There is limited knowledge on grazing impacts to long-term plant community dynamics following fire in sagebrush steppe, This study evaluated vegetation response to different intensities of deferred rotation cattle grazing over 16 years (2007–2022) on burned Wyoming big sagebrush steppe in eastern Oregon. Treatments were applied in a randomized complete block, including on grazing on burned (Non-use, n=5) and unburned (Control, n=5) steppe; and cattle grazing at low (Low, n=4), moderate (Moderate, n=4), and high (High, n=4) intensities on burned steppe. Vegetation dynamics were evaluated by repeated measures analysis of canopy cover and density of shrub and herbaceous species and functional groups. Herbaceosus functional groups were an early season bunchgrass (one species, Sandberg bluegrass), tall perennial bunchgrass, perennial forbs, annual grass (one species, cheatgrass) and annual forbs. Tall perennial bunchgrass, Sandberg bluegrass, and perennial forb cover and density did not differ among the treatments but did decrease over time in all treatments. Cover of several tall bunchgrass species were generally less in the High treatment, mainly, Idaho fescue, and Thurber's needlegrass. Cover of cheatgrass and annual forbs varied across years but were greater among the burned grazed and Non-use treatments than the Control. Native plant cover in the burned treatments (grazed and Non-use) represented 77 to 85 % of total herbaceous cover versus the Control where natives comprised 91% of the total.  Annual weather variability appears to account for most of the compositional dynamics measured in the various grazed and ungrazed treatments.

Vegetation sampling:

Collected June 2002, 2007, 2012, and 2022.

Six permanent 50-m transects.

Herbaceous canopy cover (species), bareground/rock, moss, lichen, and litter were estimated visually inside 40X50 cm frames.  Frames were placed every 3-m along the transect lines (starting at 3-m and ending at 45-m). 15 frames per transect line.

Perennial herbaceous density (species) was measured by counting all rooted plants within the 40X50 cm frames.

Herbaceous species richness was estimated by counting species presence for a 10-minute period per plot.

Shrub canopy cover was measured by line intercept along each 50-m transect line.

Shrub density was measured by belt transect by counting all rooted individuals within a 2X50-m area (1-m on each side of transect line) along each transect line. 

Data Processing:

Data was entered and summarized using Microsoft Excel. Cover, density, and richness (species and functional group) were analyzed using SAS 9.4 using the PROC MIXED procedure for a randomized complete block study design. An auto-regressive order one covariance structure was used as it provided the best fit for analysis.