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Pollen in the salmon river system, Ontario, Canada
Review of Palaeobotany and Palynology, 31 (198011981): 311--334 Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands
311
POLLEN IN THE SALMON RIVER SYSTEM, ONTARIO, CANADA
R.N. STARLING AND A. CROWDER Centre for Northern Studies, Wolcott, Vt. (U.S.A.) Department of Biology, Queen's University, Kingston, Ont. (Canada) (Received January 24, 1979; revised version accepted May 9, 1980) ABSTRACT Starling, R.N. and Crowder, A., 1981. Pollen in the Salmon River System, Ontario, Canada. Rev. Palaeobot. Palynol., 31: 311--334. The Salmon River in eastern Ontario drains approximately 1000 km 2, and flows most rapidly during the spring; a velocity profile was measured and the zone of maximal pollen transport was determined. Pollen in the water was sampled throughout the year near the river-mouth, and at the outflow and inflow of one lake within the watershed. The phenology of pollen of trees, grasses, Ambrosia and aquatic plants was studied and compared to the patterns found in aerial samplers; re-suspension phases and peaks were similar in both transporting media. R values for the ten most important arboreal taxa were calculated and were compared with those calculated from air-borne pollen. INTRODUCTION S t u d y o f t h e aerial d y n a m i c s o f p o l l e n is assisting in t h e u n d e r s t a n d i n g o f f a c t o r s w h i c h a f f e c t t h e r e p r e s e n t a t i v i t y o f m o d e r n pollen s a m p l e s ; c o n t e m p o r a r y s p e c t r a are t h e n b e i n g used as a n a l o g u e s o f p a s t c o n d i t i o n s in o r d e r t o increase t h e resolving p o w e r o f t h e t e c h n i q u e o f pollen-analysis. T h e m a i n s o u r c e s o f sub-fossil p o l l e n f r o m t h e Q u a t e r n a r y p e r i o d are sedim e n t s in b o g s a n d lakes, b o t h o f w h i c h receive i n p u t s n o t o n l y f r o m t h e air b u t f r o m r u n n i n g w a t e r , d u r i n g at least s o m e phases o f t h e i r d e v e l o p m e n t . T h e i m p o r t a n c e o f fluvially t r a n s p o r t e d pollen t o deltas, shelf s e d i m e n t s a n d valley b o g s has b e e n stressed b y Krassilov (1975). A l t h o u g h various a u t h o r s have d e s c r i b e d p o l l e n s p e c t r a o b t a i n e d f r o m r u n n i n g w a t e r t h e r e h a v e b e e n no r e p o r t s specifically dealing w i t h t h e c o r r e s p o n d e n c e b e t w e e n pollen in t h e air a n d t h a t in t h e w a t e r t h r o u g h o u t o n e y e a r . Pollen e n t e r s a river e i t h e r b y landing o n t h e s u r f a c e o r b y b e i n g w a s h e d o u t f r o m a lake. R u n - o f f a n d t r a n s p o r t o v e r l a n d or b y t h r o u g h f l o w h a v e b e e n suggested as s e c o n d a r y m e c h a n i s m s , b u t w i t h o u t s u b s t a n t i a t i o n (Peck, 1 9 7 3 ; C r o w d e r a n d C u d d y , 1 9 7 3 ; Krassilov, 1975). O n c e t h e pollen is t r a p p e d b y t h e w a t e r s u r f a c e it b e c o m e s w e t t e d (Brush a n d Brush, 1 9 7 2 ) and i n c o r p o r a t e d i n t o t h e s e d i m e n t l o a d , acting like fine silt (Muller, 1 9 5 9 ; S t a n l e y , 1 9 6 9 ; P e c k , 1 9 7 3 ; M c A t e e , 1977). A c c o r d i n g t o P e r m y a k o v ( 1 9 6 4 , q u o t e d in Krassilov, 1 9 7 5 ) , p o l l e n grains are s o r t e d d u r i n g t r a n s p o r t a n d 0034-6667/81/0000--0000/$ 02.50 O 1981 Elsevier Scientific Publishing Company
312 redistributed with the velocity profile in relation to their settling velocities. Grains may also deteriorate in the water (Sangster and Dale, 1961, 1964; Havinga, 1971) or suffer corrosion by inorganic sediment (Cushing, 1964; McAtee, 1977). Their susceptibility to deterioration depends on the structure of the exine (Brooks and Shaw, 1971; J.H. McAndrews, pers~ comm.). Deposition occurs when the velocity of flow decreases, usually as the result of the stream entering a body of standing water or through the effect of vegetation in the channel; the transport of pollen within lakes is well documented (Davis, 1967; Davis et al., 1969; Davis and Brubaker, 1973; Bonny, 1978). Erdtman (1943) called for investigations into the nature of the pollen load of rivers. Peck (1973) and Crowder and Cuddy (1973) have published details of the pollen in a stream and small river system and have compared it to the local vegetation, Federova (1952) described pollen spectra from the Volga, and Groot (1966) worked on samples from the Delaware. This paper describes the pollen transport by a river which is approximately 140 km long and drains an area of almost 1000 km:. The forest cover of the drainage basin was surveyed and analysed, and the aerial pollen was trapped at five sites along the stream course. Differences in the pollen spectra from the inflow and outflow of a lake within the network were investigated as was the response time of the river transport system. The Salmon River flows into the Bay of QuintS, a part of Lake Ontario, in southeastern Ontario (Fig.l). In order to compare this river system with others, drainage density (Da) and valley density (Dr) can be used; drainage density = total length of all streams/basin area, and valley density = total length of all valleys/basin area (Gregory and Walling, 1973). Drainage density for the whole basin = 0.72 k m / k m 2, and for the parts underlain by Ordovician limestone and the Precambrian shield, 0.41 k m / k m 2 and 0.64 k m / k m 2, respectively. These values are relatively low (Strahler, 1957), but are comparable with those for a stream in New Jersey (Horton, 1945) and a river in southwest England (Gregory, 1966). In the Salmon River basin the valley density is higher than the drainage density, which indicates that the present system was developed during a period of greater flow (Horton, 1945; Starling, 1978). Relief in the area is low and in some areas the divide with an adjacent river system is transgressed by swamps. Seven lakes, with a total surface area of 8.75 km 2, occur within the network. The most extensive is Beaver Lake, which is also the southernmost. The specimen hydrograph for 1976 from the Milltown Station (Fig.2) shows a peak of flooding in spring due to snow-melt, followed by falling water levels in the summer and a second rise in the fall which lasted until the river froze. Freezing usually occurs in mid-December. Despite the number of lakes in the system, local dams interfere with the summer flow and sections of the stream are reduced to pools during droughts, such as that of 1977. In winter segments with super-critical flow remain ice-free. The annual flow regime is similar to that of Wilton Creek (Crowder and Cuddy, 1973) and is typical of eastern Ontario (Gardner, 1976).
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Fig.1. The S a l m o n River V a l l e y . T h e w a t e r s h e d is s h o w n in black in the inset map, and its limits are s h o w n b y the d o t t e d line o n the large map. Fluvial samples were taken at M i l l t o w n and s o u t h o f Fisher Creek, at W y m a n ' s Road. Aerial pollen samplers were situated at Sites 1--5.
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Fig.2. Seasonal flow of the Salmon River in 1976. The bedrock geology of the area is structurally complex, with an anticline o f the Kaladar--Dalhousie synclinorium trending northeast--southwest across the n o r the r n section of the watershed (Bostock, 1970). The cont act between Palaeozoic limestone and Precambrian Shield rock occurs in the vicinity o f Beaver Lake, but for much of its length the cont act is masked by deposits associated with the D u m m e r Moraine. Superimposed on the diverse bedr oc k types are a complex series of surficial deposits dating from the retreat of the Wisconsin ice which vary from fine clays to coarse gravels and boulders. The associated soil-types vary f r o m dry sands to alluvium and organic swamp deposits. The varied slopes and soils lead to a wide range of microclimates {Taylor, 1977). THE VEGETATION OF THE SALMON RIVER BASIN For the purpose of this study at t ent i on has been concentrated on trees since th ey co n tri but e most of the information in a pollen spectrum (Ritchie and Lichti-Federovich, 1963). A survey of areas of closed-crown forest was made from 1974 to 1976, using the random-pairs m e t h o d (Cottam and Curtis, 1956), within a grid of 204 squares (quadrats) each 2.5 X 2.5 km. The sample comprised over 18,000 trees {Starling, 1978). Initial analyses of the entire data set showed t hat only ten taxa had an importance value greater than 10, so these taxa were given detailed consideration. The arboreal species, whether t h e y are regarded individually or in association, do n o t form simple spatial patterns primarily because o f the diversity o f the landscape and land-use during the historical period. The Salmon Valley was first settled, near the Bay o f QuintS, in the late eighteenth cen tur y, and by the 1820's settlers moved inland and established sawmills at falls up the river. Intensive lumbering t o o k place from the 1850's
315
until a b o u t 1900; cleared land (on b o t h limestone and local outwash sands on the shield) then supported mixed subsistence farming (Starling, 1978). When applying results from the study of modern pollen spectra, either airborne or waterborne, allowance should be made for changes in the characteristics of flow of the transporting agents. The aerodynamics of an agricultural landscape are different from those of a continuously forested area; deforestation and fires also affect the r u n o f f and sediment load of streams (c.f. Warwick, 1977; Likens et al., 1970; Farrar et al., 1978). METHODS
Muller (1959) and Peck (1973) among others have suggested that pollen acts like fine silt in the suspended sediment load of rivers. In order to check this in the Salmon River, a velocity profile was determined for one section of the channel, 16 km upstream from the mouth. An Ott velocity meter (type C-31, with Nr lamda propeller) was used in suspension mode from Wyman's Road Bridge, near Milltown. The profile was determined, graphed and sampled for pollen content in its different zones (Starling, 1978). For regular sampling a site which remained ice-free was selected -- it is located 20 m upstream from the Environment Canada flow gauge at Milltown. At this point the flow is super-critical all year and the suspended sediment is evenly distributed throughout the profile (Graf, 1969). Crowder and C u d d y (1973) found that a sample volume of 35 1 was necessary for a "significant" pollen catch during periods of low concentrations. A 35-1 sample was also used in this study in which the river water was sampled fortnightly during the ice-free period, monthly during the winter from December 1974 to April 1976, and weekly from April to November 1976. The hydrograph for 1976 is illustrated in Fig.2. The inflow and outflow of Beaver Lake were sampled at similar intervals. The water samples were left standing for 24 h so that the bulk of the sample could be rapidly filtered. Filtration was vacuum-assisted through Millipore Membrane filters (type SP, 8 pm pore size). Modified Millipore vacuum flasks were used (Starling, 1978). The membrane filters were dispersed using 10% KOH or NaOH (by weight) and the samples processed by the m e t h o d of Faegri and Iversen (1964); full details are given in Starling (1978). The airborne pollen was sampled at 25 sites within the watershed using modified Tauber traps (Starling, 1978). Five sites adjacent to the stream were analysed (Crowder and Starling, 1980). The pollen was concentrated by vacuum filtration and processed in the same way as that from the river. The pollen samples were m o u n t e d in 10,000 c.s. silicone oil and counted. The concentration of grains in the river samples ranged from 370 to 21,000 grains/35 1 and from 30 to 8,000 g/cm 2/day in the air samples. A predetermined pollen sum was meaningless, therefore 5--25% of the total sample volume was counted -- exceptionally the contents of the entire samples were scored.
316 All data were entered into a PDti-11 V03 microprocessor, and interactive programmes were written to calculate all values and to display requested pollen graphs on a Tektronix 4662 plotter. RESULTS The results of the measurements of stream velocity and associated pollen load taken at Wyman's Road Bridge are shown in Fig.3. The pollen load was concentrated in the zone of maximum velocity but significant amounts of pollen were also carried in the bed-load (cf. McAtee, 1977). Because the experiment was run only once, any differences in the components of the spectra, dependent on their position in the profile, were not determined; however, it was apparent that the pollen in the bed-load was more corroded (abraded) than that nearer the surface, and the echinate pollen of some pollen of the Compositae had been worn down sufficiently to appear verrucate. Table I shows the percentages of airborne pollen of the ten dominant taxa in the forest canopy together with the respective values for relative dominance (R. Dora.) and importance percentage (I.P.). R values (sensu, Davis 1963) were calculated for each pollen type based on both relative dominance and importance percentage. The values show that Pinus, Betula, Quercus, Cupressineae and Fraxinus are over-represented. Under-represented taxa are Tilia, Acer, Populus, Ulmus and Ostrya/Carpinus. The R values are based on the total data set for the watershed; the effect of different areas on the R values was investigated (Crowder and Starling, 1980); using R relative values (Livingston, 1968; Davis, 1963) did not affect patterns of over- and under-representation. Table II lists the total number of grains counted in the fluvial samples. The Beaver Lake and the second Milltown columns are comparable for the period J u n e - 4 ) c t o b e r (days 152--301, 1976), while the first column for Milltown covers January to October {days 14--301, 1976). Most pollen was caught at the outflow of Beaver Lake, and there was an exceptionally high amount at Milltown on March 22, 1976 {20,736 grains/35 1). The sum of all pollen types throughout the sampling period in 1976 is shown in Fig.4, together with the totals from two of the aerial pollen sampling points in the valley. The peak pollen load coincides with the peak flow of the river (Fig.2) when it also carries its maximal load of inorganic sediment (E. Ongley, pers. comm., 1978). The maximum also coincides with that of pollen in the air, produced by early-flowering trees. Table II shows that arboreal pollen is the major component of the fluvial pollen sum, followed by the sum of the aquatic taxa (Typha, Myriophyllum, Potamogeton, Carex, Nuphar, Nymphaea), Ambrosia and the Gramineae. The flowering sequences detected by the air-pollen samplers were closely matched by the river samples, including the earlier flowering time at Milltown (see Table III). Figures 5--11 illustrate the trends in the concentration of grains for Betula, Quercus, Ambrosia, Gramineae, sum A.P., sum
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318 TABLE I R e l a t i o n s h i p o f aerially t r a n s p o r t e d pollen a n d v e g e t a t i o n , expressed as R values
Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus
% in v e g e t a t i o n
% in pollen
R value
IP
R. Dora.
(sum A.P.)
IP
R. D o m .
6.3 10.7 12.3 4.7 7.3 8.3 4.3 28.3 3.7 5.3
9 9 12 2 5 9 :l 28 -1 4
26.63 15.02 4.01 3,28 14.62 13.73 1.54 3.97 0.33 6.98
1.20 i.40 0.33 0.76 1.99 1.65 0.36 0.15 0,09 I 30
3.00 1.67 0.33 1.64 2.92 1.53 0.39 0.14 0.08 1.75
T h e R values are calculated o n a basis o f b o t h I m p o r t a n c e P e r c e n t a g e ( I m p o r t a n c e V a l u e / 3 ) a n d Relative D o m i n a n c e . T h e t e n t a x a w i t h greatest i m p o r t a n c e value in t h e w a t e r s h e d are used. T A B L E II T o t a l n u m b e r s o f grains s a m p l e d at t h e river s t a t i o n s d u r i n g 1 9 7 6 (days 1 -365 = J a n u a r y 1 - - D e c e m b e r 31) Pollen t y p e
Milltown 14--301 (day)
Beaver lake 1 5 2 - - 3 0 1 (day)
Inflow
Outflow
Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus
478238.0 66573.0 44174.0 43549.0 108686.0 129475.0 25853.0 29504.0 4092.0 37249.0
179321.0 21019.0 10302.0 25271.0 57974.0 64186.0 8210.0 8475.0 2172.0 15664.0
70038.0 4432.0 803.0 6012.0 18642.0 23392.0 2683.0 3412.0 3483.0 2119.0
344092.0 4437.0 725.0 15719.0 54405.0 36305.0 10003.0 9392.0 3862.0 4242.0
Ambrosia Gramineae
183719.0 1736.17.0
97209.0 140524.0
93399.0 62496.0
359908.0 267034.0
1060344.0 121481.0 355791.0 179771.0 243337.0 1960724.0
417281.0 34927.0 177940.0 142154.0 80167.0 852469.0
155533.0 ]3056.0 ]31750.0 62727.0 26945.0 390010.0
532171.0 36291.0 459826.0 267855.0 112629.0 1408770.0
Sum Sum Sum Sum Sum Sum
of of of of of of
a r b o r e a l pollen s h r u b pollen herb pollen the grasses' pollen t h e a q u a t i c s ' pollen all pollen t y p e s
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Fig.4. Total pollen in the river samples; x-axis = days 1--365; y-axis = log number of pollen grains. The solid line shows the Milltown samples, the dashed line is the Beaver Lake outflow and the dotted line is the Beaver Lake inflow. The upper graph allows a comparison of the phenology and numbers of grains from Air Trap Site 1 (dashes) and Site 3 (solid line).
320
T A B L E III D a t e s o f p e a k s in p o l l e n c o n c e n t r a t i o n f r o m aerial a n d fluvial s a m p l e s (Sites ! -5 are aerial s a m p l e r s s h o w n o n Fig. 1; M = M i l l t o w n , I a n d O = Beaver L a k e i n f l o w a n d o u t f l o w ; n u m b e r s = d a y s i n t o t h e year, d a y 1 = Jan. 1, 1 9 7 6 ) Pollen T y p e
Site
River
I
2
3
4
Pinus
171
191
191
204
Cupressineae
129
130 177
177
Populus
129
177
Ostrya/Carpinus
141 171
Betula
M
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0
42 77
$2 ! 76
168 196
16] 182 210 273
191 316
14
t54 288
154
154
9
156
9
82 154 176
154
218
156
156
191
28
~2 154
154 203
168 182 210
141
156
156
191
128
82 154 196
154 196
154 168 210 273
Quercus
141
156
156
191
128
g2 154 288
154 168
154 168 210 28O
Ulmus
129
142
142
156
111
~2 189
196
196 273
Acer
141
167
142
191
128
50 140 t76
168 196
154 168 210
Til&
191
205
v
219
204
161
196
203
Fraxinus
141
177
156
191
128
82 154
168
168 189
154 168 196 267
161 182 210 238 280
S u m A.P.
141
177 303
156 316
191 310
5
142 177
82 154 176 189 288
321 T A B L E III(continued) Pollen Type
River
Site 1
2
3
4
5
M
I
O
Gramineae
171
191
191
219
204
92 176 196 267
168 189 203
182 267
Ambros&
274
288
274 302
274
48
50 267
245
252
Sum pollen
141 274
177 288
156 316
191 316
177 248
82 154 176 267 288
154 168 196 245
161 182 210 252
herbs and sum aquatics. Grass and herb pollen curves are better represented at the outflow to Beaver Lake than at either of the other t w o aquatic sampling locations. This reflects the difference in the trapping efficiency on the surface of a large b o d y of standing water compared to that of a stream channel (Starling, 1978); Currier and Kapp (1974} demonstrated the effect of the width of a stream channel or the height of the bordering vegetation on the pollen catch. There is a maximal value of refloated pollen of Ambrosia in spring, evident b o t h in samples from air and water; however, this peak is more sustained in the latter, possibly because pollen is being contributed from sedimentary sources within the system. Table IV compares the frequency of the main arboreal pollen types together with Ambrosia, grasses, shrubs and aquatics. R values for the trees, based on the information in the total and partial data sets are given in Table V. The values show major differences in representativity between the fluvially and aerially transported pollen, and the same taxa are not similarly over- or under-represented. Pinus, Betula and Quercus are overrepresented in the fluvial spectra b u t Cupressineae and Fraxinus, overrepresented in the air, are under-represented in water; Acer is less well represented in the water despite the fact that the river is f a n k e d b y numerous stands of Acer saccharinum and A. rubrum. Rrel is a value which has been used by Davis (1963) and Livingston (1968) in order to smooth local variations in pollen representativity; where the aim is to elucidate such local relationships b e t w e e n vegetation and the sampler or sampling surface, however, it is n o t a useful measure (Crowder and Starling, 1980). The conclusions of Tauber (1977), Ogden et al. (1975) and Raynor et al. (1974) suggest that Rrel should be used only in situations where the samplers or sampling surfaces are completely comparable, because the amount of trapped pollen of a particular taxon varies with the nature of the trapping surface (cf. Currier and Kapp, 1974). The " b u d g e t " study of Beaver Lake shows that a greater number of grains leave the lake than are entering it b y the inflow. This illustrates the effect of
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the trapping surface of a lake, which is particularly marked in Beaver Lake because its outflow is aligned down-wind in relation to the prevailing wind. The wind moves the surface waters of the lake, with their associated unw et t ed grains, o u t via the outflow. The total n u m b e r of grains o f Cupressineae,
323 TABLE IV Relative frequency of selected types of pollen at the three sampling sites on the river: Milltown, and the inflow and outflow of Beaver Lake Pollen type
Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus Ambrosia Gramineae Sum Sum Sum Sum Sum Sum Sum
shrub pollen herb pollen grass pollen aquatics' pollen total pollen arboreal pollen total pollen
Milltown
Beaver Lake inflow
outflow
43.00 5.04 2.47 6.06 13.89 15.38 1.97 2.03 0.52 3.75
45.03 2.85 0.52 3.87 11.99 15.04 1.73 2.19 2.24 1.36
64.66 0.83 0.14 2.95 10.22 6.82 1.88 1.76 0.73 0.80
23.30 33.68
60.05 40.18
67.63 50.18
8.37 42.64 34.07 19.21 204.29 48.95
8.39 84.71 40.33 17.32 250.76 39.88
6.82 86.41 50.33 21.16 264.72 37.78
Tilia a n d Populus is a p p r o x i m a t e l y t h e s a m e b e t w e e n t h e i n f l o w and o u t f l o w b u t t h e t o t a l n u m b e r o f grains o f Pinus, Ostrya, Betula, Quercus, Ulmus and Acer is increased in t h e o u t f l o w . T a b l e V I lists t h e ratios o f grains at t h e i n f l o w and o u t f l o w a n d s h o w s t h e " e x p o r t " o f grains o f m o s t t a x a f r o m t h e lake i n t o t h e river. T h e c h a n g e in t h e p r o p o r t i o n s o f t h e a r b o r e a l pollen d o e s not match the vegetational change from north to south. R values w e r e c a l c u l a t e d f o r t h e d a t a f r o m all t h r e e river s t a t i o n s b a s e d o n t h e relative d o m i n a n c e o f e a c h t a x o n w i t h i n t h e w a t e r s h e d , a n d f o r e a c h of the separate sections of the watershed drained by the respective segments o f t h e s t r e a m . In T a b l e V it c a n b e seen t h a t t h e values f o r Pinus a n d Ulmus increased at t h e o u t f l o w relative t o t h e i n f l o w a n d d e c r e a s e d f o r all o t h e r types; therefore the combined input from the lake surface and the inflow are increasing t h e i n f l u x o f all p o l l e n t y p e s e x c e p t Pinus a n d Ulmus t o t h e lake s e d i m e n t surface. This e x a m p l e suggests t h a t w h e n a lake has an i n f l o w t h e i n f l u x o f all p o l l e n t y p e s is i n c r e a s e d b u t t h a t t h e p r e s e n c e o f an o u t f l o w d i f f e r e n t i a l l y a f f e c t s t h e p r o p o r t i o n s o f grains w h i c h r e m a i n in t h e basin. Davis ( 1 9 6 7 ) a n d Brush a n d Brush ( 1 9 7 2 ) h a v e s h o w n t h a t t h e h y d r o d y n a m i c s o f p o l l e n t y p e s differ, a f f e c t i n g t h e i r d i s t r i b u t i o n at t h e s e d i m e n t i n t e r f a c e ; M c A n d r e w s a n d P o w e r ( 1 9 7 3 ) a n d M c A t e e {1977) d e m o n s t r a t e d t h e e f f e c t o f s t r e a m i n p u t o n p a t t e r n s o f p o l l e n d i s t r i b u t i o n in L a k e O n t a r i o
324 TABLE V A. R values for the ten most important taxa, using values from the vegetation of the whole basin, and the river samples of pollen taken at Milltown, and the inflow and outflow of Beaver Lake Milltown
Beaver Lake
4.78 0.47 0.21 3.03 2.78 t.71 0.49 0.07 0.13 0.94
Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus
inflow
outflow
5.00 0.32 0.0,1 1.9,1 2A0 1.67 0A3 0.08 0,56 0.34
7.18 0.09 0.01 1.48 2.04 0.76 0.47 0.06 0.18 0.20
B. R values for the ten most important taxa, calculated from the pollen samples from the three fluvial sampling sites, using vegetational data from the limestone and shield areas of the basin Milltown
Beaver Lake inflow
(limestone basin) Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus
8.61 0.34 0.62 2.02 4.63 2.56 0.39 0.05 0.13 0.94
4.78 0.47 0.21 3.03 2.78 1.71 0.49 0.07 0.13 0.94
3.75 0.48 0.03 1.94 1.50 1.25 0.43 0.08 0.20 0.34
outflow (shield) 5.39 0.14 0.03 1.48 1.28 0.57 0.47 0.08 0.15 0.20
and Georgian Bay, respectively, and this e x a m p l e illustrates the potential e f f e c t o f an o u t f l o w t o a l a k e in t h e s e l e c t i v e t r a n s p o r t o f p o l l e n t y p e s . W h e n a l a k e a c t s as a s o u r c e o f p o l l e n f o r t h e d o w n s t r e a m s e g m e n t o f a river t h e p r o p o r t i o n a l r e p r e s e n t a t i o n o f t h e p o l l e n is d i f f e r e n t i a l l y d i s t o r t e d in c o m p a r i s o n t o t h a t in a s t r e a m w h i c h is n o t a f f e c t e d b y l a k e s , e.g. W i l t o n C r e e k { C r o w d e r a n d C u d d y , 1 9 7 3 ) . D e s p i t e p o l l e n e n t e r i n g t h e river b e t w e e n t h e o u t f l o w o f B e a v e r L a k e a n d t h e s a m p l i n g s t a t i o n at M i l l t o w n , t h e r e is a r e d u c t i o n in t h e n u m b e r o f grains s a m p l e d at t h e l o w e r site; t h e p o t e n t i a l sinks f o r t h e p o l l e n a r e : (1) m e c h a n i c a l d e s t r u c t i o n ; (2) t r a p p i n g o n t h e v e g e t a t i o n b o t h w i t h i n t h e c h a n n e l a n d o n its b a n k s ; a n d (3) s e d i m e n t a t i o n within the stream course. M e c h a n i c a l a b r a s i o n was a p p a r e n t f r o m t h e n u m b e r o f c o r r o d e d grains in the samples and the degree of "rounding" which had affected echinate
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140
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in the river samples. Symbols asin Fig.4.
grains of the Compositae. Pollen trapped within the channel by vegetation would be released during die-back in the fall; an autumnal peak of resuspended pollen together with fragments o f leaf epidermis of Myriophyllum and Typha was recorded at a time of rising water level. Coincident with this peak
326 TABLE VI Ratio of number of grains at the outflow and inflow of Beaver Lake, showing the "export" of some types Pollen type
"Export"
Pollen type
"Export
Pin us
4.91
A m brosia
3.85
C upressineae
Grami~eae
4.27
Ace'-
1.00 0.90 2.61 2.92 ] 55 3.73 2,75
Sum Sum Sum Sum Sum
:k42 2.78 :~..i9 ~ 27 ~1.18
Tili~l Fraxmus
2.00
Populus Ostrya/Carpinus BeluZa Quercus Ulm us
A.P shrub herb grass aquatics
I . 11
Sum total
3.61
was an e f f l u x o f P e d i a s t r u m , p r e s u m a b l y f r o m shallows or lakes u p s t r e a m . The a u t u m n a l p e a k o f pollen in w a t e r f r o m Beaver L a k e was c o m p l e x , showing a s e c o n d a r y rise in t h e pollen load at t h e s a m e t i m e as t h a t in t h e air samplers. T h e p r i m a r y s o u r c e is inferred to be leaf abscission ( T a u b e r , 1 9 7 7 ; C r o w d e r and Starling, 1980). T h e a u t u m n a l p e a k registered at Milltown c o i n c i d e d w i t h rising w a t e r levels, b u t n e i t h e r air n o r w a t e r s a m p l e s t h e r e s h o w e d an increase in pollen c o n c e n t r a t i o n s e q u i v a l e n t to t h a t associated with leaf abscission f u r t h e r n o r t h . T h e highest c o n c e n t r a tion o f grains r e c o r d e d was d u r i n g the m e l t in spring w h e n s e d i m e n t transp o r t is also m o s t p r o n o u n c e d . CONCLUSIONS Rivers w h i c h have b e e n investigated all c o n t a i n pollen, or c o n t r i b u t e pollen t o o f f - s h o r e d e p o s i t s ( F e d e r o v a , 1 9 5 2 ; Muller, 1 9 5 9 ; Cross et al., 1966; G r o o t , 1 9 6 6 ; Mal'gina and Maev, 1 9 6 6 ; S t a n l e y , 1 9 6 9 ; C r o w d e r and C u d d y , 1973; P e c k , 1 9 7 3 ; Krassilov, 1 9 7 5 ; B o n n y , 1976). T h e a m o u n t o f pollen carried d e p e n d s o n t h e v o l u m e o f t h e river, its v e l o c i t y , t h e availability a n d n a t u r e o f its s e d i m e n t , its t r a p p i n g surface, t h e p r e s e n c e or a b s e n c e o f lakes in its course, and t h e a m o u n t o f pollen p r o d u c e d b y the regional v e g e t a t i o n . T h e S a l m o n River carries a g r e a t e r load t h a n the s t r e a m s studied b y P e c k ( 1 9 7 3 ) or C r o w d e r and C u d d y ( 1 9 7 3 ) b u t is o b v i o u s l y n o t c o m parable w i t h giants such as t h e V o l g a ( F e d e r o v a , 1 9 5 2 ) or t h e O r i n o c o (Muller, 1959). Pollen was c o l l e c t e d b y t h e river f r o m a lake w h i c h a c t e d as a t r a p p i n g surface (Beaver Lake), a l t h o u g h s o m e t a x a a p p e a r e d t o s e d i m e n t in the lake at t h e s a m e t i m e as o t h e r s m o v e d o n d o w n s t r e a m . Pine pollen as well as being m o s t volatile is also m o s t b u o y a n t ( P e n n i n g t o n , 1947), a n d so it a p p e a r s t o be b l o w n across t h e lake surface b e f o r e it sinks. It m a y also b e b l o w n against t h e river b a n k s and lost t o t h e s y s t e m . Beaver L a k e is so
327
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c o n c e n t r a t e d in t h e z o n e o f g r e a t e s t v e l o c i t y , b u t t h e r e was also a m i n o r c o n c e n t r a t i o n n e a r t h e s t r e a m bed. T h e silt p o r t i o n o f t h e inorganic sedim e n t l o a d similarly travels in t h e z o n e o f m a x i m u m v e l o c i t y so t h a t t h e pollen is s u b j e c t t o a b r a s i o n . S a m p l e s w e r e f o u n d t o v a r y greatly in t h e i r
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weathering, and "Ambrosia" was o f t e n sand-papered s m o o t h . The maximal pollen load was f o u n d after t h e vernal melt, and during t h a t period o f f l o o d i n g t h e maximal load o f inorganic s e d i m e n t is also carried. Pollen was carried all t h r o u g h the year, with pulses going d o w n s t r e a m
332
even w h e n t h e river was a l m o s t entirely ice-covered -- at t h a t t i m e o f y e a r the s o u r c e o f pollen m u s t be s e d i m e n t within t h e s y s t e m . In this p r o j e c t r e w o r k e d pollen was n o t distinguished. In t h e spring, Ambrosia pollen was r e s u s p e n d e d b o t h in the air and t h e river, and in t h e late fall s e c o n d a r y p e a k s o f a r b o r e a l pollen o c c u r r e d in b o t h m e d i a w h e n pollen t r a p p e d o n d e c i d u o u s leaves was freed. In this p a r t o f O n t a r i o w h o l e catkins o f Betula can be o b s e r v e d being shed f r o m the trees in a u t u m n , still c o n t a i n i n g s o m e pollen. T h e p h e n o l o g y o f t h e trees, grasses, Ambrosia, shrubs and aquatics was f o u n d to be closely f o l l o w e d b y b o t h aerial and fluvial pollen, w i t h a p p r o x i m a t e l y the s a m e time-lag. T h e s e d a t a refine t h o s e f r o m Wilton Creek, w h i c h is a p p r o x i m a t e l y 40 k m to t h e east ( C r o w d e r and C u d d y , 1973). T h e r e p r e s e n t a t i v i t y o f t h e pollen in the river was f o u n d to be d i f f e r e n t at t h e t h r e e s a m p l i n g p o i n t s , b u t t h e m a i n d i f f e r e n c e was in t h e overr e p r e s e n t a t i o n o f Pinus in w a t e r e m a n a t i n g f r o m t h e lake. C o m p a r a b l e d i f f e r e n c e s in r e p r e s e n t a t i v i t y also o c c u r b e t w e e n aerial s a m p l i n g sites within the drainage basin. T h e m o s t f r e q u e n t a r b o r e a l t y p e s were Pinus, Quercus, Betula, Ostrya/Carpinus, Cupressineae, and Fraxinus, in t h a t order. Pinus was the m o s t o v e r - r e p r e s e n t e d n e a r t h e m o u t h o f t h e river, f o l l o w e d b y Ostrya/Carpinus, Betula and Quercus, whilst the o t h e r trees were underr e p r e s e n t e d . If t h e n o r t h e r n and s o u t h e r n p a r t s o f t h e basin (on shield and Palaeozoic l i m e s t o n e s , r e s p e c t i v e l y ) are c o n s i d e r e d s e p a r a t e l y , the overr e p r e s e n t a t i o n o f t h e s e f o u r t a x a was less in t h e n o r t h e r n p a r t o f t h e basin. T h e R values derived f r o m aerial and fluvial s a m p l e s should be useful in i n t e r p r e t i n g fossil assemblages w h o s e origin and t r a n s p o r t i n g m e d i u m are k n o w n . Whereas Pinus, Betula and Quercus are o v e r - r e p r e s e n t e d in b o t h , in t h e aerial s a m p l e s Fraxinus and t h e C u p r e s s i n e a e are o v e r - r e p r e s e n t e d , and in the fluvial o n e s u n d e r - r e p r e s e n t e d . Ostrya/Carpinus is o v e r - r e p r e s e n t e d in t h e fluvial s a m p l e s and n o t in t h e aerial ones. At p r e s e n t t h e S a l m o n River is c a r r y i n g a c o n s i d e r a b l e load o f pollen into the Bay o f QuintS. T h e river, like m a n y in eastern O n t a r i o , flows in t h e o p p o s i t e d i r e c t i o n to t h e prevailing w i n d ; this f a c t m a y even o u t o p p o s i n g t r e n d s in pollen representation. ACKNOWLEDGEMENTS We should like to t h a n k all t h o s e w h o h e l p e d and advised us in w o r k i n g on rivers and lakes, and t h e C a n a d i a n N a t i o n a l R e s e a r c h Council f o r funding. REFERENCES Bonny, A.P. 1976. Recruitment of pollen to the seston and sediment of some Lake District lakes. J. Ecol., 64: 859--887. Bonny, A.P. 1978. The effect of pollen recruitment process on pollen distribution over the sediment surface of a small lake in Cumbria. J. Ecol., 66: 385--416. Bostock, H.S., 1970. Physiographic sub-divisions of Canada. In: R.J.W. Douglas (Editor), Geology and Economic Minerals of Canada. Queen's Printer, Ottawa, Ont., pp.10--30.
333 Brooks, J. and Shaw, G., 1971. The role of sporopollenin in palynology. III Int. Palynol. Conf., Novosibirsk, pp.1--23. Brush, G.S. and Brush, L.M., 1972. Transport o f pollen in a sediment-laden channel: a laboratory study. Am. J. Sci. 272: 359--381. Cottam, G. and Curtis, J.T., 1956. The use o f distance measures in phytosociological sampling. J. Ecol., 37: 451--460. Cross, A.T., Thompson, G.G. and Zaileff, Z.T.B., 1966. Source and distribution of palynomorphs in b o t t o m sediments in the southern part of the Gulf of California. Mar. Geol., 4: 467--526. Crowder, A.A. and Cuddy, D.G., 1973. Pollen in a small river basin: Wilton Creek, Ontario. In: B.J.B. Birks and R.G. West (Editors), Quaternary Plant Ecology. Blackwell, Oxford, pp. 61--77. Crowder, A. and Starling, R.N., 1980. Contemporary pollen in the Salmon River basin, Ontario. Rev. Palaeobot. Palynol., 30: 11--26. Currier, P.J. and Kapp, R.O., 1974. Local and regional pollen rain components at Davis Lake, Montcalm County, Michigan. Mich. Acad., 7: 211--225. Cushing, E.J., 1964. Redeposited pollen in the Wisconsin pollen spectra from east-central Minnesota. Am. J. Sci., 262: 1075--1088. Davis, M.B., 1963. On the theory o f pollen analysis. Am. J. Sci., 261: 897--912. Davis, M.B., 1967. Pollen deposition in lakes as measured b y sediment traps. Bull. Geol. Soc. Am., 78: 849--858. Davis, M.B. and Brubaker, L.B., 1973. Differential sedimentation of pollen grains in lakes. Limnol. Oceanogr., 18: 635--667. Davis, R.B., Brewster, L.A. and Sutherland, J., 1969. Variation in pollen spectra within lakes. Pollen Spores, 11: 557--571. Erdtman, G., 1943. Introduction to Pollen Analysis. Chronica Botanica, Waltham, Mass. Faegri, V. and Iversen, J., 1964. T e x t b o o k o f Pollen Analysis. Blackwell, Oxford, 2nd ed., 237 pp. Farrar, J., Crowder, A. and Hummel, M., 1978. Ecological Effects of Fire and Its Management in Canada's National Parks. A.D. Revill Associates, Belleville and Parks Canada, Ottawa, Ont., 343 pp. Federova, R.V., 1952. The spread o f pollen and spores by water currents. Trans. Inst. Geogr. Acad. U.S.S.R., 5 2 : 4 6 - - 7 3 (in Russian). Gardner, J.S., 1976. Natural hazards o f climatic origin in Canada. In: G.R. McBoyle and E. Sommerville (Editors), Canada's Natural Environment. Methuen, Toronto, Ont., 46--68. Graf, K., 1969. The Hydraulics of Sediment Transport. Academic Press, New York, N.Y. Gregory, K.J., 1966. Dry valleys and the composition of the drainage net. J. Hydrol., 4: 327--340. Gregory, K.J. and Walling, D.E., 1973. Drainage Basin F o r m and Process: A Geomorphological Approach. Edward Arnold, London, 456 pp. Groot, J.J., 1966. Some observations on pollen grains in suspension in the estuary of the Delaware River. Mar. Geol., 4: 409---416. Havinga, A.J., 1971. An experimental investigation into the decay o f pollen and spores in various soil types. In: J. Brooks, P.R. Grant, M.D. Muir, P. van Gijzel and G. Shaw •(Editors), Sporopollenin. Academic Press, London, pp. 446--479. Horton, R.E., 1945. Erosional development of streams and their drainage basins - - a hydrophysical approach to quantitative geomorphology. Geol. Soc. Am. Bull., 56: 275--370. Krassilov, V.A., 1975. Palaeoecology o f Terrestrial Plants. Wiley, New York, N.Y., 283 pp. Likens, G.E., Bormann, F.H., Johnson, N.M., Fisher, D.W. and Pierce, R.S., 1970. Effects of forest cutting and herbicide treatment on nutrient budgets in the Hubbard Brook Watershed System. Ecol. Monogr., 40: 23--47.
334 Livingstone, D.A., 1968. Some interstadial and post glacial pollen diagrams from eastern Canada. Ecol. Monogr., 38: 87--125. Mal'gina, E.A. and Maev, E.G., 1966. Spore pollen spectra of bottom sediments in the Caspian Sea. Izv. Akad. Nauk. U.S.S.R. Geogr. Ser., 2 : 6 1 - - 7 0 (in Russian). McAndrews, J.H. and Power, D.M., 1973. Palynology of the Great Lakes. The surface sediments of Lake Ontario. Can. J. Earth Sci., 10(5): 777--792. McAtee, C.L., 1977. Palynology of Late Glacial and Post Glacial Sediments in Georgian Bay, Ontario, Canada, As Related to Great Lakes History. Thesis, Brock University, St. Catharines, Ont., 153 pp. Muller, J., 1959. Palynotogy of recent Orinoco delta and shelf sediments. Micropalaeontology, 5: 1--32. Ogden, E.C., Raynor, G.S. and Hayes, J.V., 1975. Travels of airborne pollen. EPA-650/375-003. Peck, R.M., 1973. Pollen budget studies in a small Yorkshire catchment. In: H.J.B. Birks and R.G. West (Editors), Quaternary Plant Ecology. Blackwell, Oxford, pp. 43--68. Pennington, W., 1947. Studies of the post glacial history of British vegetation. 7. Lake sediments. Philos. Trans. R. Soc., B. 248: 205--244. Raynor, G.S., Ogden, E.C. and Hayes, J.V., 1974. Enhancement of particulate concentrations downwind of vegetative barriers. Agric. Meteorol., 13:181--188. Ritchie, J.C. and Lichti-Federovich, S., 1963. Contemporary pollen spectra in central Canada. 1. Atmospheric samples of Winnipeg, Manitoba. Pollen Spores, 5: 95--116. Sangster, A.G. and Dale, H.M., 1961. A preliminary study of differential pollen grain preservation. Can. J. Bot., 39: 35--43. Sangster, A.G. and Dale, H.M., 1964. Pollen grain preservation of under-represented species in fossil spectra. Can. J. Bot., 42: 437--449. Stanley, E.A., 1969. Marine palynology. Oceanogr. Mar. Biol. Annu. Rev., 7: 277--292. Starling, R.N., 1978. Modern Pollen in the Salmon River Basin. Thesis, Queen's University, Kingston, Ont., 464 pp. Strahler, A.N., 1957. Quantitative analysis of watershed geomorphology. Trans. Am. Geophys. Union, 38: 913--920. Warwick, W., 1977. Report on Quint6 sediments. Project Quint6 Workshop, Glenora. Environment Canada, Fisheries Service. Tauber, H., 1977. Investigations of aerial pollen transport in a forested area. Dan. Bot. Ark., 32(1): 1--121. Taylor, G., 1977. An Investigation Into the Growth and Distribution of Maianthemurn canadense Within the Thousand Island Region. Thesis, Queen's University, Kingston, Ont., 64 pp.
311
POLLEN IN THE SALMON RIVER SYSTEM, ONTARIO, CANADA
R.N. STARLING AND A. CROWDER Centre for Northern Studies, Wolcott, Vt. (U.S.A.) Department of Biology, Queen's University, Kingston, Ont. (Canada) (Received January 24, 1979; revised version accepted May 9, 1980) ABSTRACT Starling, R.N. and Crowder, A., 1981. Pollen in the Salmon River System, Ontario, Canada. Rev. Palaeobot. Palynol., 31: 311--334. The Salmon River in eastern Ontario drains approximately 1000 km 2, and flows most rapidly during the spring; a velocity profile was measured and the zone of maximal pollen transport was determined. Pollen in the water was sampled throughout the year near the river-mouth, and at the outflow and inflow of one lake within the watershed. The phenology of pollen of trees, grasses, Ambrosia and aquatic plants was studied and compared to the patterns found in aerial samplers; re-suspension phases and peaks were similar in both transporting media. R values for the ten most important arboreal taxa were calculated and were compared with those calculated from air-borne pollen. INTRODUCTION S t u d y o f t h e aerial d y n a m i c s o f p o l l e n is assisting in t h e u n d e r s t a n d i n g o f f a c t o r s w h i c h a f f e c t t h e r e p r e s e n t a t i v i t y o f m o d e r n pollen s a m p l e s ; c o n t e m p o r a r y s p e c t r a are t h e n b e i n g used as a n a l o g u e s o f p a s t c o n d i t i o n s in o r d e r t o increase t h e resolving p o w e r o f t h e t e c h n i q u e o f pollen-analysis. T h e m a i n s o u r c e s o f sub-fossil p o l l e n f r o m t h e Q u a t e r n a r y p e r i o d are sedim e n t s in b o g s a n d lakes, b o t h o f w h i c h receive i n p u t s n o t o n l y f r o m t h e air b u t f r o m r u n n i n g w a t e r , d u r i n g at least s o m e phases o f t h e i r d e v e l o p m e n t . T h e i m p o r t a n c e o f fluvially t r a n s p o r t e d pollen t o deltas, shelf s e d i m e n t s a n d valley b o g s has b e e n stressed b y Krassilov (1975). A l t h o u g h various a u t h o r s have d e s c r i b e d p o l l e n s p e c t r a o b t a i n e d f r o m r u n n i n g w a t e r t h e r e h a v e b e e n no r e p o r t s specifically dealing w i t h t h e c o r r e s p o n d e n c e b e t w e e n pollen in t h e air a n d t h a t in t h e w a t e r t h r o u g h o u t o n e y e a r . Pollen e n t e r s a river e i t h e r b y landing o n t h e s u r f a c e o r b y b e i n g w a s h e d o u t f r o m a lake. R u n - o f f a n d t r a n s p o r t o v e r l a n d or b y t h r o u g h f l o w h a v e b e e n suggested as s e c o n d a r y m e c h a n i s m s , b u t w i t h o u t s u b s t a n t i a t i o n (Peck, 1 9 7 3 ; C r o w d e r a n d C u d d y , 1 9 7 3 ; Krassilov, 1975). O n c e t h e pollen is t r a p p e d b y t h e w a t e r s u r f a c e it b e c o m e s w e t t e d (Brush a n d Brush, 1 9 7 2 ) and i n c o r p o r a t e d i n t o t h e s e d i m e n t l o a d , acting like fine silt (Muller, 1 9 5 9 ; S t a n l e y , 1 9 6 9 ; P e c k , 1 9 7 3 ; M c A t e e , 1977). A c c o r d i n g t o P e r m y a k o v ( 1 9 6 4 , q u o t e d in Krassilov, 1 9 7 5 ) , p o l l e n grains are s o r t e d d u r i n g t r a n s p o r t a n d 0034-6667/81/0000--0000/$ 02.50 O 1981 Elsevier Scientific Publishing Company
312 redistributed with the velocity profile in relation to their settling velocities. Grains may also deteriorate in the water (Sangster and Dale, 1961, 1964; Havinga, 1971) or suffer corrosion by inorganic sediment (Cushing, 1964; McAtee, 1977). Their susceptibility to deterioration depends on the structure of the exine (Brooks and Shaw, 1971; J.H. McAndrews, pers~ comm.). Deposition occurs when the velocity of flow decreases, usually as the result of the stream entering a body of standing water or through the effect of vegetation in the channel; the transport of pollen within lakes is well documented (Davis, 1967; Davis et al., 1969; Davis and Brubaker, 1973; Bonny, 1978). Erdtman (1943) called for investigations into the nature of the pollen load of rivers. Peck (1973) and Crowder and Cuddy (1973) have published details of the pollen in a stream and small river system and have compared it to the local vegetation, Federova (1952) described pollen spectra from the Volga, and Groot (1966) worked on samples from the Delaware. This paper describes the pollen transport by a river which is approximately 140 km long and drains an area of almost 1000 km:. The forest cover of the drainage basin was surveyed and analysed, and the aerial pollen was trapped at five sites along the stream course. Differences in the pollen spectra from the inflow and outflow of a lake within the network were investigated as was the response time of the river transport system. The Salmon River flows into the Bay of QuintS, a part of Lake Ontario, in southeastern Ontario (Fig.l). In order to compare this river system with others, drainage density (Da) and valley density (Dr) can be used; drainage density = total length of all streams/basin area, and valley density = total length of all valleys/basin area (Gregory and Walling, 1973). Drainage density for the whole basin = 0.72 k m / k m 2, and for the parts underlain by Ordovician limestone and the Precambrian shield, 0.41 k m / k m 2 and 0.64 k m / k m 2, respectively. These values are relatively low (Strahler, 1957), but are comparable with those for a stream in New Jersey (Horton, 1945) and a river in southwest England (Gregory, 1966). In the Salmon River basin the valley density is higher than the drainage density, which indicates that the present system was developed during a period of greater flow (Horton, 1945; Starling, 1978). Relief in the area is low and in some areas the divide with an adjacent river system is transgressed by swamps. Seven lakes, with a total surface area of 8.75 km 2, occur within the network. The most extensive is Beaver Lake, which is also the southernmost. The specimen hydrograph for 1976 from the Milltown Station (Fig.2) shows a peak of flooding in spring due to snow-melt, followed by falling water levels in the summer and a second rise in the fall which lasted until the river froze. Freezing usually occurs in mid-December. Despite the number of lakes in the system, local dams interfere with the summer flow and sections of the stream are reduced to pools during droughts, such as that of 1977. In winter segments with super-critical flow remain ice-free. The annual flow regime is similar to that of Wilton Creek (Crowder and Cuddy, 1973) and is typical of eastern Ontario (Gardner, 1976).
313
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Fig.1. The S a l m o n River V a l l e y . T h e w a t e r s h e d is s h o w n in black in the inset map, and its limits are s h o w n b y the d o t t e d line o n the large map. Fluvial samples were taken at M i l l t o w n and s o u t h o f Fisher Creek, at W y m a n ' s Road. Aerial pollen samplers were situated at Sites 1--5.
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315
until a b o u t 1900; cleared land (on b o t h limestone and local outwash sands on the shield) then supported mixed subsistence farming (Starling, 1978). When applying results from the study of modern pollen spectra, either airborne or waterborne, allowance should be made for changes in the characteristics of flow of the transporting agents. The aerodynamics of an agricultural landscape are different from those of a continuously forested area; deforestation and fires also affect the r u n o f f and sediment load of streams (c.f. Warwick, 1977; Likens et al., 1970; Farrar et al., 1978). METHODS
Muller (1959) and Peck (1973) among others have suggested that pollen acts like fine silt in the suspended sediment load of rivers. In order to check this in the Salmon River, a velocity profile was determined for one section of the channel, 16 km upstream from the mouth. An Ott velocity meter (type C-31, with Nr lamda propeller) was used in suspension mode from Wyman's Road Bridge, near Milltown. The profile was determined, graphed and sampled for pollen content in its different zones (Starling, 1978). For regular sampling a site which remained ice-free was selected -- it is located 20 m upstream from the Environment Canada flow gauge at Milltown. At this point the flow is super-critical all year and the suspended sediment is evenly distributed throughout the profile (Graf, 1969). Crowder and C u d d y (1973) found that a sample volume of 35 1 was necessary for a "significant" pollen catch during periods of low concentrations. A 35-1 sample was also used in this study in which the river water was sampled fortnightly during the ice-free period, monthly during the winter from December 1974 to April 1976, and weekly from April to November 1976. The hydrograph for 1976 is illustrated in Fig.2. The inflow and outflow of Beaver Lake were sampled at similar intervals. The water samples were left standing for 24 h so that the bulk of the sample could be rapidly filtered. Filtration was vacuum-assisted through Millipore Membrane filters (type SP, 8 pm pore size). Modified Millipore vacuum flasks were used (Starling, 1978). The membrane filters were dispersed using 10% KOH or NaOH (by weight) and the samples processed by the m e t h o d of Faegri and Iversen (1964); full details are given in Starling (1978). The airborne pollen was sampled at 25 sites within the watershed using modified Tauber traps (Starling, 1978). Five sites adjacent to the stream were analysed (Crowder and Starling, 1980). The pollen was concentrated by vacuum filtration and processed in the same way as that from the river. The pollen samples were m o u n t e d in 10,000 c.s. silicone oil and counted. The concentration of grains in the river samples ranged from 370 to 21,000 grains/35 1 and from 30 to 8,000 g/cm 2/day in the air samples. A predetermined pollen sum was meaningless, therefore 5--25% of the total sample volume was counted -- exceptionally the contents of the entire samples were scored.
316 All data were entered into a PDti-11 V03 microprocessor, and interactive programmes were written to calculate all values and to display requested pollen graphs on a Tektronix 4662 plotter. RESULTS The results of the measurements of stream velocity and associated pollen load taken at Wyman's Road Bridge are shown in Fig.3. The pollen load was concentrated in the zone of maximum velocity but significant amounts of pollen were also carried in the bed-load (cf. McAtee, 1977). Because the experiment was run only once, any differences in the components of the spectra, dependent on their position in the profile, were not determined; however, it was apparent that the pollen in the bed-load was more corroded (abraded) than that nearer the surface, and the echinate pollen of some pollen of the Compositae had been worn down sufficiently to appear verrucate. Table I shows the percentages of airborne pollen of the ten dominant taxa in the forest canopy together with the respective values for relative dominance (R. Dora.) and importance percentage (I.P.). R values (sensu, Davis 1963) were calculated for each pollen type based on both relative dominance and importance percentage. The values show that Pinus, Betula, Quercus, Cupressineae and Fraxinus are over-represented. Under-represented taxa are Tilia, Acer, Populus, Ulmus and Ostrya/Carpinus. The R values are based on the total data set for the watershed; the effect of different areas on the R values was investigated (Crowder and Starling, 1980); using R relative values (Livingston, 1968; Davis, 1963) did not affect patterns of over- and under-representation. Table II lists the total number of grains counted in the fluvial samples. The Beaver Lake and the second Milltown columns are comparable for the period J u n e - 4 ) c t o b e r (days 152--301, 1976), while the first column for Milltown covers January to October {days 14--301, 1976). Most pollen was caught at the outflow of Beaver Lake, and there was an exceptionally high amount at Milltown on March 22, 1976 {20,736 grains/35 1). The sum of all pollen types throughout the sampling period in 1976 is shown in Fig.4, together with the totals from two of the aerial pollen sampling points in the valley. The peak pollen load coincides with the peak flow of the river (Fig.2) when it also carries its maximal load of inorganic sediment (E. Ongley, pers. comm., 1978). The maximum also coincides with that of pollen in the air, produced by early-flowering trees. Table II shows that arboreal pollen is the major component of the fluvial pollen sum, followed by the sum of the aquatic taxa (Typha, Myriophyllum, Potamogeton, Carex, Nuphar, Nymphaea), Ambrosia and the Gramineae. The flowering sequences detected by the air-pollen samplers were closely matched by the river samples, including the earlier flowering time at Milltown (see Table III). Figures 5--11 illustrate the trends in the concentration of grains for Betula, Quercus, Ambrosia, Gramineae, sum A.P., sum
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318 TABLE I R e l a t i o n s h i p o f aerially t r a n s p o r t e d pollen a n d v e g e t a t i o n , expressed as R values
Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus
% in v e g e t a t i o n
% in pollen
R value
IP
R. Dora.
(sum A.P.)
IP
R. D o m .
6.3 10.7 12.3 4.7 7.3 8.3 4.3 28.3 3.7 5.3
9 9 12 2 5 9 :l 28 -1 4
26.63 15.02 4.01 3,28 14.62 13.73 1.54 3.97 0.33 6.98
1.20 i.40 0.33 0.76 1.99 1.65 0.36 0.15 0,09 I 30
3.00 1.67 0.33 1.64 2.92 1.53 0.39 0.14 0.08 1.75
T h e R values are calculated o n a basis o f b o t h I m p o r t a n c e P e r c e n t a g e ( I m p o r t a n c e V a l u e / 3 ) a n d Relative D o m i n a n c e . T h e t e n t a x a w i t h greatest i m p o r t a n c e value in t h e w a t e r s h e d are used. T A B L E II T o t a l n u m b e r s o f grains s a m p l e d at t h e river s t a t i o n s d u r i n g 1 9 7 6 (days 1 -365 = J a n u a r y 1 - - D e c e m b e r 31) Pollen t y p e
Milltown 14--301 (day)
Beaver lake 1 5 2 - - 3 0 1 (day)
Inflow
Outflow
Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus
478238.0 66573.0 44174.0 43549.0 108686.0 129475.0 25853.0 29504.0 4092.0 37249.0
179321.0 21019.0 10302.0 25271.0 57974.0 64186.0 8210.0 8475.0 2172.0 15664.0
70038.0 4432.0 803.0 6012.0 18642.0 23392.0 2683.0 3412.0 3483.0 2119.0
344092.0 4437.0 725.0 15719.0 54405.0 36305.0 10003.0 9392.0 3862.0 4242.0
Ambrosia Gramineae
183719.0 1736.17.0
97209.0 140524.0
93399.0 62496.0
359908.0 267034.0
1060344.0 121481.0 355791.0 179771.0 243337.0 1960724.0
417281.0 34927.0 177940.0 142154.0 80167.0 852469.0
155533.0 ]3056.0 ]31750.0 62727.0 26945.0 390010.0
532171.0 36291.0 459826.0 267855.0 112629.0 1408770.0
Sum Sum Sum Sum Sum Sum
of of of of of of
a r b o r e a l pollen s h r u b pollen herb pollen the grasses' pollen t h e a q u a t i c s ' pollen all pollen t y p e s
319
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Fig.4. Total pollen in the river samples; x-axis = days 1--365; y-axis = log number of pollen grains. The solid line shows the Milltown samples, the dashed line is the Beaver Lake outflow and the dotted line is the Beaver Lake inflow. The upper graph allows a comparison of the phenology and numbers of grains from Air Trap Site 1 (dashes) and Site 3 (solid line).
320
T A B L E III D a t e s o f p e a k s in p o l l e n c o n c e n t r a t i o n f r o m aerial a n d fluvial s a m p l e s (Sites ! -5 are aerial s a m p l e r s s h o w n o n Fig. 1; M = M i l l t o w n , I a n d O = Beaver L a k e i n f l o w a n d o u t f l o w ; n u m b e r s = d a y s i n t o t h e year, d a y 1 = Jan. 1, 1 9 7 6 ) Pollen T y p e
Site
River
I
2
3
4
Pinus
171
191
191
204
Cupressineae
129
130 177
177
Populus
129
177
Ostrya/Carpinus
141 171
Betula
M
J
0
42 77
$2 ! 76
168 196
16] 182 210 273
191 316
14
t54 288
154
154
9
156
9
82 154 176
154
218
156
156
191
28
~2 154
154 203
168 182 210
141
156
156
191
128
82 154 196
154 196
154 168 210 273
Quercus
141
156
156
191
128
g2 154 288
154 168
154 168 210 28O
Ulmus
129
142
142
156
111
~2 189
196
196 273
Acer
141
167
142
191
128
50 140 t76
168 196
154 168 210
Til&
191
205
v
219
204
161
196
203
Fraxinus
141
177
156
191
128
82 154
168
168 189
154 168 196 267
161 182 210 238 280
S u m A.P.
141
177 303
156 316
191 310
5
142 177
82 154 176 189 288
321 T A B L E III(continued) Pollen Type
River
Site 1
2
3
4
5
M
I
O
Gramineae
171
191
191
219
204
92 176 196 267
168 189 203
182 267
Ambros&
274
288
274 302
274
48
50 267
245
252
Sum pollen
141 274
177 288
156 316
191 316
177 248
82 154 176 267 288
154 168 196 245
161 182 210 252
herbs and sum aquatics. Grass and herb pollen curves are better represented at the outflow to Beaver Lake than at either of the other t w o aquatic sampling locations. This reflects the difference in the trapping efficiency on the surface of a large b o d y of standing water compared to that of a stream channel (Starling, 1978); Currier and Kapp (1974} demonstrated the effect of the width of a stream channel or the height of the bordering vegetation on the pollen catch. There is a maximal value of refloated pollen of Ambrosia in spring, evident b o t h in samples from air and water; however, this peak is more sustained in the latter, possibly because pollen is being contributed from sedimentary sources within the system. Table IV compares the frequency of the main arboreal pollen types together with Ambrosia, grasses, shrubs and aquatics. R values for the trees, based on the information in the total and partial data sets are given in Table V. The values show major differences in representativity between the fluvially and aerially transported pollen, and the same taxa are not similarly over- or under-represented. Pinus, Betula and Quercus are overrepresented in the fluvial spectra b u t Cupressineae and Fraxinus, overrepresented in the air, are under-represented in water; Acer is less well represented in the water despite the fact that the river is f a n k e d b y numerous stands of Acer saccharinum and A. rubrum. Rrel is a value which has been used by Davis (1963) and Livingston (1968) in order to smooth local variations in pollen representativity; where the aim is to elucidate such local relationships b e t w e e n vegetation and the sampler or sampling surface, however, it is n o t a useful measure (Crowder and Starling, 1980). The conclusions of Tauber (1977), Ogden et al. (1975) and Raynor et al. (1974) suggest that Rrel should be used only in situations where the samplers or sampling surfaces are completely comparable, because the amount of trapped pollen of a particular taxon varies with the nature of the trapping surface (cf. Currier and Kapp, 1974). The " b u d g e t " study of Beaver Lake shows that a greater number of grains leave the lake than are entering it b y the inflow. This illustrates the effect of
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Fig.5. Betula poi|en in the river samples. Symbols as in Fig.4.
the trapping surface of a lake, which is particularly marked in Beaver Lake because its outflow is aligned down-wind in relation to the prevailing wind. The wind moves the surface waters of the lake, with their associated unw et t ed grains, o u t via the outflow. The total n u m b e r of grains o f Cupressineae,
323 TABLE IV Relative frequency of selected types of pollen at the three sampling sites on the river: Milltown, and the inflow and outflow of Beaver Lake Pollen type
Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus Ambrosia Gramineae Sum Sum Sum Sum Sum Sum Sum
shrub pollen herb pollen grass pollen aquatics' pollen total pollen arboreal pollen total pollen
Milltown
Beaver Lake inflow
outflow
43.00 5.04 2.47 6.06 13.89 15.38 1.97 2.03 0.52 3.75
45.03 2.85 0.52 3.87 11.99 15.04 1.73 2.19 2.24 1.36
64.66 0.83 0.14 2.95 10.22 6.82 1.88 1.76 0.73 0.80
23.30 33.68
60.05 40.18
67.63 50.18
8.37 42.64 34.07 19.21 204.29 48.95
8.39 84.71 40.33 17.32 250.76 39.88
6.82 86.41 50.33 21.16 264.72 37.78
Tilia a n d Populus is a p p r o x i m a t e l y t h e s a m e b e t w e e n t h e i n f l o w and o u t f l o w b u t t h e t o t a l n u m b e r o f grains o f Pinus, Ostrya, Betula, Quercus, Ulmus and Acer is increased in t h e o u t f l o w . T a b l e V I lists t h e ratios o f grains at t h e i n f l o w and o u t f l o w a n d s h o w s t h e " e x p o r t " o f grains o f m o s t t a x a f r o m t h e lake i n t o t h e river. T h e c h a n g e in t h e p r o p o r t i o n s o f t h e a r b o r e a l pollen d o e s not match the vegetational change from north to south. R values w e r e c a l c u l a t e d f o r t h e d a t a f r o m all t h r e e river s t a t i o n s b a s e d o n t h e relative d o m i n a n c e o f e a c h t a x o n w i t h i n t h e w a t e r s h e d , a n d f o r e a c h of the separate sections of the watershed drained by the respective segments o f t h e s t r e a m . In T a b l e V it c a n b e seen t h a t t h e values f o r Pinus a n d Ulmus increased at t h e o u t f l o w relative t o t h e i n f l o w a n d d e c r e a s e d f o r all o t h e r types; therefore the combined input from the lake surface and the inflow are increasing t h e i n f l u x o f all p o l l e n t y p e s e x c e p t Pinus a n d Ulmus t o t h e lake s e d i m e n t surface. This e x a m p l e suggests t h a t w h e n a lake has an i n f l o w t h e i n f l u x o f all p o l l e n t y p e s is i n c r e a s e d b u t t h a t t h e p r e s e n c e o f an o u t f l o w d i f f e r e n t i a l l y a f f e c t s t h e p r o p o r t i o n s o f grains w h i c h r e m a i n in t h e basin. Davis ( 1 9 6 7 ) a n d Brush a n d Brush ( 1 9 7 2 ) h a v e s h o w n t h a t t h e h y d r o d y n a m i c s o f p o l l e n t y p e s differ, a f f e c t i n g t h e i r d i s t r i b u t i o n at t h e s e d i m e n t i n t e r f a c e ; M c A n d r e w s a n d P o w e r ( 1 9 7 3 ) a n d M c A t e e {1977) d e m o n s t r a t e d t h e e f f e c t o f s t r e a m i n p u t o n p a t t e r n s o f p o l l e n d i s t r i b u t i o n in L a k e O n t a r i o
324 TABLE V A. R values for the ten most important taxa, using values from the vegetation of the whole basin, and the river samples of pollen taken at Milltown, and the inflow and outflow of Beaver Lake Milltown
Beaver Lake
4.78 0.47 0.21 3.03 2.78 t.71 0.49 0.07 0.13 0.94
Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus
inflow
outflow
5.00 0.32 0.0,1 1.9,1 2A0 1.67 0A3 0.08 0,56 0.34
7.18 0.09 0.01 1.48 2.04 0.76 0.47 0.06 0.18 0.20
B. R values for the ten most important taxa, calculated from the pollen samples from the three fluvial sampling sites, using vegetational data from the limestone and shield areas of the basin Milltown
Beaver Lake inflow
(limestone basin) Pinus Cupressineae Populus Ostrya/Carpinus Betula Quercus Ulmus Acer Tilia Fraxinus
8.61 0.34 0.62 2.02 4.63 2.56 0.39 0.05 0.13 0.94
4.78 0.47 0.21 3.03 2.78 1.71 0.49 0.07 0.13 0.94
3.75 0.48 0.03 1.94 1.50 1.25 0.43 0.08 0.20 0.34
outflow (shield) 5.39 0.14 0.03 1.48 1.28 0.57 0.47 0.08 0.15 0.20
and Georgian Bay, respectively, and this e x a m p l e illustrates the potential e f f e c t o f an o u t f l o w t o a l a k e in t h e s e l e c t i v e t r a n s p o r t o f p o l l e n t y p e s . W h e n a l a k e a c t s as a s o u r c e o f p o l l e n f o r t h e d o w n s t r e a m s e g m e n t o f a river t h e p r o p o r t i o n a l r e p r e s e n t a t i o n o f t h e p o l l e n is d i f f e r e n t i a l l y d i s t o r t e d in c o m p a r i s o n t o t h a t in a s t r e a m w h i c h is n o t a f f e c t e d b y l a k e s , e.g. W i l t o n C r e e k { C r o w d e r a n d C u d d y , 1 9 7 3 ) . D e s p i t e p o l l e n e n t e r i n g t h e river b e t w e e n t h e o u t f l o w o f B e a v e r L a k e a n d t h e s a m p l i n g s t a t i o n at M i l l t o w n , t h e r e is a r e d u c t i o n in t h e n u m b e r o f grains s a m p l e d at t h e l o w e r site; t h e p o t e n t i a l sinks f o r t h e p o l l e n a r e : (1) m e c h a n i c a l d e s t r u c t i o n ; (2) t r a p p i n g o n t h e v e g e t a t i o n b o t h w i t h i n t h e c h a n n e l a n d o n its b a n k s ; a n d (3) s e d i m e n t a t i o n within the stream course. M e c h a n i c a l a b r a s i o n was a p p a r e n t f r o m t h e n u m b e r o f c o r r o d e d grains in the samples and the degree of "rounding" which had affected echinate
325 4
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140
168
196
224
252
280
308
336
in the river samples. Symbols asin Fig.4.
grains of the Compositae. Pollen trapped within the channel by vegetation would be released during die-back in the fall; an autumnal peak of resuspended pollen together with fragments o f leaf epidermis of Myriophyllum and Typha was recorded at a time of rising water level. Coincident with this peak
326 TABLE VI Ratio of number of grains at the outflow and inflow of Beaver Lake, showing the "export" of some types Pollen type
"Export"
Pollen type
"Export
Pin us
4.91
A m brosia
3.85
C upressineae
Grami~eae
4.27
Ace'-
1.00 0.90 2.61 2.92 ] 55 3.73 2,75
Sum Sum Sum Sum Sum
:k42 2.78 :~..i9 ~ 27 ~1.18
Tili~l Fraxmus
2.00
Populus Ostrya/Carpinus BeluZa Quercus Ulm us
A.P shrub herb grass aquatics
I . 11
Sum total
3.61
was an e f f l u x o f P e d i a s t r u m , p r e s u m a b l y f r o m shallows or lakes u p s t r e a m . The a u t u m n a l p e a k o f pollen in w a t e r f r o m Beaver L a k e was c o m p l e x , showing a s e c o n d a r y rise in t h e pollen load at t h e s a m e t i m e as t h a t in t h e air samplers. T h e p r i m a r y s o u r c e is inferred to be leaf abscission ( T a u b e r , 1 9 7 7 ; C r o w d e r and Starling, 1980). T h e a u t u m n a l p e a k registered at Milltown c o i n c i d e d w i t h rising w a t e r levels, b u t n e i t h e r air n o r w a t e r s a m p l e s t h e r e s h o w e d an increase in pollen c o n c e n t r a t i o n s e q u i v a l e n t to t h a t associated with leaf abscission f u r t h e r n o r t h . T h e highest c o n c e n t r a tion o f grains r e c o r d e d was d u r i n g the m e l t in spring w h e n s e d i m e n t transp o r t is also m o s t p r o n o u n c e d . CONCLUSIONS Rivers w h i c h have b e e n investigated all c o n t a i n pollen, or c o n t r i b u t e pollen t o o f f - s h o r e d e p o s i t s ( F e d e r o v a , 1 9 5 2 ; Muller, 1 9 5 9 ; Cross et al., 1966; G r o o t , 1 9 6 6 ; Mal'gina and Maev, 1 9 6 6 ; S t a n l e y , 1 9 6 9 ; C r o w d e r and C u d d y , 1973; P e c k , 1 9 7 3 ; Krassilov, 1 9 7 5 ; B o n n y , 1976). T h e a m o u n t o f pollen carried d e p e n d s o n t h e v o l u m e o f t h e river, its v e l o c i t y , t h e availability a n d n a t u r e o f its s e d i m e n t , its t r a p p i n g surface, t h e p r e s e n c e or a b s e n c e o f lakes in its course, and t h e a m o u n t o f pollen p r o d u c e d b y the regional v e g e t a t i o n . T h e S a l m o n River carries a g r e a t e r load t h a n the s t r e a m s studied b y P e c k ( 1 9 7 3 ) or C r o w d e r and C u d d y ( 1 9 7 3 ) b u t is o b v i o u s l y n o t c o m parable w i t h giants such as t h e V o l g a ( F e d e r o v a , 1 9 5 2 ) or t h e O r i n o c o (Muller, 1959). Pollen was c o l l e c t e d b y t h e river f r o m a lake w h i c h a c t e d as a t r a p p i n g surface (Beaver Lake), a l t h o u g h s o m e t a x a a p p e a r e d t o s e d i m e n t in the lake at t h e s a m e t i m e as o t h e r s m o v e d o n d o w n s t r e a m . Pine pollen as well as being m o s t volatile is also m o s t b u o y a n t ( P e n n i n g t o n , 1947), a n d so it a p p e a r s t o be b l o w n across t h e lake surface b e f o r e it sinks. It m a y also b e b l o w n against t h e river b a n k s and lost t o t h e s y s t e m . Beaver L a k e is so
327
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1
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aligned that the o u t f l o w is down-wind, and lined up with the longest fetch. If other saccate grains were abundant one would expect them to blow about on the surface t o o , but Picea and A bies are n o t important in this watershed• The river surface itself acted as a pollen trap, since more pollen was picked
328
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Fig.8. Pollen o f grasses in the river samples. S y m b o l s as in Fig.4. up downstream from Beaver Lake. During the late fall and early winter pollen movement was associated with that of fragments of epidermis from aquatic plants, indicating that the pollen was part of bottom deposits being shifted downstream; Pediastrum was also carried downstream at this time.
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c o n c e n t r a t e d in t h e z o n e o f g r e a t e s t v e l o c i t y , b u t t h e r e was also a m i n o r c o n c e n t r a t i o n n e a r t h e s t r e a m bed. T h e silt p o r t i o n o f t h e inorganic sedim e n t l o a d similarly travels in t h e z o n e o f m a x i m u m v e l o c i t y so t h a t t h e pollen is s u b j e c t t o a b r a s i o n . S a m p l e s w e r e f o u n d t o v a r y greatly in t h e i r
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Fig.ll. Pollen o f aquatic plants in the river samples. Symbols as in Fig.4.
weathering, and "Ambrosia" was o f t e n sand-papered s m o o t h . The maximal pollen load was f o u n d after t h e vernal melt, and during t h a t period o f f l o o d i n g t h e maximal load o f inorganic s e d i m e n t is also carried. Pollen was carried all t h r o u g h the year, with pulses going d o w n s t r e a m
332
even w h e n t h e river was a l m o s t entirely ice-covered -- at t h a t t i m e o f y e a r the s o u r c e o f pollen m u s t be s e d i m e n t within t h e s y s t e m . In this p r o j e c t r e w o r k e d pollen was n o t distinguished. In t h e spring, Ambrosia pollen was r e s u s p e n d e d b o t h in the air and t h e river, and in t h e late fall s e c o n d a r y p e a k s o f a r b o r e a l pollen o c c u r r e d in b o t h m e d i a w h e n pollen t r a p p e d o n d e c i d u o u s leaves was freed. In this p a r t o f O n t a r i o w h o l e catkins o f Betula can be o b s e r v e d being shed f r o m the trees in a u t u m n , still c o n t a i n i n g s o m e pollen. T h e p h e n o l o g y o f t h e trees, grasses, Ambrosia, shrubs and aquatics was f o u n d to be closely f o l l o w e d b y b o t h aerial and fluvial pollen, w i t h a p p r o x i m a t e l y the s a m e time-lag. T h e s e d a t a refine t h o s e f r o m Wilton Creek, w h i c h is a p p r o x i m a t e l y 40 k m to t h e east ( C r o w d e r and C u d d y , 1973). T h e r e p r e s e n t a t i v i t y o f t h e pollen in the river was f o u n d to be d i f f e r e n t at t h e t h r e e s a m p l i n g p o i n t s , b u t t h e m a i n d i f f e r e n c e was in t h e overr e p r e s e n t a t i o n o f Pinus in w a t e r e m a n a t i n g f r o m t h e lake. C o m p a r a b l e d i f f e r e n c e s in r e p r e s e n t a t i v i t y also o c c u r b e t w e e n aerial s a m p l i n g sites within the drainage basin. T h e m o s t f r e q u e n t a r b o r e a l t y p e s were Pinus, Quercus, Betula, Ostrya/Carpinus, Cupressineae, and Fraxinus, in t h a t order. Pinus was the m o s t o v e r - r e p r e s e n t e d n e a r t h e m o u t h o f t h e river, f o l l o w e d b y Ostrya/Carpinus, Betula and Quercus, whilst the o t h e r trees were underr e p r e s e n t e d . If t h e n o r t h e r n and s o u t h e r n p a r t s o f t h e basin (on shield and Palaeozoic l i m e s t o n e s , r e s p e c t i v e l y ) are c o n s i d e r e d s e p a r a t e l y , the overr e p r e s e n t a t i o n o f t h e s e f o u r t a x a was less in t h e n o r t h e r n p a r t o f t h e basin. T h e R values derived f r o m aerial and fluvial s a m p l e s should be useful in i n t e r p r e t i n g fossil assemblages w h o s e origin and t r a n s p o r t i n g m e d i u m are k n o w n . Whereas Pinus, Betula and Quercus are o v e r - r e p r e s e n t e d in b o t h , in t h e aerial s a m p l e s Fraxinus and t h e C u p r e s s i n e a e are o v e r - r e p r e s e n t e d , and in the fluvial o n e s u n d e r - r e p r e s e n t e d . Ostrya/Carpinus is o v e r - r e p r e s e n t e d in t h e fluvial s a m p l e s and n o t in t h e aerial ones. At p r e s e n t t h e S a l m o n River is c a r r y i n g a c o n s i d e r a b l e load o f pollen into the Bay o f QuintS. T h e river, like m a n y in eastern O n t a r i o , flows in t h e o p p o s i t e d i r e c t i o n to t h e prevailing w i n d ; this f a c t m a y even o u t o p p o s i n g t r e n d s in pollen representation. ACKNOWLEDGEMENTS We should like to t h a n k all t h o s e w h o h e l p e d and advised us in w o r k i n g on rivers and lakes, and t h e C a n a d i a n N a t i o n a l R e s e a r c h Council f o r funding. REFERENCES Bonny, A.P. 1976. Recruitment of pollen to the seston and sediment of some Lake District lakes. J. Ecol., 64: 859--887. Bonny, A.P. 1978. The effect of pollen recruitment process on pollen distribution over the sediment surface of a small lake in Cumbria. J. Ecol., 66: 385--416. Bostock, H.S., 1970. Physiographic sub-divisions of Canada. In: R.J.W. Douglas (Editor), Geology and Economic Minerals of Canada. Queen's Printer, Ottawa, Ont., pp.10--30.
333 Brooks, J. and Shaw, G., 1971. The role of sporopollenin in palynology. III Int. Palynol. Conf., Novosibirsk, pp.1--23. Brush, G.S. and Brush, L.M., 1972. Transport o f pollen in a sediment-laden channel: a laboratory study. Am. J. Sci. 272: 359--381. Cottam, G. and Curtis, J.T., 1956. The use o f distance measures in phytosociological sampling. J. Ecol., 37: 451--460. Cross, A.T., Thompson, G.G. and Zaileff, Z.T.B., 1966. Source and distribution of palynomorphs in b o t t o m sediments in the southern part of the Gulf of California. Mar. Geol., 4: 467--526. Crowder, A.A. and Cuddy, D.G., 1973. Pollen in a small river basin: Wilton Creek, Ontario. In: B.J.B. Birks and R.G. West (Editors), Quaternary Plant Ecology. Blackwell, Oxford, pp. 61--77. Crowder, A. and Starling, R.N., 1980. Contemporary pollen in the Salmon River basin, Ontario. Rev. Palaeobot. Palynol., 30: 11--26. Currier, P.J. and Kapp, R.O., 1974. Local and regional pollen rain components at Davis Lake, Montcalm County, Michigan. Mich. Acad., 7: 211--225. Cushing, E.J., 1964. Redeposited pollen in the Wisconsin pollen spectra from east-central Minnesota. Am. J. Sci., 262: 1075--1088. Davis, M.B., 1963. On the theory o f pollen analysis. Am. J. Sci., 261: 897--912. Davis, M.B., 1967. Pollen deposition in lakes as measured b y sediment traps. Bull. Geol. Soc. Am., 78: 849--858. Davis, M.B. and Brubaker, L.B., 1973. Differential sedimentation of pollen grains in lakes. Limnol. Oceanogr., 18: 635--667. Davis, R.B., Brewster, L.A. and Sutherland, J., 1969. Variation in pollen spectra within lakes. Pollen Spores, 11: 557--571. Erdtman, G., 1943. Introduction to Pollen Analysis. Chronica Botanica, Waltham, Mass. Faegri, V. and Iversen, J., 1964. T e x t b o o k o f Pollen Analysis. Blackwell, Oxford, 2nd ed., 237 pp. Farrar, J., Crowder, A. and Hummel, M., 1978. Ecological Effects of Fire and Its Management in Canada's National Parks. A.D. Revill Associates, Belleville and Parks Canada, Ottawa, Ont., 343 pp. Federova, R.V., 1952. The spread o f pollen and spores by water currents. Trans. Inst. Geogr. Acad. U.S.S.R., 5 2 : 4 6 - - 7 3 (in Russian). Gardner, J.S., 1976. Natural hazards o f climatic origin in Canada. In: G.R. McBoyle and E. Sommerville (Editors), Canada's Natural Environment. Methuen, Toronto, Ont., 46--68. Graf, K., 1969. The Hydraulics of Sediment Transport. Academic Press, New York, N.Y. Gregory, K.J., 1966. Dry valleys and the composition of the drainage net. J. Hydrol., 4: 327--340. Gregory, K.J. and Walling, D.E., 1973. Drainage Basin F o r m and Process: A Geomorphological Approach. Edward Arnold, London, 456 pp. Groot, J.J., 1966. Some observations on pollen grains in suspension in the estuary of the Delaware River. Mar. Geol., 4: 409---416. Havinga, A.J., 1971. An experimental investigation into the decay o f pollen and spores in various soil types. In: J. Brooks, P.R. Grant, M.D. Muir, P. van Gijzel and G. Shaw •(Editors), Sporopollenin. Academic Press, London, pp. 446--479. Horton, R.E., 1945. Erosional development of streams and their drainage basins - - a hydrophysical approach to quantitative geomorphology. Geol. Soc. Am. Bull., 56: 275--370. Krassilov, V.A., 1975. Palaeoecology o f Terrestrial Plants. Wiley, New York, N.Y., 283 pp. Likens, G.E., Bormann, F.H., Johnson, N.M., Fisher, D.W. and Pierce, R.S., 1970. Effects of forest cutting and herbicide treatment on nutrient budgets in the Hubbard Brook Watershed System. Ecol. Monogr., 40: 23--47.
334 Livingstone, D.A., 1968. Some interstadial and post glacial pollen diagrams from eastern Canada. Ecol. Monogr., 38: 87--125. Mal'gina, E.A. and Maev, E.G., 1966. Spore pollen spectra of bottom sediments in the Caspian Sea. Izv. Akad. Nauk. U.S.S.R. Geogr. Ser., 2 : 6 1 - - 7 0 (in Russian). McAndrews, J.H. and Power, D.M., 1973. Palynology of the Great Lakes. The surface sediments of Lake Ontario. Can. J. Earth Sci., 10(5): 777--792. McAtee, C.L., 1977. Palynology of Late Glacial and Post Glacial Sediments in Georgian Bay, Ontario, Canada, As Related to Great Lakes History. Thesis, Brock University, St. Catharines, Ont., 153 pp. Muller, J., 1959. Palynotogy of recent Orinoco delta and shelf sediments. Micropalaeontology, 5: 1--32. Ogden, E.C., Raynor, G.S. and Hayes, J.V., 1975. Travels of airborne pollen. EPA-650/375-003. Peck, R.M., 1973. Pollen budget studies in a small Yorkshire catchment. In: H.J.B. Birks and R.G. West (Editors), Quaternary Plant Ecology. Blackwell, Oxford, pp. 43--68. Pennington, W., 1947. Studies of the post glacial history of British vegetation. 7. Lake sediments. Philos. Trans. R. Soc., B. 248: 205--244. Raynor, G.S., Ogden, E.C. and Hayes, J.V., 1974. Enhancement of particulate concentrations downwind of vegetative barriers. Agric. Meteorol., 13:181--188. Ritchie, J.C. and Lichti-Federovich, S., 1963. Contemporary pollen spectra in central Canada. 1. Atmospheric samples of Winnipeg, Manitoba. Pollen Spores, 5: 95--116. Sangster, A.G. and Dale, H.M., 1961. A preliminary study of differential pollen grain preservation. Can. J. Bot., 39: 35--43. Sangster, A.G. and Dale, H.M., 1964. Pollen grain preservation of under-represented species in fossil spectra. Can. J. Bot., 42: 437--449. Stanley, E.A., 1969. Marine palynology. Oceanogr. Mar. Biol. Annu. Rev., 7: 277--292. Starling, R.N., 1978. Modern Pollen in the Salmon River Basin. Thesis, Queen's University, Kingston, Ont., 464 pp. Strahler, A.N., 1957. Quantitative analysis of watershed geomorphology. Trans. Am. Geophys. Union, 38: 913--920. Warwick, W., 1977. Report on Quint6 sediments. Project Quint6 Workshop, Glenora. Environment Canada, Fisheries Service. Tauber, H., 1977. Investigations of aerial pollen transport in a forested area. Dan. Bot. Ark., 32(1): 1--121. Taylor, G., 1977. An Investigation Into the Growth and Distribution of Maianthemurn canadense Within the Thousand Island Region. Thesis, Queen's University, Kingston, Ont., 64 pp.