Includes montane and plains riparian. These forest types provide critical habitat in the semi-arid climate of Colorado. Roughly one-third of montane riparian acres are on private land while approximately three-quarters of plains riparian acres are privately owned.

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Montane riparian forests occur along rivers and streams in Colorado’s foothill and mountain regions, beginning around 6,000 to 7,500 feet in elevation.

Leaves on an Alder, a Common Riparian Tree

Montane riparian forests occupy roughly 1 million acres in Colorado and account for 4 percent of the state’s forested lands. These forests tend to be dominated by alder and blue spruce, but may be imbedded within several other forest types, including ponderosa pine, aspen and spruce-fir. The U.S. Forest Service manages the majority of Colorado’s montane riparian (40 percent) and private landowners (36 percent). Riparian forests may be found within the flood zone of rivers, on islands, sand or cobble bars, and immediately adjacent to streambanks. The health and sustainability of these systems depends on a natural hydrologic regime, especially annual to episodic flooding.

The Importance of Montane Riparian Forests

In a semi-arid state such as Colorado, the benefit of riparian areas to wildlife often is disproportionate relative to their size. The vast majority of species that occupy montane habitats rely on riparian forests at some point in their life cycle. This is especially true of many amphibian species, as well as such water-dependent species as beaver and river otter. Elk, mule deer and moose also favor montane riparian habitats.

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About plains cottonwood trees

About narrowleaf cottonwood trees

Low-elevation plains riparian systems are found along rivers and streams throughout the western Great Plains.

Leaves On A Narrow Leaf Cottonwood

At 250,000 acres, these plains riparian forests represent just 1 percent of the state’s forested lands, but they support a tremendous amount of biodiversity. Where plains riparian systems support forests, those forests typically are dominated by plains cottonwood in association with several species of willow and a variety of shrubs, grasses and forbs. Like montane riparian forests, plains riparian areas have a disproportionate benefit to wildlife species relative to their size. Native prairie fishes and amphibians (especially leopard frogs) are typical indicators of healthy plains riparian systems. Bald eagles occur here year-round and neotropical songbirds are common inhabitants during migration and breeding season. Other typical species include deer (white-tail and mule), Merriam’s turkey and a variety of owls.

Threats to the Plains Riparian Forest

Low-elevation riparian systems often are subjected to heavy grazing and/or other agricultural use, and can be significantly degraded. This degradation leaves them vulnerable to invasion by non-native grasses, forbs and shrubs. Tamarisk and Russian olive are particularly prominent. Riparian forests also may be seriously impacted by pollution, surface water diversions and groundwater depletions. Overall, prairie riparian and wetland ecological systems (along with shortgrass prairie) are the most altered of Colorado’s ecosystems.

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About plains cottonwood trees

About narrowleaf cottonwood trees

Data Sources

Landfire

NatureServe. 2018. International Ecological Classification Standard: Terrestrial Ecological Classifications. NatureServe Central Databases. Arlington, VA. U.S.A. Data current as of 28 August 2018.

2017 Colorado Wildfire Risk Assessment, Colorado State Forest Service.