Marshes, Playa Wetlands, Wet Meadows, and Fens - Mountains and Plains: The Ecology of Wyoming Landscapes - page 67

Fig. 5.2. (above) Marsh in Hutton Lake national Wildlife
Refuge in the Laramie Basin. Hardstem bulrush is the most
common plant in this area and becomes abundant when
water levels are favorable. this marsh is dependent on water
from creeks and irrigation canals. elevation 7,150 feet. Photo
by Rhonda Foley / U.S. Fish and Wildlife Service.
Fig. 5.3. (left) the yellow-headed blackbird is a summer resi-
dent of lowland marshes. Photo by Ken Driese.
only 5 percent of Wyoming's wetlands are perma-
nently flooded, and two-thirds of them are dry by mid-
to late summer nearly every year. 3 At low elevations,
about half of the wetlands are sustained in part by irri-
gation waters, whether by flood irrigation, leakage from
irrigation canals, or runoff from irrigated fields.4 4 it is
likely that natural wetlands have a higher biological
diversity than those maintained by irrigation waters.
However, that has not been documented, and many
have water during years when natural wetlands are dry.
of the 2,692 vascular plant species found in Wyo-
ming, 12 percent are obligate wetland indicators, that
is, plants that cannot tolerate upland environments.
this proportion is surprisingly high, considering that
wetlands occupy such a small area in the state. An addi-
tional 13 percent of the plants are ranked as facultative
wetland indicators, that is, plants that usually grow