Nature loves diversity. A walk through a healthy Central Arizonan riparian (streamside) corridor would reveal a rich forest composed of ash, walnut, boxelder maple, hackberry, three to four different species of willow, three different species of cottonwood, and numerous species of shrubs, graminoids (grasses and grass-like plants), forbs, and aquatic plants. Each of these plants provides unique physical structure and unique resources available to wildlife, allowing wild critters to specialize in their food sources, nesting behavior, and other essential parts of their life cycle.
Should you choose to take this walk along one of the several streams within Prescott, however, you will be presented with a much narrower palette of plants. Although there is a smattering of the native trees and shrubs one would expect, our riparian forests are dominated by Siberian elm. Introduced to the United States in the 1860s, Siberian elm is often planted as a windbreak due to its rapid growth in even the most marginal soils, its hardiness, and its ability to tolerate both severe drought and moderately high moisture. Early each spring, long before native trees are ready to release seeds, every mature Siberian elm drops tens of thousands of half-inch round, winged seeds that collect along gutters and other low-lying nooks. Their ability to reproduce rapidly and their flexible growth requirements allow Siberian elms to colonize disturbed riparian areas and grasslands. These disturbed areas are in the greatest need of robust, diverse habitat, but instead are converted into near-monocultures.
As a part of our mission to achieve healthy watersheds and clean waters, Prescott Creeks invests substantial effort into managing invasive plant species. Our regular bimonthly volunteer events have most recently focused on removing Siberian elm from Watson Woods Riparian Preserve, and we have seen amazing results without using any poisons. In fact, if you have spent time in Watson Woods you may have seen trees that look like they’ve had their bark chewed off by beavers – this is actually a method we have been using to control Siberian elms called girdling. When the inner bark layer, called the cambium, is removed from a tree, it becomes incapable of moving sugars and other nutrients between the leaves and roots. This is a simple, cost-effective way to kill larger trees while leaving a snag, a standing dead tree that can continue to provide habitat while desirable plants have a chance to recover in the area.