Geoscience Reference
In-Depth Information
A
Figure 6-23.
Tangled mass of pondweed with a small
feather on top, l oating in a slow-moving stream. Photo
by J.S. Aber; Wascana Creek, Regina, Saskatchewan,
Canada.
B
Figure 6-22.
Lesser duckweed (
Lemna minor
).
A. Duckweed covers the water surface with a small
arrowhead emerging in the center. B. Close-up view of
duckweed fronds, which resemble split green peas.
Photos by J.S. Aber; drainage ditch in Middle Loup
River valley, north-central Nebraska, United States.
Figure 6-24.
American white waterlily (
Nymphaea
odorata
), Okefenokee Swamp, Georgia, United States.
Note the distinctive notch in the l oating leaf and white
emergent l ower. Photo courtesy of M. Martin.
plant supplements its diet to survive in nutrient-
poor waters. Bladderworts have a wide cir-
cumpolar distribution extending as far south as
California, Texas and Florida in the United States
(Lahring 2003).
Coontail
(
Ceratophyllum demersum
) - Also
known as hornwort, this plant resembles the tail
of a raccoon, hence its common name. It grows
on long stalks that may reach 2 m or more in
length, but it is not rooted (Fig. 6-28). It may
grow in relatively deep water (down to 7 m) and
has a circumpolar distribution (Lahring 2003).
In North America it extends from Alaska to
Florida. The seeds and leaves provide food for
waterfowl, and muskrats also eat the leaves.
Dense stands of coontail are excellent shelter
for i sh and invertebrates.
6.2.5 Plant zonation
Wetland vegetation is typically found in distinct
zones that are related mainly to water depth and
salinity (see Fig. 6-12). As the groupings above
suggest, many wetland plants have strict prefer-
ences for soil moisture and water depth. Some
occupy primarily shoreline or emergent habi-
tats, whereas others grow in l oating or sub-
merged situations. Thus, distinct zones of
