COTTON WOOD CORRIDORS

©By Susan B. Eirich, Ph.D.

From the hot hard glare of sunlight in our high mountain valley we instinctively move toward the promised relief of the cottonwoods – cool, green, moist, restful. These corridors, essential habitat for many species and a critical link between terrestrial and aquatic environments, are another of our valley’s remarkable treasures. They are veritable hot spots of life. It is estimated that there are just 3% left in the country and we have several here in Teton Valley. Though many have been impoverished by development they are still invaluable. The best of these is South Leigh Creek, home to an astounding variety of life and two unusual plant communities, one of them rare world wide, and to the great gray owls written about last week. 

These narrow bands of green next to our streams are not just trees or even corridors, but are a vibrant interconnected community that harbors astonishing amounts of life of all kinds; from plants, trees, animals, and birds to the fungi that connect the trees underground; to the majestic moose who depend on the browse that grows under the protection of the cottonwoods when there are no more greens to stave off winter starvation.

The cottonwoods, the anchor of the community, are wonders in themselves. A communal tree, they grow in stands interconnected with each other by way of roots, and by way of fungi called mycorrhizae. This fungus, associated with the roots, forms an interconnected unseen mass underground and  help the trees absorb nutrition from the earth.

Pollinated by the wind, evolved in exquisite timing with their surroundings, the trees come to seed just as the spring floods slow down, sending delicate white fluffs of seeds everywhere. Any earlier, they would be washed away. Any later, the moisture would not last long enough for them to survive. The seeds themselves are only viable for 1-2 weeks, and in that time must alight on a moist area in order to have their chance at life. Once a seed is wetted it needs to be deposited within 2-3 days, the germination itself taking about 24 hours. They send roots down into the earth at the rate of almost ½ inch per day, in a race to reach enough depth before the moisture disappears. Once they survive the many early dangers of life from grazing and trampling to starvation, dehydration, to being scoured away by the next spring floods, the very floods that gave them life, they develop into magnificent trees up to 60 feet high, home to hawks and eagles, capable of living 100-200 years. But they need the floods to regenerate.

We are not the only ones attracted to these corridors of life. It is estimated that 70-80% of wildlife depend on these riparian corridors in some way, many for their very survival. They do not have to live here to depend on them. Our valley corridors are in the path of migration paths for birds flying up from Central and South America on their way to their northern breeding grounds. Their journeys may involve non-stop flights more than a thousand miles at a time. When they finally touch down they must urgently find a safe place to rest and refuel. Intact corridors provide “drop in” sites with the cover, roosting spots and food they so desperately need. 

Under the canopy of the cottonwoods lies a complex “vertical structure,” a major factor in making it a biological hotspot. There are “layers” of differing habitat offering a rich selection of essential habitat. More levels means more foraging and nesting sites. The ground level of grasses and flowering plants house and feed species such as robins and veeries, the common yellowthroat warbler and the western jumping mouse. The shrubs offer nesting space to birds such as the Macgillivrays warbler and the dusky flycatcher; and cover, shade and browse for moose and deer. Serviceberries and chokecherries provide food for dozens of species. The canopy is essential home to arboreal nesting hawks such as the Swenson’s and red tail hawks, and the great horned owl. The soft wood of the cottonwood trunks are home to downy and hairy woodpeckers and northern flickers who drill their home for one season only, providing homes for “secondary” cavity nesters such as the screech owl, sawhet owl, the black capped chickadee, swallows and the American kestrel. The downed woody debris offers habitat for amphibians, reptile and small mammals that help feed the larger ones. Under the canopy of the cottonwoods move porcupines, coyotes, foxes, deer, moose and black bear.

Food, safety, water, protection from heat and wind, homes to raise families, water….these corridors are valley gems for wildlife and for we who live here. We are all attracted to the cottonwoods, humans and animals. But we have a choice of where to live- the animals do not. It is for us build wisely so that we can enjoy them for generations and the wildlife they sustain. 

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