Abstract
Four species of aquatic plants known to occur in the Prince George region were observed at various field locations. Qualitative observations of morphology, habitat, community structure, and relative densities were made in the field. Comparisons between published material and field observations were made regarding morphological, ecological, and distributional aspects of Potentilla palustris, Beckmannia syzgnache, Ranunculus gmelinii, and Ceratophyllum demersum. These four species were found to utilize a variety of habitats in the Prince George region and to conform to expected morphological and ecological characteristics.
Introduction
Plants are important members of aquatic communities and play significant roles in ecosystem functioning. Submerged macrophytes have a strong influence on the biological structure, nutrient cycles, and sediment stability of aquatic habitats (Middelboe and Markager, 1997). In addition, aquatic plants provide essential habitat, food, and refugia from predators for many invertebrate species (Parsons and Matthews, 1995).
Aquatic plants have many growth forms. These range from canopy primary producers that concentrate their biomass at or near the waters surface, to fully submerged forms occupying deeper regions of aquatic systems and living in close association with underwater substrates (Chambers and Kalff, 1987).
The natural distribution of aquatic plants within a habitat is largely regulated by the spatial area and hydrological characteristics of the habitat, as well as the light requirements and maximum colonization depth of a particular species (Middelboe and Markager, 1997). Distributions of aquatic species are also influenced by other physical factors including nutrient availability, turbidity, irradiance, and substrate characteristics (Chambers and Kalff, 1987).
The distributions and habitat characteristics of P. palustris, B. syzgnache, R. gmelinii, and C. demersum in the Prince George region are accurate reflections of their morphological forms and aquatic characteristics. C. demersum is a fully submerged species while P. palustris, B. syzgnache, and R. gmelinii are partially emergent aquatic plants. All of these species were observed locally in marsh and/or lake habitats in varying abundances. The plant communities examined were similar across several spatially seperated habitats, however some interesting variations in abundance and plant associations were observed.
Methods
Field observations were qualitative in nature. Observations were made at various sites around the Prince George region through Sept-Oct, 1997. Three marsh, seven lake, and one stream habitat were visited (see Appendix A for site location details). Peripheral marsh areas were often observed at the lake sites. Records were kept noting presence or absence of the species of interest. Observations were also made regarding habitat, other aquatic or semi-aquatic species in the area, morphological characteristics, ecology, and relative abundances of the species of interest. Searching time and area varied across sites, with more time being spent where a species of interest was observed.
Results
P. palustris, B. syzgnache, R. gmelinii, and C.demersum were
observed in various habitats located
throughout the Prince George region (see Table 1). P.
palustris was observed the most across the sites examined and B. syzgnache
the least. All four species were never observed to co-occur.
P. palustris and R. gmelinii were often observed to occur
simultaneously in a habitat. C. demersum was only observed
in the form of small apical specimens found near shore at three lake habitats.
B. syzgnache was only observed in one of the 11 areas visited and
was in low abundance at this site.
Table 1: Observation record for local survey of aquatic plant species.
+ observed / - not observed
Location
Potentilla palustris Beckmannia syzgnache Ranunculus
gmelinii Ceratophyllum demersum
(see appendix A)
Shane Lake
+
-
-
-
Cluculz Lake
-
-
-
+
Cluculz Marsh
-
-
+
-
West Lake
-
-
-
-
Old Summit Lake Marsh +
+
+
-
MacMillan Creek
-
-
-
-
Tabor Lake
+
-
+
+
Buckhorn Lake
+
-
+
-
97 South Marsh
-
-
-
-
Ness Lake
-
-
-
+
Nukko Lake
+
-
-
-
Discussion
Potentilla palustris is a member of the family Rosaceae which is comprised of 100 genera including Potentilla which contains over 300 species (Smith, 1977). P. palustris is a perennial dicot found in marshes, bogs, wet meadows, and lake margins, from low to medium elevations (MacKinnon et al., 1992).
This species is a stoloniferous plant with a large belowground biomass
(Saarinen, 1996). Its morphology is representative of stoloniferous
plants wherein resources are often differentially allocated to stems and
petioles in response to varying light intensities (Huber, 1996).
This species has long, creeping, woody rhizomes that are often floating
or partially submerged with emergent flowering stems often reddish in colour
(MacKinnon et al., 1992; Johnson et al., 1995). The leaves of P.
palustris are palmate and usually divided into 5 - 7 oblong leaflets with
coarsely toothed edges (MacKinnon et al., 1992). Flowers are reddish-purple
and arranged in loose terminal clusters (MacKinnon et al., 1992).
P. palustris is the only species of Potentilla with purple petals and sometimes
has 6, rather than 5, petals and sepals (Johnson et al., 1995). Another
distinguishing floral characteristic of this species is that its floral
sepals are twice as long as the petals (Hotchkiss, 1972). This species
is entomophollous and its flowers emit a fetid odour attracting carrion
feeding insects as pollinators (MacKinnon et al., 1992).
Figure 1: Potentilla palustris at Old Summit Lake marsh, Prince George, B.C. 10/10/97.
This species has been traditionally used for various herbal and medicinal
purposes. These include use of the stem by the Haida in a medicinal
preparation for tuberculosis, use of dried leaves in making a common tea
throughout arctic regions, and use of roots which are bitter and astringent
in concoctions for the treatment of stomach cramps and dysentery (Johnson
et al., 1995).
P. palustris is known to occur across boreal forest zones north
to the arctic coast and is common in the northern B.C. region (MacKinnon
et al., 1992; Johnson et al., 1995).
In the Prince George region, P. palustris was observed at five locations. These include Old Summit Lake marsh (see Fig.1), Buckhorn Lake, Nukko Lake, Tabor Lake, and Shane Lake. At the four lake locations, this species was observed in peripheral marsh-like habitats on the edges of the lakes. The plant was found either emerging from shallow water or growing out of water on muddy substrate close to the waters edge. Morphologically this species was similar at all observation sites, however variation in leaf number and colour existed within sites. Leaves consistently had either five or seven leaflets and were various shades of green, red, and brown. No flowers were observed due to the season in which observations were made. Stems and rhizomes were thick and consistently reddish-brown in color. Rhizomes were often observed partially submerged in still or slow-moving, shallow water.
P. palustris was not observed on lake margins that were sandy
and relatively open (Cluculz Lake, West Lake, Ness Lake) nor was it observed
in the stream habitat with gravel/rock substrate and rapid water movement
(MacMillan Creek). These observations suggest that P. palustris
grows favorably in habitats with slow water movement, soft substrates (mud,
silt, and organics) and at shallow depths. Nevertheless, this species
was the most commonly observed and found in the greatest range of habitats.
B. syzgnache is a member of the large grass family Poaceae.
This family contains over 10,000 species which occur in a vast range of
habitats worldwide (Smith, 1977). Many members of Poaceae are known
best for their economic importance as food plants and forage crops (Smith,
1977). The genus Beckmannia is comprised of two semi-aquatic species
that occur in cool, temperate regions of the northern hemisphere (Cook
et al., 1974).
B. syzgnache is a stout, erect, annual monocot with flat blade leaves
and numerous short ascending spikes in a narrow interrupted panicle (Hubbard,
1969). The spikelets are one or two flowered, laterally compressed,
and arranged in two rows along one side of a slender continuous rachis
(Hubbard, 1969). Flower clusters and leaves can both grow up to a foot
long (Hotchkiss, 1972). B. syzgnache is palatable to livestock
and is sometimes sufficiently abundant to be an important forage grass
or cut for hay (Hubbard, 1969).
B. syzgnache is commonly found in wet meadows, ditches, and inland
freshwater marshes from Alaska to Ontario (Hubbard, 1969). In British
Columbia, it is known to occur in the Prince George and Cariboo regions,
Creston Flats, and Ootsa Lake (Hubbard, 1969).
Figure 2: Beckmannia syzgnache at Old Summit Lake marsh,
Prince George, B.C. 10/10/97.
In the Prince George region this species was only observed at one of
eleven field sites, the Old Summit Lake marsh (see Fig.2). At this
site the species was observed at only two locations, growing in small clusters,
on either side of a road, emerging from slow-moving, shallow water.
Ten to fifteen stems were observed clustered near both outlets of two culverts
spanning the roadway. Other species observed in the direct vicinity
of B. syzgnache included other tall grasses (Glyceria grandis, Phragmites
communis) and P. palustris. Generally, the habitat here
was marshy, stagnant, and somewhat polluted due to the close proximity
to the road. The low abundance of observations of this species among
habitats seems strange for what is considered a common marsh grass.
Similarly, the concentration and low abundance of B. syzgnache in
the habitat where it was observed is interesting. Perhaps this species
requires particular microhabitat characteristics which have yet to be delineated.
R. gmelinii is a perennial aquatic plant usually found creeping on mud or floating in water, with stems freely rooting at the nodes (MacKinnon et al., 1992). The leaves of this species are small and deeply divided into three lobes, each of which is again divided linearly into smaller, more elongate lobes (MacKinnon et al., 1992). The leaf forms of this species are strongly heterophyllous and the lobes of submerged leaves are more delicate and often finer than those of floating leaves (MacKinnon et al., 1992). The flowers of this species are small, yellow, five-petaled, and seen in late spring and summer in loose clusters emerging slightly above the waters surface (Hotchkiss, 1972; MacKinnon et al., 1992). Another name for this species is yellow water-crowfoot, derived from the resemblance of the leaves to the foot of a crow (MacKinnon et al., 1992).
R. gmelinii is commonly found in mudflats, shallow ponds, ditches,
drained beaver ponds, and lake shore margins (MacKinnon et al., 1992).
This species is common at lower elevations throughout the northern B.C.
region (MacKinnon et al., 1992).
Figure 3: Ranunculus gmelinii at Old Summit Lake marsh, Prince George, B.C. 10/10/97.
In the Prince George region, R. gmelinii was observed mainly
in marsh habitats. It was observed in two distinct marshes (Old Summit
Lake marsh [see Fig.3] and Cluculz marsh) and two marsh areas on the margins
of small local lakes (Tabor and Buckhorn Lakes). This species was
most often observed growing in mat-like, submerged formations in shallow
and still or slow-moving water. Differences in leaf size and structure
between floating and submerged leaves was observed at all sites.
R. gmelinii was not observed to be present in lakes near relatively clean
shores exposed to greater wind and water velocities. R. gmelinii
was often observed in the same locality as P. palustris suggesting
that these two aquatic species have similar habitat requirements and distributions
in the Prince George region.
C. demersum is a member of the monotypic family Ceratophyllaceae, to which there belongs 2-10 species of unisexual aquatic plants (Smith, 1970). All Ceratophyllum species are obligately submerged aquatics and cannot tolerate periods of emergence (Cook et al., 1974).
C. demersum is a submerged herb with slender, freely branched
stems lacking roots but sometimes possessing modified branches forming
rhizoids (Cook et al., 1974; Johnson et al., 1995). The leaves of
this species are rigid and forked (2 or 3 times) into slender spiny-toothed
fragments in whorls of 5-12 often coated with lime (Johnson et al., 1995).
The forked leaves distinguish this species from other submerged aquatics
with similar forms (ie. Myriophyllum spp.) (Hotchkiss, 1972). The
flowers of this species are tiny and inconspicuous and located in the leaf
axils (Johnson et al., 1995). The sexes are in seperate flowers on
the same plant and do not bear sepals or petals (Johnson et al., 1995).
C. demersum is adapted to grow at relatively low light intensities
and therefore may be expected to inhabit deeper portions of aquatic systems
relative to emergent plants requiring greater radiance regimes (Parsons
and Matthews, 1995). Particular morphological features of this species,
including thin submerged leaves and large surface to weight ratios, make
it an important habitat species for many aquatic invertebrates (Mjelde
and Faafeng, 1997).
C. demersum is found in ponds, lakes, ditches and quiet streams
either floating in the water column or loosely anchored in silt (Johnson
et al., 1995; Cook et al., 1974). This species is circumpolar in
distribution although less common in more northern regions (i.e. >60
lat.) (Johnson et al., 1995).
Figure 4: Ceratophyllum demersum. Top specimen collected
from Ness Lake, Prince George, B.C. 10/05/97.
Bottom two specimens collected at Cluculz Lake, Prince George, B.C.
09/20/97.
In the Prince George area this species was observed in three lake habitats (Cluculz, Ness, and Tabor Lakes). All of these habitats had fairly open shores with high environmental exposure and large amounts of vegetation washed around the periphery of the lake. Small specimens of C. demersum were found amongst this vegetation (see Fig.4) but the species was not observed to be free growing in these shallow zones. This suggests that this species is more common in deeper regions of aquatic habitats and does not grow close to lake margins. In all three lakes where this species was observed there were large populations of Elodea canadensis. In two of the lakes several Potamogeton species were also observed. These species, including C. demersum, seem to be more associated with clear water, open lake systems than they do to marsh-like or standing water pools.
Conclusions
Aquatic plants are distributed geographically according to hydrological, physical, and climatic requirements and play important functional roles as members of aquatic ecosystems. Freshwater macrophytes occupy a wide range of aquatic systems varying from roadside ditches to large clear water lakes. In the Prince George region, several families of aquatic plants are represented and commonly occur in a variety of habitats. P. palustris, B. syzgnache, R. gmelinii, and C. demersum are four species of aquatic plants found in the Prince George region. These species represent a variety of aquatic plant life forms including that of a fully submerged dicot macrophyte and that of an emergent semi-aquatic monocot.
P. palustris and R. gmelinii appear to be common inhabitants of slow-moving or still water marshes and ponds in the region. C. demersum, as an obligately submerged species, seems to be more closely associated with lake systems and is commonly found in plant communities that include species of the genera Elodea and Potamogeton. B. syzgnache was only observed in one location suggesting that it occurs less commonly in the Prince George region than the other species of interest.
A small qualitative survey of particular plant species of interest can provide information regarding their relative abundance, morphological variation, and community associations in a small geographical region. This information may contribute to current inventories or distributional analyses of aquatic plant species and communities within a region.
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Appendix A: Site location descriptions.
Shane Lake - located at Forests For the World Regional Park,
north-west of Prince George on
Cranbrook Hill. Observations were made on the north side of the
lake near the observation deck and in the marshy area to the east of the
deck.
Cluculz Lake - located ~ 40 km. west of Prince George, south
of Hwy. 16. Observations were made on
the south-east edge of the lake. Turn south off of Hwy. 16 onto
Lloyd Dr. and follow west to fork. Go right at fork to Exmoor Path
Dr. and follow to end. Follow path (~50 m.) to waters edge.
Cluculz marsh - located ~ 40 km. west of Prince George.
Turn south off of Hwy. 16 onto Lloyd Dr.
and follow ~ 500 m. Marsh is located on north side of Lloyd Dr.
West Lake - located ~ 20 km. south-west of Prince George off
of Hwy. 16 west. Observations were
made on the north-east side of the lake via access from the main parking
lot.
Old Summit Lake marsh - located ~ 15 km. north of Prince George.
Follow Hwy. 97 north to
Northwood Pulpmill Rd. Follow east to Old summit Lake Rd.
Follow north for ~ 6 km.
and marsh is located on west side of road. Observations were
made around periphery of marsh
and at culvert outlets on either side of Old Summit Lake Rd. directly
north of main marsh area.
MacMillan Creek - located ~ 10 km. north of Prince George, east
off of Hwy. 97 north. Observations
were made along ~ 100 m. of stream starting from culvert south of Hoferkamp
Rd. and continuing
south along the edge of the creek.
Tabor Lake - located ~ 20 km. east of Prince George. Observations
were made at south-east edge of
lake near lake outlet.
Buckhorn Lake - located ~ 25 km. south-east of Prince George.
Observations were made on north side
of lake,~ 1.5 km. down the Willow Forest Service Rd. Observations
were made at the lakes
edge and in a marsh area on the lake margin.
97 South marsh - located ~ 12 km. south of Prince George.
Follow Hwy. 97 south for ~12 km. and
marsh is located on west side of Hwy. Observations were
made near culvert outflow and around eastern margin of marsh area.
Ness Lake - located ~ 25 km. north-west of Prince George.
Observations were made on the west side
of the lakeshore accessed from the Regional Park trail.
Nukko Lake - located ~ 25 km. north-west of Prince George.
Observations were made on the east side
of the lakeshore accessed via Chief Lake Rd.
