Soil resource availability: The journey from cheatgrass to perennial grass dominance

Authors: Harmon, Daniel; Clements, Darin; Phillips, Jacob; Allen, Fay

Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/30/2024
Publication Date: 2/11/2025
Citation: Harmon, D.N., Clements, D.D., Phillips, J.D., Allen, F.L. 2025. Soil resource availability: The journey from cheatgrass to perennial grass dominance. Society for Range Management Meeting Abstracts. 78:93.

Interpretive Summary:

Technical Abstract: One of the greatest challenges in restoring annual grass dominated Great Basin landscapes back to perennial grass dominated ecosystems are limited soil resources, such as soil moisture and nitrogen which are necessary for newly germinated seedings to establish and persist. With extremely limited precipitation during the growing season in many parts of the Great Basin, lack of soil moisture is the primary cause of most seeding effort failures. We have measured cheatgrass using over 50% of available soil moisture and decreasing available soil nitrogen 10-fold. This can severely limit seeded perennial grass establishment. To overcome this limitation, pre-emergent herbicides are used to temporarily reduce cheatgrass competition to increase the available soil resources during the seedling establishment year. Cheatgrass can also be limited or suppressed by soil resource deficiencies created by established competitive perennial grasses utilizing a high degree of soil resources. Soil moisture and nitrate (NO3-) data was collected throughout the year, over multiple years, under various management strategies. Our data demonstrate the competitive negative effect of cheatgrass and other undesirable weeds on soil resource availability, as well as the great positive increases in soil resources from effective pre-emergent herbicide use. We will present soil data collected along a timeline starting from pre-treatment to the herbicide fallow year, to a failed seeding effort, as well as five years after a successful seeding effort where perennial grasses now dominate the site and suppresses cheatgrass. Our research found that the dominant plant species, whether undesirable, such as cheatgrass, or desirable perennial grasses, both use a strategy of competitive soil resource depletion to limit other competitors. We also found that effective pre-emergent herbicide control of annual weeds can temporarily eliminate soil resource deficiencies and greatly increase the chance of success for perennial grass establishment.