A matter of timing: sagebrush steppe restoration seeding outcomes altered by species responses to warmer spring temperatures and interannual weather variation

Authors: Copeland, Stella; Bates, Jonathan; Davies, Kirk; GERMINO, MATTHEW - Us Geological Survey

Submitted to: Restoration Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2026
Publication Date: 1/26/2026
Citation: Copeland, S.M., Bates, J.D., Davies, K.W., Germino, M.J. 2026. A matter of timing: sagebrush steppe restoration seeding outcomes altered by species responses to warmer spring temperatures and interannual weather variation. Restoration Ecology. doi: 10.1111/rec.70330. https://doi.org/10.1111/rec.70330.
DOI: https://doi.org/10.1111/rec.70330

Interpretive Summary: What is the problem? What did you do related to the problem? What did you find out/what were your results? Why does your answer to #3 matter (i.e., what’s the impact?)? Species differences, like early or late seedling emergence timing, are likely affect dryland rangeland restoration, where high variability in spring temperatures and precipitation are common. We addressed this potential with a complex warming experiment involving many common sagebrush steppe rangeland plant species across multiple years. We found that species emergence timing and the timing of warmer temperatures in the spring affected outcomes, via exposure to specific weather conditions in different years. Our results suggest that seed mixes crafted to target favorable spring weather for emergence are more likely to lead to improved restoration outcomes.

Technical Abstract: Introduction Seed-based restoration outcomes in cold desert ecosystems like sagebrush steppe are strongly affected by weather variability, particularly during the spring establishment season. Phenological timing of emergence and associated traits vary strongly among herbaceous species in these ecosystems, and different proportions of early- or late-season emerging seedlings in seed mixes could affect restoration seeding and their response to spring weather. Objectives The purpose of this study was to evaluate the effects of higher spring temperatures and species differences, related to seedling emergence and survival, on restoration outcomes. We tested the hypothesis that emergence timing would affect species response to spring warming. We also tested for indirect effects of warming on outcomes via changes in invasive annual grass cover. Methods We tested warming effects in a field experiment with diverse seed mixes across multiple years and variable weather conditions in sagebrush steppe, Oregon, USA, including both an early, and late, spring warming treatment to test outcomes related to different species emergence timing. Results The effects of spring warming treatments varied with yearly weather and species emergence timing relative to rest of the seed mix. Species with later emergence timing emerged at lower rates, particularly when exposed to late spring warming. In contrast, later emergence timing was associated with higher seedling survival with late spring warming or without warming, and lower survival with early spring warming. Seed mixes targeted to weather conditions outperformed mixes with early or late emergence timing and even proportion mixes. Invasive annual grasses increased with early spring warming, and were associated with long-term lower seedling survival.