Colorados Front Range represents a region of the Southern Rockies LCC that is both ecologically and economically significant. It is home to the majority of Colorados residents, including the major population centers of Denver, Fort Collins, Boulder, and Colorado Springs, and provides critical ecosystem services such as clean and abundant water, wildlife habitat, recreation opportunities, and aesthetic values to the rest of the state. Ponderosa pine (Pinus ponderosa) dominated forests span the majority of the Front Range mountains and foothills, covering approximately 700,000 acres of the Front Range landscape between 5000 and 8500 ft elevation. The lower-montane zone ponderosa pine forests (~5500-7000 ft) form the backdrop to many Front Range cities, towns and an ever-expanding wildland-urban interface (WUI). Major recent and potential disturbances include uncharacteristically severe wildland fires, insect epidemics, and invasion of exotic plants. Several large, intense, and costly wildfires have recently occurred in lower-montane ponderosa forests from Colorados largest-recorded Hayman Fire (138,000 acres burned in 2002; approx. $183 million in subsequent water supply impacts) to the states most destructive FourMile Canyon Fire in 2010 (6,200 acres, 166 homes, $217 million in property damage costs.) Epidemic populations of the native mountain pine beetle are now affecting ponderosa pine after causing extensive tree mortality in higher-elevation lodgepole pine forests throughout several western states. The disruptive magnitude and intensity of all these disturbances have largely been attributed to forest conditions that currently are significantly different from their identified historic range of variability; changing climate trends will continue to have both direct and indirect effects on the outcomes (Veblen and Donnegan 2005, Kauffmann et al 2008, Raffa et al 2008.)
In light of climate change and altered natural and human-caused disturbance processes, effective adaptive management of ponderosa pine forests is essential, to increase their resilience to further disturbance (Allen et al 2002). Not only do these forests represent key resources for human communities, they are crucial habitat for wildlife. In Colorado, ponderosa pine is the only forest type designated as a high-priority habitat in the states Wildlife Action Plan and represents primary habitat for 28 of Colorados Species of Greatest Conservation Need (CSFS Statewide Assessment 2009). Many of these sensitive species are found in other regions of the Southern Rockies LCC and represent positive indicators of fully functional ecosystem conditions (e.g. northern goshawk, Aberts squirrel); many are economically as well as ecologically important (e.g. elk, bear, wild turkey). In the Front Range, several imperiled species are dependent on particular understory vegetation. The threatened Pawnee Montane Skipper, for example, requires Liatris punctata (dotted blazing star) and Bouteloua gracilis (blue grama) for habitat and food. Other species are currently threatened by habitat loss due to invasion of exotic plants such as leafy spurge, Canada thistle and cheatgrass. Historically, understory plant communities in Front Range ponderosa pine stands were likely a diverse and abundant mix of native grasses, forbs, and shrubs (Schneider 1911; Veblen and Donnegan 2005; Fornwalt et al. 2009), but increases in forest stand density during the 20th century have left understories sparse and depauperate in many locations. Restoration treatments that reduce forest stand density are expected to increase native understory plant diversity and cover. Results of studies conducted in restored ponderosa pine stands of Montana and Arizona suggest that native perennial species already present may expand following forest restoration treatments in the Front Range, while new species, particularly short-lived forbs, may become established (Metlen and Fiedler 2006; McGlone et al. 2009). T
