Buffelgrass is a 1- to 4-foot-tall, drought-tolerant perennial bunchgrass with many stems arising from a base. It is fire-tolerant and can colonize disturbed and undisturbed sites. In Organ Pipe Cactus National Monument in Arizona, buffelgrass was first recorded in 1984. Its abundance increased rapidly. By the late 1980s, the grass had colonized more small areas, and by the mid-1990s the native vegetation along the southern boundary of the monument was being replaced by monotypic stands of buffelgrass. The prospect of losing an important piece of the most biologically diverse North American desert seemed imminent. The dismal thought of buffelgrass replacing the organ pipe cactus, with its sweet nectar and fruit; the giant saguaro, with its distinctive shape; and the ironwood tree, with its life-giving shade; spurred action by park resource managers.
Many plant ecologists were against mechanical removal because they feared disturbance of the soil would favor the species, not eradicate it. Despite those concerns, the staff at Organ Pipe Cactus National Monument tried to mechanically remove the buffelgrass from a small test area. The next year, some seedlings were removed from the same area. Since then the area has been free of buffelgrass.
Impetus for further action came from consulting the NPS Natural Resources Report Handbook for Ranking Exotic Plants for Management and Control. 1 This publication outlines an analytical approach (modified for our purposes) to prioritizing management actions by considering the significance of impacts from an exotic species and the feasibility of control. In view of the potential for ecosystem-wide effects and the success in the test area, the scope of the project was broadened during 1998. In just several months, about 40 tons of buffelgrass were removed from thousands of acres. By the end of winter 1998–99, about 41,472 hectares, or 10,240 acres (95%), of the formerly infested area was free of buffelgrass.
For monitoring the effectiveness of the removal, plots were established and inspected every three months during the first year. Early results suggested that mechanical removal was effective if seedlings were removed the following year. Few new plants have established themselves in most plots. Reestablishment of plants was primarily a problem only in sites where wildland fires had occurred accidentally.
Control of buffelgrass will require continued vigilance and removal; however, this effort seems worthwhile. Time spent removing the grass—accomplished by part-time staff and volunteers—was roughly the same as or less than that spent picking up refuse along the single highway through the monument. With an ecosystem at stake, this time is a small cost.
1 Hiebert, R. D., and J. Stubbendieck. 1993. Handbook for Ranking Exotic Plants for Management and Control. Natural Resources Report NPS/NRMWRO/NRR93/08. National Park Service, Denver, Colorado.
sue_rutman@nps.gov
Plant Ecologist, Organ Pipe Cactus National Monument, Arizona
LAKE MEAD SWAT TEAM
The exotic plant SWAT team headquartered at Lake Mead National Recreation Area (Nevada and Arizona) and funded through FY 1999 was busy in 1998 treating six nonnative species in nine units of the national park system in the Southwest. The crew of 10 spent nearly 3,600 hours treating or following up on earlier treatments of tamarisk, Russian olive, ailanthus, pampas grass, oleander, and date palm at the parks. This regional approach to exotic species control is proving efficient and effective and may be used elsewhere in the national park system.
Back to Chapter 4: Resource Disturbances
Jean Lafitte learns from 3-D seismic oil exploration experience
by Sandee Dingman
Exotic insect jeopardizes eastern hemlocks
by James Åkerson
Parks cultivate partnerships to tackle noxious weeds
by Jeff Connor and Greg Waters
Source of chemicals that feminize Lake Mead fish discovered
by Roy Irwin
Protecting the natural “soundscape” in parks
by William B. Schmidt