Vegetation Recovery and Fuel Reduction after Seasonal Burning of Western Juniper

[摘要] The decrease in fire activity has been recognized as a main cause of expansion of North American woodlands. Piñon-juniper habitat in the western United States has expanded in area nearly 10-fold since the late 1800s. Woodland control measures using chainsaws, heavy equipment, and prescribed fire are used to restore sagebrush steppe plant communities. We compared vegetation recovery following cutting and prescribed fire on three sites in late Phase 2 (mid succession) and Phase 3 (late succession) western juniper (Juniperus occidentalis Hook.) woodlands in southeast Oregon. Treatments were partial cutting followed by fall broadcast burning (SEP); clear-cut and leave (CUT); and clear-cut and burn in early winter (JAN), late winter (MAR), and spring (APR); and untreated controls. Cover and density of herbaceous, shrub, and tree layers were measured. Five years after treatment, perennial bunchgrasses dominated two sites and co-dominated, with invasive annual grasses, at one site. Except for Sandberg blue-grass (Poa secunda J. Presl), cover and density of bunchgrasses, perennial and annual forbs, and annual grasses increased following treatments at all three sites and were greater than in controls. At each site, shrub, herbaceous, and ground cover response variables equalized or had begun to converge among treatments during the fourth or fifth year following application. SEP and APR treatments were mostly effective at reducing fuel sizes up to and including 1000-hr fuels while JAN and MAR treatments only consumed 1-hr and 10-hr fuels. Winter burning treatments (JAN, MAR) and the CUT treatments did not kill small junipers and seedlings and require additional tree control for sites to fully recover to functional sagebrush-herbaceous plant communities. The results demonstrate that juniper treatments are needed to recover sagebrush steppe plant communities.

[学科分类] 生态、进化、行为和系统

[关键词] cheatgrass;fuel reduction;Great Basin;Juniperus;prescribed fire;sagebrush