NPS PHOTO

Figure 1. The Clear Trap prescribed fire burned approximately 4,400 acres in fall 2004. This view is representative of the mixed burn severity in ponderosa pine communities, in which the fire return interval is normally four to seven years, and in the pinyon-juniper communities, in which fire is much less frequent, with an average return of 160 years. Historically, fires in Zion National Park were suppressed.

PRESCRIBED FIRE IS A VALUABLE TOOL FOR MANAGING ECOSYSTEMS because it promotes species diversity and productivity and reduces wildland fuels. In some communities, for example ponderosa pine, fire is critical for productivity. However, prescribed fire can also promote the spread of nonnative plant species and affect ecosystem composition, diversity, structure, and function. Land use history and climate change have contributed to the invasion of nonnative plant species into an expanding variety of ecosystems, including higher-elevation plant communities. This expansion of nonnative plants has the potential to change the fire regimes of the plant communities of which they are a part (Westerling et al. 2006). For instance, managers ignited the Clear Trap prescribed fire in a juniper-pinyon-ponderosa (Juniperus osteosperma, Pinus edulis, and P. ponderosa, respectively) system in Zion National Park in fall 2004 (fig. 1, above). Composed of the Clear Creek and Deer Trap burn units, the 4,400-acre (1,780 ha) Clear Trap fire is the largest prescribed burn undertaken to date in Zion National Park. It is also the first of several National Park Service (NPS) fire treatments in the East Zion Focus Area, a designated wildland-urban interface of high priority for protecting human life and property values at risk from wildland fire. The primary goals of this prescribed fire were to improve the defensibility of the park boundary and help restore fire to park ecosystems (NPS 2001). Though the focus of the burn was fuel reduction, in spring 2005 (the season after the burn), park natural resource managers identified another result: significant increases in nonnative plant species within the burn unit. As a result, in 2006 the vegetation program at Zion National Park enlisted the help of the NPS Northern Colorado Plateau Inventory and Monitoring Network to map the extent of nonnative plant infestations in this area.