Daniel F. BRUNTON
216, Lincoln Heights Road, Ottawa (Ontario) K2B 8A8 and
Bruce M. Dl LABIO
62, Grange Street, Ottawa (Ontario) K1 Y 0N9
Résumé
La flore vasculaire de vingt-trois plages émergeant de la rivière des Outaouais a été inventoriée lors de baisses records du niveau de l'eau, entre juin et octobre 1987. Divers types de substrats (sable, limon, argile, calcaire et grès) ont été visités. Cent trente-six taxons ont été notés sur des sites qui sont normalement inondés au moins jusqu'au début de l'été. Plusieurs de ces taxons sont rare à l'échelle locale et certains, à l'échelle provinciale : Potamogeton vaseyi, Fimbristylis autumnalis et Gratiola aurea (au Québec), ainsi que Isoetes riparia, Alisma grami-neum et Elatine triandra (en Ontario). L'abondance et la répartition des taxons rares sont briè-vement discutées. Près de 11 % des taxons sont adventices, alors que plus de 50 % sont indi-gènes et ont de vastes aires de répartition géographique. Les espèces nordiques sont favorisées par la fraîcheur du microclimat et se classent au deuxième rang par leur abondance (16 °/0). La persistence des feuilles, la tolérance au stress, ainsi que l'habilité à croître en milieu perturbé semblent être d'importants atouts pour la survie de ces plantes. Des plantes annuelles de terrain sec furent également notées sur les substrats qui émergent de façon saisonnière.
Abstract
A survey of the vascular flora of 23 emergent beach sites along the Ottawa River in Québec and Ontario was undertaken during record low water levels, between June and October 1987. A variety of beaches on different infertile substrates (sand, silt, clay, limestone and sand-stone bedrock, and granite cobble) were surveyed. A total of 136 taxa were recorded at sites normally under water until at least early summer. Many of these were rare at a local lèvel and several were provincially rare : Potamogeton vaseyi, Fimbristylis autumnalis and Gratiola aurea (Québec); Isoetes riparia, Alisma gramineum and Elatine triandra (Ontario). The status and dis-tribution of these and other locally rare taxa are discussed briefly. Approximately 11% of the beach flora are introductions. Over 50% of the native taxa are common species with wide geo-graphic ranges. Northern species, presumably favoured by the cool microclimate, represent the second largest group (16%). Evergreenness, stress tolerance and the ability to benefit from site disturbance appear to be important survival strategies. Upland annuals were also found on the seasonally available emergent substrate.
Introduction
While much research in Canada concerning the ecology and floristics of aquatic and terrestrial hab-itats has been undertaken, only relatively recently have botanists and ecologists turned a critical eye to the transition between those systems — the beach. The importance of regeneration
by
buried seed resulting from cyclical disturbances has received attention (Keddy & Reznicek, 1982;Keddy, 1983, 1985), as have investigations of pro-ductivity (Boston & Adams, 1987), the relation-ships between species richness and standing crop (Moore & Keddy, 1989b), and succession (Savile, 1951; van der Valk, 1981). A rich literature exists in Québec and Ontario in which aquatic and emer-gent flora are treated within general floristic studies
(e.g.
Dore & Gillett, 1955; Lavoie, 1984; Morton &Venn, 1984; Reznicek & Catling, 1989), but few studies focus on the distribution, survival strategies
180 LE NATURALISTE CANADIEN. VOL 116. 1989 and status of the stress-tolerant flora of infertile wet
beach habitats (Moore & Keddy, 1989b).
The summer of 1987 witnessed the lowest water levels ever recorded along the Ottawa River in western Québec and eastern Ontario, exposing large areas of wet beach that rarely, if ever, had been examined botanically (Fig. 1). This offered an excellent.opportunity to survey the vascular flora of these emergent habitats and to enumerate the species growing there. Accordingly, we undertook a survey of sites along the Ottawa River in order to characterize the vascular flora of these emergent beaches. The present paper reports the results of this survey, and discusses the floristic affinities of the emergent beach flora and some of the main survival strategies employed on these infertile wet beach habitats.
Methods
Between June and October 1987 we con-ducted over 40 visits to sites along the Ottawa River between Quyon, Pontiac County, Québec and Cumberland, Russell County, Ontario (Fig. 2).
All of these are within the Ottawa-Hull region, viz within a 50 km radius of the Parliament Buildings
in Ottawa (Anonymous, 1981). This region, also known as the Ottawa District, has served as the limit for local natural history investigations for over a century.
The sites varied considerably in size, substrate and situation. Some were visited repeatedly while others were examined only once. In most cases Di Labio collected samples of all species observed during his visits and brought them back for deter-mination. Brunton made notes in the field on the taxa observed and collected vouchers for rare and unknown species. Most vouchers have been deposited in DAO, TRT and/or Brunton's personal herbarium (DFB), with pteridophytes being depos-ited in OAC (acronyms of Boivin, 1980).
We attempted to identify all vascular taxa observed at each of the 23 study sites (Table I).
We recorded the species present and collected voucher specimens only from the areas of emer-gent beach, viz, river bottom submerged by normal post-spring water levels but now exposed.
Records of rare species provincially (Bouchard et al., 1983; Argus et al., 1982-1987) and locally (Gillett & White, 1978; Brunton, 1985a, 1985b, 1985c), or of taxa not previously recorded in the
Figure 1. Sparsely and heavily vegetated pure sand and silty sand emergent beach at Site 1, Quyon (20 September 1987).
BRUNTON & DI LABIO: BEACH FLORA OF THE OTTAWA RIVER 181
11 *
und
1....•••••
4
•—•
5 20
o--19 17 18
21
••••••
ed.
22
Owntled.ou
23
0
Figure 2. Ottawa River study sites (see text).
TABLE I
Émergent vascular flora study sites along the Ottawa River (UTM references in parentheses) QUÉBEC
1. Quyon Beach, Onslow Township, Pontiac Co.
(VF 383247)
2. Onslow Beach, Onslow Township, Pontiac Co.
(VF 125424)
3. Breckenridge Bay, Eardley Township, Gatineau Co.
(VF 234373)
4. The Cedars, Aylmer, Gatineau Co.
(VF 320277)
5. Deschênes Rapids, Aylmer, Gatineau Co.
(VF 374255) ONTARIO
6. Morris Island, Fitzroy Township, Regional Municipality of Ottawa-Carleton (R.M.O-C) (VF 010347)
7. Mohr's Landing, Fitzroy Township, R.M.O-C.
(VF 046404)
8. McLaren's Landing, Torbolton Township, R.M.O-C.
(VF 089404)
9. Constance Bay North, Torbolton Township, R.M.O-C.
(VF 135399)
10 Constance Bay South, Torbolton Township, R.M.O-C.
(VF 165364)
11. Buckham Bay, Torbolton Township, R.M.O-C.
(VF 144379)
12. Horseshoe Bay, Torbolton Township, R.M.O-C.
(VF 178373)
An extensive, heavily vegetated, moderately slop-ing sand and silty sand beach downstream of a large boat pier.
An extensive, gently sloping silty sand beach behind a protective sand spit with areas of sparse to dense aquatic and emergent vegetation.
A sparsely vegetated, gently sloping clay beach in a quiet bay.
A narrow, sparsely vegetated, moderately sloping limestone bedrock and sand beach exposed to the main river flow.
A narrow, sparsely vegetated, silt and sandstone bedrock beach in a side bay below a major rapids.
Narrow, sparsely vegetated, moderately sloping sand and limestone bedrock beach amongst small Islands.
Narrow, sparsely vegetated, moderately sloping sand and clay beach downstream of small boat pier.
Extensive, moderately vegetated, gently sloping sand and silt beach in a quiet bay.
Large, moderately to heavily vegetated, almost flat pure sand beach.
Large, moderately vegetated, gently sloping to almost flat sand and silty sand beach.
Extensive, sparsely vegetated, gently sloping sand beach in a quiet bay.
Large, densely vegetated, gently sloping sand and clay beach with granite cobble margin, in quiet, shallow bay.
182 LE NATURALISTE CANADIEN. VOL. 116. 1989
TABLE I (continued)
13. Beatty Point, Nepean, R.M.0-C.
(VF 320234)
14. Stillwater Park, Nepean, R.M.O-C.
(VF 351231)
15. Ottawa Beach, Haydon Park, Nepean, R.M.O-C.
(VF 361223)
16. Scrivens Avenue Beach, Ottawa, R.M.O-C.
(VF 369230)
17. Britannia Pier, Ottawa, R.M.O-C.
(VF 371236)
18. Britannia Filtration Plant, Ottawa, R.M.O.-C.
(VF 383247)
19. Deschênes Lookout, Ottawa, R.M.O.-C.
(VF389252)
20. Kitchissipi Lookout, Ottawa, R.M.O-C.
(VF 403271)
21. Remic Rapids, Ottawa, R.M.O-C.
(VF 415383)
22. Petrie Island, Cumberland, R.M.O-C.
(VF 610387)
23. Ministry of Transport Picnic Area, Cumberland, R.M.O-C.
(VF 662403)
Narrow, sparsely vegetated, gently sloping lime-stone bedrock and silt beach exposed to main river flow.
Extensive, sparsely vegetated, gently sloping limestone bedrock, silty sand and granite cobble beach in quiet bay.
Vast, moderately to sparsely vegetated, gently sloping to almost level sand and clay beach.
Vast, sparsely to moderately vegetated, gently sloping to almost level clay beach.
Extensive, moderately to sparsely vegetated, almost level sand and silty sand beach with scat-tered shale and sandstone outcroppings.
Narrow, densely vegetated, gently sloping silty sand and sandstone bedrock beach in a quiet shallow bay below rapids.
Narrow, moderately sloping, sparsely vegetated sandstone and shale bedrock beach exposed to main river flow.
Narrow, moderately sloping, sparsely vegetated sand and shale bedrock beach exposed to main river flow.
Small, gently sloping, sparsely vegetated sand and shale bedrock and silt beach in bay below large rapids.
Narrow, moderately sloping, sparsely vegetated sand beach along Island edge in river channels.
Narrow, steeply sloping, sandstone bedrock and silty clay, sparsely vegetated beach exposed to the main river flow.
Ottawa-Hull region were supported by voucher specimens wherever possible.
Results
There was a great floristic diversity on the emergent beaches that we surveyed along the Ottawa River (Table I). We noted 136 taxa (Table Il), a majority of which (57%) were monocots. This high figure presumably reflects the higher propor-tion of monocots than dicots that are adapted to the ecological advantages and constraints of pro-longed submergence (cf. Fassett, 1972).
Almost half (48%) of the emergent beach flora consisted of species described as uncommon, sparse or rare by Gillett & White (1978). This is a much higher figure than that for upland areas in the Ottawa-Hull region. About 35% of the flora in the Mer Bleue and Stony Swamp Conservation Areas
(in Gloucester/Cumberland and Nepean, respec-tively), for example, have comparable status (Brunton, 1982, 1984).
Several species are considered to be provin-cially rare in Québec or Ontario. They are briefly mentioned below, as are those locally rare or sparse taxa represented by 12 or fewer records in the Ottawa-Hull region.
lsoetes riparia
Sites 1, 2 and 6; Québec and Ontario
It was found uncommonly in sand and gravel and open silty sand, often deeply inset into the substrate, in formerly deep water (>0.5 m) sites.
This is a species of the Atlantic coastal plain and the eastern slope of the Appalachian Mountains that is uncommon in Québec (Kott & Britton, 1983) and rare in Ontario (Kott, 1983).
BRUNTON & DI LABIO: BEACH FLORA OF THE OTTAWA RIVER 183 TABLE II
Species observed at Ottawa River study sites
(site numbers are those used in Table I ; introduced species are indicated by**)
Species Sites [Bold Face indicates voucher specimen(s)]
ISOETACEAE Isoetes x dodgei Eat.
1. echinospora Dur.
I. x hickeyi Taylor & Luebke I. macrospora Dur.
I. riparia Engelm.
EQUISETACEAE Equisetum x litorale Kuhl.
ASPLENIACEAE Onoclea sensibilis L.
TYPHACEAE Typha latifolia L.
SPARGANIACEAE
Sparganium chlorocarpum Rydb.
S. fluctuans (Morong) Robins.
POTAMOGETONACEAE Potamogeton epihydrus Raf.
P. gramineus L.
P. natans L.
P. obtusifolius Merl. & Koch P. perfoliatus L.
P. richardsonii (A. Benn.) Rydb.
P. robbinsii Oakes P, spirillus Tuckerm.
P. vaseyi Robbins P. zosteriformis Fern.
ZANNICHELLIACEAE Zannichellia palustris L.
NAJADACEAE
Najas flexilis (Willd.) R. & S.
ALISMATACEAE Alisma gramineum Gmel.
A. triviale Pursh
Sagittaria graminea Michx.
S. latifolia Willd.
S. rigida Pursh HYDROCHARITACEAE Elodea canadensis Michx.
Hydrocharis morsus-ranae L."*
Vallisneria americana Michx.
POACEAE
Agrostis stolonifera L.
Digitaria ischaemum (Schreb.) Muhl.""
Echinochloa crusgalli (L.) Beauv.**
E. wiegandii (Fassett) McNeill & Dore Eragrostis minor Host*"
E. pectinacea (Michx.) Nees**
Glyceria borealis (Nash) Batch.
Leersia otyzoides (L.) Sw.
Panicum capillare L.
1, 2, 7, 12 1, 8, 10, 12, 19, 20 2
2 1, 2, 6 1 19 15, 17 18, 21 1 1-3, 11, 12 3, 9, 11, 12, 15, 17 6
5
1-4, 7, 9, 12, 15,18 1, 9, 17, 18 6, 7, 12, 18 5, 6, 8, 17-20 2, 6, 18 18 14-16
1, 9, 11, 16-18 15
1, 3, 7, 8, 12-19, 21, 23 1, 4, 5, 7, 8, 9, 12, 17, 18, 19, 1-23
16, 17, 18
1, 6, 7, 9, 12, 15-18, 22 17
1, 7, 9,10, 12, 15, 16-19, 23 21
11, 17 1 11, 16-19 17 2, 10, 18 1, 11, 18 12, 18 1, 7, 12, 15, 17
20, 23
184 LE NATURALISTE CANADIEN, VOL. 116, 1989 TABLE II (continued)
Species Sites [Bold Face indicates voucher specimen(s)]
Phalaris arundinacea L. 10, 12,18
Setaria glauca (L.) Beauv. 18
Spartina pectinata Link 15, 17, 18, 21
Zizania palustris L. 1, 9, 12, 15, 16
CYPERACEAE
Carex lacustris Willd. 18
C. lenticularis Michx. 18
Cyperus aristatus Rottb. 1, 2, 7, 10, 12, 16
C. bipartitus Torr. 1, 7, 11, 12, 17
C. diandrus Torr. 1, 3, 7, 18
C. odoratus L. 12, 18
C. strigosus L. 1, 7, 18
Dulichium arundinaceum (L.) Britt. 16
Eleocharis acicularis (L.) R. & S. 1, 2-4, 5, 6-9, 10, 11-18, 19, 20-23
E. erythropoda Steudl. 1, 2, 7, 12, 20, 21
E. intermedia (Muhl.) Schultes 1, 15, 16
E. obtusa (Willd.) Schultes 1, 16, 22
ovata (Roth) R. & S. 1
E. palustris (L.) R. & S. 1-23
E. tenuis (Willd.) Schultes
var. borealis (Svenson) Boivin 1, 17
(E. elliptica Kunth.)
Fimbristylis autumnalis (L.) R.& S. 3, 12
Scirpus cyperinus (L.) Kunth 1, 17
S. fluviatilis (Torr.) Gray 1, 7
S. pungens Vahl. 1, 9, 10, 12-23
S. lacustris L.
var. condensatus Peck 1-23
var. glaucus (Sm.) Bôck 3, 18
LEMNACEAE
Lemna minor L. 15,18
L. trisulca L. 16, 19
ERIOCAULACEAE
Eriocaulon septangulare With. 1, 3, 10, 12, 18 PONTEDERIACEAE
Pontederia cordata L. 7, 12, 16, 18
Zosterella dubia (Jacq.) Small 2, 5, 12, 13, 15, 16, 17, 22 JUNCACEAE
Juncus alpinoarticulatus Chaix. ex Vill. 1, 16
J. articulatus L. 1, 9, 11, 16, 21
brevicaudatus (Engelm.) Fern. 9, 11, 16
J. bufonius L. 1, 15, 22
J. compressus Jacq."* 21
J. dudleyi Wieg. 17
J. effusus L. 7, 18
J. filiformis L. 3, 10, 12
J. nodosus L. 1, 10, 20, 21
J. pelocarpus E. Mey. 1-3, 7, 9, 10-12,16, 17, 19
J. subtilis E. Mey 1, 9
IRIDACEAE
Iris versicolor L. 18
SALICACEAE
Populus deltoides Marsh. 1, 7, 15-18
POLYGONACEAE
Polygonum hydropiper L. 18
BRUNTON & DI LABIO: BEACH FLORA OF THE OTTAWA RIVER 185 TABLE II (continued)
Species Sites [Bold Face indicates voucher specimen(s)]
P. lapathifolium L.- 7, 17,21
P. neglectum Bess. 1,18
P. pensylvanicum L. 1, 17, 18
P. persicaria L.- 1,7, 12, 17
Rumex verticillatus L. 18
CHENOPODIACEAE
Chenopodium glaucum L.- 16
MOLLUGINACEAE
Mollugo verticillata L.** 1
NYMPHAEACEAE
Nuphar microphylium Morong 17, 18
N. variegatum Engelm. 12, 16, 17
Nymphaea odorata Ait. 10, 16, 22
RANUNCULACEAE
Ranunculus aquatilis L. 1, 7, 10, 16, 18
R. reptans L. 1, 3, 6. 12, 18, 19, 21
R. sceleratus L.- 1
BRASSICACEAE
Erysimum asperum (Nutt.) DC.- 18
Rorippa palustris (L.) Bess.(s. I.) 7, 12, 17, 18 ROSACEAE
Potentilla anserina L. 21
EUPHORBIACEAE
Acalypha rhomboidea Raf. 18
Euphorbia maculata L. 18, 21
CALLITRICHACEAE
Callitriche hermaphroditica L. 21
C. verna L.
BALSAMINACEAE
Impatiens capensis Meerb. 1,18
CLUSIACAE
Hypericum boreale (Britt.) Bickn. 18
H. ellipticum Hook. 12
H. majus (Gray) Britt. 1
ELATINACEAE
Elatine triandra Schkr. 6
VIOLACEAE
Viola lanceolata L. 12, 18
LYTHRACEAE
Lythrum salicaria L."" 1, 3, 5, 7-23 ONAGRACEAE
Epilobium ciliatum Raf.
ssp. g/andulosum (Lehm) Hoch & Raven 18
Ludwigia palustris (L.) Ell. 1, 7, 12
HALORAGACEAE
Myriophyllum alterniflorum DC. 1, 6, 7, 11, 17
M. sibiricum Komarov 1, 2, 6, 7, 17, 18
M. tenellum Bigel. 1, 2-4, 9, 10, 12, 20, 21
186 LE NATURALISTE CANADIEN, VOL. 116, 1989 TABLE II (continued)
Species Sites [Bold Face indicates voucher specimen(s).1
APIACEAE Cicuta bulbifera L.
Sium suave Walt.
PRIMULACEAE
Lysimachia terrestris (L.) BSP.
MENYANTHACEAE
Nymphoides cordata (EII.) Fern.
LAMIACEAE
Lycopus americanus Muhl.
L. uniflorus Michx.
Mentha arvensis L.
SCROPHULARIACEAE Gratiola aurea Pursh Lindernia dubia (L.) Penn.
Mimulus ringens L.
LENTIBULARIACEAE Utricularia vulgaris L.
PLANTAGINACEAE Littorella americana Fern.
Planta go major L.**
ASTERACEAE
Ambrosia artemisiifolia L.
Aster lateriflorus (L.) Britt. (s. I.) Bidens beckii Torr.
B. cernua L.
B. frondosa L.
Euthamia graminifolia (L.) Nutt.
Gnaphalium uliginosum L.
Taraxacum officinale Weber"*
1, 17 1, 17, 21 17
1, 2, 8, 10, 11 1, 12 7 6, 18 9, 12, 18 1, 18 12, 18, 21 6 12 7, 17, 18 1, 18 12 1,19
1,2,7, 12, 16-18 1,7,12,17, 18 18
1,7, 17 1,12,17,18
Isoetes x dodgei
Sites 1, 2, 7 and 12; Ontario and Québec The discovery of hybrids between I. echino-spora and I. riparia during the present study lead to the recombination and description of this taxon (Britton & Brunton, 1989). Site 12 constitutes the cytological type location for I. x dodgei. It grew atone or with either or both parent species in pop-ulations of varying sizes in silt and sand in formerty deep water situations. It is otherwise found locally at scattered sites along the Ottawa River and in lakes in Gatineau and Papineau Counties.
lsoetes x hickeyi Site 2; Québec
Taylor & Luebke (1988) described this hybrid between I. echinospora and I. macrospora from a single site in Wisconsin. A second population was found along the Ottawa River during our study,
growing with an abundance of I. echinospora and I. x dodgei, moderate numbers of I. riparia and a small number of I. macrospore in silty sand over clay in a formerly shallow water (<0.5 m) site.
Equisetum x litorale Site 1 ; Québec
One small population grew in open, wave-washed sand in a formerty shallow water site. This hybrid between E. arvense L. and E. palustre L. is otherwise known in the Ottawa-Hull region from five sites along major rivers in Ontario and Québec (Lafontaine, 1973; Brunton, 1980).
Sparganium fluctuans Site 1; Québec
It was found uncommonly in open sand in a for-merly deep water site. This widespread aquatic of central Ontario and Québec is approaching the