Weak effects of a soil contrast on Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) transplant survival in a northern Great Basin case study suggest importance of microsite selection and non-soil factors

Authors: Copeland, Stella

Submitted to: Rangelands
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2023
Publication Date: 2/19/2024
Citation: Copeland, S.M. 2024. Weak effects of a soil contrast on Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) transplant survival in a northern Great Basin case study suggest importance of microsite selection and non-soil factors. Rangelands. 46(3):88-97. https://doi.org/10.1016/j.rala.2023.12.003.
DOI: https://doi.org/10.1016/j.rala.2023.12.003

Interpretive Summary: Increasing big sagebrush cover is a major goal of post-fire sagebrush steppe restoration, because of high sagebrush mortality with fire and slow dispersal into larger burned areas. Transplanting big sagebrush rather than seeding is an increasingly common restoration method, due to the higher survival rates of transplants in variable weather conditions. However, transplants are more costly than seed, and transplant survival rates are also highly variable. Identifying site environmental factors linked to survival, such as soil type, could increase the cost-effectiveness of this restoration practice by guiding selection of areas for transplant projects. In this study I tested the effect of a strong soil type contrast between a sandy loam and a rocky clay soil on big sagebrush transplant survival outcomes as well as associated indicators of water stress in a post-fire restoration site. Unexpectedly, soil type had little impact on survival outcomes, though modest declines in survival were associated with competition from surrounding vegetation, which did vary with soil type. A planting strategy focused on microsites within the rocky clay soil, suspected herbivory, and high post-planting mortality rates in both soil types may have led to low differences between soil types. These results suggest that managers may successfully transplant sagebrush alongside perennial grass seedings and in marginal soil types by selecting appropriate microsites with respect to soils and competition, but further research is also needed to address the fine-scale patterns of transplant mortality linked to variability in restoration outcomes with this method.

Technical Abstract: Restoring a dominant shrub, Artemisia tridentata (big sagebrush), is a key goal in post-fire management across the Great Basin due to the species high mortality with fire and episodic natural recovery from seed. Transplants are increasingly used for sagebrush restoration because of their higher survival with variable weather conditions in this region, despite their greater expense compared to seed. A number of abiotic and biotic factors may limit the success of big sagebrush transplant projects, with soil type previously identified as a major factor. I evaluated the effects of a soil contrast on sagebrush transplant survival and associated measurements of water availability and stress across locations with variable plant community characteristics. Contrary to expectations, there were few survival differences associated with soil type and/or water stress. Various factors that may be associated with the lack of differences include a planting strategy focused on microsites within one soil type, high mortality post-planting during favorable weather conditions, and loss of transplants due to suspected herbivory. Competition from surrounding vegetation cover was associated with higher mortality, and the effects did not vary by soil type. These results suggest that managers may successfully transplant sagebrush alongside perennial grass seedings and in marginal soil types by selecting appropriate microsites with respect to soils and competition. Further research is needed to address the factors associated with sagebrush transplant mortality at relatively fine spatial scales than major soil type to increase the cost-efficiency of this restoration practice.