Long-Term Successional Trends Following Western Juniper Cutting

Abstract

Western juniper (Juniperus occidentalis spp. occidentalis Hook.) expansion into sagebrush steppe plant communities in the northern Great Basin has diminished shrub-steppe productivity and diversity. Chainsaw cutting of western juniper woodlands is a commonly applied practice for removing tree interference and restoring understory composition. Studies reporting understory response following juniper cutting have been limited to early successional stages. This study assessed successional dynamics spanning 13 years following tree cutting. Total herbaceous standing crop and cover increased significantly in the CUT. Total standing crop was 10 times greater in the CUT vs. WOODLAND. Herbaceous standing crop and cover, and densities of perennial grasses in the CUT did not change between 1996 and 2004 indicating that by the 5th year after cutting, remaining open areas had been occupied. In the early successional stages, perennial bunchgrasses and Sandberg’s bluegrass were dominant. By the 5th year after treatment, cheatgrass had supplanted Sandberg’s bluegrass and was codominant with perennial bunchgrasses. In 2003 and 2004, perennial bunchgrasses dominated herbaceous productivity in the CUT, representing nearly 90% of total herbaceous standing crop. A pretreatment density of 2-3 perennial bunchgrasses m-2 appeared to be sufficient to permit natural recovery after juniper control. Perennial bunchgrass density peaked in the 6th year after treatment and the results suggested that 10-12 plants m-2 were sufficient to fully occupy the site and dominate herbaceous composition in subsequent years. In the CUT, juniper rapidly reestablished from seed and from the presence of seedlings not controlled in the initial treatment. The shifts in herbaceous composition across years suggests that long term monitoring is important for evaluating plant community response to juniper control and to develop appropriate post treatment management to promote continued site improvement.