Long-Term Monitoring Indicates Stability of Summer Range Forage Resources at the US Sheep Experiment Station

Vegetation monitoring data can help managers better understand plant community dynamics and herbivore ecology, thereby supporting the resilience of rangelands. Monitoring data can be useful for managers of high-elevation grazing areas used by livestock during the summer months, where relatively little grazing ecology research has been conducted, and social acceptance of livestock grazing is declining. In this study, we examine plant community composition data collected across grassland, tall forb, open conifer, and sagebrush-dominated locations ( n = 59) in 1959, 1978, and 1994 at the US Sheep Experiment Station Summer Range in Beaverhead County, Montana. Are research questions are: 1) to what extent do plant communities in four vegetation types in 1959 differ from one another?; 2) what environmental gradients are correlated with these differences?; and 3) to what extent do plant community composition, biomass, and rangeland cover characteristics in the four vegetation types differ over the 35 yr study period (1959–1994)? After processing the data with modern quality assurance methods, physically verifying plots, and cleaning the species database, we used a combination of linear mixed models and unconstrained ordination analyses. We detected 122 species or species groups. We found separation in the composition between sagebrush and grassland vegetation types, with notable overlap between open conifer, tall forb, and sagebrush communities. We detected little directional change in plant communities over the study period. Herbaceous biomass measurements tracked precipitation, remaining similar in 1959 and 1994 but peaking in 1978 for all vegetation life forms except shrubs. These results illustrate the resilience of diverse summer range plant communities under long-term range sheep grazing. The continued sustainability of these systems will depend on adaptive, flexible grazing management and continued research exploring relationships between disturbance regimes, plant communities, and agroecological management.