Grant-Kohrs Ranch National Historic Site vegetation composition, structure, and soils: 2009–2019 status and trend

Borgman, Erin; Smith, Jason

doi:10.36967/nrr-2293402

In 2006 the Rocky Mountain Inventory and Monitoring Network began an effort to determine status and trends in upland vegetation structure, species composition, and soil condition in Grant-Kohrs Ranch National Historic Site (NHS) in Montana to help inform park management. The upland vegetation and soils protocol directly addresses 2 high priority natural resource vital signs in the network’s small parks: 1) vegetation composition, structure, and soils, and 2) invasive/exotic plants. The protocol is also relevant to 3 other vital signs: 1) landscape dynamics, 2) weather and climate, and 3) wet and dry deposition. This report summarizes status and trend results from upland monitoring at Grant-Kohrs Ranch from 2009 to 2019. We monitor vegetation community structure and composition by documenting native species richness and the cover of grasses, forbs, and shrubs. We monitor invasive species by documenting the cover and frequency of cheatgrass as well as noxious weeds on state and county noxious weed lists (Canada thistle (Cirsium arvense), field bindweed (Convolvulus arvensis), leafy spurge (Euphorbia esula), spotted knapweed (Centaurea stoebe), yellow toadflax (Linaria vulgaris), and whitetop (Cardaria draba)). We monitor soil chemistry and erosion potential by documenting soil stability and the cover of litter and bare soil. Due to the nature of the park as a working ranch, some areas of the park are heavily managed. As such, the network’s 32 monitoring sites fall into 5 zones based on park management actions: irrigated west and irrigated central (primarily used for hay cultivation); riparian (near the Clark Fork River), upland west (periodically grazed), and upland east (area surrounding former effluent field and railroad inholding)(see figure below). We report results at the management zone-scale to be most relevant to the park. We provide estimates of condition and trend for several specific indicators (see below) and provide summary statistics of metal concentrations in soil.

Grant-Kohrs Ranch National Historic Site vegetation composition, structure, and soils: 2009–2019 status and trend

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