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Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only Publication Acceptance Date: 5/23/2017 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Wildfire and introduced annual grasses have caused widespread degradation of Great Basin ecosystems in the Intermountain West. Cheatgrass (Bromus tectorum) and medusahead wildrye (Taeniatherum caput-medusae) aggressively displace native species by pre-empting resources and creating continuous fuel loads that increase the size and frequency of wildfire. Introduced annual grasses have a number of adaptive traits that allow them to successfully compete with native perennial vegetation in this highly-variable weather environment, including high seed production, rapid establishment and growth, and the ability to avoid summer drought in the seed phase. Native perennial species have a much more restrictive set of microclimatic requirements for establishment, growth and survival, even in the absence of competitive annual weeds. Seed germination is a critical life-stage transition for successful range-plant establishment but the predominant cause of seeding failure in these systems appears to be post-germination/pre-emergence mortality from relatively short-term soil freezing and/or drought events. We used long-term weather data, seedbed-microclimatic simulation and hydrothermal-germination models to assess the impact of weather variability and planting date on cumulative germination response and subsequent mortality of both native perennial bunchgrasses and cheatgrass. Long-term field simulations reveal alternative germination syndromes for mortality avoidance. Planting date differences of only a few weeks in the fall may significantly affect the probability of successful seedling establishment. |
