Title: Vegetation response to western juniper slash treatments Authors
|O'Connor, Casey -|
|Miller, Rick -|
Submitted to: Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 2, 2013
Publication Date: August 26, 2013
Citation: O'Connor, C., Miller, R., Bates, J.D. 2013. Vegetation response to western juniper slash treatments. Environmental Management. 52:553-566. Interpretive Summary: Piñon-juniper woodland dominance of sagebrush steppe has several negative consequences including reductions in herbaceous production and diversity, decreased wildlife habitat, higher erosion and runoff potentials. We compared three treatments used to control western juniper in open ponderosa pine and mountain mahogany rangelands of the northwestern United States; cut and leave (CUT), cut and broadcast burn (BURN), and cut, pile and burn (PILE). The study demonstrated that; 1) pine and mahogany were retained in CUT and Pile treatments but were severely reduced in the BURN treatment; 2) though cheatgrass, an invasive annual, increased, the native bunchgrass-forb understory has largely recovered in all treatments after 4 years; and 3) the most effective fuel reduction method was the PILE treatment because most of the juniper was removed and ecological impacts were confined to a small portion of the landscape (<12%).
Technical Abstract: The expansion of piñon-juniper woodlands the past 100 years in the western United States has resulted in large scale efforts to remove trees and recover sagebrush steppe rangelands. It is important to evaluate vegetation response in order to develop best management practices for controlling expanding woodlands. In this study, we compared three treatments used to control western juniper (Juniperus occidentalis spp. occidentalis Hook.) of the northwestern United States; cut and leave (CUT), cut and broadcast burn (BURN), and cut, pile and burn (PILE). A randomized complete block design was used with five replicates of each treatment located in a Ponderosa pine (Pinus ponderosa Dougl.)-curl leaf mahogany (Cercocarpus ledifolius Nutt. ex Torr. & A. Gray)/mountain big sagebrush (Artemisia tridentata Nutt. spp. vaseyana (Rydb.) Beetle)/Idaho fescue (Festuca idahoensis Elmer) association. In the BURN treatment there was increased bare ground, lower litter cover, lower cover and density of Sandberg’s bluegrass (Poa secunda J. Pres), lower cover of perennial bunchgrasses, greater cheatgrass cover (Bromus tectorum L), lower density and cover of mahogany, lower juniper density, and greater rubber rabbitbrush density compared to the PILE and CUT treatments. In the BURN treatment juniper density was about 25% of the pretreatment density of about 400 trees/ha. In PILE and CUT treatments juniper density was about 30% of pretreatment densities. To prolong desired vegetation conditions, follow up management will be necessary to control juniper re-establishment. To encourage recovery of curl-leaf mahogany our results indicate that mechanical methods and pile burning may provide the best management alternative as broadcast fire (BURN treatment) reduced mahogany presence. The increase in perennial bunchgrass density and cover makes it unlikely that cheatgrass will persist as a major understory component in similar juniper treatment areas.