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ARS Home » Pacific West Area » Burns, Oregon » Range and Meadow Forage Management Research » Research » Publications at this Location » Publication #331580
Title: Plant community dynamics 25 years after juniper control

Author
item Bates, Jonathan - Jon
item SVEJCAR, ANTHONY - Oregon State University
item MILLER, RICHARD - Oregon State University
item Davies, Kirk

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2016
Publication Date: 5/1/2017
Publication URL: http://handle.nal.usda.gov/10113/5586971
Citation: Bates, J.D., Svejcar, A., Miller, R., Davies, K.W. 2017. Plant community dynamics 25 years after juniper control. Rangeland Ecology and Management. 70(3):356-362. doi:10.1016/j.rama.2016.11.003.

Interpretive Summary: The expansion of piñon-juniper woodlands the past 150 years in the western United States has resulted in large scale efforts to kill trees and recover sagebrush steppe rangelands. This study assessed successional dynamics spanning 25 years following juniper cutting. Cutting increased standing crop and yield, on average, 8 fold compared to uncut woodlands. Invasive annual grass yield increased in yield and as percentage of total yield from 3 to 20 %, between 2005 and 2016. Increase in woody plant cover and density and greater annual grass yields in the cut have likely contributing to declines in perennial bunchgrass density and yields. Juniper control will be necessary within 5 years to maintain progression to sagebrush steppe, indicating a maximum initial treatment longevity of 25-30 years.

Technical Abstract: The expansion of piñon-juniper woodlands the past 100 to 150 years in the western United States has resulted in large scale efforts to kill trees and recover sagebrush steppe rangelands. Western juniper (Juniperus occidentalis spp. occidentalis Hook.) expansion in the northern Great Basin has reduced sagebrush-steppe productivity and habitat. Prescribed fire and chainsaw cutting of western juniper woodlands is a commonly applied mechanical practice to kill trees and restore understory composition. Studies reporting understory response following juniper cutting have been generally limited to early successional stages. This study assessed successional dynamics spanning 25 years following tree cutting. Herbaceous standing crop and yield, and plant densities were compared between chainsaw cut (Cut) and untreated woodland (Control) treatments. Cut plots were treated in 1991. In the Cut, total standing crop and yield have remained fairly consistent since 1996 and on average were 8 times greater than the Control. Perennial grass yield was 2 to 20-fold greater in the Cut than the Control across measurement years, and peaked 14 years (2005) after treatment. Perennial bunchgrass yield declined to 30 to 40% of its peak value and bunchgrass density declined from about 11 plants m-2 in 2005 to 7 plants m-2 between 2005 and 2016. Invasive annual grass yield increased in yield and as percentage of total yield from 3 to 20 %, between 2005 and 2016. Juniper and shrub cover and density increases and greater annual grass yields in the Cut have likely contributing to declines in perennial bunchgrass density and yields. Juniper control will be necessary within 5 years to maintain progression to sagebrush steppe, indicating a maximum initial treatment longevity of 25-30 years. To lengthen the life expectancy of cutting and other mechanical control of piñon-juniper woodlands requires that all age classes of trees must be controlled in the initial treatment.