Determining the effectiveness of native and introduced plant material seed mixes for rehabilitating degraded rangelands

Authors: Harmon, Daniel - Dan; Clements, Darin - Charlie

Submitted to: Eastern Nevada Landscape Coalition (ENLC)
Publication Type: Abstract Only
Publication Acceptance Date: 12/9/2019
Publication Date: 1/9/2020
Citation: Harmon, D.N., Clements, D.D. 2020. Determining the effectiveness of native and introduced plant material seed mixes for rehabilitating degraded rangelands. Eastern Nevada Landscape Coalition (ENLC). January 8-9, 2020, Ely, NV.

Interpretive Summary:

Technical Abstract: The decision-making process in regards to rangeland rehabilitation seeding efforts is critical to maximize successful outcomes. Choosing which species to seed and at what rates to seed can be a complex decision. Often the goal of such rangeland rehabilitation efforts is to restore lost ecosystem function and decrease the dominance of exotic weeds such as cheatgrass. This requires the establishment of an effective density of perennial plants more specifically long-lived competitive perennial grasses. A suite of introduced plant material developed by USDA-Agricultural Research Service is readily available to achieve such goals. Managers, however must also consider the need to maintain a native plant diversity. This leads to the one of the most debated questions in rangeland management. To what degree do we use introduced plants versus native plants in seeding efforts? The Great Basin Rangeland Research Unit (GBRRU) has been testing the performance of plant materials, introduced and native, for rangeland seeding efforts for more than 3 decades. In recent years, we have tested the use of native, introduced and a combination of native and introduced plant material seed mixes at multiple sites in northern Nevada. Seed mixes were seeded in October 2016-2018 following weed control practices using pre-emergent herbicides to control and reduce cheatgrass competition. Seed mixes were determined based on actual site potential (soil type and climate). Seedling emergence and establishment were recorded throughout the first 2 growing seasons, after which the effectiveness of the established plants to suppress cheatgrass and or exotic weeds was then measured. We determined that annual precipitation as well as the level of weed competition were the primary factors determining the need to use introduced species versus native species. At sites receiving less than 8” of average annual precipitation (which consists of more than 90% of Nevada rangelands) or with a high degree of weed competition native species consistently failed. We define failure as not establishing a density of plants sufficient enough to suppress cheatgrass and or other weeds. At more productive sites, especially during years of above average precipitation and with decreased weed competition, native plants equally performed and were as effective as introduced seeded species. Averaging all years and sites, introduced species were more effective at establishing with a range of 4.3 introduced plants/ft2 versus 3.0 native plants/ft2. Once a sufficient density of plants was established, both introduced and native seed mixes were effective at suppressing cheatgrass and or weeds. Successful rangeland rehabilitation seeding efforts significantly reduce the chance, rate, spread and season of wildfires which in turn improves sustainability of grazing resources, improves wildlife habitat values and reduces the threat to adjacent critical habitats.