Gradient analysis and classification of tall forb communities in the Bridger-Teton National Forest, United States

Authors: ZOBELL, R.A. - Us Forest Service (FS); SPAETH JR., K - Natural Resources Conservation Service (NRCS, USDA); Williams, Christopher - Jason; GOODRICH, S. - Us Forest Service (FS); JACOBSON, B. - Us Forest Service (FS); CAMP, C. - Us Forest Service (FS); CAMERON, A. - Us Forest Service (FS)

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2023
Publication Date: 9/1/2023
Citation: Zobell, R., Spaeth Jr., K., Williams, C.J., Goodrich, S., Jacobson, B., Camp, C., Cameron, A. 2023. Gradient analysis and classification of tall forb communities in the Bridger-Teton National Forest, United States. Rangeland Ecology and Management. 90:294-307. https://doi.org/10.1016/j.rama.2023.04.002.
DOI: https://doi.org/10.1016/j.rama.2023.04.002

Interpretive Summary: Tall forb upland-herb plant communities in Intermountain West, USA, are a unique vegetation type and provide a host of ecosystem services including important habitat for wildlife and forage for livestock grazing. Ecological classifications and monitoring guidelines for assessing health and condition of these communities remain limited and are needed by private and public land managers. This study sampled vegetation and a suite of other site attributes at 23 tall forb upland sites in the Intermountain West. Analyses of these data identified seven distinctive tall forb cluster groups as potential ecological sites, each with specific correlated attributes such as elevation, average annual precipitation, surficial geology, geomorphology, soil clay content, foliar and ground cover, and diversity dynamics. The seven tall forb clusters are characteristic of specific and unique plant species composition, species diversity, and environmental factors. Results from the study provide a basis for developing ecological site descriptions of specific tall forb upland-herb vegetation assemblages and for refinement of rangeland health and conditions metrics for monitoring and guiding management of this important vegetation type.

Technical Abstract: Tall forb plant mixed upland-herb communities are exemplified by high plant diversity and a profusion of luxuriant wildflowers throughout subalpine mountain parklands of the interior western United States. Ecological sites pertaining to tall forb communities have not been developed; therefore, 23 sites from three subalpine areas representing historic plant community status in the Bridger Teton National Forest were identified and selected for analysis after a sustained cessation of grazing activities. The study purpose was to explore and characterize potential ecological sites within this type and respective rangeland health and condition for those sites. Establishing ecological sites and associated rangeland health and condition criteria are central to guiding monitoring and applying conservation measures. Seven tall forb cluster groups were identified as potential ecological sites, each with specific correlated environmental gradients such as elevation, average annual precipitation, surficial geology, three-dimensional geomorphic descriptions, soil clay content, foliar and ground cover, and diversity dynamics. On the sample sites, we identified 31 families, 112 genera, and 158 plant species (61 species representing native indicator reference species and 97 native secondary species). Beta diversity and plant species turnover between the seven cluster groups ranged from 6.7 to 41.9% indicating discrete differences in plant species assemblages and site dynamics. None of the seven identified tall forb cluster groups met criterion for proper functioning condition as suggested in historical literature. The seven tall forb clusters are characteristic of specific and unique plant species composition, species diversity, and environmental factors. Developing an overarching set of parameters for determining rangeland health and condition for the identified tall forb community clusters is not possible given the distinctive characteristics associated with each cluster identified in this study. Results suggest establishing criteria for conservation, management (watershed dynamics, and livestock and wildlife grazing) and monitoring will require specific consideration of environmental factors (foliar and ground cover, litter) and key dominant native indicator reference species and native secondary species composition.