Shrubs facilitate perennial bunchgrass recruitment in drylands under experimental precipitation change

Authors: SWANSON, ELIZABETH - Oregon State University; Sheley, Roger; JAMES, JEREMY - University Of California Agriculture And Natural Resources (UCANR)

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2020
Publication Date: 1/15/2021
Citation: Swanson, E.K., Sheley, R.L., James, J.J. 2021. Shrubs facilitate perennial bunchgrass recruitment in drylands under experimental precipitation change. Journal of Arid Environments. 187:104432. https://doi.org/10.1016/j.jaridenv.2020.104432.
DOI: https://doi.org/10.1016/j.jaridenv.2020.104432

Interpretive Summary: Restoration of invasive plant infested rangeland is central to establishing healthy plant communities that provide the goods and services necessary for life. One concept that may be of use during restoration is that of nurse crops of plants that help one another become established. We tested whether sagebrush can increase the establishment of native grass and forb species during drought years, since its known to pump water to near the soil surface. Shrubs increased seedling abundance by 40.9% in drought. In high precipitation, shrubs increased seedling abundance by 20% at one site and juvenile abundance 15% at both sites. These findings support the notion that shrubs can improve recruitment in both severe precipitation and drought years but the strength of this effect likely varies with soil. Our results indicate that resource islands generated by shrubs may be an important factor driving establishment in arid systems.

Technical Abstract: Increasing extremes in climate related weather events pose a major threat to plant recruitment in drylands. Research has shown facilitation effects by shrubs to improve recruitment in arid regions, however it remains unclear if these effects vary between soil types, early life stages and in both severe precipitation and drought events. We test if shrubs facilitate abundance of both seedlings and juveniles between two soil types in artificial high precipitation, ambient and severe drought conditions. When the effect of shrubs was considered, seedling and juvenile responses were similar between sites. Shrubs increased seedling abundance by 40.9% in drought. In high precipitation, shrubs increased seedling abundance by 20% at one site and juvenile abundance 15% at both sites. These findings support the notion that shrubs can improve recruitment in both severe precipitation and drought years, but the strength of this effect varies with soil. Our results indicate that resource islands generated by shrubs in high precipitation years, may be an important factor driving population dynamics in arid systems as years oscillate between wet and dry.