Colorado Statewide Forest Resource Assessment

Ponderosa pine forests are the only forest type designated as a high-priorityhabitat in Colorado’s State Wildlife Action Plan. Twenty-eight of Colorado’sSpecies of Greatest Conservation Need rely on ponderosa pine forests astheir primary habitat (CDOW 2006). One of the most signifi cant of thesespecies is the Pawnee montane skipper. This butterfl y is federally listed asThreatened and is restricted to the Upper South Platte watershed in Coloradowhere it inhabits ponderosa pine forests in which blue grama grass andprairie gayfeather are found in the understory. Other species include theMexican spotted owl, northern goshawk, Townsend’s big-eared bat and theAmerican three-toed woodpecker. Primary threats to ponderosa pine forestsinclude urban development, noxious weeds and the long-term impactsof fi re exclusion. Ponderosa pine forests evolved with natural cycles offrequent, low-intensity fi re that allowed mature pine trees to survive, but killedcompeting conifer seedlings. Several decades of near total fi re exclusion haveresulted in signifi cantly increased tree density in many of these forests, aswell as encroachment from Douglas-fi r. Such conditions increase the risk oflarge, high-intensity crown fi res in ponderosa pine forests and have increasedtheir susceptibility to native insects and diseases. The Colorado BiodiversityScorecard ranks ponderosa pine forests as one of the state’s weaklyconserved forest types (CNHP and TNC 2008).Piñon-JuniperPiñon-juniper woodlands are widespread in the lower elevations ranging from4,900 to 8,000 feet on Colorado’s West Slope and exist in limited distributionin south-central Colorado and on the Eastern Plains. The most commonspecies within this type are Colorado piñon pine and Utah and one-seedjuniper, although Rocky Mountain juniper may codominate or replaceone-seed at higher elevations. Piñon-juniper woodlands account for just over5 million acres or approximately 21 percent of the state’s forested lands. Fullyhalf of Colorado’s piñon-juniper landscapes are managed by the Bureau ofLand Management (BLM) with another 32 percent in private ownership. Piñonjuniperstands vary considerably in appearance and composition, dependingon soil depth, elevation and geographic locations. While piñon and junipermay co-occur in some landscapes, either species may be dominant on itsown in others. Some believe that the ecological dynamics of these woodlandshave changed since European settlement, resulting in increased density andencroachment on grasslands, but limited research is available to verify theseconcerns (Romme and others 2008). The research that does exist suggeststhat piñon-juniper forests likely were diverse historically, as they are today.Although not a traditional timber species, piñon-juniper forests have longbeen important to local communities for such products as fuelwood, fenceposts, pine nuts, forage for livestock and watershed protection. More recently,communities and businesses have begun to turn to piñon-juniper forests asa source of biomass for fuel and energy. Piñon-juniper forests also providehabitat for many of Colorado’s rarest plants along with the gray vireo, one ofthe state’s rare birds. Piñon-juniper forests are signifi cant habitat for reptiles,in general, and for lizards in particular. They are extensively used as winteringgrounds by elk on the Western Slope and as year-round cover by elk on theEastern Plains (e.g., Purgatoire Canyon). A notable 32 of the state’s Speciesof Greatest Conservation Need rely on piñon-juniper forests as a primaryhabitat (CDOW 2006).11