Response of conifer-encroached shrublands in the Great Basin to prescribed fire and mechanical treatments

Authors: MILLER, RICHARD - Oregon State University; RATCHFORD, JAIME - Oregon State University; ROUNDY, BRUCE - Brigham Young University; TAUSCH, ROBIN - Us Forest Service (FS); Hulet, April; CHAMBERS, JEANNE - Us Forest Service (FS)

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2014
Publication Date: 9/1/2014
Publication URL: http://handle.nal.usda.gov/10113/60849
Citation: Miller, R.F., Ratchford, J., Roundy, B.A., Tausch, R.J., Hulet, A., Chambers, J. 2014. Response of conifer-encroached shrublands in the Great Basin to prescribed fire and mechanical treatments. Rangeland Ecology and Management. 67:468-481. DOI: 10.2111/REM-D-13-00003.1.

Interpretive Summary: Numerous piñon and juniper woodland removal projects have been implemented at sites having a wide range of environmental conditions with varied responses from successful restoration, to conversion to exotic weedy species. To evaluate the response of understory vegetation to tree removal in conifer encroached shrublands, we set up a region-wide study that measured treatment-induced changes in understory vegetation. Eleven study sites across the Great Basin were evaluated that each contained fire, mechanical, and control treatments. There was an immediate increase in bare ground and decrease in tall perennial grasses following the burn, but both recovered by the second and third growing season. Tall perennial grass cover increased in the mechanical treatments by the second growing season. Exotic grasses and forbs did not increase in the burn and mechanical treatments in the first year but increased in the second and third year post-treatment. This study indicates that a general pattern of vegetation responses can be expected to occur following treatment of piñon and juniper however, composition of pre-existing vegetation for recovery is a primary driver.

Technical Abstract: In response to the recent expansion of piñon and juniper woodlands into sagebrush steppe communities in the northern Great Basin region, numerous conifer removal projects have been implemented at sites having a wide range of environmental conditions. Response has varied from successful restoration to conversion to exotic weedy species. To evaluate the response of understory vegetation to tree removal in conifer encroached shrublands, we set up a region-wide study that measured treatment-induced changes in understory vegetation. Eleven study sites located across the Great Basin were set up as statistical blocks, each containing fire, mechanical, and control treatments. Different cover groups were measured prior to and during the first three years following treatment. There was an immediate increase in bare ground and decrease in tall perennial grasses following the burn, but both recovered by the second or third growing season. Tall perennial grass cover increased in the mechanical treatment by the second and in the burn levels by year three. Exotic grasses and forbs did not increase in the burn and mechanical treatments in the first year but increased in the second and third year. Perennial forbs increased in both the burn and mechanical treatments. The recovery and increase in tall perennial grasses and perennial forbs did not appear to be the result of increased seedling establishment following treatment but an increase in size of individual plants present on the site prior to treatment. Both shrubs and soil biological soil crusts declined in the burn treatment with very limited recovery of sagebrush an no recovery of soil biological crusts. This study indicates that a general pattern of vegetation response can be expected to occur following treatment of piñon and juniper across a wide variety of sites in the Great Basin region. However, composition of pre-existing vegetation for recovery is a primary driver.