Virtual reciprocal garden assessment of germination syndromes for Elymus elymoides ssp. brevifolius and Elymus multisetus

Authors: Hardegree, Stuart; Richards, Christopher; Sheley, Roger; Reeves, Patrick; Jones, Thomas; Walters, Christina; Schantz, Merilynn; Flerchinger, Gerald

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2024
Publication Date: 6/22/2024
Citation: Hardegree, S.P., Richards, C.M., Sheley, R.L., Reeves, P.A., Jones, T.A., Walters, C.T., Schantz, M.C., Flerchinger, G.N. 2024. Virtual reciprocal garden assessment of germination syndromes for Elymus elymoides ssp. brevifolius and Elymus multisetus. Rangeland Ecology and Management. 96:1-11. https://doi.org/10.1016/j.rama.2024.04.013.
DOI: https://doi.org/10.1016/j.rama.2024.04.013

Interpretive Summary: Bottlebrush and big squirreltail are high priority species for restoration of millions of hectares of rangeland in the western US that have been degraded by wildfire and introduced annual weeds. Increasingly, restoration specialists are interested in using locally-adapted plant materials that evolved and are pre-adapted to the locations in which they are planted. In this experiment, we used 32 seedlots of squirreltail that were collected in either the Snake River Plain of southern Idaho, or in the Rocky Mountain region and asked whether those seeds appear to be better adapted to their region of origin. We tested this by comparing seasonal climate across all collection sites, and simulating seed germination response of all seeds to historical patterns of seasonal climate in each region. In these simulations we confirmed that there are significant differences in the germination syndromes of these seeds that confer site-specific advantages when those seeds are planted in their region of origin. The rapid germination characteristics of seeds collected in southern Idaho would be detrimental in the Rocky Mountain region where there is an increased danger of seedling mortality from winter freezing. The slower germination of seeds collected in the Rocky Mountains protects seeds from premature germination in their region of origin, but would inhibit germination during the relatively brief period of post-winter soil moisture in southern Idaho. This study generally supports the use of region-specific seed sources for restoration activities with these species. Identification of these restoration traits may be especially important for systems that are under pressure from invasive weeds and habitat migration caused by global climate change.

Technical Abstract: Bottlebrush squirreltail (Elymus elymoides) and big squirreltail (Elymus multisetus) are high priority species for restoration of millions of hectares of rangeland in the western United States that have been degraded by wildfire and the proliferation of introduced annual grasses. Previous research has compared potential germination and seedling performance of these species in a common environment and noted significant species differentiation that may confer suitability to the respective collection environments. In this experiment, we used wet-thermal germination models and long-term seedbed simulations to conduct a virtual reciprocal-garden analysis of species-specific germination syndromes. We confirmed significant species differentiation in germination response and that these differences appear to confer site-specific advantages for initial seedling establishment. Our results specifically highlight the relative importance of late-fall seeding for the more rapidly germinating E. multisetus, and the inherent hazard avoidance of post-germination freezing mortality of the slower-germinating E. elymoides ssp. brevifolius (A). Virtual simulations of this type might lead to identification of complex-trait genetic markers that are associated with intra and inter-specific adaptations to specific environments. Identification of these traits could also inform management of plant communities that are under pressure from invasive weeds and habitat migration caused by global climate change.