Submitted to: Eastern Oregon Agricultural Research Center
Publication Type: Experiment Station
Publication Acceptance Date: January 15, 1998
Publication Date: June 1, 1998
Citation: BATES,J.D., MILLER,R.F., SVEJCAR,A.J., UNDERSTORY DYNAMICS IN A CUT JUNIPER WOODLAND (1991-1997), EASTERN OREGON AGRICULTURAL RESEARCH CENTER, 1998 SPECIAL REPORT 991, PP.24-33A Interpretive Summary: Western juniper has been aggressively expanding into sagebrush plant communities for the past 100 years. On sites with relatively shallow soils, juniper invasion can result in a nearly complete loss of shrub and grass species. We compared intact juniper woodlands to adjacent plots where the juniper trees had been cut and left in place during fall of 1991. There was over a 10-fold increase in forage production on cut compared to uncut plots by 1993, and by 1997 there was a 13-fold increase. There were comparable increases in the cover and density of understory species. Removal of western juniper on this type of site can dramatically increase forage available to livestock and wildlife.
Technical Abstract: In this study we assessed understory dynamics after tree cutting in a western juniper woodland during a 7-year period (1991-97). Community dynamics monitored were understory cover, biomass, diversity, and density. The study site was on Steens Mountain in southeast Oregon. After cutting, significant treatment differences were observed for most of the understory response variables measured. Cover, density, and biomass of the understory were generally greater in the cut treatment than compared to the uncut woodland. Understory biomass was nearly 9 times greater in the cut treatment than in the uncut woodland in 1993, 1996, and 1997. Understory response did not become significant until the second year post-cutting (1993), when there were large increases in biomass, density, and cover. The main increases in plant productivity and plant densities on-site occurred in two stages, the first increase occurring in 1993, and the second increase between 1995 and 1997. Because cutting can be expensive, sites for treatment need to be carefully selected and should contain adequate densities of understory perennial grasses. The density of perennial grasses necessary for recovery after cutting depends on site potential. A site lacking a perennial grass component and dominated by annual species will likely remain dominated by annual species unless seeded to perennials.