  P a u l Tang and Mr...Ron T o t h  and d a t a l o g g i n g . C.S.  work  from the N a t i o n a l Research  Council of  through (CFS  and  Canada.  - v i i L I S T OF  SYMBOLS  D  Drainage  E  Evapotranspiration  G  S o i l heat f l u x  density  L  Latent  heat of  vapourization  LE  Latent  heat f l u x  LE  eq  M R  n  v.p.d. AT AT  w  E q u i l i b r i u m l a t e n t heat f l u x ^  density J  S t o r a g e o f s e n s i b l e and canopy  l a t e n t heat w i t h i n the  Net r a d i a n t energy f l u x  density  Vapour p r e s s u r e  deficit  Dry-bulb temperature d i f f e r e n c e over  height  Wet-bulb temperature d i f f e r e n c e over  height  A9  Change i n s o i l  g  Bowen r a t i o  9  Volumetric m  density  water  s o i l water  storage  content  S o i l water matric p o t e n t i a l r  INTRODUCTION Evapotranspiration  i s an i m p o r t a n t  term i n both  the w a t e r b a l a n c e and t h e energy b a l a n c e o f a f o r e s t . However, t h e c o m p l e x i t y  of the surface  f e a t u r e s and  p h y s i c a l .geometry, a s w e l l a s t h e s h e e r s i z e o f a f o r e s t c a n o p y , makes t h e a p p l i c a t i o n , o f t h e o r e t i c a l e x p r e s s i o n s for  evapotranspiration  hydrometeorologist. actively  seeking  task  f o rthe forest  Nonetheless, researchers  have been  a means o f m a k i n g u s e f u l e s t i m a t e s  evapotranspiration meteorological  a difficult  of  t a k i n g i n t o account the basic  and h y d r o l o g i c a l parameters o f a v a i l a b l e  e n e r g y a n d a v a i l a b l e w a t e r i n a p r a c t i c a l way. If  p o t e n t i a l e v a p o t r a n s p i r a t i o n w e r e t a k e n t o be t h e  e v a p o t r a n s p i r a t i o n when f e t c h a n d s o i l w a t e r a r e a d e q u a t e , t h e n t h i s p a r a m e t e r i s o f n e c e s s i t y a m e t e o r o l o g i c a l one. I t h a s b e e n shown t h a t t h i s "equilibrium" rate f o r e s t environment. evapotranspiration  i s approximately  t o apply,  slightly  to the  (McNaughton, 1974) f o r a w e s t - c o a s t When u s e d a s an e s t i m a t e  of  under s u i t a b l e c o n d i t i o n s , t h e  e q u i l i b r i u m model i s p h y s i c a l l y j u s t i f i e d simple  equal  since i trepresents  and e x t r e m e l y  essentially  a  temperature-dependent f r a c t i o n o f the d a i l y  net r a d i a t i o n .  - 2 The  simplicity  o f t h e e q u i l i b r i u m m o d e l i s due i n  part t o the fact that i tapplies only to a system, and i t a v o i d s rate with  soil  i n t o account.  the question  moisture  well-watered  o f an e v a p o t r a n s p i r a t i o n  and p h y s i o l o g i c a l p a r a m e t e r s  taken  A t h e o r e t i c a l modification of the  e q u i l i b r i u m model a p p l y i n g t o a l l c o n d i t i o n s o f s o i l moisture  and p l a n t w a t e r s t r e s s would r e n d e r i t u n w i e l d y  from a p r a c t i c a l p o i n t o f view. d a i l y net r a d i a t i o n represented provides  However, t h e f r a c t i o n o f i n the equilibrium rate  a useful vehicle f o ra straightforward  of the reduction  i n e v a p o t r a n s p i r a t i o n under  study  conditions  of water s t r e s s . Some e a r l i e r  studies of the reduction of  evaporation  a s s o c i a t e d w i t h water s t r e s s i n a g r i c u l t u r a l p l a n t s reported  by Denmead a n d Shaw (19 62)  (1963).  Further  s t u d i e s on c r o p s  and Gardner and E h l i g  carried-out:.in-."field  p l o t s w e r e made b y . a number o f o t h e r w o r k e r s 19 67;  (van Bavel,  Denmead a n d M c l l r o y , 1 9 7 0 ; D a v i e s a n d A l l e n ,  Ritchie,  1973).  were  Only a few have l o o k e d  197 3;  a t the problem  r e l a t e d t o f o r e s t v e g e t a t i o n , and t h e s e have been p r i m a r i l y on s e e d l i n g s Ferrel,  i n the laboratory  1968; L o p u s h i n s k y and K l o c k ,  difficulty  i n m a k i n g . i n situ  transpiration of a forest  ( Z a t i k o v s k y and  1974), owing t o t h e  measurements o f evapo-  stand.  - 3 The  f a c t t h a t such  a s t u d y o f a f o r e s t s t a n d must  u l t i m a t e l y be made i n t h e f i e l d , confidence in  gained  together with the  i n the technique  t h e Bowen r a t i o a p p r o a c h  and apparatus  used  ( B l a c k and McNaughton, 1 9 7 1 ) ,  provides the basis f o r the objectives of t h i s  study.  T h e s e o b j e c t i v e s c a n be s u m m a r i z e d a s f o l l o w s : 1.  To d e t e r m i n e  whether t h e e v a p o t r a n s p i r a t i o n  rate at the experimental not  limiting  r a t e , thereby  s i t e when w a t e r i s  i s equal t o the e q u i l i b r i u m p r o v i d i n g a f u r t h e r c h e c k on  the r e s u l t s p r e v i o u s l y obtained coast Douglas f i r stand Black, 2.  i n a west-  (McNaughton and  1973).  To measure e v a p o t r a n s p i r a t i o n f r o m a d r y Douglas f i r s t a n d , and observe of decreasing s o i l  moisture  the effect  on t h e f r a c t i o n  of d a i l y net r a d i a t i o n used i n e v a p o r a t i n g water. Diurnal trends insight and  i n t h e energy balance  into the processes  therefore w i l l  emphasis o f t h i s  provide  some  controlling evapotranspiration,  be t o u c h e d  upon.  Nevertheless, the  s t u d y w i l l be upon d a i l y c h a n g e s i n t h e  e v a p o t r a n s p i r a t i o n component o f t h e w a t e r b a l a n c e ,  and i t s  r e l a t i o n t o d a i l y changes i n s o i l w a t e r s t a t u s and n e t radiation.  - 4 EXPERIMENTAL PROCEDURE A.  Experimental  Site  Selection of a site  f o r this  s t u d y was c o n t i n g e n t  upon t h e n e c e s s i t y f o r a n a r e a w h i c h c o u l d be c o n s i d e r e d simple from a m i c r o m e t e o r o l o g i c a l p o i n t o f view,  and y e t  one w h i c h r e p r e s e n t s a n a t u r a l e n v i r o n m e n t f r o m w h i c h practical effort  c o n c l u s i o n s c o u l d be d r a w n .  was t h e n p u t i n t o f i n d i n g  w h i c h met t h e f o l l o w i n g 1.  Considerable  an e x i s t i n g  forest  stand  criteria:  The s i t e must e x p e r i e n c e  water s t r e s s  d u r i n g t h e summer. 2.  The s i t e must be f r e e o f a d v e c t i v e  effects,  r e q u i r i n g an e x t e n s i v e f o r e s t e d a r e a o f reasonably  uniform vegetation,  t o p o g r a p h y , a n d good 3.  The s t a n d  4.  The s i t e  The s i t e  flat  fetch.  s h o u l d be p r i m a r i l y D o u g l a s f i r . s h o u l d be a c c e s s i b l e by r o a d .  c h o s e n was on Crown Z e l l e r b a c h Company  property approximately  17 m i l e s n o r t h w e s t  of  Courtenay,  B. C., on t h e e a s t e r n c o a s t o f V a n c o u v e r I s l a n d .  The  s i t e met most o f t h e r e q u i r e m e n t s  from  f o r t h e study  both a m i c r o m e t e o r o l o g i c a l and an o p e r a t i o n a l p o i n t of view.  The m e a s u r e m e n t s were made i n a n u n t h i n n e d  - 5 stand  o f Douglas f i r p l a n t e d  relatively and  e x t e n s i v e c o a s t a l p l a i n between Courtenay  Campbell R i v e r .  summers e x p e r i e n c e d soil is  moisture  The w e t , m i l d w i n t e r s by t h e a r e a p r o v i d e d  needed f o r t h e s t u d y .  generally f l a t ,  of approximately  although  a n d d r y , warm  t h e range o f  The t o p o g r a p h y  there are several ridges  20-30 m r e l i e f , a n d some d e p r e s s i o n a l  a r e a s o f a swampy n a t u r e summer.  i n 1953, l o c a t e d on t h e  which dry out during the  The s i t e was l o c a t e d a t a n e l e v a t i o n o f 150 m.  At the time o f the r e s e a r c h , the t r e e s in height 15  f r o m 7 t o 10 m, a n d a v e r a g e d  cm i n d i a m e t e r .  ha  2  to  s t r e s s index  o f 34 0.  17 3 0 stems  -1  , a n d t h e b a s a l a r e a was 2 7.5 m h a  competitive  approximately  T h e r e were a p p r o x i m a t e l y  -1  ranged  , with a  The s o i l ,  belonging  t h e Dashwood s e r i e s , was a w e l l - d r a i n e d g r a v e l l y  s a n d y l o a m o f 45-6 0 cm d e p t h o v e r l y i n g a d e e p l a y e r of compacted b a s a l t i l l .  Measurements o f r o o t  density  i n d i c a t e d t h a t t h e b u l k o f t h e r o o t s were i n t h e u p p e r 45  cm o f t h e s o i l . Operationally, the s i t e  provided  good a c c e s s  with  main l o g g i n g roads l e a d i n g t o w i t h i n 2 m i l e s o f t h e study  area  from t h e I s l a n d Highway.  right to the s i t e , two  trailers  a l o n g s i d e w h i c h were p l a c e d t h e  and t h e g e n e r a t o r .  instrumentation  Smaller roads l e d  t o w e r was p l a c e d  The 12.2 m h i g h 30 m f r o m t h e t r a i l e r s .  - 6 It for  i s felt  t h a t t h e a r e a i s an e x c e l l e n t one  a micrometeorological  were f e l t  Advective  effects  n o t t o be p r e s e n t , w i t h f i v e m i l e s o f f o r e s t e d  land separating the s i t e and  study.  f o r e s t extending  from the S t r a i g h t o f Georgia,  u p w a r d s o f 20 m i l e s i n . e i t h e r  d i r e c t i o n along the coast.  Although  the  west-to-southeast  s e c t o r i n c l u d e d i r r e g u l a r t e r r a i n and d e f o r e s t e d on t h e s l o p e s o f m o u n t a i n s r i s i n g  areas  i n t o the Forbidden  P l a t e a u a r e a w i t h i n 2 m i l e s o f t h e s i t e , winds were virtually  never from t h a t d i r e c t i o n .  Prevailing  winds  were f r o m t h e n o r t h t o n o r t h e a s t . B.  Experimental  Methods  C o n t i n u o u s h a l f - h o u r l y measurements o f  evapotrans-  p i r a t i o n w e r e made f r o m J u n e 14 u n t i l A u g u s t 1 5 , 1974 u s i n g t h e Bowen r a t i o / e n e r g y b a l a n c e Bowen r a t i o  technique.  g was m e a s u r e d a t t h e 8.5 m l e v e l  the psychrometric McNaughton ( 1 9 7 1 ) .  apparatus  The  using  d e s c r i b e d i n B l a c k and  Optimum p l a c e m e n t o f t h e s e n s o r  t h e c a n o p y was s o u g h t a f t e r some e x p e r i m e n t a t i o n  over  with  v a r i o u s h e i g h t s and p o s i t i o n s r e l a t i v e t o t h e t o p o f the tower.  The s e n s o r  J u n e 17 u n t i l A u g u s t 1. apparatus first  r e m a i n e d i n t h e same l o c a t i o n On A u g u s t 1, a s e c o n d Bowen  i d e n t i c a l t o t h e f i r s t was p l a c e d a b o v e t h e  o n e , a n d t h e p o s i t i o n s o f t h e two m a c h i n e s were  from ratio  periodically  s w i t c h e d i n o r d e r t o check on t h e  o p e r a t i o n o f e a c h , and t o t e s t f o r any s e n s o r problems. i n the next  Placement o f t h e sensors i s d i s c u s s e d  briefly  section.  Net r a d i a t i o n R n canopy  placement  was m e a s u r e d a t t h e t o p o f t h e ^  with a Swissteco S - l net radiometer, continuously  v e n t i l a t e d w i t h d r i e d a i r from an aquarium-type  pump.  S o i l h e a t f l u x G was m e a s u r e d a t t h e 5 cm l e v e l w i t h two h e a t f l u x p l a t e s , and c o r r e c t e d f o r s t o r a g e i n t h e upper 5 cm u s i n g a n i n t e g r a t e d t e m p e r a t u r e m e a s u r e d w i t h a diode i n t e g r a t i n g thermometer  (Tang et a l . , 1 9 7 4 ) .  S t o r a g e o f s e n s i b l e and l a t e n t h e a t w i t h i n t h e canopy was  M  e s t i m a t e d from wet and d r y b u l b t e m p e r a t u r e s t a k e n  e v e r y 15 m i n u t e s a t t h e 3, 5 a n d 7 m l e v e l s , a n d f r o m e s t i m a t e s o f t h e heat c a p a c i t y o f t h e canopy t h e work o f S t e w a r t a n d Thorn ( 1 9 7 3 ) .  b a s e d on  Evapotranspiration  E was t h e n c a l c u l a t e d u s i n g t h e e q u a t i o n E = (R  - G - M)/[L(1 + 6)]  where L i s t h e l a t e n t h e a t o f v a p o u r i z a t i o n . S u p p o r t i n g c l i m a t o l o g i c a l m e a s u r e m e n t s w e r e made of i n c i d e n t s o l a r r a d i a t i o n R  g  a t the top o f the tower,  and a t v a r i o u s l e v e l s t h r o u g h t h e c a n o p y times.  at selected  Wind s p e e d a n d d i r e c t i o n w e r e m o n i t o r e d  a C a s s e l a s e n s i t i v e anemometer a n d C l i m e t w i n d  using vane  - 8 mounted a t t h e t o p o f t h e t o w e r . r e c o r d e d e a c h day w i t h a 10.2 cm  Precipitation (4") diameter  was rain  gauge a t t h e t r a i l e r . Data s i g n a l s were c a r r i e d back t o t h e d a t a l o g g i n g trailer  by 7 5 m s h i e l d e d c a b l e s w h e r e t h e y w e r e  r e c o r d e d w i t h a H e w l e t t - P a c k a r d 2707 A d a t a and R , n  R , and Bowen r a t i o d a t a s i g n a l s were  using voltage integrators ratio  logger,  1974).  Bowen  d a t a was f u r t h e r m o n i t o r e d on a H o n e y w e l l  strip-  chart recorder.  ( B l a c k et al.,  integrated  The s y s t e m was p o w e r e d by a 6.5  kW  Kohler d i e s e l generator. S o i l w a t e r c o n t e n t was m e a s u r e d b o t h  gravimetrically  and by u s e o f t h e n e u t r o n m o i s t u r e m e t e r .  Neutron  m o i s t u r e m e a s u r e m e n t s were made e v e r y 2 t o 3 d a y s i n six of  access tubes.  The b a s a l t i l l  t h e t u b e s t o 45-60 cm.  l i m i t e d the depth  Gravimetric sampling of the  r o o t zone-was t a k e n - e v e r y 5 t o 16 d a y s , d e p e n d i n g on t h e state o f the drying  period.  S o i l w a t e r p o t e n t i a l b e t w e e n 0 and -1 b a r was m e a s u r e d by a t e n s i o m e t e r - t r a n s d u c e r s y s t e m .  Four  t e n s i o m e t e r s w e r e u s e d and w e r e l o c a t e d a t d e p t h s o f 1 5 , 30, 45 and 60 cm.  S o i l water p o t e n t i a l  less  -1 b a r was m e a s u r e d u s i n g a C a m p b e l l S c i e n t i f i c dew p o i n t m i c r o v o l t m e t e r and PT-10 h y g r o m e t e r s .  than HR-33T Six  - 9 h y g r o m e t e r s , two e a c h a t t h e 15 a n d 3 0 cm d e p t h , a n d one  e a c h a t t h e 45 a n d 6 0 cm d e p t h , w e r e u s e d .  Soil  w a t e r p o t e n t i a l by t h e t e n s i o m e t e r - t r a n s d u c e r s y s t e m was  r e c o r d e d a t 15 m i n u t e  intervals, while s o i l  water  p o t e n t i a l s b y t h e h y g r o m e t e r s was m e a s u r e d t h r e e t i m e s each day.  In this  study, only d a i l y values of s o i l  water p o t e n t i a l a r e used i n t h e a n a l y s i s . S o i l w a t e r r e t e n t i o n c u r v e s were d e t e r m i n e d i n the  l a b o r a t o r y by ( i ) h a n g i n g column  method  from  s a t u r a t i o n t o a w a t e r p o t e n t i a l o f -0.12 b a r a n d ( i i ) p r e s s u r e p l a t e e x t r a c t i o n f r o m -0.33 b a r t o -15 b a r s . In  a d d i t i o n , t e x t u r e , b u l k d e n s i t y , and r o o t  distribution  m e a s u r e m e n t s w e r e made. .Stomatal r e s i s t a n c e r  a t t h e 10 m h e i g h t was s  &  m e a s u r e d on a r o u t i n e b a s i s t h r e e t i m e s a d a y on t h e m a j o r i t y o f days d u r i n g t h e p e r i o d June  14 t o A u g u s t  18  and m e a s u r e m e n t s were made e v e r y two h o u r s d u r i n g t h e d a y t i m e on 16 s e l e c t e d d a y s . u s i n g t h e v e n t i l a t e d porometer (1974).  A t l e a s t two s a m p l e s  used t o o b t a i n a v a l u e o f r .  The measurement was made described  i n B l a c k et al.  o f f o u r n e e d l e s each were  - 10 RESULTS AND A.  Soil  water  The  content  DISCUSSION  and  matric  average water r e t e n t i o n curve  d e p t h s i s shown i n F i g u r e  1.  The  average of l a b o r a t o r y analyses bars  f o r the  curve  curve.  water content The  0-60  cm  represents  the  f o r four depths, with  i n d i c a t i n g the range of d e v i a t i o n s .  ments o f s o i l this  potential  and  Field  the  measure-  matric p o t e n t i a l confirm  a v a i l a b l e water c a p a c i t y i s  approximately  3 - 3 0.14  cm  bar.  cm  The  f o r the m a t r i c  p o t e n t i a l r a n g e -1/3  r e s u l t s of the m e c h a n i c a l a n a l y s i s of  p a r t i c l e s w i t h a d i a m e t e r l e s s t h a n 2 mm 21.9%  silt,  of stones  and  14.6%  c l a y by w e i g h t .  ( p a r t i c l e s g r e a t e r t h a n 2 mm)  was  The was  to  -15  soil  63.5%  volume  sand, fraction  20%.  F i g u r e 2 shows t h e a v e r a g e s o i l w a t e r m a t r i c p o t e n t i a l it. f o r t h e p e r i o d J u n e 17 t o A u g u s t 19 , 1974 f o r t h e r o o t m c  zone (0-45 included be  cm).  D a i l y values  for reference.  of p r e c i p i t a t i o n  I t can  divided into three periods:  late  s p r i n g , w h i c h was  e q u i p m e n t was mid-July, occurred  s e t up  already  be  i n mm  seen t h a t the  summer  ( i ) a drying period i n i n progress  when  summer's  ( p r e c i p i t a t i o n f o r J u l y , 1974  can the  the  i n June, ( i i ) a w e t t i n g p e r i o d  when t h e b u l k o f t h e  are  in  precipitation was  abnormally  high),  - 11 -  i  1  1  1  F i g u r e 1.  1  1  1  r  1  I  I  I  r  1  W a t e r r e t e n t i o n c u r v e f o r Dashwood s e r i e s g r a v e l l y sandy loam. Each p o i n t i s the average water content 6- o f t h e 1 5 , 30, 45 and 60 cm d e p t h s a m p l e s a t a s i n g l e v a l u e ,of s o i l water matric p o t e n t i a l ty . Bars i n d i c a t e range of water c o n t e n t s . m  - .12 -  i  1  I  i  i  i  i  i  r  o  -5 (0"45cm  depth, bar) I  -10  Precip. 20 (mm) J  20  I  ft-fl i n  June  Figure  30  0  JL  20 30 July 1974  J  i  t_  10 August  2... S o i l w a t e r m a t r i c p o t e n t i a l f o r June ' 17-August 19, 1974. Each p o i n t i s . t h e average v a l u e of the matric p o t e n t i a l s a t t h e 1 5 , 30 a n d 4-5 cm d e p t h s .  20  - 13 r e s t o r i n g the  soil  -  t o z e r o m a t r i c p o t e n t i a l , and  (iii)  a s e c o n d d r y i n g p e r i o d w i t h no p r e c i p i t a t i o n o c c u r r i n g throughout u n t i l a f f o r d e d two  t h e end  separate  of water contents  of the p e r i o d .  p e r i o d s a t t h e d r y end  i n the  stones.  percent The  60 cm may matter  will  i s again B.  be  shown i n F i g u r e  l a y e r was  used i n t h i s  t h a t water content  significant be  of the  3,  discussed  i n the  c h a n g e s down t o  f o r e s t water balance.  i n more d e t a i l l a t e r .  i n c l u d e d i n the f i g u r e f o r r e f e r e n c e .  Daytime  course  of  net  radiation  and  latent  heat  flux  balances  r e s t r i c t e d p r i m a r i l y t o f i n e d a y s when r e s o l u t i o n was  t h a t t h e s m a l l g r a d i e n t s o f wet  and  dry bulb  I t was  of these AT  through  the course  o f t h e day  w i t h t h e g r a d i e n t s shown i n F i g u r e (1971).  been expected.  g r a d i e n t s i s e v i d e n t when F i g u r e 4,  found  temperatures  t h e d r y f o r e s t p r o d u c e d more s c a t t e r i n t h e  t r a n s p i r a t i o n measurement than, had  and  This  Precipitation  good i n d i u r n a l f l u c t u a t i o n s o f e n e r g y f l u x e s .  over  ranged  average  D e t a i l e d computation of h a l f - h o u r l y energy was  range  on a v o l u m e t r i c b a s i s w h i c h i n c l u d e s  0 t o 60 cm  because i t i s f e l t  weather  soil.  Average s o i l water content, f r o m 9-23  This  evapoThe  showing  on J u n e 18,  6 i n B l a c k and  size AT  i s compared McNaughton  - 14 -  T  Figure  3.  1  1  i  i  i  i  i  I  r  Average v o l u m e t r i c water content f o r J u n e 2 0 - A u g u s t 20 o f the- 0-60 cm d e p t h o f s o i l f r o m g r a v i m e t r i c sampling.  - 15 -  T  ~~  i  i  J  -i  0  :—i  1  4  1  1  —i  1  1  I  J  I  8 Hour  Figure  4.  12 PST  r  i  16  i  L  20  L  - 16 Negative  v a l u e s o f AT,  LE f r e q u e n t l y e x c e e d i n g  R  -  causing overestimates  , were c o n s i s t e n t l y s e e n i n  the p e r i o d from s u n r i s e u n t i l I t was  felt  approximately  t h a t t h e p r o b l e m was  b e i n g p l a c e d t o o l o w and  consequently  i n v e r s i o n s and Also,  of the  times.  profile  c o u l d e x p l a i n morning  sloped g e n t l y to the  h e i g h t o f t h e s e n s o r was  were f r o m t h e n o r t h e a s t , w h i c h was d i r e c t i o n i n the  sensor  measuring g r a d i e n t s  s u c c e s s f u l a f t e r n o o n Bowen r a t i o  since the t e r r a i n  the apparent  PST  PST.  i t at certain  A s e t t l i n g o f t h e maximum t e m p e r a t u r e 1000  1000  c a u s e d by t h e  w i t h i n the canopy r a t h e r than over  i n t o the canopy a f t e r  of  measurements.  northeast,  g r e a t e r when w i n d s  the predominant wind  afternoon.  S i n c e a d v e c t i v e e f f e c t s were c o n s i d e r e d a b s e n t , i t was  felt  than R at  n  t h a t t h e t r u e v a l u e o f LE s h o u l d be during t h i s time p e r i o d . ^ 6  Haney ( M c N a u g h t o n and  R e s u l t s from the  B l a c k , 1973)  value closer to one-half of R  somewhat  would suggest  lower  forest that a  w o u l d be a b e t t e r e s t i m a t e . n  I n d e p e n d e n t e s t i m a t e s o f LE u s i n g t h e M o n t e i t h observed  values of stomatal r e s i s t a n c e to c a l c u l a t e  resistance  shew good a g r e e m e n t w i t h e n e r g y b a l a n c e  ments i n t h e a f t e r n o o n , b u t R  R  equation  relationship  tend to support  i n the morning.  the  and  surface measure-  one-half  F i g u r e 5 compares  resistance r_ with surface resistance r_ calculated  stomatal from  - 17  6  9  Figure  5.  12  -  Hour  15  18  PST  Daytime c o u r s e ' o f s u r f a c e r e s i s t a n c e r (from energy b a l a n c e measurements) and s t o m a t a l r e s i s t a n c e r (projected l e a f a r e a b a s i s ) f o r J u n e 18 and J u l y 25, 1974. The d i s a g r e e m e n t o f t h e two v a l u e s i s l a r g e on a percentage b a s i s i n the morning.. c  s  the  energy balance estimates  equation. differ  o f LE and  Note t h a t i n the morning r  by  o v e r a f a c t o r o f two,  g  the  Monteith  and  r  often  c  whereas i n the  afternoon  t h e y show good a g r e e m e n t on a p e r c e n t a g e b a s i s . At was  t i m e s when t h e  placed  above the  s e c o n d Bowen r a t i o  first  suggest t h a t the one-half estimate.  The  one, R  n  i t s measurements a l s o  r e l a t i o n s h i p i s a good.  success of the  p o s i t i o n tends to support the  second machine i n conclusion  s m a l l g r a d i e n t s , placement of the too  low  a s e n s o r may  t h e m o r n i n g , and sufficiently be  be  subject  this  that with  s e n s o r s can  be  such  critical:  to inversion e f f e c t s i n  t o o h i g h a s e n s o r may  r e s o l v e the  apparatus  not  be  smaller gradients.  able  to  I t may  well  t h a t t h e most v i a b l e a l t e r n a t i v e t o v a r i a b l e p l a c e m e n t  of the  sensor with height  separation  of the  Figure ° (a) J u n e 18, show t h e represent  and  LE  estimates  i s an  increased  f o r e s t measurements.  d i u r n a l course of R (b) J u l y 25,  energy balance values  Daily totals solid  sensors f o r dry  6 shows t h e 1974,  o v e r t h e day  1974.  n  The  o f LE, w h i l e  from stomatal  and  LE  solid  the  o f m e a s u r e d LE  eye.  r e s i s t a n c e measurements.  Note the apparent  o v e r what i s f e l t  t o be  a t i o n i n the d a y l i g h t p e r i o d before  dots  circles  o f e v a p o t r a n s p i r a t i o n were o b t a i n e d  l i n e , d r a w n by  for  from  overestimation  the b e t t e r  1000  hrs.  the  approxim-  This  - 19 -  T  _i  I  _  L  0  I  j  r  t  4  r  1  i  i  8  6a.  1  I  1  12 Hour  Figure  1  1  1  r  i  16  i  20  PST  D i u r n a l t r e n d i n R a n d LE f o r J u n e 18, 1974. S o l i d dots are energy b a l a n c e measurements o f L E , w h i l e c i r c l e s show LE estimated from stomatal r e s i s t a n c e measurements.. The s o l i d l i n e f o r LE was drawn by e y e . n  i  I 24  - 20 -  60 0  Wm 400r-  200  Hour F i g u r e 6b.  PST  D i u r n a l t r e n d i n R and LE f o r J u l y 25, 1974. S o l i d dots are energy b a l a n c e measurements o f L E , w h i l e c i r c l e s show LE e s t i m a t e d from s t o m a t a l r e s i s t a n c e measure- • ments.. The s o l i d l i n e f o r LE was drawn by e y e . n  - 21  overestimation usually percent of  the  Figures contrast  amounted t o a p p r o x i m a t e l y  daily total  6 (a) and  -  evapotranspiration.  (b)  are  t h e i r c u r v e s o f LE  combined i n F i g u r e 7  and  R  .  July  n day  sufficiently  was  no  water could of  -0.7  display  l o n g a f t e r the  f r e e w a t e r on be  bar. the  The  rainy  t r e e s , yet  not  a f t e r the  (1973).  period  pronounced i n the  that  when  July  25  there  soil potential does  not  by  l a t e n t heat  (shown i n F i g u r e 8 ) , t h e  wetting period.  first  was flux  clear  T h i s s u g g e s t s more present at  o f peak a f t e r n o o n v a p o u r p r e s s u r e  2 4 - h o u r v a l u e s o f LE/R  fine  In f a c t , a l t h o u g h i t  r e s t r i c t i o n t o t r a n s p i r a t i o n t h a n was  The  period  a day  l a t e n t h e a t f l u x on  Black  p l o t f o r J u l y 19  the  a  m i d - a f t e r n o o n peak o b s e r v e d a t Haney  p r e s e n t , i t was  in  25 was  to  J  c o n s i d e r e d adequate at a m a t r i c  M c N a u g h t o n and  day  the  ten  of  0.54  and  0.58  Haney deficit.  for July  n and  25 respectively  v a l u e s of  0.61  and  evaporation rate. of the coarse  low  are 0.63 The  hydraulic  19  J  slightly  lower than the  predicted  by  the  r e s t r i c t i o n may  conductivity  respective  equilibrium  w e l l be  associated  a  function  with  a  very  soil.  J u n e 18, bars f o l l o w i n g  a day  when t h e  several  m a t r i c p o t e n t i a l was  weeks o f g e n e r a l l y  p r e s e n t s a much d i f f e r e n t p i c t u r e .  clear  Note, f i r s t ,  -6.5 weather, that  R  -  -  22  25 July, 1974 600  Y  m  — Y  = - 0 . 7 bar  18 June, 1974 m  = 6 . 5 bars -  Wm'2 400  200  0  0  8  12 Hour  Figure  7.  16 PST  F i g u r e s 6a a n d 6b t o g e t h e r t o i l l u s t r a t e the e f f e c t s of • decreased s o i l water matric p o t e n t i a l i | ^ on L E . N o t e t h a t R i s h i g h e r on J u n e 18. n m  to  20  24  - 23 -  l_  0  I  1  I  :  i  4  I  I  8  L  1  12 Hour  I  16  I  I  20  PST  F i g u r e 8. •' R and LE on J u l y 1 9 , t h e f i r s t c l e a r day a f t e r t h e r a i n y p e r i o d i n m i d - J u l y . The m i d - a f t e r n o o n peak i n LE i s p r e s e n t , but.not pronounced. n  I  I  24  - 24 -  i s h i g h e r on J u n e 1 8 , b e i n g o n l y 3 d a y s f r o m t h e summer solstice.  The c u t b a c k  10 00 PST, a t w h i c h reached  i n LE was a p p a r e n t  a s e a r l y as  time the e v a p o t r a n s p i r a t i o n r a t e  i t s d a i l y maximum.  The l a t e n t h e a t  flux  decreased  d u r i n g t h e l a t e m o r n i n g and e a r l y a f t e r n o o n t o a minimum of  80 Wm~  2  a t 1430 PST when t h e v . p . d . a n d s t o m a t a l  r e s i s t a n c e both reached 1975).  maximum d a i l y v a l u e s ( B l a c k et al.,  Resistance t o t r a n s p i r a t i o n i s obvious  w i t h t h e 24-hour v a l u e o f LE/R July in day  being only  n  8, whose d i u r n a l c o u r s e s  o f LE and R  o f t h e summer, w i t h an a v e r a g e ^  a r e shown  n  The  observed  o f -10.5 b a r s , R . n  o f o n l y 0.26.  n  t h e wet a n d d r y b u l b t e m p e r a t u r e s observed  m  case  0.38.  F i g u r e 9, c a n be c o n s i d e r e d t h e most s e v e r e  • o f 6.75 mm " e q u i v a l e n t , a n d L E / R  C.  i n this  Gradients i n  w e r e so s m a l l t h a t t h e  v a p o u r p r e s s u r e g r a d i e n t was n e g l i g i b l e a t 1600 PST. relationship  between  LE/R  n  and  i>  m  As m e n t i o n e d i n t h e i n t r o d u c t i o n , t h e e q u i l i b r i u m e v a p o r a t i o n r a t e p r e d i c t s an a p p r o x i m a t e l y of  the r a t i o  LE/R  n  f o r adequate s o i l water.  constant  value  Since the  e v a p o t r a n s p i r a t i o n r a t e d e p e n d s on e v a p o r a t i v e demand a s w e l l as water  s u p p l y , we w i l l  examine t h e e f f e c t o f  d e c r e a s i n g s o i l w a t e r m a t r i c p o t e n t i a l on L E / R , n  F i g u r e 10 shows t h e 2 4 - h o u r v a l u e o f t h e r a t i o as a f u n c t i o n o f  f o r t e n s e l e c t e d f i n e days  LE/R  including  n  - 25 -  T  i  J  i  0  :  i  1  r  r-  1  1——\  i  i  i  i  i  i  4  8  12 Hour  Figure  9.  i  16  1  T  i  i  20  PST  R and LE on J u l y 8, t h e l a s t day o f t h e f i r s t d r y i n g p e r i o d , and t h e most s e v e r e o b s e r v e d day f r o m t h e a s p e c t of water s t r e s s . LE/R was o n l y 0.26. n  i  I  24  - 26 -  0-8,  i  1  0-6 LE  x  i  i  i  i  i  i  25/7  e  .19/7  \ ^. 2 / 8  0-4 -  17/6  3/8^~^  19/6  -  l8/6^~~——  -  25/6  0-2  8/7-  -  0  i  0  -2  i  i  -4  •  i  I  I  - 6 . - 8 ^ ( 0 - 4 5 c m depth, bar.)'  -10  m  F i g u r e 10.  LE/R as a f u n c t i o n o f s o i l w a t e r m a t r i c n . p o t e n t i a l ^ f o r ten s e l e c t e d f i n e days. The number a d j a c e n t t o e a c h p o i n t i s t h e date . m  - 27  -  the f o u r days p r e v i o u s l y d i s c u s s e d . a v e r a g e v a l u e f o r t h e r o o t zone, as  i n Figure  drawn by  LE/R^  continuously to approximately  maximum v a l u e as that less  magnitude of R t h i s defeat  curve  IJJ^ a p p r o a c h e d -10  s c a t t e r w o u l d be  s u c h f a c t o r s as  The  represents  m  o f b e s t f i t was decreased  eye.  ^  by  A  half i t s  It i s possible  taking into  s t o m a t a l r e s i s t a n c e , v . p . d , , and , but  simple  high value of LE/R  the  somewhat h i g h e r v . p . d . on t h a t d a y ,  s p e c u l a t i o n w o u l d n o t be  f o r J u n e 19  justified  doing  approach used  The  n  account  the  the c o m p l e x i t i e s i n v o l v e d i n  the purpose of the  curve  indicates that  bars.  obtained  2,  the  ( 0 . 4 1 ) may  be  here.  due  to  but f u r t h e r  without  a great  deal  more d a t a . Workers i n a g r i c u l t u r e have o f t e n used v a r i a t i o n s on t h e Penman p o t e n t i a l e v a p o r a t i o n R  R  to normalize  LE t o e v a p o r a t i v e  equation rather  demand.  The  than  difficulties  i n c a l c u l a t i n g '-and i n t e r p r e t i n g t h e Penman p o t e n t i a l evaporation Black  r a t e h a v e b e e n d i s c u s s e d by M c N a u g h t o n  (1973).  f u n c t i o n of  F i g u r e 11  shows t h e r a t i o  LE/LE  as a eq , where LE i s the e q u i l i b r i u m e v a p o r a t i o n m eq ^ ^  r a t e d e t e r m i n e d f r o m d a i l y a i r t e m p e r a t u r e s and radiation.  and  The  net  s i m i l a r i t y b e t w e e n t h i s g r a p h and  Figure  10  e s s e n t i a l l y u n d e r l i n e s the degree to which the e q u i l i b r i u m r a t e c a n be  expressed  as a c o n s t a n t  f r a c t i o n of R  .  Because  - 28 -  0.4  r-  I  I  0  • I  -  Figure  11.  I  2  I  -  4  I  I  6 (bar)  1—.  -  1  1  8  1  -10  L E / L E q as a f u n c t i o n o f ty where LE q represents the d a i l y e q u i l i b r i u m evaporation rate. Differences i n this c u r v e and F i g u r e 10 a r e due o n l y t o d i f f e r e n c e s i n d a i l y , mean t e m p e r a t u r e s . e  e  m  - 29 -  o f t h e f r e q u e n t l y s t r o n g dependence o f water on h i g h v a l u e s  of ^  m  f o r most a g r i c u l t u r a l  such as t h a t i n F i g u r e logarithmic a curve,  from F i g u r e  along with various other (19 67)  f o r comparison.  determination for  soils,  ^  range.  m  Such  1 1 , i s shown i n F i g u r e  curves  taken  I t should  from van  be n o t e d  12  Bavel  that  o f maximum r a t e s o f LE i s n o t t h e same  a l l authors.  Also  i n the coarse  soil  of this  h y d r a u l i c c o n d u c t i v i t y tends t o drop o f f f a s t e r decreasing  curves  11 a r e o f t e n shown w i t h il> on a m  s c a l e t o expand t h e h i g h  taken  content  m a t r i c p o t e n t i a l t h a n i n most  study,  with  agricultural  soils. W h i l e t h e e n e r g y - b a s e d p a r a m e t e r I|J i s u s e d e x t e n s i v e l y by e n v i r o n m e n t a l a g r i c u l t u r a l i s t s often find v o l u m e t r i c water content It  should  p h y s i c i s t s , h y d r o l o g i s t s and i t more c o n v e n i e n t  6 as a measurement o f s o i l  be p o s s i b l e , t h e n ,  .between L E / R  n  f o r the s o i l  use  F i g u r e 13.  of a d a i l y g r a v i m e t r i c or neutron  evapotranspiration.  n  data  ;  Such a  1 a n d 1 0 , i s shown  The u s e o f s u c h a c u r v e  of 8 along w i t h d a i l y R of  10 and a w a t e r  under study.  r e l a t i o n s h i p , d e r i v e d from Figures in  water.  t o "draw a r e l a t i o n s h i p  a n d 8 by use. o f F i g u r e  r e t e n t i o n curve  t o use  would a l l o w the m e t e r measurement  to estimate  daily  values  -  r~  30  i  -  i  1  r  a u t h o r s ( t a k e n f r o m van B a v e l , 1967). N o t e t h a t t h e maximum evapotranspiration rate L E i s determined d i f f e r e n t l y f o r d i f f e r e n t a u t h o r s , and i n t h i s s t u d y i s t a k e n as t h e e q u i l i b r i u m rate . m a x  - 31 -  .25  .20  .6 9  Figure  13.  .10  (cm cm" ) 3  3  L E / R as. a f u n c t i o n o f v o l u m e t r i c water content. T h i s and F i g u r e 10 are r e l a t e d through the water r e t e n t i o n c u r v e f o r t h e s o i l , and allow evapotranspiration estimates from w a t e r c o n t e n t measurements t o be made. n  .05  -  D.  Evapotranspiration c r  daily  and  evapotranspiration ij^.  yet  Figure i n mm of R  ,LE/R  14  shows t h e  and  seasonal  trend  in  from F i g u r e m •  i n mm),  14  using  i t can  evapotranspiration f r a c t i o n of the  2 and  LE  long  Appendix I .  values  J  and  and  are  -  apply  seen i n F i g u r e  on d a y s o f low  are  given  of  should  on d a y s when R  14  shown  i> . m  i s low  n  14  :  10  LE  derived  While only  to  fine  that  i s only a  demand a r e n o t Values of R  i n tabulated  were  as  small.errors in  term p r e d i c t i v e estimates.  shown i n F i g u r e  daily •  n  summer t o t a l , and  evapotranspiration for  be  of  moisture.  Values of-  f o r those days,  10  used  more  f o r days used t o o b t a i n F i g u r e  argued t h a t Figure n  be  the.relationshipbetween  f r o m t h e r e l a t i o n s h i p b e t w e e n LE/R  days of h i g h R ,  can  evapotranspiration  t r i a n g l e s t o d i s t i n g u i s h them f r o m v a l u e s  be  data  e q u i l i b r i u m approach,  if; drawn i n Figure,. 10.  used i n F i g u r e  may  10  i>m  u s i n g measured v a l u e s  than the  from  evapotranspiration  it  and  T h i s a p p r o a c h r e q u i r e s o n l y one  (expressed n  Rn  u  i t a p p l i e s t o a wide range of s o i l  estimated  n  usinq  s u c h as t h a t i n F i g u r e  measurement, t h a t of and  -  estimates  A relationship to estimate  32  small  estimating critical  n  and  form i n  -  8r  -T  1  1  33  1  -  i  r  r  Rn  IV, and LE (mm)  01  20  June  30  F i g u r e 14.  10  July  20  30 1974  j i_  10 20 August  D a i l y t o t a l o f R a n d LE f o r J u n e 1 7 - A u g u s t 14, 19 74. P o i n t s used t o o b t a i n F i g u r e 10 a r e shown as t r i a n g l e s . .R ' a n d LE a r e shown a s mm w a t e r e q u i v a l e n t , n  - 34 -  E.  Water While  balance  of  the  forest  the changes i n s o i l water  content  shown i n  F i g u r e 3 c o u l d be u s e d t o c h e c k on t h e e s t i m a t e d  values  of  e v a p o t r a n s p i r a t i o n , the s i g n i f i c a n c e o f such a  is  d o u b t f u l s i n c e no  were made.  On  independent  measurements o f  the o t h e r hand, a water  o b t a i n e d u s i n g e v a p o t r a n s p i r a t i o n and  balance  drainage  could  s o i l water  be  content  v a l u e s , w i t h d r a i n a g e as t h e r e s i d u a l u s i n g t h e balance  comparison  water  equation P = E + -A9 + D  where P i s t h e p r e c i p i t a t i o n , c o n t e n t i n t h e 0-60 S u r f a c e r u n o f f was  cm  A9  i s t h e change i n water  l a y e r o f s o i l , and  not observed  v a l u e s o f A 9 were o b t a i n e d from  at the s i t e . the curve  the e i g h t p e r i o d between d a t a p o i n t s . and  D i s the'drainage. Average  i n Figure 3 for  Daily values of P  E f o r t h e c o r r e s p o n d i n g p e r i o d s were a v e r a g e d  Figures  3 and  14 r e s p e c t i v e l y , and  d r a i n a g e were t h e n c a l c u l a t e d . thus obtained are presented t a b u l a r form  The  from  average d a i l y values water  balance  i n F i g u r e 1 5 , and  given i n  i n Appendix I I .  t o the r o o t zone.  While  the negative  of  components  N o t e t h a t d r a i n a g e a p p e a r s as an i n p u t as w e l l an o u t p u t  daily  as  drainage  - • 35 -  ~T  i  i  1——i  (  1  1  1  1  r  16 • |  I T Precipitation  12  ["^] Evapotranspiration8  Depthi (mm)  |  | Residual  4  0 -4  [ Outputs  -8 I2| 8 Depth (mm)  0  Storage change  -4 -ft I  1  20  Figure  1  June  15-  :  I  30  I  U  10  July  20  JL  30 1974.  I  l_  10 August  W a t e r b a l a n c e o f t h e 0-60 cm d e p t h o f s o i l f o r J u n e 17A u g u s t 1 4 , 19 74. Values are d a i l y a v e r a g e s i n mm o f w a t e r . The r e s i d u a l t e r m i s - d i s c u s s e d i n the text. 1  - 36 -  calculated  f o r the period  J u l y 14-17 c o u l d  e a s i l y be  caused by s m a l l e r r o r s i n measurements o f p r e c i p i t a t i o n and an for  s o i l water storage obvious trend d r i e r periods  f o rthis  short  i n the r e s i d u a l o f the water balance that  indicates that  continued  at progressively higher  predicted  from s o i l  little the  period, there i s  evapotranspiration  r a t e s t h a n w o u l d be  moisture depletion.  evidence t o i n d i c a t e that roots  4 5 cm l e v e l , t h e r e  Since  there i s  extended  below  i s an apparent s o u r c e o f water  which i s not taken i n t o account i n a conventional balance of the root  water  zone.  T h e r e i s some e v i d e n c e t h a t t h i s  source i s , i n p a r t ,  upward movement o f w a t e r i n t o t h e 0-4 5 cm l a y e r .  For  t h i s r e a s o n t h e w a t e r c o n t e n t a t t h e 6 0 cm l e v e l was included of s o i l  i n c a l c u l a t i n g A6. matric  Inspection  p o t e n t i a l (Figure  indeed gradients  existed during  of the p r o f i l e  16) i n d i c a t e s  that  the d r i e r periods  that  w o u l d t e n d t o i n d u c e f l o w upwards f r o m b e l o w t h e 6 0 cm level. and  Application of.Carey's/  law t o these  t h e magnitude o f t h e negative  values  of unsaturated  become p r o g r e s s i v e l y  negative  drainage values  gives  hydraulic conductivities that are  reasonable f o r a coarse s o i l . should  gradients  drainage increases.  However, t h i s  conductivity  l o w e r as t h e a p p a r e n t I t i s also d i f f i c u l t  to  - 37 -  1  T  20  June  Figure  30  16.  r~  i  10  1  1  20 July  1  ~T  30 1974  i~  r  10 20 August  S o i l water matric p o t e n t i a l a t f o u r d e p t h s f o r J u n e 17A u g u s t 1 9 , 1974, i n d i c a t i n g d i r e c t i o n of gradients i n the vertical axis.  \f  - 38 -  b e l i e v e that over h a l f of the water t r a n s p i r e d the d r y p e r i o d in. mid-August, balance, originated of basal t i l l  during  as i n d i c a t e d by t h e w a t e r  f r o m the: n e a r l y  impermeable  layer  b e l o w 60 cm.  I t has been r e c e n t l y  s u g g e s t e d t h a t t h e amount o f  water capable o f being stored  i n t h e wood o f c o n i f e r s  c a n be i m p o r t a n t i n t h e t r a n s p o r t o f w a t e r t h r o u g h t h e trees  ( R u n n i n g et al. , 1 9 7 5 ) .  S i g n i f i c a n t amounts o f  w a t e r may be r e l e a s e d by t h e wood when s u p p l y a t t h e r o o t s becomes i n a d e q u a t e , i n o r d e r t o r m e e t e v a p o r a t i v e demand.  T h i s i s i n a c c o r d w i t h some r e c e n t . e x p e r i m e n t a l  f i n d i n g s f o r Douglas- f i r  ( L a s s o ' i e , 1973 ) a n d W h i t e  ( H i n c k l e y and B r u c k e r h o f f , 1975). potentials  The f a c t t h a t  i n t h e t w i g s and r o o t s o f t h e t r e e s  study decrease throughout the drying c y c l e 1975)  Oak  water  under  ( B l a c k et al. ,  i n d i c a t e s that the t r e e s a r e l o s i n g water  which  has n o t e x p l i c i t l y b e e n t a k e n i n t o a c c o u n t i n t h e w a t e r balance.  A l t h o u g h measurements o f t r e e w a t e r c o n t e n t  w e r e n o t made, i t i s r e a s o n a b l e t o s p e c u l a t e t h a t p r o g r e s s i v e l y more o f t h e " n e g a t i v e d r a i n a g e " t e r m i n t h e w a t e r b a l a n c e i s due t o c h a n g e s i n t r e e w a t e r s t o r a g e than i n s o i l water storage.  T h i s amounts t o o v e r  the d a i l y average e v a p o t r a n s p i r a t i o n i n t h e l a s t I t i s expected that the negative drainage term  half period.  would  - 39 -  begin t o decrease  u n d e r more e x t r e m e d r y i n g c o n d i t i o n s ,  c a u s i n g a more marked d e c r e a s e The  water balance  i n transpiration.  a n a l y s i s serves t o i l l u s t r a t e  t h e u s e f u l n e s s o f m i c r o m e t e o r o l o g i c a l measurements i n understanding it  t h e w a t e r r e g i m e o f a f o r e s t , and i n d e e d  h a s p r o v i d e d some i n s i g h t  t r a n s p o r t through is  i n t o the process  trees i n a water-stressed forest.  quite conceivable that with a better  o f t h e r e l a t i o n s h i p between s o i l  moisture  t h e wood, a r e a s o n a b l y  It  understanding and t h e  p r o p o r t i o n o f t r a n s p i r e d water r e l e a s e d from in  of water  storage  accurate water balance  could  be p r e d i c t e d f r o m e s t i m a t e s o f d a i l y , n e t r a d i a t i o n a n d p r e c i p i t a t i o n alone. of s o i l  moisture  B e g i n n i n g w i t h a known c o n d i t i o n  i n the e a r l y part of t h e season,  e v a p o t r a n s p i r a t i o n f o r e a c h day c a n be u s e d , a l o n g  with  an e s t i m a t e o f t h e p r o p o r t i o n o f t h e d a y ' s t r a n s p i r e d water taken  from t r e e stem s t o r a g e , t o c a l c u l a t e a  v a l u e o f IJJ f o r t h e n e x t m to  determine  day. J  LE/R^ f o r t h e n e x t  This w i l l day.  i n t u r n be u s e d  I n t h i s way good  h y d r o l o g i c a l p r e d i c t i o n s c o u l d be made f r o m t h e s t r a i g h t f o r w a r d measurements o f p r e c i p i t a t i o n and n e t r a d i a t i o n .  CONCLUSIONS Evapotranspiration fir  from a water s t r e s s e d  Douglas  f o r e s t has been measured t h r o u g h o u t t h e range o f  soil  matric  values  p o t e n t i a l s f r o m 0 t o -10.5 b a r s ,  o f LE/R  and d a i l y  have been c a l c u l a t e d f o r s e l e c t e d  days.  n These v a l u e s  J  have been used t o e x p r e s s a r e l a t i o n s h i p  between e v a p o t r a n s p i r a t i o n , n e t r a d i a t i o n , and s o i l matric  p o t e n t i a l t o be u s e d t o p r e d i c t  from r a d i a t i o n and s o i l w a t e r d a t a . conclusions 1.  nearly equal felt  of LE/R  The f o l l o w i n g  c a n be d r a w n :  Evapotranspiration  .is  evapotranspiration  at the experimental  t o t h e e q u i l i b r i u m r a t e when s o i l  n o t t o be l i m i t i n g . n  site i s  were s l i g h t l y  Calculated daily  lower than those  water values  associated  w i t h e q u i l i b r i u m r a t e s even f o r f i n e days f o l l o w i n g r a i n , and i t i s seen f r o m t h e d i u r n a l t r e n d that there in  i n LE  a p p e a r s t o be a r e s t r i c t i o n t o t r a n s p i r a t i o n  the afternoon  period.  This  r e d u c t i o n may be t h e  r e s u l t o f low h y d r a u l i c c o n d u c t i v i t y near t h e r o o t s preventing Haney.  t h e m i d - a f t e r n o o n peak, i n LE o b s e r v e d a t  While i t appears t h a t the e q u i l i b r i u m r a t e  w o u l d be a good e s t i m a t e the  soil  i s completely  of evapotranspiration  saturated, these r e s u l t s  when  - 41 -  s u g g e s t t h a t i t may s l i g h t l y o v e r e s t i m a t e t h e t r u e v a l u e e v e n a t m a t r i c p o t e n t i a l s as h i g h as -0.5 b a r i f t h e s o i l  2.  d i s p l a y s poor  retention  characteristics.  The r a t i o  LE/R  its at  water  decreases t o approximately h a l f  n  maximum v a l u e a s \\>. d e c r e a s e s t o -10 b a r s m this  site.  The r e l a t i o n s h i p b e t w e e n  provides a simple approach  LE/R  n  to estimating  e v a p o t r a n s p i r a t i o n from a water s t r e s s e d  forest  using only daily values of R d e p e n d e n c e o f LE/R v  of  n  on R  n  and . The n m i t s e l f i s f e l t t o be  l e s s e r i m p o r t a n c e when e s t i m a t i n g e v a p o t r a n s - :  p i r a t i o n over the l o n g term. of  LE/R  The  relationship  t o s u c h f a c t o r s as s p e c i e s , s o i l  n  type,  p h y s i o l o g y a n d m a c r o - c l i m a t e h a s y e t t o be determined. 3.  The d e c r e a s e i n LE/R  f o r the experimental s i t e n  appears  t o be i m m e d i a t e  from s a t u r a t i o n .  r  f o l l o w i n g a d r o p i n <P  m  E v a p o t r a n s p i r a t i o n appears t o  be more s e n s i t i v e t o a g i v e n c h a n g e i n m a t r i c p o t e n t i a l a t t h e wet end o f t h e r a n g e t h a n a t t h e dry in  end.  While the s o i l  i s a t h i g h ip , c h a n g e s  s o i l water storage account f o r the d a i l y  -  42  -  average e v a p o t r a n s p i r a t i o n r a t e s reasonably H o w e v e r , a t l o w i|> at a r a t e higher water storage  evapotranspiration  than that r e f l e c t e d  change,  well.  continues i n the s o i l  i n d i c a t i n g a source o f water  t h a t i s r e l e a s e d o n l y when s o i l w a t e r i s n o t adequate.  W h i l e some upward f l o w o f w a t e r  below t h e r o o t potential  zone i s i n e v i d e n c e f r o m  matric  g r a d i e n t s , i t i s b e l i e v e d that: r e l e a s e  o f w a t e r s t o r e d w i t h i n t h e t r e e stems primarily  from  will  account f o r the c o n t i n u i n g evapotrans-  p i r a t i o n under f a i r l y  extreme  drying  conditions.  - 43 REFERENCES B l a c k , T.A. a n d K..G. M c N a u g h t o n . 1971. P s y c h r o m e t r i c a p p a r a t u s , f o r Bowen r a t i o d e t e r m i n a t i o n o v e r f o r e s t s . B o u n d a r y - L a y e r M e t e o r o l . 2: 246-254. B l a c k , T.A., P.A. T a n g , C.S. T a n , J.R. C u r t i s a n d K.G. McNaughton. 19 74. Measurement t e c h n i q u e s used i n f o r e s t h y d r o m e t e o r o l o g y . F i n a l Report for the D i r e c t o r , P a c i f i c Forest Research Centre, D e p a r t m e n t o f t h e E n v i r o n m e n t , V i c t o r i a , B.C. B l a c k , T.A., C.S. T a n , J.R. C u r t i s a n d J . U . Nnyamah. 1975. F a c t o r s a f f e c t i n g e v a p o t r a n s p i r a t i o n o f an. unthinned Douglas-fir f o r e s t . F i n a l Report t o t h e D i r e c t o r , P a c i f i c F o r e s t Research C e n t r e , Department o f t h e E n v i r o n m e n t , V i c t o r i a , B.C. D a v i e s , J.A. a n d C D . A l l e n . 1973. E q u i l i b r i u m , p o t e n t i a l , and a c t u a l e v a p o r a t i o n f r o m c r o p p e d s u r f a c e s i n Southern Ontario. J . A p p l . M e t e o r o l . 12: 649-657. Denmead, O.T. a n d I . C . M c l l r o y . 1970. M e a s u r e m e n t s o f n o n - p o t e n t i a l e v a p o r a t i o n f r o m wheat. Agric. M e t e o r o l . 7: 285-302. Denmead, O.T. a n d R.H. Shaw. 1962. A v a i l a b i l i t y o f s o i l w a t e r t o p l a n t s a s a f f e c t e d by s o i l m o i s t u r e c o n t e n t and m e t e o r o l o g i c a l c o n d i t i o n s . Agronomy J . 54: 385-390. G a r d n e r , W.R. a n d C F . E h l i g . 1 9 6 3 . The i n f l u e n c e o f s o i l w a t e r on t r a n s p i r a t i o n by p l a n t s . J . Geophys. R e s . 6 8 : 5719-5724. H i n c k l e y , T.M. a n d D.N. B r u c k e r h o f f . 1 9 7 5 . The e f f e c t s o f d r o u g h t on w a t e r r e l a t i o n s a n d s t e m s h r i n k a g e o f Quercus alba. Can. J . B o t . 53: 62-72. L a s s o i e , J . P . 1973. D i u r n a l d i m e n s i o n a l f l u c t u a t i o n i n a D o u g l a s - f i r stem i n response t o t r e e water s t a t u s . F o r e s t S c i e n c e 1 9 ( 4 ) : 251-255. L o p u s h i n s k y , W. a n d G.O. K l o c k . 1974. T r a n s p i r a t i o n o f c o n i f e r seedlings i n r e l a t i o n t o s o i l water p o t e n t i a l . F o r e s t S c i e n c e 20: 181-186.  - 44 -  M c N a u g h t o n , K.G. 1974. A study of the energy b a l a n c e of a Douglas-fir forest. Ph.D. T h e s i s , D e p a r t m e n t o f S o i l Science, U n i v e r s i t y of B r i t i s h Columbia, V a n c o u v e r , B.C. M c N a u g h t o n , K.G. and T.A. B l a c k . 1973. A study of e v a p o t r a n s p i r a t i o n from a D o u g l a s - f i r f o r e s t using the energy b a l a n c e approach. W a t e r R e s o u r c e s Res. 9: 1579-1590. R i t c h i e , J.T. 1973. I n f l u e n c e o f s o i l w a t e r s t a t u s and m e t e o r o l o g i c a l c o n d i t i o n s on e v a p o r a t i o n f r o m a c o r n canopy. A g r o n . J . 65: 893-897. R u n n i n g , S.W., R.H. W a r i n g and R.A. R y d e l l . 19 7^. P h y s i o l o g i c a l c o n t r o l of water f l u x i n c o n i f e r s . O e c o l o g i a • 1 8 : 1-16. S t e w a r t , J.B. and A.S. Thorn. 197 3. Energy budgets i n a pine forest. Q u a r t . J . R. M e t e o r o l - . S o c . 99 :! 154-170. T a n g , P.A., K.G. M c N a u g h t o n and T.A. B l a c k . 1974. I n e x p e n s i v e diode thermometry u s i n g i n t e g r a t e d components. Can. J . F o r e s t Res . 4 :.. 2 5 0-2 54 .  circuit  v a n B a v e l , C.H.M. 1967. Changes i n c a n o p y r e s i s t a n c e water l o s s from a l f a l f a induced.by s o i l water depletion. A g r . M e t e o r o l . 4: 165-176. Z a v i t k o v s k i , J . and upon r a t e s o f . transpiration Douglas-fir.  to  W.K. Ferrell. 1968. E f f e c t of drought p h o t o s y n t h e s i s , r e s p i r a t i o n , and o f s e e d l i n g s o f two e c o t y p e s o f B o t . Gaz. '129: 346-350.  - 45 -  APPENDIX I Date June  1974  17 18 19 20 21 22 23 24 25 26 27 28 29 30 July 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  R —n  (mm)  7.03 7 .27 7.29 7 . 41 4.69 6 .57 5 . 44 A aa* t* _f_ 6 .49 0.97 4.66 2 .84 1.92 3 .43 3.73 5 .58 4 .28 4.73 7 .40 7 . 38 6 .87 6 .75 1.23 1.76 ' 4.60 3.40 6.61 5.62 3.03 0 . 84 3 .97 3.72 6 . 54 6 .55 3 .32 3.69 4.99 5 .65 5 .66 ft  LE  (mm)  2 .69 2 .62 2.99 2.45 1.50 2 . 04 1.69 AAA 1.78 4a 0 .27 1.33 0 .80 0 .55 0 .98 1.05 1.56 1.16 1.28 2 .00 1.96 1. 79 1.74 0 .32 0 .45 1.38 1.09 2 .38 2 .19 1.27 0 . 36 2 .38 2 . 22 3 .55 3.83 1.94 2 .14 2 . 89 3 .14 3 . 31 rft  4\  n  ^„ ( b a i —m  . 38 . 36 .41 .33 . 32 . 31 . 31 ,» j». .27 .28 . 28 .28 .28 .28 .28 .28 . 27 .27 .27 .26 .26 .26 .26 .25 .30 .32 .26 . 39 .42 .43 .60 . 59 .54 .58 .58 . 58 .58 .55 .58  -5 . 8 -6 . 5 -7 . 3 -7 .4 -7 . 6 -8.1 -8 . 3 -8.4 -8 . 7 -9.4 -9 . 3 -9 .-4 -9 . 3 -9 . 3 -9 . 5 -9.6 -9.9 -10 .1 -10.1 -10. 3 -10 . 4 -10 . 5 -10 . 6 -10 . 8 -8 . 8 -7.6 -6 .1 -4.9 -3.9 -3.4 -0.1 -0.2 -0 . 2 -0 . 3 -0 . 3 -0.3 -0.4 -0.4 -0.7  LE/R  ?  - 46 -  D a t e 1974 July  26 27 28 29 30 31 Aug. 1 2 3 4 5 6 7 8 9 10 11 12 13 14  R  (mm) 5 . 69 5 .77 5 .67 5.96 5 . 39 5 . 82 6 . 29 6 .51 6 .49 6.44 5 .99 6 .00 6.27 6 . 26 6 .11 5.68 5 .52 6.03 6.23 2.08  LE (mm) 3 . 07 3 .12 3 .00 3 .16 2.80 2 .73 2.92 2.98 2 . 75 2 .84 2 .55 2 . 46 2 . 51 2 . 31 2 . 29 2 . 04 1.88 1.99 2.03 0.66  LE/R  -n  . 54 . 54 .53 .53 .52 .47 .46 .46 . 42 .44 .42 .41 . 40 . 37 . 37 . 36 . 34 .33 .32 . 31  tjj  (bars)  ' Tin  -0.9 -0 . 9 T-l. 0 -1.1 -1.3 -2 . 3 -2.4 -2 . 7 -3.0 -3.2 -3 . 6 -4 . 2 -4 . 6 -5 . 0 -5.4 -6 .1 -6 . 7 -7.1 -7 . 5 . -7.9  - 47 -  APPENDIX I I Water B a l a n c e Data D a i l y a v e r a g e s g i v e n i n mm Period  P  E  J u n e 20June 2 6  0.00  1.50  -0.90  J u n e 2 6July 5  1.19  1.19  0.00  July July  514  5.50  1.48  3.27  } July  J"!} 17  12.33  1.34  14.80  T 3"  y  io  0-80  2 . 74  -7 . 32  July  22  T ^  ll~  0-00  3.09  -2.60  0.00  2.88  -2.14  0 .00  2 .07  -0 .90  J  n  y  T  U  J  U  Y  July  28  ^  I4 '  Uly  Aug.  8  Aug. -4Aug. 14  A0  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0093176/manifest

Comment

Related Items