Get reliable rangeland science

Big sagebrush (Artemisia tridentata Nutt.) is important ecologically in shrub-steppe ecosystems but dense, competitive stands lack perennial herbaceous diversity and abundance.  To determine the ability of sagebrush thinning treatments to retain shrub and herbaceous components while improving diversity, we evaluated the effects of 6 mechanical treatments and revegetation on a Wyoming big sagebrush community in northern Utah. We measured shrub, residual, and seeded herbaceous cover at 1, 2, 5, and 10 years post treatment. Mechanical treatments were one-way and two-way pipe harrowing, disking and imprinting, one-way Ely chaining, and fall and spring aerating. The treatments were seeded with a mixture of grasses, forbs, and fourwing saltbush. By 10 years after treatment, seeded grass cover was < 2% on all treatments except the drill imprinter treatment, which had 14% cover. Seeded forbs followed the same trend while residual forbs decreased then returned to pretreatment cover after 10 years. All treatments increased perennial grass cover by about 10%, but disk and imprinting increased it by > 20% by increasing establishment of seeded grasses. Sagebrush cover was reduced from about 20 to < 5% for all treatments but was recovering to 8-14% on all treatments except disk imprint. Thus, most successful herbaceous revegetation was associated with greatest sagebrush control. Mechanical treatments to increase herbaceous cover might best be applied in a mosaic when sagebrush cover needs to be preserved. Treatments such as these may be useful while understanding ecological departure of the communities vegetation structure to create a mosaic of successional classes.