Bandelier Elk Herbivory Study

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FIRE, ELK, AND ASPEN POPULATION DYNAMICS IN BANDELIER NATIONAL MONUMENT: RECOMMENDATIONS FOR POST-FIRE ASPEN SUSTAINABILITY STEPHEN M. FETTIG,* MATTHEW C. BOSSLER, KEVIN J. BUFFINGTON, M. ADAM ULLOM Resource Management Division, Bandelier National Monument, 15 Entrance Road, Los Alamos, NM 87544. Department of Biology, University of Wisconsin,- Eau Claire, Eau Claire, WI 54702 (KJB) Department of Conservation Biology, College of Santa Fe, Santa Fe, NM 87505 (MAU) *Correspondent: Stephen_fettig@nps.gov ABSTRACT—The influence of browsing by elk (Cervus elaphus) on aspen (Populus tremuloides) and other woody shrubs in Bandelier National Monument has been a controversial topic throughout the last decade. Using two seasons of observational and statistical data we examined the hypothesis that physical barriers such as fallen trees help to protect aspen and other woody shrubs from ungulate browse. In 2005, we explored randomly selected sites in our search for refuged trees. In 2006, we traversed the entire study area searching for definitively refuged trees. Our findings suggest that refuges of fallen trees with a height greater than 80 cm allowed aspen to escape ungulate browse and attain heights above 2 m. RESUMEN—Utilizando dos temporadas de datos empíricos y estadísticos, pusimos a prueva la hipótesis que barreras físicas tales como árboles caídos ayudan a proteger a Populus tremuloides y otros arbustos de la herbivoría de ungulados. Atravesamos los sitios de alta elevación de Cerro Grande en el Monumento Nacional Bandelier en busca de árboles protegidos por barreras. Nuestros hallazgos sugieren que árboles caídos con un diámetro mayor a 80 cm permiten que el Populus alcance alturas mayores a 2 m . Following the 1988 Yellowstone National Park fires, researchers observed that fallen conifer, which had been killed in the fire, provided “refugia” for regenerating aspen sprouts (Ripple and Larson, 2001). These “safe zones” of woody debris or “jackstraw” offered aspen ramets (individual members of a clone) protection from ungulate browse (Turner et al., 2003). The Ripple and Larsen study provoked us to question to if this phenomenon was present in Bandelier National Monument, where a similar regime of fire and heavy ungulate browse has been well documented (S.M. Fettig et al., 2005, unpublished report, Bandelier National Monument, Los Alamos, NM). The elk (Cervus elaphus) population in the Jemez Mountains of New Mexico has fluctuated throughout the last decade. Due to over hunting, elk were extirpated from the region by 1900. In 1948 and again from 1964 to 1965 elk were reintroduced to the area and their population grew exponentially (Allen, 1994). Data from the New Mexico Department of Game and Fish suggests that by the late 1980s or early 1990s, the Jemez Mountains population of reintroduced elk had grown to levels greater than were known since the year 1200 (Allen, 1994). A survey in 2002 estimated the Jemez Mountains elk population to be approximately 5,200 individuals (New Mexico Department of Game and


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