Background and objectives: The Great Basin Desert with its critical sage grouse habitat is at a “tipping point” wherein fires that were rare and patchy historically are increasing in frequency, size and severity. Wildfire is now the largest driver of ecosystem change accounting for more than 60% of all landscape transformations in the Great Basin. Due to the large scale of wildfires across Great Basin landscapes, seed applications are the most viable strategy for re-establishing native vegetation following fire. To improve rangeland seeding success we need a better understanding of the biotic and abiotic limitations to germination and seedling establishment and develop technologies that overcome them. There is evidence that rodents remove as much as 80% of the native seeds land managers place to restore sagebrush landscapes. Native seeds that escape predation by rodents often experience high levels of pre-emergent mortality by germinating to early or too late resulting in mortality due to water deficit or freezing temperatures. Seeds that sit dormant through winter and germinate in the spring often face intense competition from invasive annual grasses. The central objective of our research project was to evaluate the potential for seed coating technologies to overcome what we hypothesize are the three major limitations to native plant germination and establishment: 1) seed predation by rodents, 2) suboptimal germination timing leading to frost and drought mortality, and 3) competition from annual weeds. During our project we were able to develop appropriate seed coating protocols and test their efficacy to overcome constraints of rodent granivory, suboptimal germination timing, and competition from invasive annual grasses.

Methodology Synopsis: We tested ten seed-coating formulations containing products expected to deter rodent granivory: ghost and cayenne pepper powders; essential oils from bergamot, neem, and pine; methyl- nonyl-ketone, anthraquinone, activated carbon, beta-cyclodextrin and a blank coating containing no rodent deterrents to serve as a control treatment applied to bluebunch wheatgrass seeds. In a second study we treated sagebrush seed with plant growth regulators ABA, GA3 and ACC to create variation in germination timing to coincide with windows of optimal temperature and soil moisture. In a final study, we tested two methods to protect native seeds from herbicide: activated carbon was applied as a seed coating with the intent of protecting native seeds from the effects of herbicides, and furrows were used to side-sweep soil sprayed with herbicide away from the planted seeds.

Results and Conclusions: Rodents strongly avoided coated seeds with deterrents in favor of uncoated control seeds. Notably, the blank coating, lacking active ingredients, still elicited 99% avoidance. However, these results indicated avoidance behavior when alternative food sources are readily available, a scenario rare in nature. To address this, a second feeding experiment was conducted to observe feeding under calorie-restricted conditions while only offering one treatment. Under these conditions, many subjects chose to consume coated seeds, but to a lesser degree than subjects offered control seeds. Seeds coated in ghost pepper, neem oil, and activated carbon reduced consumption by 47-50% compared to blank coated seeds. We would expect these treatments to increase native plant establishment by protecting seeds with seed coatings from rodent predation. Our seed germination experiments demonstrated that hormones can delay or accelerate germination dramatically. For example, ABA delayed germination for sagebrush seeds by up to 38 d and the germination promoters accelerated germination by 11 d. These results suggest that germination can be accelerated or delayed to reach critical germination windows depending on climate conditions. Our herbicide and furrow studies indicate that imazapic application decreased cheatgrass cover 91% after one year, and 39% after two years. Imazapic also had strong negative effects on Pseudoroegneria spicata (Bluebunch wheatgrass). Combining carbon seed coatings and furrow treatments mitigated harmful herbicide effects on all plant stages (seedling emergence, plant densities, and growth). Our results suggest that combining activated carbon seed coatings and furrows resulted in similar establishment of a native perennial as a non-herbicide seeding and lowered cheatgrass abundance.