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Paleoecology of postglacial sediments in the Fraser lowland region of British Columbia 1973

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PALEOECOLOGY OF POSTGLACIAL SEDIMENTS IN THE FRASER LOWLAND REGION OF BRITISH COLUMBIA by Rolf Walter Mathewes B.Sc, Simon Fraser University, 1969 A THESIS SUBMITTED IN PARTIAL FULFILMENT THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY i n the Department ° f Botany We accept t h i s thesis as conforming to th required standard THE UNIVERSITY OF BRITISH COLUMBIA May, 1973 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make i t freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver 8, Canada Date 11 ABSTRACT The p o s t g l a c i a l v e g e t a t i o n h i s t o r y o f 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 and the Yale area i n the F r a s e r Lowland r e g i o n was i n v e s t i g a t e d u s i n g percentage and a b s o l u t e p o l l e n a n a l y s i s , m a c r o f o s s i l a n a l y s i s , and r a d i o - carbon d a t i n g . A marine c l a y d e p o s i t from the U.B.C. F o r e s t r e c o r d s the o l d e s t (12,690 ± 190 B.P.) assemblage of t e r r e s - t r i a l p l a n t remains so f a r r e c o v e r e d from the p o s t g l a c i a l o f s o u t h - c o a s t a l B r i t i s h Columbia. Lodgepole p i n e dominated t h i s e a r l y v e g e t a t i o n , although some f i r , spruce, a l d e r and herbs were a l s o p r e s e n t . Four l a k e s were a l s o s t u d i e d p a l e o e c o l o g i c a l l y . The o l d e s t i s Marion L., where a p r e v i - o u s l y u n d e s c r i b e d p o l l e n assemblage of Pinus aontortat Salixt and Shepherdia i s reco r d e d i n c l a y o l d e r than 12,350 ± 190 B.P. By a t l e a s t 11,000 B.P., the t h r e e o t h e r l a k e s were a l s o a c c umulating p o l l e n - r i c h d e p o s i t s , dominated i n the e a r l y - stages by Pinus eontortat Abiest Piaea and Alnus, The f i r s t e vidence o f cedar (Thuja and perhaps Chamaecyparis) h i s t o r y i n southwestern B r i t i s h Columbia i s presented from p o l l e n and m a c r o f o s s i l a n a l y s e s . P o l l e n o f D o u g l a s - f i r began a r a p i d i n c r e a s e about 10,500 B.P. at a l l f o u r l a k e s , prob- a b l y i n response t o a c l i m a t i c a m e l i o r a t i o n . Between approx- i m a t e l y 10,000 B.P. and 8,000 B.P. i n the Ya l e a r e a , p o l l e n assemblages suggest t h a t the c l i m a t e was r e l a t i v e l y warm and dr y , a l t h o u g h n a t u r a l s u c c e s s i o n , topography, and f i r e s might account f o r the i n c r e a s e o f n o n - a r b o r e a l v e g e t a t i o n observed i n the i n t e r v a l . At Marion and S u r p r i s e l a k e s n e a r e r the i i i coast, palynological evidence of a s i m i l a r xerothermic i n t e r v a l i s s l i g h t , probably r e f l e c t i n g an ameliorating oceanic influence. Evidence of warm and dry conditions i s r e s t r i c t e d to t h i s period between 10,000 B,P. and 8,000 B.P., i n contrast to the c l a s s i c a l concept of a Hypsithermal i n t e r v a l between 8,500 and 3,000 B.P. i n the P a c i f i c North- west. iv TABLE OF CONTENTS PAGE LIST OF TABLES v i LIST OF FIGURES v i i LIST OF PLATES v i i i ACKNOWLEDGEMENTS ix INTRODUCTION 1. PART I. PALEOECOLOGY OF POSTGLACIAL SEDIMENTS FROM THE UNIVERSITY OF BRITISH COLUMBIA RESEARCH FOREST. INTRODUCTION 4. The Study Area 4. Study Sites 7. METHODS F i e l d Methods 11. Laboratory Methods 12. RESULTS Stratigraphy 14. Radiocarbon dates and sedimentation 17. Absolute pollen concentrations 20. Pollen and spore i d e n t i f i c a t i o n 23. Palynology of marine clay 25. Pollen diagrams 28. The macrofossil record 28. Pollen zonation 32. Marion Lake Zone ML-1 33. Zone ML-2 35. Zone ML-3 36. Zone ML-1* 36. Zone ML-5 37. Surprise Lake Zone SL-1 39. Zone SL-2 39. Zone SL-3 40. DISCUSSION AND CONCLUSIONS 11. Xerothermic theory i n the Northwest 4 6, V PART I I . PALEOECOLOGY OF POSTGLACIAL SEDIMENTS FROM THE LOWER FRASER RIVER CANYON REGION OF BRITISH COLUMBIA. INTRODUCTION .51. The Study Sites 51. METHODS 54. RESULTS Stratigraphy and radiocarbon dates 55. Pollen diagrams and zonation 58. Pinecrest Lake Zone PL-1 58. Zone PL-2 59. Zone PL-3 59. Squeah Lake Zone SqL-1 59. Zone SqL-2 60. DISCUSSION AND CONCLUSIONS 61. THESIS SUMMARY 65. BIBLIOGRAPHY 70. APPENDIX 74. LIST OF TABLES Carbon-14 dates and sedimentation rates from Marion and Surprise Lakes, B r i t i s h Columbia Pollen and spore assemblage from marine clay (12,690 ± 190). Marion Lake macrofossils (except mosses) Occurrence of bryophyte subfo s s i l s i n Marion Lake sediment. Volcanic ash analyses. Recalculated to 100% waterfree. Pollen zone co r r e l a t i o n s in the Fraser Lowland area. v i i LIST OF FIGURES FIGURES PAGE 1. Map of southwestern B r i t i s h Columbia showing the two study areas (crosshatched). 2, 2. Map showing lo c a t i o n and drainage pattern of the U.B.C. Research Forest. 5, 3. Morphometric map of Marion Lake. 8. 4. Southern end of the U.B.C. Research Forest showing extent of Whatcom glacio-marine deposits (crosshatched) and f o s s i l si-te. 10. 5. Pollen diagram f o r Marion Lake, (insert)in^eckeT 6. Pollen diagram f o r Surprise Lake. ( " ) 11 7. Sediment weight and palynomorph concentra- tions of Marion Lake sediment, 22. 8. Sediment weight and palynomorph concentra- tions of Surprise Lake sediment, 22, 9. Enlargement of study area i n F i g . 1, showing r e l a t i v e positions of Pinecrest and Squeah Lakes. 52. 10, Pollen diagram f o r Pinecrest Lake, ( i n s e r t JinpocksT 11. Pollen diagram f o r Squeah Lake. ( 11 ) '' LIST OF PLATES The Surprise Lake basin, looking west- northwest toward a p a r t i a l l y logged ridge. A. Gyttja subsamples before oven-drying B. Photomicrograph of g y t t j a C. Marion Lake sediment core with Mazama ash D. Photomicrograph of Mazama ash E. Pollen grain of Thuja-Chamaeoyparis type F. Chitinous test of microforaminiferan G. Pollen grain of Shepherdia canadensis H. Elaeagnaceous trichome fragment I. Peltate trichome of Shepherdia canadensis J , Pollen grain of Plantago lanceolata K, Pollen grain of Sarcobatus type Shepherdia canadensis growing together with lodgepole pine i n Manning Park, B.C. ix ACKNOWLEDGEMENTS My indebtedness for various aspects of t h i s thesis extends to many sources because of the i n t e r d i s c i p l i n a r y nature of the research. F i n a n c i a l support was provided mainly by National Research Council of Canada grants to Dr. G.E. Rouse and three scholarships to myself. F i n a n c i a l assistance f o r some parts of the research was also received from a Canada Council grant to Dr. C.E. Borden (Archaeology U.B.C), and from the International B i o l o g i c a l Programme (Marion Lake Project) through Dr. I.E. Ef f o r d . F i e l d work was made easier by the capable assistance of D. Archer, G, B u r n i k e l l , G, Hanson and e s p e c i a l l y Mr. G. Svisdahl, I would also l i k e to thank the s t a f f of the U.B.C, Research Forest for t h e i r advice and assistance. Gerhard B i h l assisted in various aspects of laboratory work, as did Miss Wynne Gor- man. My wife, Donna, helped i n d r a f t i n g the pollen diagrams and displayed admirable tolerance of e r r a t i c graduate student timetables. Mrs. Colleen Dixon kindly typed the manuscript, I am indebted to Dr. J.A, Westgate (University of Alberta, Edmonton) f o r analyzing the volcanic ash samples described i n t h i s study, and to Dr. W.B. Schofield (U.B.C.) fo r i d e n t i f y i n g the s u b f o s s i l mosses. Discussions of plant ecology with Dr, V.J, Krajina (U.B.C.) and Dr, R.C. Brooke (Simon Fraser Uni- v e r s i t y ) are also g r a t e f u l l y acknowledged. Special thanks go to the members of my thesis committee; Drs, R.E, Foreman, V.J. Krajina, J.R. Maze (Department of X Botany, U.B.C.) and W.H. Mathews (Department of Geology, U.B.C.) f o r t h e i r help and advice during t h i s study. I have l e f t my supervisor, Dr. G.E, Rouse, u n t i l l a s t because I do not have space to thank him adequately. . Instead, I would l i k e to close with the following: One rainy morning i n May, A student ar r i v e d at Point Grey, He knocked at the house Of professor Glenn Rouse And l e f t saying "This i s my lucky day!" 1. INTRODUCTION The Fraser Lowland ( F i g . 1) i s a triangle-shaped part of the Georgia Lowland, It d i f f e r s from the l a t t e r by having a depositional rather than erosional o r i g i n (Holland 19 64). The Fraser Lowland i s bounded on the north by the P a c i f i c Ranges of the Coast Mountains, and on the southeast by the Cascade Moun- ta i n s . It includes the Fraser River Delta, where sedimentary deposits up to 4,57 0 m thick overly g r a n i t i c basement rocks (Holland 1964). Here the sediments range i n age from Upper Cretaceous to recent, many containing macroscopic plant remains as well as pollen and spores. G l a c i a l a c t i v i t y during the Pleistocene r a d i c a l l y modified the topography of the Lowland, Much of the area was depressed below present sea l e v e l (Mathews et al 1970), many val l e y s and depressions were carved by i c e , and a complex of t i l l s , outwash, glacio-marine, and marine deposits was formed. With r e t r e a t , o f the Vashon ice sheet about 13,000 years ago, and subsequent* i s o s t a t i c rebound, parts of the Fraser Lowland became av a i l a b l e fo r r e c o l o n i z a t i o n by t e r r e s t r i a l plants. i The main purpose of t h i s study i s to reconstruct the h i s t o r y of p o s t g l a c i a l vegetation i n t h i s area from the e a r l y colonizing stages to the present. Pollen analysis has proven to be the most successful technique f o r t r a c i n g the development of vegetation i n many parts of the world. In t h i s study i t i s supplemented by macrofossil analysis and radiocarbon dating of important sediment l e v e l s . Absolute pollen analysis i s also used to complement standard percentage analyses at two of the four study s i t e s . 2. Fig . 1. Map of southwestern B r i t i s h Columbia showing the two study areas (crosshatched). Dashed, l i n e shows approximate boundary of Fraser Lowland. Numbered c i r c l e s show palynological study s i t e s of previous workers: 1 and 2, (Hansen 1940), 3 - Pangborn Lake (Heusser 1960). 2a o 3. The present i n v e s t i g a t i o n i s based mainly on four lake- sediment cores obtained from two separate l o c a l i t i e s i n the Fraser Lowland region. The p r i n c i p a l research area i s the University of B r i t i s h Columbia (U.B.C.) Research Forest north of Haney; the second i s situated between Hope and Yale, outside the Fraser Lowland proper ( F i g . 1), The Yale area was chosen for i t s archaeological importance and i t s l o c a t i o n near the t r a n - s i t i o n from the coast r a i n f o r e s t to the d r i e r I n t e r i o r of B r i t i s h Columbia. Comparison of pollen diagrams from these two areas should make i t possible to d i s t i n g u i s h between pollen f l u c t u a t i o n s of a regional nature, and those that r e f l e c t only l o c a l changes near the lake basins. Species names and a u t h o r i t i e s used i n t h i s study follow Hitchcock et al (1955-1969) f o r vascular plants and Crum et al (1965) f o r bryophytes (see Appendix). •+. PART I PALEOECOLOGY OF POSTGLACIAL SEDIMENTS FROM THE UNIVERSITY OF BRITISH COLUMBIA RESEARCH FOREST. INTRODUCTION The primary aim of t h i s i n v e s t i g a t i o n i s to e s t a b l i s h a detailed account of p o s t g l a c i a l vegetation changes fo r the U.B.C. Research Forest, and to place observed changes within an absolute chronological framework, using radiocarbon dating, A r e l a t e d objective i s to t r y and evaluate whether observable s h i f t s i n pollen frequency are a t t r i b u t a b l e to macroclimatic changes or to r e l a t e d phenomena such as natural forest succession, s o i l maturation or f i r e s . In the past i t has been d i f f i c u l t to ascribe primary importance to any single f a c t o r , although c l a s s i c a l l y , most long-term changes tend to be interpreted as r e s u l t i n g from c l i m a t i c f l u c t u a t i o n s . Hansen (1940) and Heusser (1960) studied peat deposits i n the Fraser River Valley ( c f . s i t e s 1, 2, 3, F i g . 1) and both indicated that p o s t g l a c i a l c l i m a t i c changes have probably taken place. The present study i s an attempt to enhance and r e f i n e these interpretations by u t i l i z i n g percentage and absolute pollen analyses, macroscopic s u b f o s s i l a n a l y s i s , and radiocarbon dating, THE STUDY AREA The U.B.C, Research Forest i s an e c o l o g i c a l l y well-studied area about 50 km east of Vancouver and north-northeast of the v i l l a g e of Haney (Fig , 2), It i s approximately 3,960 hectares 5. Fig. 2. Map showing l o c a t i o n and drainage pattern of the U.B.C. Research Forest. Arrow (inset) points to Surprise Lake.  6. (9,8 00 acres) i n area and includes a number of accessible lakes p o t e n t i a l l y suitable f o r pollen a n a l y s i s . The bedrock underlying the Forest i s mainly granodiorite and quartz d i o r i t e , commonly mantled by g l a c i a l t i l l and outwash deposits of v a r i a b l e thickness and extent. F o s s i l i f e r o u s marine deposits occur i n the southwestern corner of the Forest. Topography i s v a r i a b l e , but about 86% of the area can be described as h i l l y to mountainous (Lacate 1965). Elevations range from sea l e v e l at P i t t Lake to 790 m (2,600') north of Loon Lake (Fig. 2), Most of the Forest i s included within the Coastal Western Hemlock Zone (CWHZ) as characterized by Krajina (1969 p. 35). Annual p r e c i p i t a t i o n i n t h i s zone ranges from 165 - 665 cm (65 - 262") and the mesic s o i l s are podzolic. In the U.B.C. Forest the primary tree species are western hemlock (Tsuga heterophylla), western red cedar (Thuja p l i o a t a ) , and Douglas- f i r (Pseudotsuga menziesii var. menziesii). Less common are grand f i r (.Abies grandis), l o v e l y f i r (A. amabilis), western white pine (Pinus monticola), yellow cedar (Chamaeoyparis nootkatensia), and S i t k a spruce (Pioea s i t c h e n s i s ) . Logging, f i r e s , and other disturbances tend to promote angiosperm trees, with the r e s u l t that red alder (Alnus rubra), broadleaf maple (Acer maorophyllum), and vine-maple (A. cirainatum) are l o c a l l y abundant. Ei s (1962) has shown that extensive f i r e s occurred i n the U.B.C. Research Forest i n 1550, 1660, and 1770. Other major f i r e s were recorded about 184 0 and i n 18 68, and logging began i n 1921. Subsequent burns were recorded i n 1925, 1926, and 7. 1931 (Lacate 1965). STUDY SITES Two lakes were investigated i n t h i s study. Marion Lake (Fi g . 2) was chosen because i t i s part of an International B i o l o g i c a l Programme study of ecosystem dynamics. The lake occupies a v a l l e y depression at 305 m (1,002') elevation, and i s 800 m long and about 200 m across at i t s widest point ( F i g . 3). It has a permanent i n l e t stream at the northern end and a permanent o u t l e t . Maximum depth fluctuates between about 5 m and 7m. A detailed d e s c r i p t i o n of the lake and i t s physio- chemical features i s given i n E f f o r d (1967). Surprise Lake i s a small, boggy pond (Plate 1) located about 1 km due northwest of Marion L. (F i g . 2 arrow). Its approximate s i z e and shape r e l a t i v e to Marion L. i s shown i n F i g . 3. The lake occupies a depression on a ridge of bedrock at an elevation of about 540 m (1,775') and i s drained by an int e r m i t t e n t l y dry overflow o u t l e t . Although Surprise L. i s very small, water depth reaches about 5.6 m at one point. Sphagnum peat deposits r i n g the lake, but are most extensive on the northern shore. Scattered yellow cedar trees growing near the water's edge indicate that t h i s l o c a l i t y l i e s within the wet subzone of the CWHZ. Marion L. can probably be included i n the wet subzone also but i t may l i e i n a t r a n s i t i o n between the dry and wet subzones (Klinka 1973). Surprise L. was chosen to serve as a point of comparison f o r Marion L. Because of t h e i r proximity, regional vegetation changes should be r e f l e c t e d i n pollen diagrams from both s i t e s . F i g . 3. Morphometric map of Marion Lake. The s i z e and shape of Surprise Lake r e l a t i v e to Marion L. i s also shown, along with the locations of coring s i t e s (black dots) f o r both lakes. 200 m 2 9 I n c o n t r a s t , l o c a l d i f f e r e n c e s i n v e g e t a t i o n a n d d r a i n a g e w o u l d b e e x p e c t e d t o p r o d u c e v a r i a t i o n s p e c u l i a r t o e a c h s i t e . A c o m p l e x o f s a n d s , s i l t s , a n d c l a y s m a p p e d a s W h a t c o m g l a c i o - m a r i n e d e p o s i t s ( A r m s t r o n g 1 9 5 7 ) o c c u p y t h e s o u t h w e s t e r n c o r n e r o f t h e U . B . C . R e s e a r c h F o r e s t ( F i g . 4 ) . I n 1 9 7 0 , m a r i n e s h e l l s w e r e d i s c o v e r e d i n a f r e s h r o a d c u t a t a b o u t 1 0 7 m ( 3 5 0 ' ) e l e v a t i o n . A s a m p l e o f p e l e c y p o d s h e l l s w a s c o l l e c t e d f o r r a d i o c a r b o n d a t i n g , a n d t h e s h e l l - b e a r i n g s i l t y c l a y w a s s a m p l e d f o r p o l l e n a n a l y s i s . P l a t e 1 . T h e S u r p r i s e L a k e b a s i n , l o o k i n g w e s t - n o r t h w e s t t o w a r d a p a r t i a l l y l o g g e d r i d g e . T h e v e g e t a t i o n n e a r t h e l a k e i s s u c c e s s i o n a l , c o n s i s t i n g m a i n l y o f y o u n g w e s t e r n h e m l o c k , r e d c e d a r , a n d e r i c a c e o u s s h r u b s . T h e d r o o p i n g f o l i a g e o f a y e l l o w c e d a r t r e e i s v i s i b l e a t t h e e x t r e m e r i g h t o f t h e p i c t u r e . 10. F i g . 4. Southern end of the U.B.C. Research Forest showing extent of Whatcom glacio-marine deposits (crosshatched) and f o s s i l s i t e ( F ) . Aft e r Armstrong (19 57). Contours i n feet.  11. METHODS FIELD METHODS Lake deposits were chosen for t h i s study because po l l e n grain preservation i s generally better than i n peats (Faegri S Iversen 1964). Also, limnic sediments can e a s i l y be cored with a piston sampler. Core samplers (as opposed to side- wall samplers) minimize sediment d i s t o r t i o n and provide uncontaminated samples large enough f o r radiocarbon dating. Coring s i t e s f o r both lakes were located i n the deepest parts of the basins ( F i g . 3) i n order to obtain as complete a sequence of p o s t g l a c i a l sediments as possible. Sampling was car r i e d out between two boats bolted together with s t e e l cross-bars, and s t a b i l i z e d with four concrete anchors. A casing of 3-inch aluminum i r r i g a t i o n pipe (Mott 196 6) was used to prevent excessive bending of the extension rods as the sampler was pushed into the sediment. The water-sediment i n t e r f a c e and upper meter of sediment were c o l l e c t e d using a Brown sampler (Mott 1966 PI. IV). Deeper sediments were c o l l e c t e d i n approximately one-metre sections, using a square-rod piston sampler with a sampling tube 5 cm i n diameter (Wright 1967). Each core, segment was extruded i n the f i e l d , measured, wrapped i n aluminum f o i l , l a b e l l e d and placed i n a core-box. The cores were then frozen and stored i n preparation f o r laboratory a n a l y s i s . 1 2 . LABORATORY METHODS In order to gain as much information as possible from the sediment samples, laboratory preparation followed a scheme that would allow f o r c a l c u l a t i o n of absolute pollen concentra- tions as well as standard pollen percentages. The uppermost meter of each core was extruded from i t s sample tube while frozen and cut into 5 cm long samples. These were placed into beakers and thawed i n preparation f o r sub- sampling. A c a l i b r a t e d p l a s t i c 2 cc syringe was modified and used to extract 1 cc "plugs" from the core segments. Five such plugs constitute a sediment subsample (Plate 2-A). Each subsample was oven-dried at 7 0°C f o r 24 hours, and then weighed to the nearest .1 mg. The mean dry weight f o r f i v e r e p l i c a t e subsamples from a sample of homogeneous sediment from Marion L. was c a l c u l a t e d as 1.0317 ± .0534 grams with a standard deviation of 5,2% of the mean. Subsampling accuracy i s reduced somewhat i n regions where the sediment i s coarse or fi b r o u s . Lower sections of the core were thawed without sectioning and also subsampled at 5 or 10 cm i n t e r v a l s . A f t e r subsampling, the core segments were re-wrapped and frozen. Each subsample was treated using a standard technique that included b o i l i n g i n 5% KOH, screening, HF and a c e t o l y s i s . The remaining residue was dehydrated in an alcohol s e r i e s , mixed with s i l i c o n e o i l , and the r e s u l t i n g mixture was weighed to the nearest ,1 mg. A f t e r thorough mixing, a small drop of the s i l i c o n e o i l with residue was placed on a tared microscope s l i d e and also weighed to .1 mg. A round c o v e r s l i p was then placed over the drop and the s l i d e sealed with molten p a r a f f i n . The area under each c o v e r s l i p was then systematically scanned under 400X magnification and a l l pollen and spores i d e n t i f i e d and counted. The above procedure was modified from Traverse and Ginsburg (1966 p. 427), who give the following formula f o r computing m i c r o f o s s i l s per gram of sediment: X . § D where: X = no. of m i c r o f o s s i l s per gram A = grams of sediment sample B = t o t a l grams of maceration residue plus mounting medium C = grams of residue plus mounting medium on s l i d e D = t o t a l number of m i c r o f o s s i l s on s l i d e This formula can be modified to also give the number of m i c r o f o s s i l s per cubic centimeter of wet sediment ( X c c ) because the o r i g i n a l volume of each subsample was 5 cc i X c c = I D Thus by s t a r t i n g with a known volume of sediment, i t i s possible to gain a maximum amount of information from t h i s procedure. The same s l i d e s used f o r c a l c u l a t i n g absolute pollen concentrations can also be used to calc u l a t e r e l a t i v e pollen frequencies. When the pollen analyses from both lakes were completed, the cores were again thawed and samples f o r radiocarbon analysis were taken to date p a r t i c u l a r changes in the pollen diagrams 14, and to c a l c u l a t e sedimentation rates. Zones containing macroscopic plant remains were screened, and wood, f o l i a g e , cones, seeds and mosses were saved f o r i d e n t i f i c a t i o n . RESULTS STRATIGRAPHY Sediment cores 8.9 m and 5,2 m long were obtained from Marion and Surprise lakes r e s p e c t i v e l y . The stratigraphy of each core i s summarized at the l e f t of t h e i r respective pollen diagrams (Fig. 5 and F i g . 6), The whole Surprise L. core and most of the Marion L. core consist of g y t t j a , a mixture of plant fragments, diatom f r u s t u l e s , mineral grains and animal remains, together with pollen and spores (Plate 2-B). Fresh g y t t j a from Marion L. i s generally olive-brown in colour, changing r a p i d l y to black on exposure to a i r . Surprise L. sediment i s more brownish by comparison, i n d i c a t i n g the probable presence of humus c o l l o i d s derived from the surroun- ding peat deposits. The colour indicates that Surprise L. sediment i s at l e a s t t r a n s i t i o n a l to dy, a g y t t j a mixed with unsaturated humus c o l l o i d s (Hansen 19 59), Considerable amounts of s i l t and f i n e sand are present i n the Marion L. core, whereas both are rare or absent i n Surprise L. samples. At the base of the Marion L. core, g y t t j a grades r a p i d l y into a blue-gray clay of undetermined depth. No clay was found in Surprise L., suggesting that the e a r l i e s t p o s t g l a c i a l sediments may be missing from t h i s basin. 15. A conspicuous c h a r a c t e r i s t i c of the Marion L. core i s the intermittent presence of layers of heterogeneous plant debris and sand, here termed d e t r i t u s zones. They vary i n thickness from about 1 - 15 cm and range from compact debris to g y t t j a interspersed with l e s s e r amounts of d e t r i t a l m a terial. It i s c l e a r that much of the material i n the Marion L. det- r i t u s zones i s allochthonous i n o r i g i n , brought i n by the stream and perhaps by slopewash. Charcoal fragments were detected i n a t h i n d e t r i t u s zone 15 cm below the gyttja-water i n t e r f a c e , i n d i c a t i n g that at lea s t some of the zones could have formed i n response to erosional runoff following f i r e s . The macrofossil remains, which include well-preserved mosses i n most d e t r i t u s zones, w i l l be discussed i n d e t a i l l a t e r . A s i n g l e layer of white volcanic ash was encountered i n each core. At Marion L., the ash forms a compact layer 5 cm th i c k § (Plate 2-C), whereas i n Surprise L. i t i s 3.5 cm t h i c k . Micros-?.; - copic examination revealed glass shards t y p i c a l of volcanic ash deposits (Plate 2-D). •„ The occurrence of a d i s t i n c t volcanic ash layer i n post- g l a c i a l bogs of Washington State has been known f o r many years (Hansen 1947a). More than 200 bogs i n Washington are known to contain such an ash l a y e r , mistakenly ascribed to an eruption of Gl a c i e r Peak by Hansen (1947a) and Rigg and Gould (19 57). Powers and Wilcox (1964) have used petrographic and chemical charac- t e r i s t i c s to c o r r e l a t e t h i s p o s t g l a c i a l a s h f a l l i n the P a c i f i c Northwest with the eruption of Mount Mazama (Crater Lake) about 16. Plate 2 A. Two 5 cc g y t t j a subsamples before oven-drying. B. Photomicrograph of g y t t j a from Marion Lake, ca. 100X. C. Portion of Marion Lake sediment core showing 5 cm thi c k layer of Mazama volcanic ash at r i g h t , D. Photomicrograph of Mazama ash from Marion Lake, 450X. E. Pollen grain of Thuja-Chamaecyparis type, 900X. F. Chitinous t e s t of microforaminiferan from U.B.C, Forest marine clay deposit, *4 50X, G. Pollen grain o f - S h e p h e r d i a canadensis from Marion Lake pollen zone ML-1, 90OX, H. Portion of a peltate elaeagnaceous trichome ( c f . Shepherdia) from Marion Lake pollen zone ML-1, 300X, I. Part of a modern peltate trichome of Shepherdia canadensis from the U.B.C. Herbarium, 30OX, J, Pollen grain of Plantago lanceolata from zone ML-5, 900X. K, Pollen grain of Sarcobatus type from Marion Lake, 900X, J K 17. 6,600 years ago. Although the single ash layers i n Marion and Surprise lakes were not dated d i r e c t l y , t h e i r positions r e l a t i v e to radiocarbon dates of sediment above and below confirm t h e i r Mazama o r i g i n . RADIOCARBON DATES AND SEDIMENTATION Heusser (1960) has pointed out the need f o r chronological control i n p o l l e n - s t r a t i g r a p h i c c o r r e l a t i o n s i n the P a c i f i c Northwest. Variations i n sediment types and sedimentation rates hinder comparisons of pollen diagrams from various deposits, necessitating the establishment of an absolute time-scale. In t h i s study, 14 radiocarbon dates were used to determine the age of each deposit, the times of major f l u c t u a - tions i n the pollen diagrams, and the sedimentation rates between successive dates. A large sample of pelecypod s h e l l s (mainly Maaoma sp.) was separated from the marine clay described e a r l i e r . The outer 65% of the s h e l l s was removed with HCl p r i o r to dating, and a radiocarbon age of 12,690 ± 190 (1-5959) was determined. This date compares c l o s e l y to the early part of p o s t g l a c i a l time i n the western and central Fraser Lowland (Mathews et al 197 0, Fulton 1971). The " p o s t g l a c i a l " as used i n t h i s study begins with the time that any s i t e i n question became fre e of g l a c i e r i c e . Eight radiocarbon samples from Marion L. and f i v e from Surprise L. were also submitted f o r dating to Teledyne Isotopes 18. Inc., New Jersey. The r e s u l t s are summarized i n Table I. The basal radiocarbon dates indicate that organic sedimen- t a t i o n began i n Marion L. about 1,100 years e a r l i e r than i n Surprise L. It i s u n l i k e l y that such an age difference could be due to d i f f e r e n t times of deglaciation f o r each basin because the lakes are only 1 km apart. The lack of a basal clay l a y e r i n Surprise L. suggests that l o c a l physiographic factors could account f o r the absence of the e a r l i e s t s e d i - ments. Although no d i r e c t evidence i s a v a i l a b l e , a l a n d s l i d e from the steep slope on the northern edge of the lake may have dammed the basin around 11,2 30 years ago, allowing sediment to accumulate. Tectonic disturbances associated with p o s t g l a c i a l rebound may also have affected the drainage of the basin. The calculated sedimentation rates f o r both lakes (Table I) indicate large d i f f e r e n c e s , both within each lake, and between lakes. P a r t i c u l a r l y noticeable i s the higher rate of sediment accumulation above the volcanic ash l a y e r i n Marion L. compared to Surprise L. Sedimentation rates i n Marion L. were also more variable (;026 - .146 cm/yr) than i n Surprise L. (.024 - .073 cm/yr.) Intervals of rapid sedimentation i n Marion L. are usually associated with d e t r i t u s zones, where sediments apparently accumulated more r a p i d l y than i n the interbedded g y t t j a . For example, the i n t e r v a l between 4,860 ± 105 B.P. and 4,035 ± 105 B.P. exhibits both the greatest concentration of fibrous material and sand, and the highest sedimentation rate (.146 cm/yr). 19. Table I. Carbon-14 dates and sedimentation rates from Marion and Surprise lakes, B r i t i s h Columbia. Isotopes Inc. Radiocarbon age* Sedimentation Depth (cm) Sample number Years before 19 50 rate (cm/yr.) MARION LAKE .043 20-25 I - 6833 520 + 115 .074 17.5-52.5 I - 5961 890 + 90 .106 180-185 I - 6832 2,140 + 125 .079 330-335 I - 6823 4,035 + 105 .146 450-455 I - 6822 4,860 + 105 .085 600 V. ash 6,600 .093 700-705 I - 6821 7,645 + 340 .026 810-867 I - 5960 12,350 + 190 SURPRISE LAKE .039 55-65 I - 6964 1,555 + 130 .024 130-140 I - 6965 4,715 + 100 .058 245 V. ash 6,600 .037 305-315 I - 6966 8,275 + 135 .073 455-465 I - 6967 10,340 + 155 .065 515-520 I - 5816 11,230 + 230 AA11 errors are one standard deviation Because sedimentation rates i n both lakes are so va r i a b l e , one cannot assume a constant rate even within each dated i n t e r v a l . Hence the i n t e r p r e t a t i o n of absolute pollen data i s much more d i f f i c u l t and speculative than would be the case i f sedimentation rates were uniform. ABSOLUTE POLLEN CONCENTRATIONS Concentrations of pollen and spores per cc of wet sedi- ment are plotted f o r Marion and Surprise lakes in Figs. 5 and 6 resp e c t i v e l y . A notable feature i s the generally much higher palynomorph content of Surprise L. sediment. For example, around 10,370 B.P. i n Surprise L. , the pollen and spore concentration i s about 160,000 per cc, and i n Marion L. only 35,000 per cc. The magnitude of these differences i s v a r i a b l e , and i n t h i s case can be par t l y a t t r i b u t e d to the det r i t u s i n the Marion L. sample. Sharp drops i n pollen concentrations can be observed wherever a d e t r i t u s zone was sampled, supporting the idea that d e t r i t u s accumulates more r a p i d l y than g y t t j a . I f d e t r i t u s zones are formed during periods of high runoff, then the s e l e c t i v e removal of f i n e p a r t i c l e s , including pollen and spores, would also contribute to lower pollen concentrations. S i m i l a r l y , the presence of the i n l e t stream probably accounts f o r the comparatively low pollen concentrations of Marion L. g y t t j a . It has been estimated that during heavy rainstorms the equivalent of the t o t a l lake volume may be flushed out i n less than 2,3 days (Efford 1967), I f Marion L, 21. undergoes s i g n i f i c a n t pollen resuspension and redeposition (Davis 1968) , then such flushing i s l i k e l y to remove pollen and spores that had previously s e t t l e d as well as palynomorphs just introduced to the system. The higher palynomorph concen- t r a t i o n s i n Surprise L. sediment would therefore seem to r e f l e c t more accurately the pollen production of the surrounding vegetation. Palynomorph concentrations can be expressed i n grains per gram of sediment as well as per volume of sediment ( c f . Traverse and Ginsburg 1966). Fig. 7 shows the weight of 5 cc oven-dried, sediment r e l a t i v e to the pollen concentration per gram f o r Marion L., and F i g . 8 f o r Surprise L. As expected, Marion L. d e t r i t u s zones are characterized by sharp decreases i n pollen per gram, p a r a l l e l i n g the figures f o r pollen and spores per cc. Other highs and lows also tend to correspond between curves of pollen per cc and pollen per gram, although not always proportionately. For example, i n Marion L. the pollen content per cc of sediment at 8,6 m i s about 2,7 times as high as at 1 m. For the same two l e v e l s , numbers of pollen per gram of sediment are about the same. From the sediment dry weight curve i n Fig, 7 i t i s cle a r that the lower-than-expected value of pollen per gram at 8.6 m i s due to a sediment weight increase (ca. l g to ca. 2g), Some of t h i s weight increase can be attributed to a higher mineral content, although sediment compaction also seems to be a fa c t o r . 22. F i g . 7. Sediment weight and palynomorph concentrations of Marion L . sediment. Horizontal bars indicate detritus zones. F i g . 8. Sediment weight and palynomorph concentrations of Surprise L . sediment. 1 2 Dry weight of 5cc sediment (grams) 1 2 Pollen and spores per gram dry sediment xlO* At Surprise L., a s i m i l a r dependence on sediment weight i s shown by d e c l i n i n g amounts of pollen per gram as sediment weight increases from the surface down to the ash layer (F i g . 8). These examples indicate that factors other than sedimentation rate sometimes a f f e c t pollen concentrations i n g y t t j a . In view of the v a r i a b i l i t y of sedimentation rates and sediment densities within these lakes, absolute pollen diagrams f o r i n d i v i d u a l species such as those given by Davis and Deevey (19 64) or Ritchie (19 69) would not be meaningful. These findings concur with the conclusions of Faegri and Iversen (1964 p. 103) that absolute pollen contents of peats and sediments are too dependent on the nature of the deposit to be generally applicable. POLLEN AND SPORE IDENTIFICATION I d e n t i f i c a t i o n s of s u b f o s s i l palynomorphs were made using a modern pollen and spore reference c o l l e c t i o n prepared from P a c i f i c Northwest species. Descriptions of c e r t a i n pollen types given by Hansen (1947a) and Heusser (1960) were also con- sulted, and f o r the i d e n t i f i c a t i o n of common circumboreal taxa, Erdtman et al (1961, 1963) proved u s e f u l . Where some uncertainty exists regarding the stated a f f i n i t y of any pollen or spore, the i d e n t i f i c a t i o n i s followed by the designation "type", following the practice of Janssen (1967). A major de f i c i e n c y i n a l l previously published pollen diagrams from the P a c i f i c Northwest i s the lack of data on pollen of the Cupressaceae, generally considered to be 24. poorly preserved i n peat deposits (Hansen 1940, Heusser 1960), Preliminary inspection of g y t t j a samples from Marion and Surprise lakes, however, revealed generally good preservation of cupressaceous p o l l e n , here designated Thuja-Chamaecyparis type (Plate 2-E). The abundance of Thuja plioata i n the U.B.C. Research Forest indicates that most pollen frequency f l u c t u a t i o n s , p a r t i c u l a r l y at Marion L., are probably a t t r i b u t - able to t h i s species. Although pollen of the maples i s usually grouped under Acer sp., i n t h i s study a l l i d e n t i f i c a t i o n s have been extended to species using the c r i t e r i a of Helmich (1963). The long-standing problem of separating the pollen of Pinus species by size-range methods has been discussed by Mack (1971). He found considerable geographic v a r i a t i o n i n the pollen s i z e of Pinus oontorta, P. ponderosa, P. montioola and P. albioaulis tand concluded that the size-range method i s not accurate enough to d i s t i n g u i s h them. Pollen of the yellow pines (P. oontorta and P. ponderosa') can however be e a s i l y distinguished from the white pines on a morphological basis (Ting 1965). Yellow pine pollen encountered i n t h i s study i s designated as Pinus oontorta type because P. ponderosa i s a species r e s t r i c t e d to the dry i n t e r i o r of B.C., and probably never grew i n the study area. Also, macrofossils from both Marion and Surprise lakes indicate that Pinus oontorta i s the represented species. Macrofossil evidence from Surprise L. and modern d i s t r i b u t i o n patterns also suggest that the white pine pollen i s assignable l a r g e l y to Pinus monticola. Pollen grains of Abies and Piaea have not been i d e n t i f i e d to species because the size-range method of Hansen (1947a) i s probably subject to the same c r i t i c i s m s given by Mack (1971) f o r Pinus, U n t i l more r e l i a b l e pollen i d e n t i f i c a t i o n methods are a v a i l a b l e , i t appears advisable to avoid s p e c i f i c determinations f o r these and c e r t a i n other genera to minimize the p o s s i b i l i t y of errors i n paleoecological i n t e r p r e t a t i o n s . PALYNOLOGY OF MARINE CLAY Recovery of palynomorphs from the marine deposit i s considered s i g n i f i c a n t because of the nature of the material as well as i t s age (12,690 ± 190 B.P.), which i s greater than the e a r l i e s t dated g y t t j a from e i t h e r lake. Although i t i s 34 0 years older than the first-formed organic sediment i n Marion L., the marine clay contains an abundance of pollen and spores, l i s t e d i n Table I I , Rare pollen types encountered, a f t e r the o r i g i n a l count of 500 grains was completed include Tsuga heterophylla, Shepherdia canadensis t Gramineae, Compositae ( T u b u l i f l o r a e ) , and Typha l a t i f o l i a . The predom- inance of Pinus contorta type would be expected i n an early p o s t g l a c i a l environment, although the high f i g u r e of 91% probably indicates some overrepresentation of t h i s species. This marine pollen assemblage corresponds very c l o s e l y to one described by Terasmae and Fyles (19 59) from an approx- imately 12,00 0 year old marine d e l t a i c deposit on Vancouver Island. Both assemblages seem to indicate that pollen from Table I I , Pollen and spore assemblage from marine clay (12,690 + 190). TREES AND SHRUBS % of t o t a l p o l l e n and spores counted (500) Pinus oontorta type 91 Abies 1 Picea 1.2 Tsuga mertensiana .4 Ainu 8 1.6 ANGIOSPERMS Artemisia .8 Polygonaceae .4 Onagraceae .2 Compositae ( L i g u l i f l o r a e ) .2 Unknown .4 CRYPTOGAMS Monolete Polypodiaceae 1.4 Poly podium vulgar e type .8 Cryptogramma .2 Lycopodium annotinum .2 Selaginella wallaoei type .2 Total pollen and spores per cc wet sediment - ca. 5,000 Total pollen and spores per gram dry sediment - ca. 3,000 these deposits r e f l e c t the presence of nearby successional vegetation. Reworking of older Pleistocene deposits i s an u n l i k e l y source f o r these pollen and spores because grains observed i n t h i s study were both well-preserved and abundant. Long-distance d i s p e r s a l may account f o r some of the palyno- morphs, but i n view of t h e i r concentration of 5,000 per cc, a l o c a l o r i g i n i s more p l a u s i b l e . Whether the observed pollen concentration r e f l e c t s abundant or sparse t e r r e s t r i a l vegetation i s unknown, and only a detailed study of modern marine deposits i n the Fraser Lowland area could provide a means of comparison and i n t e r p r e t a t i o n . Chitinous inner l i n i n g s of microforaminifera (Plate 2-F) were also observed i n the marine clay preparation. Such m i c r o f o s s i l s serve to confirm the marine o r i g i n of sediments (Faegri and Iversen 1964) j unfortunately i t i s not possible to derive data on water temperature or s a l i n i t y from them. 28. POLLEN DIAGRAMS The basic sum used f o r r e l a t i v e frequency (%) c a l c u l a - t ions includes pollen and spores of a l l non-aquatic plants except fungi. Pteridophyte spores are included because many species are important members of coast r a i n f o r e s t communities. For the majority of pollen spectra, between 500 and 1,000 pollen and spores were counted. Spectrum (sample) numbers are given on each pollen diagram (Figs. 5 and 6) f o r purposes of reference and discussion. Percentages of each taxon are plotted on two scales i n both diagrams. Black curves indicate calculated percentages and the accompanying grey curves show a 10X exaggeration of the true percentage values. This method was chosen to in d i c a t e f l u c t u a t i o n s i n the r e l a t i v e abundance of rare pollen types. For discussion purposes, the pollen diagrams are divided into informal pollen assemblage zones, using the convention of designating each zone by the i n i t i a l s of the s i t e ( c f . Cushing 1967, Janssen 1968). Thus the Marion L. zones are prefixed by ML- and Surprise L. zones by SL-. This pollen assemblage approach was chosen i n preference to the geologic- climate units used by Heusser (1960, 1964) f o r the P a c i f i c Northwest. THE MACROFOSSIL RECORD Paleoecological i n t e r p r e t a t i o n s w i l l be enhanced by a j o i n t comparison of the pollen and spore record with the record of wood, f o l i a g e , cones, seeds, and s u b f o s s i l bryophytes. In Surprise L., needles of Pinus oontorta were consis- t e n t l y present i n the basal g y t t j a (11,230 + 230 B.P.) up to the 10,340 + 155 B.P. l e v e l . Another notable feature i s a small macrofossil zone at 135 cm. depth (4,715 + 100 B.P.) con- t a i n i n g five-needle f a s c i c l e s of Pinus monticola as well as Thuja p l i a a t a f o l i a g e . Other s i g n i f i c a n t macrofossil concentrations were not observed, although scattered f r a g - ments of Thuja f o l i a g e were common i n the upper 1.5 meters of sediment. The d e t r i t u s zone areas of Marion L. sediment yielded diverse assemblages of macrofossils, summarized i n Table I I I . I d e n t i f i c a t i o n s of vascular plants were checked with modern material from the U.B.C, Vascular Plant Herbarium and with descriptions i n Hitchcock et al (1955-1969) and Hosie (1969). Bryophytes were i d e n t i f i e d by W.B. Schofield, Department of Botany, U.B.C. Most of the macrofossils probably originated from vegetation growing close to the lakeshore or along the i n l e t stream. The high degree of c e l l u l a r preservation, even of d e l i c a t e mosses, suggests that transport of t h i s material p r i o r to b u r i a l was not extensive. A l l the macrofossil taxa i d e n t i f i e d during t h i s study can s t i l l be found growing i n the U.B.C. Forest today. Of s p e c i a l i n t e r e s t are occurrences of a number of sub- f o s s i l bryophyte assemblages between 10,37 0 B.P. and about 3,600 B.P, Twenty-two species have been i d e n t i f i e d from 10 l e v e l s (Table IV) and a number of other specimens have not 30. T a b l e I I I . Marion Lake m a c r o f o s s i l s (except mosses). CO tt a) tt 0) a, « Hi CO CO o H-> 0) *, 3 CD a ft o CD rH o >> •u M -«-» • E a> c <» «~» O 3 O e A: <D fx, a) 1 CD O tt) o •«* rrj •H bO h0 bO bO rf! U ft tt ro tt (0 eo cd to rrj to O 0) ttvH <» 'ri 3 - H s -a ft c 3 rH 3 rH rH JS H K o <o >> «0 O rf! O »Q O M O t-J o X O cu 6-. <U ^ «4H MH ^ 5 O w p o l l e n spectrum nos see F i g . 5 41 + c+ + 47-49 + c+s + + 54-55 + s+ + + + 62-63 + s+ + + 66 c+ + 73-75 + + + + 76-78 c+w *+ + + 84 + + + 88 + + 99-100 + s+ + 113-114 + V. ash + = p r e s e n t , c = o v u l a t e cone, s = s e e d ( s ) , w = wood, = b r a c t from Abies amabilis cone. 31. Table IV. Occurrence of bryophyte su b f o s s i l s i n Marion Lake sediment. Pollen spectrum (sample) See F i g . 5 numbers A n t i t v i c h i a ourtipendula 99-100, 73-75, 66, 62-63, 54-55,4j Bartramia pomiformis 54-55 Dendroalsia abietina* 73-75 Diohodontium pellucidwn 84, 73-75 Dioranella p a l u s t r i s 66 Dioranum fuscescens 47-49 Eurhynohium praelongwn 73-75, 66, 47-49 Heterocladium maoounii 47-49 Homalotheoium fulgeaoens* 62-63 Hylooomium splendens 73-75, 66, 54-55 Hypnum c i r o i n a l e * 73-75 Hypnum aubimponens 66 Isotheoium stoloniferum* Leuaolepi8 menziesii* 99-100,84,7 6-7 8,7 3-7 5,66, 54-55,47-49 62-63 62-63, Mnium inaigne* 66 Neckera douglasii* 73-75 Povotriohum b i g e l o v i i * 66 Rhytidiadelphu8 loreu.8 73-75, 66, 62-63, 54-55 Sphagnum magellanioum 62-63 Sphagnum palustre 99-100, 76-78, 41 Sphagnum papillosum 99-100, 88, 66, 54-55 Sphagnum aubseaundum 54-55, 47-49 * - Western North American endemic 32. been recorded because of uncertainties i n i d e n t i f i c a t i o n s . As in other paleoecological work, only the presence of a species i n a p a r t i c u l a r sample i s s i g n i f i c a n t . Absence from a sample has no diagnostic value unless i t i s t i e d i n with a broad regional record. The presence of Isothecium stotoniferum i n the majority of macrofossil zones i s a s i g n i f i c a n t discovery. This species i s a Western North American endemic, and i s " . . . . l a r g e l y r e s t r i c t e d to the humid coastal c l i m a t i c area and associated with coniferous forest or vegetation that precedes closed coniferous f o r e s t . " (Schofield 1969 p. 162), The other species i n Table IV are also extant i n the area of the U.B.C. Forest today. Although they are more: sporadic in the core than Isothecium, they contribute to the t e n t a t i v e suggestion that since about 10,370 years ago, the climate and vegetation of the study area have been of a humid coastal type. The time of 10,370 B.P, corresponds to a period of change i n the pollen diagrams from both lakes, allowing the e c o l o g i c a l i n t e r p r e t a t i o n s based on macrofossils to be checked against those suggested by the corresponding pollen assemblages, POLLEN ZONATION The pollen diagrams from Marion and Surprise lakes have been a r b i t r a r i l y divided into zones containing d i s t i n c t i v e pollen assemblages. The Marion L, core was divided i n t o f i v e zones, and Surprise L, into three. Such zones aid i n discussions of changes i n the diagrams, and c o r r e l a t i n g s i m i l a r events between lakes. U n t i l further work i s done, however, they should not be considered as t y p i c a l f o r the whol Fraser Lowland area. Some of the changes are l o c a l i n nature, and only further study and comparison can determine i f any of these zones can be correlated over wider areas. MARION LAKE (F i g . 5) Zone ML-1 (spectra 116-112, older than 12,350 B.P This narrow basal zone i s characterized by r a p i d l y r i s i n g percentages f o r Pinus oontorta type, terminating with.peak values f o r pine (90%), S a l i x p o l l e n i s r e l a t i v e l y high, and Alnust Artemisia and Polypodiaceae are also represented. Pollen of Shepherdia canadensis (Plate 2-G) i s the best i n d i c a t o r f o r the zone, reaching a value of 14% at the base. Because Shepherdia i s i n s e c t - p o l l i n a t e d and a low pollen producer, a value of 14% i s very s i g n i f i c a n t . The presence of trichome fragments (Plate 2-H) comparable i n shape and size to modern Shepherdia trichomes (Plate 2-1), confirms the i d e n t i - f i c a t i o n and indicates that the shrubs probably grew near the s i t e of deposition. S i m i l a r l y , abundant Pinus oontorta needles i n the clay of zone ML-1 indicate that t h i s species also grew at the lake. As with Ainus spp,, the presence of n i t r o g e n - f i x i n g bacteria i n the roots of Shepherdia canadensis (Stewart 1967) probably aids t h i s species i n colonizing immature s o i l s . Shepherdia canadensis i s found on poor s o i l s i n semi-open 34. f o r e s t a r e a s t h r o u g h o u t B r i t i s h C o l u m b i a , e x c e p t i n t h e w e t c o a s t a l s t r i p . I n M a n n i n g P a r k , a b o u t 150 km e a s t o f V a n c o u v e r , i t g r o w s t o g e t h e r w i t h Pinus oontorta a n d o t h e r s e r a i s p e c i e s a t e l e v a t i o n s o f a r o u n d 1,200 m ( P l a t e 3) , T h i s o b s e r v a t i o n s u g g e s t s t h a t c o o l , c o n t i n e n t a l c o n d i t i o n s p r o b a b l y p r e v a i l e d i n t h e M a r i o n L . a r e a f o r t h e d u r a t i o n o f z o n e ML-1. P l a t e 3, Shepherdia canadensis ( r i g h t c e n t r e ) g r o w i n g t o g e t h e r w i t h l o d g e p o l e p i n e i n M a n n i n g P a r k , B . C . , a t a p p r o x i m a t e l y 1 , 2 0 0 m e l e v a t i o n . T h e s h r u b o n t h e l e f t i s s n o w b r u s h (Ceanothus v e l u t i n u s ) . 35. Low absolute pollen concentrations at the base of t h i s zone (640 per cc) r i s e very quickly to about 140,000 per cc at the top (ca. 12,400 B.P.), suggesting a rapid rate of colonization by pine and other species. This i s not sur p r i s i n g i n view of the i n d i c a t i o n from the older marine clay that the same species were already present in the southern U.B.C. Forest area around 12,690 ± 190 B.P. Zone ML-2 (spectra 112-102, ca, 12,400 -ca. 10,500 B.P,) At the t r a n s i t i o n from zone 1 to zone 2 the percentages of Pinus oontorta pollen s t a r t to decrease. This decline i s steady and i s accompanied by concomitant increases of Abies, Pioea, Tsuga mertensiana, Alnus, and fern spores. Trace amounts of Tsuga heterophylla appear i n the lower parts of the zone and increase at the t r a n s i t i o n to zone 3, The pattern observed here suggests a natural succession, with more shade- tolerant conifers s t a r t i n g to replace lodgepole pine i n favourable s i t e s . A p o s t g l a c i a l amelioration of climate may have contributed to t h i s replacement process, although the small peak of Tsuga mertensiana at the top of the zone points to generally cool and moist conditions. The average sedimen- t a t i o n rate f o r t h i s zone i s very low (.026 cm per year), making t h i s i n t e r v a l appear too narrow i n r e l a t i o n to the rest of the pollen diagram. The termination of t h i s i n t e r v a l just p r i o r to 10,37 0 + 14 5 B.P. corresponds c l o s e l y to the date of 10,500 B.P. designated by Heusser (1960 p. 179) as the boundary between the La t e - G l a c i a l and the P o s t g l a c i a l . 36. Zone ML-3 (spectra 102-75, ca. 10,500 - 6,600 B.P.) The sudden appearance of abundant Pseudotsuga pollen around 10,370 + 14 5 B.P. marks the beginning of t h i s i n t e r v a l . Maximum values for Douglas-fir (11%) occur i n the bottom part of the zone. Also recorded are decreases i n Pinus oontorta, Abies, Picea, and Tsuga mertensiana. Tsuga heterophylla values increase slowly at the beginning, reaching about 27% just below the Mazama ash. Alnus, monolete fern spores, and Pteridium aquilinum spores reach t h e i r highest l e v e l s i n t h i s zone. A number of angiosperms including Corylus, Querous, and Aroeuthobium are represented f o r the f i r s t time i n t h i s i n t e r v a l . Macrofossil evidence (Table III) shows that western red cedar was already present near Marion L. around 10,000 years ago. Pollen of the Cupressaceae i s very rare and scattered at t h i s time, suggesting that the macrofossils were probably derived from the i n i t i a l immigrants to the area. Thuja-like pollen i s low throughout the zone, reaching a maximum of 1% near the Mazama ash, a natural upper boundary fo r the zone. Zone ML-4 (spectra 75-4, 6,600 - ca. 500 B.P.) Above the ash l a y e r , the percentages of Cupressaceae pollen r i s e e r r a t i c a l l y to about 4 0% at spectrum 18. Tsuga heterophylla reaches i t s highest values (ca. 40%) i n the lower h a l f of the zone and declines to about 20% at the top. This apparent drop i n Tsuga corresponds to increases i n Thuja- Chamaecypari8 type pollen. Foliage, cones, and seeds of Thuja p l i o a t a are also abundant i n t h i s i n t e r v a l (Table I I I ) , and clumps of cedar pollen were sometimes observed, possibly i n d i c a t i n g l o c a l concentrations of trees along the lakeshore and i n l e t stream. Skunk cabbage (Lysichitum amerioanum) i s a common associate of Thuja i n seepage s i t e s , and i t s pollen increase i n the upper part of t h i s zone suggests that p a l u d i f i c a t i o n may have contributed to more favourable growth of red cedar around Marion L. Pinus oontorta type i s consistently, present i n low amounts (less than 5%) and Pinus montioola type i s more consis- t e n t l y and strongly represented here than i n lower zones. Abies pollen i s s l i g h t l y more abundant than i n most of ML-3. The only i n d i c a t i o n of the species of f i r i s an ovulate cone bract of Abies amabilis from the uppermost part of ML-3, This species requires very wet climates with constantly moist s o i l s (Krajina 1969 p. 59), and can be used as an indicator for the wet subzone of the Coastal Western Hemlock Zone. Pseudotsuga pollen i s present throughout the zone i n low amounts, and Alnus representation i s between 2 0 and 3 5%. The abundance of fern spores fluctuates around 10%. Zone ML-5 (spectra 4-1, ca. 500 B.P. to the present) ML-5 i s a short zone r e f l e c t i n g vegetation changes that have occurred since about 520 ± 115 B.P. Alnus percentages increase from 2 5% to about 40%, and Betulat Rosaceae, and Pteridium record small increases. In the uppermost sample 38. (0-5 cm), grass pollen reaches i t s highest l e v e l f o r the whole core (3,5%) and three pollen grains of the introduced weed Plantago lanoeolata (Plate 2-J) were found. Corres- ponding decreases are indicated f o r the dominant c o n i f e r s , Tsuga heterophylla and Thuja-Chamaecyparis type. From the patterns observed here, i t i s c l e a r that the decrease i n climax species and increase of successional types started about 500 years ago, well before commercial logging started in the area. The presence of charcoal chunks up to 1,5 cm long i n the sediment of samples 2, 3, and 4 (5-20 cm) indicates that f i r e has played a r o l e i n these vegetation changes. A d e t r i t u s zone at 10-15 cm contains the greatest concentration of charcoal and sand, and by extrapolation from the underlying date of 520 ± 115 B.P,, an approximate age of 330 yrs, B.P, i s derived f o r the s t a r t of t h i s layer. This date i s s i g n i f i - cant i n view of Schmidt's (1957 p. 7) findings that around 300 yrs. ago, a f i r e of gigantic proportions consumed about 2,000,0 acres of forest 'on Vancouver Island. He states further that f i r e s also occurred on the Mainland coast at t h i s time, although t h e i r extent i s l e s s known. E i s (1962), however, has shown that a major f i r e occurred i n the U.B.C. Research Forest around 1660 A.D., perhaps i n i t i a t i n g the formation of t h i s Marion L. charcoal zone. SURPRISE LAKE (F i g . 6) Zone SL-1 (spectra 67-59, 11,230 - ca. 10,500 B.P.) Pinus oontorta i s abundant at the beginning of t h i s zone (60%) and declines slowly to about 47% at the top. Needles of lodgepole pine occur throughout the sediment of t h i s i n t e r v a l . Abies and Piaea percentages are greater than 1% and Tsuga mertensiana reaches 1.5% at the upper boundary. Alnus pollen ranges between 27 and 49%, and Tsuga heterophylla, Artemisia^ and Pteridium are present but not abundant. The lower boundary of SL-1 (11,230 ± 230 B.P.) i s much younger than the beginning of ML-2 (ca. 12,400 B.P.) Both on chronological and palynological grounds, the s t a r t of SL-1 correlates approximately with Marion L, spectrum no. 10 6. The upper l i m i t i s placed at around 10,500 B.P., based on a date of 10,340 ± 145 just above the designated boundary. From radiocarbon dates and c o n i f e r pollen curves, the upper boundaries of SL-1 and ML-2 co r r e l a t e almost exactly, i n d i - cating a synchronous regional vegetation change. Zone SL-2 (spectra 59-41, ca. 10,500 - 7,700 B.P.) This zone begins with a sudden increase of Pseudotsuga p o l l e n , r a p i d l y reaching a peak value of 13%. Abiest Pioea, and Tsuga mertensiana values drop i n the early part of SL-2, and Pinus oontorta type declines slowly throughout t h i s i n t e r v a l . Tsuga heterophylla pollen i s less than 5% f o r the lower two-thirds of the zone, increasing to about 2 0% at the 40. upper boundary. Thuja-Chamaecyparis type i s low and Alnus i s high throughout. Pteridium r i s e s to a maximum of 14% near the top of the zone, and monolete Polypodiaceae occur at les s than 3%, Curves f o r c o n i f e r pollen i n zone SL-2 generally c o r r e l a t e well with those of ML-3. Percentages of Pinus oontorta type, however, are cons i s t e n t l y higher at Surprise L., probably r e f l e c t i n g l o c a l differences i n elevation, topography and s o i l s between the two s i t e s . S i m i l a r l y , the abundance of monolete fern spores i n ML-3 (12-40%) can probably be ascribed to the v a l l e y p o s i t i o n of Marion L,, where r i c h s o i l s and abundant moisture promote fern growth. The more rugged t e r r a i n and shallow s o i l s of the Surprise L, area provide fewer suitable s i t e s f o r ferns (except Bracken), and t h i s difference seems to be r e f l e c t e d i n the pollen diagrams. Zone SL-3 (spectra 1-41, ca. 7,700 B.P. to the present) This zone i s characterized by r i s i n g percentages of Thuja-Chamaeayparis type. Cedar pollen i s low (2%) at the s t a r t of the zone, but increases to a maximum of 68% at 1,555 + 130 B.P. A decline to 48% i s recorded from 1,555 B.P. to the present. Higher percentages of cedar pollen are reached at Surprise L. than at Marion L., perhaps due to heavier growths of cedar at the water's edge. Scattered fragments of Thuja f o l i a g e were commonly observed i n the upper 1.5 m of sediment, where pollen percentages were also highest. Pollen of Pinus oontorta type i s low within t h i s i n t e r v a l , as i s Pinus montioola type. Western white pine, however, i s a good indicator f o r t h i s zone since i t i s usually represented at 1% or more. In lower zones i t i s usually absent, but may occur sporadically at frequencies less than 1%. Other taxa represented most strongly i n SL-3 include Betula, Acer macrophyllum, Queroust and Lysiohitum americanum* There i s no strong i n d i c a t i o n of e c o l o g i c a l disturbance i n the most recent sediments. A small peak of Pteridium aquilinum and low Tsuga heterophylla percentages suggest that f i r e or logging may be r e f l e c t e d i n the uppermost g y t t j a , although the d i s t i n c t changes associated with ML-5 are not evident. DISCUSSION AND CONCLUSIONS The r e s u l t s of t h i s i n v e s t i g a t i o n indicate that soon a f t e r the Vashon i c e started to re t r e a t from the Fraser Lowland about 13,0 00 years ago, vegetation quickly recolonized the deglaciated t e r r a i n i n the area of the U.B.C, Research For- est. By 12 ,690-± 190 B.P., a f a i r l y diverse palynomorph assem- blage dominated by Pinus oontorta type pollen was preserved i n a marine clay. Whether these early immigrants to the Fraser Lowland existed only along a near-ocean s t r i p or also i n upland areas i n unknown, Marion L. at 3 05 m elevation was i c e - f r e e sometime before 12,350 + 190 B.P., when pollen of lodgepole pine, Shepherdia canadensist willow and alder were deposited i n clay underneath the f i r s t dateable organic sediment. The e a r l i e s t organic sediments record abundant lodgepole pine pollen associated with f i r , spruce, and mountain hemlock u n t i l about 10,37 0 + 14 5 B.P, Cool and moist conditions are indicated f o r t h i s i n t e r v a l which seems to record the replacement of shade- intolerant lodgepole pine by more shade-tolerant c o n i f e r s . High percentages (31% of t o t a l alder) of 4-pored alder grains from t h i s period suggest that mountain alder (Alnus incana) may have been present i n the U.B.C. Forest at t h i s time. The sudden appearance of abundant Douglas-fir pollen around 10,500 years ago at Marion and Surprise lakes i s associated with decreases i n lodgepole pine, f i r , spruce, and mountain hemlock. A trend toward warmer and perhaps somewhat d r i e r conditions at t h i s time may have favoured Douglas-fir, but high alder pollen with macrofossils of Thuja and Isothecium stoloniferum indicate abundant moisture. Between about 10,500 B.P. and the approximate l e v e l of the Mazama ash layer at 6,600 B.P,, the pollen diagrams record a successional type of vegetation with Douglas-fir, alder, bracken fern (.Pteridium aquilinum) and d e c l i n i n g lodge- pole pine. Western hemlock was present during the early part of t h i s i n t e r v a l , but did not increase strongly u n t i l about 8,275 ± 135 B.P. at Surprise L.» and about 7,300 B.P. at Marion L. This "lag phase" of western hemlock development has been previously noted i n Puget Sound, where i t s slow expansion was p a r t l y a t t r i b u t e d to increased p o s t g l a c i a l warming and drying (Hansen 1947a p. 82). 43. In the U.B..C, Research Forest, the slow r i s e of western hemlock percentages may not r e f l e c t a primary influence of climate. An alternate explanation may r e f l e c t the fact that Tsuga heterophylla grows best on podzolized s o i l s , and regener- ates most e f f e c t i v e l y on mor humus or decaying c o n i f e r wood (Krajina 1969), It i s conceivable, therefore, that the early spread of hemlock was dependent on the formation of edaphic s i t e s favourable for i t s growth. This explanation has also been suggested by Hansen (19 50) f o r the slow increase of western hemlock on southeastern Vancouver Island, The percentages of western hemlock continue to increase at the ash la y e r , where hemlock wood, f o l i a g e , and an ovulate cone occur i n the Marion L. core. The same macro- f o s s i l horizon contains a well-preserved bract from an ovulate cone of Abies amabilis t i n d i c a t i n g heavy p r e c i p i t a t i o n around 6,600 B.P. Isothecium stoloniferum s u b f o s s i l s above and below the ash support the i n t e r p r e t a t i o n that humid coastal conditions prevailed at t h i s time. Thuja macrofossils indicate that western red cedar was* present i n the U.B.C. Forest about 10,370 ± 14 5 B.P,, although low numbers of cedar pollen suggest that these trees were rare u n t i l about 6,6 00 B.P. Above the ash l a y e r , cedar pollen reaches maximum percentages of 43% i n Marion L, and 68% i n Surprise L. At Surprise L., both red and yellow cedar are probably represented i n the diagram, whereas at Marion L. the present vegetation and abundant macrofossils i n the sediments indicate that red cedar was the major contributor of 4 4 . cupressaceous pollen. Since the same general trends of increasing Thuja- Chamaeoyparis pollen are observed at both lakes, they are not l i k e l y to be a r t i f a c t s of d i f f e r e n t i a l p ollen preservation. Examination of cedar pollen from various spectra indicate that although abundance d i f f e r s , the preservation of i n d i v i d u a l grains i s not markedly d i f f e r e n t between surface and deeper samples. Comparable trends of cedar pollen are also present in two lakes about 90 km east of the U.B.C. Forest, and Easterbrook (1971) has mentioned the presence of a Tsuga heterophylla-Cnpressaceae zone above an ash layer i n Puget Lowland bogs. C l i m a t i c a l l y , the combined dominance of hemlock and cedar above the Mazama ash indicates wet, mesothermal conditions approximating those of the present. This i n t e r p r e t a t i o n i s supported by the diverse s u b f o s s i l moss assemblages from Marion L., consisting t o t a l l y of species that occur i n the U.B.C. Forest area today. The inf e r r e d pattern of Pinus montioola immigration into the U.B.C. Forest d i f f e r s noticeably from the pattern described by Hansen and Heusser f o r the P a c i f i c Northwest. Hansen (1947a p. 7 9) stated that western white pine was next i n importance to lodgepole pine as an early p o s t g l a c i a l invader, Heusser (1960 p. 133) mentions the tendency of white pine percentages ' to follow the trend of the lodgepole pine p r o f i l e s . These trends are not apparent i n the Marion and Surprise L. p r o f i l e s , where Pinus montioola type i s v i r t u a l l y absent before 10,000 B.P., 45. and does not reach values greater than ,7% below the Mazama ash laye r . It's maximum representation above the ash i s 6.2% at spectrum 24 from Marion L. Whether these differences represent biogeoclimatic differences o r differences i n i d e n t i f i c a t i o n methods i s d i f f i c u l t to assess. Although oak pollen ( c f . Queraus garryana) i s present i n some samples from Marion and Surprise lakes, t h i s species does not occur i n the U.B.C, Forest today. The presence of oak pollen has been used by Hansen (1947a) and Heusser (1960) to indicate warmer and/or d r i e r conditions i n parts of Oregon and Washington during p o s t g l a c i a l time. In t h i s study, however, the low amounts of oak pollen were probably derived from scattered stands of Garry oak growing i n edaphically dry s i t e s i n the Fraser Lowland area. Even under the present c l i m a t i c regime, Queraus garryana can grow i n t h i s area as shown by a population of oak on Sumas Mountain, about 3 0 km southeast of the U.B.C. Forest, An enigmatic phenomenon i n the Marion L. pollen diagram i s the occasional occurrence of Sarcobatus type pollen ( c f . spectra 15, 63, 95, 5 113). These grains (Plate 2-K) are v i r t u a l l y i d e n t i c a l to extant pollen of Sarcobatus vermioulatus (grease- wood), a shrub of a l k a l i n e areas i n deserts or grasslands. It does not occur i n B r i t i s h Columbia, but grows i n the dry eastern part of Washington State. The presence of these grains i n sediments of the humid coast must be a r e s u l t of long-distance d i s p e r s a l , since the ec o l o g i c a l requirements of greasewood do not coincide with the vegetation indicated by the r e s t of the pollen assemblage. Long-distance d i s p e r s a l has also been in f e r r e d f o r sparse amounts of Sarcobatus and Ephedra pollen in northwestern Minnesota (McAndrews 1966). XEROTHERMIC THEORY IN THE NORTHWEST This theory assumes that there was at least one segment of time since the l a s t major g l a c i a t i o n when the climate was d r i e r and warmer than at present (Sears 1942). Although t h i s c o n t r o v e r s i a l concept originated i n Europe, i t has also been extended to North America to explain disjunct d i s t r i b u t i o n s of continental plant species beyond t h e i r usual l i m i t s (Sears 1935). Hansen (1947a) postulated the existence of a p o s t g l a c i a l period of maximum warmth and dryness f o r the P a c i f i c Northwest of North America. The strongest evidence f o r t h i s stage came from the dry Columbia River Basin of eastern Washington, where pollen of xerophytes c o n s i s t e n t l y reached maximum values around the Mazama ash layers i n several bogs. In the wetter Puget Lowland of western Washington, the postulated period of warm, dry climate was l e s s strongly expressed than in the Columbia Basin (Hansen 1947b). Here, the pattern of p o s t g l a c i a l forest development was ascribed p r i m a r i l y to natural succession, modified r e g i o n a l l y by f i r e , s o i l conditions, and to a l i m i t e d extent by climate. For southeastern Vancouver Island, Hansen (1950) concluded that the warm, dry i n t e r v a l was not evident. The observed changes i n forest composition were again ascribed to normal forest succession i n response to a general amelior- ation of climate and s o i l maturation. 47. A x e r o t h e r m i c p e r i o d c o r r e l a t e d w i t h t h e warm, dry i n t e r v a l i n e a s t e r n Washington was r e c o g n i z e d by Hansen (1955) i n s o u t h - c e n t r a l and c e n t r a l B r i t i s h Columbia. T h i s p e r i o d was p l a c e d between 7,500 and 3,500 B.P,, w i t h a "thermal maximum" around 6,600 B.P, T h i s c l i m a t i c i n t e r p r e t a t i o n r e l i e d h e a v i l y on an i n f e r r e d abundance of Pinus ponderosa p o l l e n d u r i n g the xe r o t h e r m i c i n t e r v a l . C a u t i o n must be used i n e v a l u a t i n g t h e s e d a t a , however, i n view o f Mack's (1971) f i n d i n g s t h a t the s i z e - r a n g e method o f i d e n t i f y i n g Pinus ponderosa p o l l e n i s not r e l i a b l e . Deevey and F l i n t (19 57) used the term " H y p s i t h e r m a l " t o d e s c r i b e a p o s t g l a c i a l p e r i o d d u r i n g which mean annual temperatures i n most o f t h e world are b e l i e v e d t o have ex- ceeded those o f the p r e s e n t . T h i s concept was used by Heusser (1960), who p l a c e d the Hypsithermal between 8,500 and 3,000 B.P. i n Washington S t a t e and southwestern B r i t i s h Columbia. In a p o l l e n diagram from Pangborn L. ( F i g . 1, s i t e 3) i n the F r a s e r Lowland, Heusser (1960 F i g . 38) i n t e r p r e t e d t h e Hypsithermal i n t e r v a l as o c c u r r i n g between t h e b a s a l sediments at 9 meters and the 4 meter l e v e l . The base o f t h e Pangborn L. bog was subsequently dated at 9,920 + 760 B.P. ( E a s t e r - brook 1969), w e l l b e f o r e the 8,50 0 B.P. lower boundary f o r the H y p s i t h e r m a l . Changes i n the p o l l e n s p e c t r a a l s o do not seem s u f f i c i e n t l y d i s t i n c t t o warrant a boundary a t the 4 m l e v e l . I b e l i e v e t h a t the Pangborn L. diagram, as w e l l as those presented i n the present study, p o i n t out the l a c k o f u n e q u i v o c a l p a l y n o l o g i c a l evidence f o r a Hy p s i t h e r m a l i n t e r v a l i n t h e western F r a s e r Lowland. I f m a c r o c l i m a t i c changes d i d 48. occur between 8,500 and 3,000 B.P., they evidently were not of s u f f i c i e n t i n t e n s i t y to cause detectable vegetation s h i f t s at low elevations. The generally wide tolerance ranges of most tree species together with the ameliorating oceanic influence along the coast probably masked any c l i m a t i c changes; changes that would be detectable i n more continental regions where temperature and moisture are often more l i m i t i n g . It i s not s u r p r i s i n g , therefore, that the strongest evidence f o r warming and/or drying comes from continental rain-shadow areas such as the Columbia Basin and south-central B r i t i s h Columbia, Palynological studies by the author are presently underway i n a t r a n s i t i o n area between the humid coast and the d r i e r I n t e r i o r of B r i t i s h Columbia to see whether or not a xerothermic influence can be detected i n t h i s region. Another area where c l i m a t i c s h i f t s should be pronounced exists at alpine and subalpine elevations i n the Coast Moun- t a i n s . Evidence that timberlines were once higher than at present has been presented f o r parts of the Coast Mountains by Mathews (19 51), Samples of in situ wood from tree remains c o l l e c t e d above present timberline have been dated between 5,950 ± 140 and 5,260 ± 200 B.P. (Lowdon and Blake 1968 p. 226), probably i n d i c a t i n g warmer temperatures at these times than p r e v a i l at present. Further work i s necessary to determine how widespread these timberline s h i f t s were, as well as the cause and duration of the i n f e r r e d montane warm period. Pollen analysis and radiocarbon dating of subalpine and alpine bogs or lakes i n the Coast Mountains may supply some answers to t h i s 49. problem. Pollen diagrams from Marion and Surprise lakes also seem to i n d i c a t e that vegetation disturbance was common during p o s t g l a c i a l time. The continuously high percentages of alder are e s p e c i a l l y s i g n i f i c a n t , as are the pollen of the pines, Douglas-fir, willow, b i r c h , hazel, broadleaf and vine maples, various ferns and other shrubs and herbs. F i r e s have probably played an important r o l e i n the h i s t o r y of P a c i f i c Northwest forest vegetation (Isaac 1940, Hansen 1947b, Schmidt 1957, Eis 1962). Low p r e c i p i t a t i o n and high temperatures during midsummer promote forest f i r e s i n t h i s region today, even though the average annual r a i n f a l l i s high. As a r e s u l t of f i r e s , or other destructive phenomena such as windstorms, insect i n f e s t a t i o n s , or fungal diseases, the presence of successional species i s maintained within the region. The patterns of secondary succession following f i r e s i n the U.B.C. Forest have been described by McMinn (1951), who determined that forest regeneration patterns were controlled l a r g e l y by differences i n a v a i l a b l e moisture, s o i l , and distance from seed sources. Bracken fern (.Pteridium aquilinwn) and vine-maple occur on most parts of burned areas, and red alder quickly colonizes moist v a l l e y bottoms. In most areas, regeneration of a western hemlock-red cedar forest i s r a p i d , making the detection of i n d i v i d u a l periods of disturbance i n pollen diagrams very d i f f i c u l t . Even 5 cm long sampling i n t e r v a l s are too large to record a successional cycle from a 50 . f i r e back to coniferous f o r e s t . Instead, the continual presence of large amounts of pollen from s e r a i species i s testimony that disturbances, whether of physical or b i o l o g i c a l o r i g i n , have continually influenced the p o s t g l a c i a l forests of t h i s area. 51. PART II PALEOECOLOGY OF POSTGLACIAL SEDIMENTS FROM THE LOWER FRASER RIVER CANYON REGION OF BRITISH COLUMBIA. INTRODUCTION Results of pollen analysis of cores from two lakes i n the Yale area are presented here to o u t l i n e the h i s t o r y of post- g l a c i a l vegetation in t h i s area, both f o r archaeological purposes and f o r comparison with s i m i l a r studies to the west (Part I ) . An archaeological sequence dating back to 9,000 ± 1 5 0 B.P. was established by Borden (1965, 1968) from excavations on terraces of the Fraser River at South Yale, B r i t i s h Columbia. As part of the South Yale Archaeological Project, sediment cores for p o l l e n sanalysis and radiocarbon dating were c o l l e c t e d from two lakes about 10 Jon south of the archaeological s i t e s , in a study area between Hope and Yale ( F i g . 1), Radiocarbon dates from the study area and t h e i r implications were discussed i n an e a r l i e r paper (Mathewes et al 1972), THE STUDY SITES The locations of Pinecrest and Squeah lakes within the study area are shown in F i g . 9. Squeah L. occupies a depres- sion about 205 m (675') above sea l e v e l i n the western Cascade Mountains. Pinecrest L. at 320 m (1,100*) elevation i s located on the eastern slopes of the Coast Mountains. Both lakes are characterized by narrow, steeply sloping l i t t o r a l 52. zones with sparse macrophytic vegetation (mainly Nuphar poly- sepalum). Maximum water depths are approximately 11.5 m at Squeah L., and 9.9 m at Pinecrest L, Fig. 9. Enlargement of study area i n F i g . 1, showing r e l a t i v e positions of Pinecrest and Squeah lakes. Contour i n t e r v a l i s 500 feet. Forest vegetation grows to the water's edge a l l around Pinecrest L., leaving l i t t l e room fo r semi-aquatic vegetation. At Squeah L,, thick peat deposits occur on the western shore and a large sedge swamp occupies the outlet region. Hardhack (Spiraea douglasii) forms dense thickets on the d r i e r parts of boggy areas, and grasses (Gramineae), willows ( S a l i x ) , and Umbelliferae are l o c a l l y abundant. Scattered i n d i v i d u a l s of crabapple (Pyrus fusoa) occur i n swampy areas, Douglas-fir (Pseudotsuga menziesii), western hemlock (Tsuga heterophylla), and western red cedar (Thuja pliaata) are the most common conifers near both lakes. White pine (Pinus montioola) and lodgepole pine (P. oontorta) are also present, and several trees of grand f i r (Abies grandis) were noted near Squeah L. The most abundant angiosperm trees i n the study area are red alder (Alnus rubra) and paper b i r c h (Betula papyrifera), although vine-maple (Acer oiroinatum)> broadleaf maple (A, maorophyllum) and mountain maple (A, glabrum) are l o c a l l y abundant. Black cottonwood (Populus triohocarpa) i s common along the lower terraces of the Fraser River, Although both lakes are situated within the Coastal Western Hemlock biogeoclimatic Zone (Krajina 1969), the study area i s close to the t r a n s i t i o n between the CWHZ and the d r i e r I n t e r i o r Douglas-fir Zone. In the Fraser River Canyon between Yale and Boston Bar ( F i g . 1), broadleaf maple and western hemlock disappear from the lowland vegetation and ponderosa pine (Pinus ponderosa) becomes noticeable near Boston Bar, Just north of Boston Bar the t r a n s i t i o n 54. into the I n t e r i o r Douglas-fir Zone i s complete. Here the annual p r e c i p i t a t i o n ranges between 36 and 56 cm (14-22") and the vegetation i s correspondingly more x e r i c i n character, METHODS The sediment core from Pinecrest L, was taken from the side of a f l o a t i n g dock under 2.5 m of water, approximately 10 m out from the shoreline. The Squeah L. core was recovered at a l a t e r date from the deepest part of the lake (11.30 m) as determined by soundings with a chain and disk. A square- rod piston sampler with a coring tube 5 cm in diameter was used to c o l l e c t both cores. The Squeah L, core was taken both to obtain a basal radiocarbon date f o r a second lake i n the area, and to provide a more complete sequence of the e a r l i e s t p o s t g l a c i a l sediments f o r pollen a n a l y s i s . Because of time l i m i t a t i o n s , only the portion of core below the volcanic ash layer i n Squeah L. was used f o r pollen a n a l y s i s , whereas a l l of the Pinecrest L. core was investigated p a l y n o l o g i c a l l y . Both cores were subsampled at 10 cm i n t e r v a l s to provide material f o r laboratory processing. Unused portions of cores were frozen and stored. Each sediment subsample was treated with b o i l i n g 5% KOH, HF, and a c e t o l y s i s to remove as much non-polliniferous material as possible. Pinecrest L. samples were stained with Safranin '0' and mounted on microscope s l i d e s i n polyvinyl alcohol (Elvanol) and Gelva r e s i n . Samples from Squeah L. were dehydrated i n alcohol and mounted i n s i l i c o n e o i l ; a more 55. s a t i s f a c t o r y procedure because pollen grains can be turned on the s l i d e s for viewing at a l l angles. Each s l i d e was then scanned at 400X magnification and palynomorphs were i d e n t i f i e d and counted. Approximately 600 pollen and spores were counted f o r most Pinecrest L. samples, and about 500 f o r Squeah L. Detritus zones from the Squeah L. core were c a r e f u l l y screened and investigated f o r plant macrofossil remains and charcoal. RESULTS STRATIGRAPHY AND RADIOCARBON DATES The t o t a l length of core recovered from Pinecrest L, i s 4.5 m. As shown i n the summary of sediment stratigraphy i n Fig. 10, the deepest sediment i s a blue-gray g r a v e l l y clay. A gray-green c l a y - g y t t j a was subsequently formed, grading up into a dark-olive g y t t j a containing f i n e f i b e r s (perhaps root- l e t s ) . Gyttjas oxidize quickly to a dark colour on exposure to a i r , suggesting that t h i s sediment may have formed i n shallower water, where periodic oxidation could have taken place. Just below the ash la y e r , the sediment becomes l i g h t e r i n colour and le s s f i b r o u s . Fine-grained o l i v e g y t t j a makes up the res t of the core. A 2 cm thick layer of white volcanic ash occurs at 3,8 6 m. Chemical analysis of the ash (Table V) shows that i t corre- l a t e s with the eruption of Mt, Mazama, 6,600 years ago. The Pinecrest L, pollen diagram indicates that approximately 4,400 years of p o s t g l a c i a l time are represented by only 72 cm 56. Table V. Volcanic ash analyses. Recalculated to 100% waterfree.* Pinecrest L, Squeah L. Average Mazama sample sample (58 analyses) (UA-423) (UA-424) S i 0 2 72.59 + 0.27 72.17 72.56 T i 0 2 0.48 + 0.02 0.44 0.47 A1 20 3 14.42 + 0.16 14. 55 14.48 FeO ( t o t a l iron) 2.08 + 0.06 2.15 2.16 MgO 0.54 + 0.08 0.62 0.59 CaO 1.71 + 0.09 1.66 1.64 Na 20 5.15 + 0.16 5.45 5.15 K 20 2.70 + 0.06 2.77 2.76 CI 0.18 + 0.02 0.20 0.20 *The analyses f o r Pinecrest and Squeah lakes were kindly supplied by Dr. J . A, Westgate, Department of Geology, University of Alberta, Edmonton. Average Mazama analyses were taken from Lichti-Federovich (1970). of sediment below the ash l a y e r . To obtain a longer i n t e r v a l that might give a more detailed picture of pollen changes i n p r e - a s h f a l l time, a 6,7 m core was obtained from Squeah L. In the Squeah L, core (Fig, 11), a 2.5 cm t h i c k layer of Mazama ash (Table V) was encountered at 4,08 m, leaving about 2.6 m between the base of the core and the ash, thus providing the longer i n t e r v a l f o r a n a l y s i s . In the Squeah L, core, sandy stringers and occasional varving were noted i n the grayish basal c l a y - g y t t j a , underlain by an undetermined depth of non-organic varved clay. Screening of d e t r i t u s zones in spectra (samples) 3 and 7 revealed the presence of f i n e l y - d i v i d e d charcoal as well as bryophyte remains, i d e n t i f i e d by Dr. W. B, Schofield, Spectrum 3 contained Bryum sp,, Diohodontium pellucidum, and Isothecium stoloniferum. Well-preserved fragments of Diohodontium pellucidum, Eurhynchium praelongum, Isothecium stoloniferum, Leucolepis menziesii and Scleropodium obtusifolium were recovered from spectrum 7, A l l these mosses can be found in the same general area today. A piece of wood i d e n t i f i e d as Douglas-fir was recovered from spectrum 4. Radiocarbon dates f o r the basal 10 cm of c l a y - g y t t j a i n both cores were determined by Isotopes Inc., New Jersey. Pine- crest L. was dated at 11,000 + 170 B.P. (1-5346) and Squeah L. at 11,140 ± 260 B.P. (1-6058). An age of 8,620 + 135 B.P. (1-5815) was obtained for c l a y - g y t t j a between 5,60 and 5.6 5 m at Squeah L,, allowing f o r c a l c u l a t i o n of the average sedimen- t a t i o n rate (.040 cm/yr) between t h i s l e v e l and the base of the core. 58. POLLEN DIAGRAMS AND ZONATION The procedure used i n Part I for i d e n t i f i c a t i o n of pollen and spores and c a l c u l a t i o n of pollen percentages was also used i n t h i s study. True percentage curves are drafted i n black, and curves i n d i c a t i n g a 10X exaggeration of r e a l percentages are plotted in gray f o r both Pinecrest'(Fig. 10) and Squeah (F i g . 11) lakes. As i n Part I, the pollen diagrams are divided into informal zones to f a c i l i t a t e discussion of changes in the pollen p r o f i l e s , and to c o r r e l a t e changes among lakes. Pine- crest L. zones are prefixed by PL-, and Squeah L. zones by SqL-. PINECREST LAKE (F i g . 10) Zone PL-1 (spectrum 46, 11,000 B.P.) This very narrow zone i s l i m i t e d to the basal 10 cm of c l a y - g y t t j a from the core. I t i s characterized by high Pinus oontorta type pollen (ca. 4 0%) and the highest amount of Pioea pollen i n the core (ca. 5%). Alnus, Abies, and Artemisia are also prominent i n t h i s zone, which probably appears shorter i n duration than normal because of a slow rate of sediment accumulation. A radiocarbon date of 11,430 + 150 (1-6057) from basal sediment i n the deepest part of the lake basin (Mathewes et al 197 2) indicates that the e a r l i e s t p o s t g l a c i a l sediment i s not included i n Fig. 10, probably r e f l e c t i n g the po s i t i o n of the core on the sloping l i t t o r a l area. Zone PL-2 (spectrum 4 5 to Mazama ash) The sudden appearance of abundant Pseudotsuga pollen, along with spores of S e l a g i n e l l a wallaaei type, marks the beginning of t h i s zone. Tsuga heterophylla pollen i s c h a r a c t e r i s t i c a l l y low i n t h i s i n t e r v a l (less than 5%), but S e l a g i n e l l a , S a l i x , Pteridium and Gramineae reach t h e i r highest percentages. Alnus i s also high i n PL-2 (ca. 50%), together with Betula which r i s e s from less than 1% at the base of the zone to about 2 5% just below the ash lay e r . Artemisia and Cyperaceae are also prominent, and Acer glabrum p o l l e n , although sparse, i s c h a r a c t e r i s t i c a l l y present. Zone PL-3 (Mazama ash to the present) Approximately the l a s t 6,600 years are represented in t h i s zone, characterized by abundant Tsuga heterophylla, Pseudotsuga, Alnus and Betula pollen, Thuja-Chamaeoyparis type pollen i s ca, 10% at the base of the zone, r i s i n g to ca. 2 5% i n the upper h a l f . Pinus montioola type i s continuously represented at greater than 1%, reaching a maximum of 8% i n spectrum 9. SQUEAH LAKE (Fig, 11) Zone SqL-1 (spectra 26-23, 11,140 - ca, 10,400 B.P.) Pinus oontorta type, Abies, and Alnus pollen predominate i n t h i s zone, together with r e l a t i v e l y high amounts of Pioea and Artemisia. Correspondence with zone PL-1 i s suggested by s i m i l a r i t i e s of the assemblages. The age f o r the upper l i m i t 6 0 . of the zone was obtained by extrapolating from the two subtending radiocarbon dates, assuming a constant sedimentation rate of .040 cm/yr. Zone SqL-2 (spectrum 22 to Mazama ash, ca. 10,400 - 6,600 B.P.) Correlation of t h i s zone with PL-2 i s obvious, e s p e c i a l l y i n the peak percentages of Gramineae, Artemisia, Pteridium, and S e l a g i n e l l a wallaoei type. Declining Pinus oontorta type, low Tsuga heterophylla, r i s i n g Betula percentages and the appearance of abundant Pseudotsuga pollen at the lower boundary also correspond to PL-2. Low amounts of Thuja-Chamaecyparis type at Squeah L, contrast the r e l a t i v e abundance of cupressaceous pollen at Pinecrest L. The higher percentages of cupressaceous pollen i n Pinecrest L. are probably exaggerated, however, due to large amounts of hyaline plant debris i n the basal sediments. Some of t h i s material c l o s e l y resembles the thin-walled pollen grains of the cedars, making accurate i d e n t i f i c a t i o n d i f f i c u l t . Increased a c e t o l y s i s treatment of Squeah L. samples removed most of t h i s debris, suggesting that the l i m i t e d d i s t r i b u t i o n of Thuja-Chamaecyparis type below the ash at Squeah L. r e f l e c t s more accurately the regional vegetation picture. The d i v e r s i t y and abundance of non-arboreal pollen i s PL-2 i s high, suggesting that forest cover was les s complete than at present in the Yale area. Pollen of several herbs and shrubs not found at Pinecrest L, are present i n t h i s zone. 61. Rhamnaceae pollen i s f a i r l y abundant and probably includes both Rhamnu8 purshiana (Cascara) and Ceanothus sp„ P h i l a - delphus (mock orange) type pollen was also found, along with Shepherdia canadensis, Symphoricarpos, Epilobium, and S a g i t t a r i a , Although S a g i t t a r i a (Indian potato) no longer grows at Squeah L., i t was d e f i n i t e l y present i n pre-Mazama time. DISCUSSION AND CONCLUSIONS The pollen zonation patterns from Pinecrest and Squeah lakes suggest the following reconstruction of p o s t g l a c i a l vegetation succession i n the Yale area. Following the retreat of g l a c i e r s from the study s i t e s , sandy and gravelly meltwater clays containing l i t t l e organic material were deposited in the lake basins. As plants invaded the deglaciated t e r r a i n around the lakes, pollen and spores as well as other t e r r e s t r i a l organic remains s e t t l e d i n the lake basins, together with limnic f l o r a l and faunal remains. Radiocarbon-dateable clay-gyttjas were formed as organic matter increased i n the sediments, eventually grading into highly organic fine-grained gyttjas which are s t i l l being formed today. The pioneer vegetation recorded at the bases of the pollen diagrams consists of abundant Pinus oontorta ^nd Alnus, with l e s s e r amounts of Abies, Pioea, S a l i x , Artemisia, and various ferns (Polypodium, Adiantum, Cryptogramma and others). Climatic patterns f o r most pollen diagrams are d i f f i c u l t to assess, inasmuch as macroclimatic e f f e c t s are often complicated by natural succession patterns of vegetation and s o i l development. It must also be remembered that pollen analysis primarily provides data on the composition of past vegetation, and that explanations to account f o r these vegetation types are necessarily speculative. By analogy, however, the early p o s t g l a c i a l vegetation seems to indicate cool and moist conditions, with Artemisia occupying open, well- drained areas. At the t r a n s i t i o n s to zones PL-2 and SqL-2 about 10,400 years ago, several well-defined changes take place. Pseudotsuga pollen increases sharply, whereas Pinus oontorta type decreases, suggesting a natural replacement of pine by the more shade-tolerant Douglas-fir. At the same time, pollen of gras- ses and spores of Pteridium and Selaginella wallaoei type begin to increase, reaching peak l e v e l s around 8,620 ± 135 B.P. Together with Artemisia, Chenopodiaceae, T u b u l i f l o r a e , Rhamnaceae (Ceanothus) and Philadelphus type pollen, t h i s assemblage indicates d r i e r and warmer conditions than pre- v a i l e d during e a r l i e r p o s t g l a c i a l times. The previous suggestion that water l e v e l s may have been lower at Pinecrest L. i n pre-Mazama time also t i e s i n with the suggestion of d r i e r c l i m a t i c conditions. R e l a t i v e l y abundant Cyperaceae pollen i n PL-2 suggests that semi-aquatic sedges may have occupied shoreline areas exposed by a lowered lake l e v e l . High Alnus p o l l e n , together with increasing Tsuga hetero- phylla, Abies and Betula since about 8,500 B.P., suggest a return to somewhat wetter conditions. The s u b f o s s i l mosses recovered from Squeah L. spectra 3 and 7 also support t h i s view, since a l l species can presently be found in the Yale area. Again, i t i s d i f f i c u l t to separate the natural rate of d i s p e r s a l of c e r t a i n genera (Betula, Corylus) from "migration" induced by c l i m a t i c change. The i n t e r v a l from the Mt, Mazama ash to the present i s represented by zone PL-3, B a s i c a l l y , there i s a continuation of the trend toward wetter conditions observed i n the upper part of zone PL-2, Tsuga heterophylla, Thuj a-Chamaeeyparis type, and Pinus montioola type reach t h e i r highest l e v e l s here. Pollen of Acer macvophyllum and Acer oivcinatum are often present, whereas the more continental-montane Acer glabvum i s absent from most samples above the ash. It i s c l e a r from the foregoing that t h i s study does not support a c l a s s i c a l xerothermic i n t e r v a l between 7,50 0 and 3,500 B.P, (Hansen 1955) or a Hypsithermal between 8,500 and 3,000 B.P, (Heusser 1960), Instead, i t i s apparent that f a i r l y warm and/or dry conditions prevailed during deposition of the lower parts of zones PL-2 and SqL-2, with a trend toward wetter conditions already apparent before the Mazama ash layer was deposited at 6,60 0 B.P, It i s s i g n i f i c a n t that t h i s compares c l o s e l y with evidence f o r a warm i n t e r v a l i n northwestern Alaska between 10,000 B.P. and 8,300 B.P., during which forest biota expanded f a r beyond t h e i r present l i m i t s (McCulloch and Hopkins 1966). This study, although providing a s o l i d basis f o r the in t e r p r e t a t i o n of p o s t g l a c i a l events i n the Lower Fraser Canyon region, indicates that a d d i t i o n a l research i s necessary to determine i f the palynological patterns established for the Yale area can be correlated over wider areas. Also, the cl i m a t i c i n t e r p r e t a t i o n s , although based on sound evidence, must be considered tent a t i v e , as the p o s s i b i l i t y exists that the palynological i n d i c a t i o n s of a warm and/or dry i n t e r v a l may a c t u a l l y r e f l e c t a stage i n a longterm natural succession. It i s conceivable that due to the mountainous t e r r a i n of the Yale area, the development of a closed forest was hindered in many l o c a l i t i e s . Shallow, rocky s o i l s together with unstable mountain slopes may have promoted the continual presence of heliophytes such as Pteridium, grasses, and Selaginella, which i n more mesic and stable s i t e s would have been quickly supplanted by forest vegetation. In addition, as indicated by charcoal fragments in the de t r i t u s zones from Squeah L., f i r e s have also played a r o l e i n the h i s t o r y of the Yale area, perhaps promoting the presence of non- arboreal vegetation at many s i t e s . Further work, e s p e c i a l l y in the d r i e r parts of the Fraser Canyon above Boston Bar, i s necessary to es t a b l i s h well-dated pollen sequences f o r comparison with the Yale area. Only by comparing s i t e s i n d i f f e r e n t physiographic settings can we s a t i s f a c t o r i l y resolve the problems of separating c l i m a t i c changes from natural successional processes c o n t r o l l e d by l o c a l factors of topography, s o i l , and f i r e . 65. THESIS SUMMARY A general summary of pollen zonations established during t h i s study of the Fraser Lowland region i s given i n Table VI, In conjunction with the detailed pollen diagram from each lake, the following conclusions can be drawn: 1_. The oldest p o l l i n i f e r o u s p o s t g l a c i a l deposits so f a r described from south-western B r i t i s h Columbia are presented in t h i s study. A marine clay with abundant lodgepole pine pollen extends the record of t e r r e s t r i a l vegetation i n the Fraser Lowland back to 12,69 0 B.P, Recorded in the basal sediment from Marion L, i s a previously undescribed pollen assemblage consisting of lodgepole pine, willow and Shepherdia, This assemblage i s older than 12,350 B.P,, extending the record of p o s t g l a c i a l vegetation beyond the ca, 11,500 B.P. l e v e l established by Heusser (1960 Table 6) fo r south-coastal B r i t i s h Columbia, Five pollen zones are described from Marion L. and three from Surprise and Pinecrest lakes. Two zones were recognized from the pre-Mazama sediment at Squeah L. 3_. A l l four lakes i n t h i s study were accumulating p o l l i n i - ferous sediments by 11,000 B.P. Lodgepole pine, spruce, f i r and alder predominated i n the pioneer vegetation at a l l s i t e s , with mountain hemlock reaching r e l a t i v e l y high l e v e l s only in the U.B.C. Forest s i t e s . 4. A synchronous vegetation change i s recorded i n a l l cores 66. U.B.C. RESEARCH FOREST HOPE - YALE AREA YEARS B.P. I INE CLAY LAKE SURPRISE LAKE PINECREST LAKE SQUEAH LAKE 1,000 2,000 - 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 Mazama ash 5 Alder increase Redcedar Cedar 3 Western Hemlock Western White Pine 3 Ferns Pteridi um Douglas-fir Cedar 3 Western Hemlock W. White Pine Douglas-fir Birch Grami neae Selaginella Artemisia Pteridium Douglas-fir Lodgepole Pine, Spruce, 1_ F i r , Mountain Henlock 1 Lodgepole P i n e J ,4 • T Lodgepole Pine Shepherdia WI 1 Ion 1 Lodgepole Pine, Spruce, Fir, Artemisia Table VI, Pollen zone cor r e l a t i o n s i n the Fraser Lowland area. Horizontal s o l i d l i n e s i n dicate radiocarbon- dated boundaries; dotted l i n e s are extrapolations from radiocarbon dates. Plants l i s t e d are assemb- lage indicators f o r each zone (see pollen diagrams f o r d e t a i l s ) , around 10,500 to 10,400 B.P., when Douglas-fir pollen began to increase markedly, probably i n response to a c l i m a t i c amelioration. _5. Peak percentages of grass, bracken f e r n , Artemisia, and S e l a g i n e l l a i n the Yale-area pollen assemblages suggest a f a i r l y warm and dry period beginning about 10,000 B.P. and terminating before the Mazama a s h f a l l at 6,600 B.P. The U.B.C. Forest diagrams show only a f a i n t trace of such a xerothermic period, and s u b f o s s i l mosses indicate that a t y p i c a l l y wet coastal climate has prevailed since about 10,500. B.P, It i s possible that i n d i c a t i o n s of warming and drying merely r e f l e c t a stage i n a natural long-term succession controlled by s o i l development, topography and f i r e s . 6_. The presence of a Hypsithermal i n t e r v a l between 8,50 0 and 3,000 B.P, i s not c l e a r l y apparent i n the pollen diagrams. Although the l a t e r part of the warm-dry i n t e r v a l recognized in t h i s study overlaps the Hypsithermal as defined by Heusser, the climate was wet during most of c l a s s i c a l Hypsithermal time, 7_. This study demonstrates that although red cedar was present in the U.B.C. Forest about 10,000 B.P,, i t has increased i n importance only during post-Mazama time. Cedar percentages (red and perhaps yellow cedar) are also highest above the ash layer i n the Yale-area lakes, £. In contrast to p r i o r studies, western white pine was found to be unimportant as an early p o s t g l a c i a l invader, 68. being most strongly represented above the Mazama ash i n a l l areas. At Surprise L., white pine pollen i s v i r t u a l l y absent before 6,600 B.P, 9_. Although pollen of b i r c h i s r e l a t i v e l y rare at Marion and Surprise lakes, i t i s abundantly represented at Pinecrest and Squeah lakes. S i m i l a r l y , Douglas-fir pollen i s much more strongly represented above the ash i n the Yale area than i n the U.B.C, Forest. Since both bi r c h and Douglas-fir are generally more abundant in the I n t e r i o r Douglas-fir Zone than i n the coastal zones, t h e i r palynological patterns suggest that the presently t r a n s i t i o n a l biogeoclimatic condi- tions i n the Yale area have persisted during most of post- g l a c i a l time, 10. The presence of abundant pollen of alder and other succes- sional species throughout p o s t g l a c i a l time i n the Fraser Lowland indicates that disturbances have always influenced the vegetation of t h i s area. 11, Evidence of major vegetation changes during the l a s t few centuries i s r e s t r i c t e d to Marion L, The presence of charcoal and peak percentages of alder, grasses, and other successional species indicates that f i r e and probably logging have played an important r o l e in these recent changes. Both factors have c e r t a i n l y contributed to the s t r i k i n g pollen decreases of commercially important species such as western hemlock, Douglas- f i r and red cedar i n the surface sediments. This study has incorporated a va r i e t y of paleoecological techniques to e s t a b l i s h a well-dated p o s t g l a c i a l h i s t o r y of forest vegetation i n the Fraser Lowland region. It i s hoped that my r e s u l t s w i l l stimulate further researches into the paleoecology of B r i t i s h Columbia, because to f u l l y under- stand and manage our present environment, we must recognize the successional, paleoclimatic, and biogeographic changes that have moulded i t s present form. 70. BIBLIOGRAPHY Armstrong, J.E. 19 57. S u r f i c i a l geology of New Westminister map-area, B r i t i s h Columbia. GSC Paper 57-5, Borden, C.E, 196 5. Radiocarbon and geological dating of the lower Fraser Canyon archaeological sequence. Proceed. 6th Internat, Conf. Radiocarbon and Tritium Dating, Pullman, Wash.: 165-178. i 1968. A Late Pleistocene pebble t o o l industry of south-western B r i t i s h Columbia. In: Early man i n western North America. C. Irwin-Williams (Ed.)t E. New Mex. Univ., Contrib. Anthropol., 1(4): 55-69. Crum, H., W.C. Steere, and L.E. Anderson 1965. A l i s t of mosses of North America. Bryologist 68: 377-432. Cushing, E.J, 1967. Late-Wisconsin pollen stratigraphy and the g l a c i a l sequence i n Minnesota. In Quaternary Paleoecology, ed. by E.J, Cushing and H.E, Wright J r . Yale U. Press: 59-88. Davis, M.B. 1968, Pollen grains i n lake sediments: redeposi- t i o n caused by seasonal water c i r c u l a t i o n . Science 162: 796-798. Davis, M.B. and E.S. Deevey J r . 1964. Pollen accumulation rates: estimates from l a t e - g l a c i a l sediment at Rogers Lake. Science 145: 1293-1295. Deevey, E.S. and R.F. F l i n t 1957. P o s t g l a c i a l Hypsithermal i n t e r v a l . Science 125: 182-184. Easterbrook, D.J. 1971, Palynology and stratigraphy of E a r l y - Wisconsin to recent sediments i n the Puget Lowland, Washing- ton. GSA abstracts 1971, Vol. 3(7): 551-552. E f f o r d , I.E. 1967. Temporal and s p a t i a l differences in phyto- plankton productivity i n Marion Lake, B r i t i s h Columbia. J . F i s h . Res. Bd. Canada 24: 2283-2307. E i s , S. 1962. S t a t i s t i c a l analysis of several methods f o r estimation of forest habitats and tree growth near Vancouver, B.C., U.B.C. Forestry B u l l e t i n 4. Erdtman, G., G. Berglund, and J, Praglowski 1961, An introduc- t i o n to a Scandinavian pollen f l o r a , Almqvist S Wiksells, Uppsala. Erdtman, G., J , Praglowski, and S. Nilsson 1963. An introduc- t i o n to a Scandinavian pollen f l o r a I I . Almqvist S Wiksells, Uppsala. 71. Faegri, K. and J . Iversen 1964. Textbook of pollen analysis, 2nd ed. Hafner, N.Y, Fulton, R.J. 1971, Radiocarbon chronology of southern B r i t i s h Columbia. GSC Paper 71-37. Hansen, H.P, 1940, Paleoecology of two peat bogs in south- western B r i t i s h Columbia. Am. J . Bot. 27: 144-149, 1947a, P o s t g l a c i a l forest s u c c e s s i o n , climate, and chronology i n the P a c i f i c Northwest, Trans* Am. P h i l . S o c , n.s. 37, part 1. 194 7b, Climate versus f i r e and s o i l as factors in p o s t g l a c i a l forest succession i n the Puget Lowland of Washington. Am. J , S c i . 245: 265-286, 19 50. Pollen analysis of three bogs on Vancouver Island, Canada. J . Ecol, 38: 270-276, m m m m_ m_ m m m m m^_ m m_ t^ 19 55. P o s t g l a c i a l forest i n south central and central B r i t i s h Columbia. Am. J . S c i , 253: 640-658, Hansen, K. 1959. Sediments from Danish lakes. J . of Sed. P e t r o l . 29: 38-46. Helmich, D.E, 1963. Pollen morphology i n the maples (Aaer L,), Papers of the Michigan Acad, of S c i , , A r t s , and Letters XLVIII: 151-164. Heusser, C.J, 1960, Late-Pleistocene environments of North P a c i f i c North America. Am. Geog. Soc. s p e c i a l publ. 35. 1964, Palynology of four bog sections from the western Olympic Peninsula, Washington. E c o l . 45: 23-4 0. Hitchcock, C.L.j'A, Cronquist, M, Owenby, and J.W. Thompson 1955-1969. Vascular plants of the P a c i f i c Northwest. 5 vols. Univ. of Washington Press, Seattle. Holland, S.S, 1964, Landforms of B r i t i s h Columbia: a physio- graphic o u t l i n e , B.C. Dept. of Mines and P e t r o l . Resources. B u l l . 48. Hosie, R,C. 1969. Native trees of Canada. 7th ed. Queen's Prin t e r f o r Canada, Ottawa. Isaac, L,A. 1940. Vegetative succession following logging in the Douglas-fir region with s p e c i a l reference to f i r e . J . of Forestry 38: 716-721. 72. Janssen, C.R. 1967, Stevens Pond: a p o s t g l a c i a l pollen diagram from a small Typha swamp i n northwestern Minnesota, i n t e r - preted from pollen indicators and surface samples. Ecol. Monographs 37: 14 5-17 2. ' 1968. Myrtle Lake: a l a t e - and p o s t - g l a c i a l pollen diagram from northern Minnesota. Can. J . Bot. 46: 1397-1408. Klinka, K. 1973, Personal Communication. Krajina, V.J. 1969, Ecology of forest trees i n B r i t i s h Colum- bi a . Ecology of western North America, Vol. 2(1). Dept. of Botany, Univ. of B r i t i s h Columbia, Lacate, D.S. 196 5 Forest land c l a s s i f i c a t i o n f o r the Univer- s i t y of B r i t i s h Columbia Research Forest, Dept. of Forestry Publ. no. 1107, Lowdon, J.A. and W, Blake J r . 1968. Geological Survey of Canada Radiocarbon dates VII. Radiocarbon 10: 207-245. McAndrews, J.H. 1966. P o s t g l a c i a l h i s t o r y of p r a i r i e , savanna, and forest i n northwestern Minnesota, Mem. Torrey Bot. Club 22: 1-68. McCulloch, D, and D.M, Hopkins 1966. Evidence for an Early Recent warm i n t e r v a l i n Northwestern Alaska. Geol. Soc. of Am. B u l l . 77: 1089-1108. McMinn, R.G. 1951. The vegetation of a burn near Blaney Lake, B r i t i s h Columbia. Ecol, 32: 135-140, Mack, R.N, 1971, Pollen s i z e v a r i a t i o n i n some western North American pines as r e l a t e d to f o s s i l pollen i d e n t i f i c a t i o n . Northwest S c i . 45: 257-269. Mathewes, R.W., C.E. Borden, and G.E, Rouse 1972. New radio- carbon dates from the Yale area of the Lower Fraser River Canyon, B r i t i s h Columbia. Can. J . Earth S c i . 9: 10 55-1057. Mathews, W.H. 1951. H i s t o r i c and p r e h i s t o r i c f l u c t u a t i o n s of alpine g l a c i e r s i n the Mount G a r i b a l d i map-area, south- western B r i t i s h Columbia. J , of Geology 59: 357-380. Mathews, W.H., J.G. Fyles, and H.W. Nasmith 1970. P o s t g l a c i a l c r u s t a l movements i n southwestern B r i t i s h Columbia and adjacent Washington State. Can. J . Earth S c i . 7: 690-702. Mott, R.J. 1966. Quaternary palynological sampling techniques of the Geological Survey of Canada. GSC Paper 66-41. 73. Powers, H,A, and R.E. Wilcox 1964. Volcanic ash from Mount Mazama (Crater Lake) and from G l a c i e r Peak. Science 144: 1334-13336. Rigg, G.B. and H.R. Gould 19 57. Age of Glacier Peak eruption and chronology of p o s t - g l a c i a l peat deposits i n Washington and surrounding areas. Am.J. S c i . 255: 341-363. Ri t c h i e , J.C. 1969, Absolute pollen frequencies and Carbon-14 age of a section of Holocene lake sediment from the Riding Mountain area of Manitoba. Can. J . Bot, 47: 1345-1349. Schmidt, R.L, 19 57, The s i l v i c s and plant geography of the genus Abies i n the coastal forest of B r i t i s h Columbia, Dept. of Lands and Forest, B.C. Forest Service, Tech, Publ, T. 46. Schofield, W.B, 1968. A s e l e c t i v e l y annotated l i s t of B r i t i s h Columbia mosses. Syesis 1: 163-175, . 1969, Some common mosses of B r i t i s h Columbia, B.C. P r o v i n c i a l Museum handbook no. 28. A, Sutton, Queen's Pr i n t e r of B.C. Sears, P.B. 1935. G l a c i a l and p o s t g l a c i a l vegetation. Bot. Revue 1: 37-51. 1942. Xerothermic theory. Bot. Revue 8: 708-736. Stewart, W.D.P. 1967. Nitrogen-fixing plants. Science 158: 1426-1432. Terasmae, J . and J.G. Fyles 19 59. Paleobotanical study of l a t e - g l a c i a l deposits from Vancouver Island, B r i t i s h Colum- bia . Can. J . Bot. 37: 815-817, Ting, W.S. 1965, The saccate pollen grains of Pinaceae mainly of C a l i f o r n i a . Grana Palynologica 6: 270-289, Traverse, A. and R.N, Ginsburg 1966. Palynology of the surface sediments of Great Bahama Bank, as rel a t e d to water movement and sedimentation. Marine Geol. 4: 417-459. Wright, H.E. J r . 1967, A square-rod piston sampler f o r lake sediments. J . of Sed, P e t r o l . 37; 97 5-97 6, APPENDIX L i s t of plant species names used i n the text or on the pollen diagrams. A. Alphabetical l i s t o f hryo'phytes. Names and a u t h o r i t i e s follow Crum et al (196 5) except for Isotheoium which follows Schofield (1968), A n t i t r i o h i a ouvtipendula (Hedw.) Brid, Bartramia pomiformis Hedw. Dendroalsia abietina (Hook.) B r i t t . Diohodontium pelluaidum (Hedw.) Schimp. Dioranella p a l u s t r i s (Dicks.) Crundw. ex E, Warb, Diaranum fusoesoens Turn, Eurhynohium praelongum (Hedw.) B.S.G. Heterooladium maaounii Best Homalotheoium fulgescens (Mitt, ex C. Mull.) Lawto Hylooomium splendens (Hedw.) B.S.G, Hypnum o i r o i n a l e Hook, Hypnum subimponens Lesq, Isotheoium stolonifevum (Hook.) Br i d . Leuoolepis menziesii (Hook.) Steere ex L. Koch Mnium insigne Mitt, Neokera douglasii Hook, Porotriohum b i g e l o v i i (Sull.) Kindb, Rhytidiadelphus loreus (Hedw.) Warnst. Soleropodium obtusifolium (Hook, ex Drumm.) Kindb, ex Mac, S Sphagnum magellanioum Brid, Kindb, Sphagnum palustre L, Sphagnum papillosum Lindb. Sphagnum subseoundum Nees ex Sturm B, Vascular plants by f a m i l i e s . (Hitchcock et al 1955-1969). DIVISION LYCOPODIOPHYTA LYCOPODIACEAE Lyaopodium annotinum L, Lyoopodium olavatum L. Lyaopodium indundatum L. Lyoopodium selago L, SELAGINELLACEAE S e l a g i n e l l a wallaoei Hieron, 75. DIVISION POLYPODIOPHYTA POLYPODIACEAE *Polypodium vulgare L. Pteridium aquilinum (L.) Kuhn DIVISION PINOPHYTA CUPRESSACEAE Chamaeoyparis nootkatensis (D. Don) Spach Thuja p l i a a t a Donn PINACEAE Abies amabilis (Dougl.) Forbes Abies grandis (Dougl.) L i n d l . Piaea sitahensis (Bong.) Carr. Pinus a l b i o a u l i s Engelm. Pinus oontorta Dougl. ex Loud, Pinus montioola Dougl, ex D. Don Pinus ponderosa Dougl, ex Loud, Pseudotsuga menziesii (Mirb.) Franco Tsuga heterophylla (Raf.) Sarg. Tsuga mertensiana (Bong.) Carr, DIVISION MAGNOLIOPHYTA TYPHACEAE Typha l a t i f o l i a L, ARACEAE Lysiohitum amerioanum Hulten S St, John SALICACEAE Populus triohoaarpa T, 8 G, BETULACEAE Ainus inoana (L.) Moench Ainus rubra Bong, Betula papyrifera Marsh, Spores treated as Polypodium vulgare type on the pollen diagrams were proabably derived from a complex of species now treated as Polypodium glyoyrrhiza D.C. Eat., P. hesperium Maxon, and P. soouleri Hook, 5 Grev, FAGACEAE Queraus garryana Dougl, CHENOPODIACEAE . Sarcobatus vermiculatus (Hook.) Torr. NYMPHAEACEAE Nuphar polysepalum Engelm, ROSACEAE Pyrus fusca Raf, Spiraea douglasii Hook. CELASTRACEAE Pachistima myrsinites (Pursh) Raf. ACERACEAE Acer circinatum Pursh Acer glabrum Torr, Acer macrophyllum Pursh RHAMNACEAE Ceanothus velutinus Dougl, Rhamnus purshiana DC, ELAEAGNACEAE Shepherdia canadensis (L.) Nutt. ARAL I ACE AE Oplopanax horridum (Smith) Miq, CORNACEAE Cornus s t o l o n i f e r a (Michx,) OLEACEAE Fraxinus l a t i f o l i a Benth, MENYANTHACEAE Uenyanthes t r i f o l i a t a L, PLANTAGINACEAE Plantago lanoeola CAPRIFOLIACEAE Linnaea borealis  G Y T T J A DETRITUS ZONE % f g l | 10 X EXAGGERAT ION OF % E A C H DIVISION = 5 % PINECREST LAKE, ROLF M A T H E W E S Fig. 10 BRITISH COLUMBIA Z O N E PL-3 MAZAMA 6,600- ASH Z O N E P L - 2 4.7 11,000 ±170 Z O N E PL-1 Each Division = 5 % ICLAY-GYTTJA jCLAY ] % 0 ° j J G R A V E L L Y CLAY • 10 X EXAGGERATION OF % SQUEAH LAKE, B.C Fig. 11 Mazama ash ^ 6 , 6 0 0 B.P. ZONE SqL-2 8,620 * 135 • ZONE SqL-1 11,140* 260 clay j clay-gyttja

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