Effects of grazing and trampling by Rocky Mountain elk (Cervus elaphus nelsoni) on the vegetative community of Bandelier National Monument, New Mexico

The increase in the Jemez region elk (Cervus elaphus nelsoni) population is a concem to local managers. Threats to archeological resources and naturally fijnctioning ecosystems through accelerated soil erosion, degrading plant communities, and unnatural vegetation change rank as the highest management priorities at Bandelier National Monument, New Mexico.

In summer 1998, Bandelier National Monument erected a series of ungulate exclosures and paired reference areas to evaluate elk impacts on the vegetative community in piilon-juniper (PJ), ponderosa grassland (PG), and mixed-conifer (MC) habitat types. A two-factor factorial randomized block design was established to evaluate simulated grazing/trampling treatment combinations applied at different intensities and frequencies from January through May of 1999 and 2000. Unfenced reference areas were compared with non-treated units inside exclosures to evaluate the effects of grazer exclusion. Parameters measured included density, percent foliar/litter cover, mean basal area/plant, productivity, and species richness and composition.

Analysis of covariance (ANCOVA) was used to account for pre-treatment patterns that existed among treatment plots. Pre-treatment and first-year response data indicated large amounts of variation between and within exclosures for all parameters measured which may reflect the inherent variability present in vegetative communities at Bandelier National Monument. Few significant responses were detected following a single year's treatment application and two unseasonably warm winter/spring periods may have confounded or obscured treatment effects.