Do plant-soil feedbacks promote coexistence in a sagebrush steppe?

Authors: CHUNG, Y - University Of Georgia; Monaco, Thomas; Taylor, Joshua - Bret; ADLER, PETER - Utah State University

Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2023
Publication Date: 4/20/2023
Citation: Chung, Y.A., Monaco, T.A., Taylor, J.B., Adler, P.B. 2023. Do plant-soil feedbacks promote coexistence in a sagebrush steppe? Ecology. 104(7). Article e4056. https://doi.org/10.1002/ecy.4056.
DOI: https://doi.org/10.1002/ecy.4056

Interpretive Summary: Negative plant-soil feedbacks (PSFs) promote stable coexistence among plant species. For example, prior studies showed stabilized coexistence among four dominant species in a sagebrush steppe during the recruitment stage. To follow up on this study, we tested the role of PSFs in stabilizing coexistence among these four dominant species using field experiments and bootstrapping statistics (e.g. mimicking the sampling process) to integrate the effects of treatments and soil environments on focal species across germination, survival, and first-year growth. We found that soil microbes had consistent, negative effects on the growth of all four species but positive feedbacks in germination. These results indicate that PSFs mediated by microbes may not be a common mechanism of coexistence in this plant community, yet they still could affect the relative abundances of species that may be more susceptible to pathogens.

Technical Abstract: While recent studies have shown the potential for negative plant-soil feedbacks (PSFs) to promote stable coexistence, they have not quantified the stabilizing effect or their importance relative to other coexistence mechanisms. In a sagebrush steppe, previous population models fit to long-term, observational data indicated strongly stabilized coexistence among the four dominant species by interactions during the recruitment stage. We conducted a temporally and spatially replicated field experiment to test the role of PSFs in stabilizing coexistence among four dominant sagebrush steppe species in situ. We then used a bootstrap model to integrate the effects of treatments and soil environments on focal species across germination, survival, and first-year growth. We found that soil microbes had consistent, negative effects on the growth of all four species. When contrasting intra- and interspecific soil environment effects, we found positive feedbacks in germination and negative feedbacks in growth that were infrequent, but of large magnitude. Our results suggest that while microbially-mediated PSF may not be a common mechanism of coexistence in this community, it could still affect the relative abundances of species that are more susceptible to pathogens via changes in host fitness. Our work also serves as a blueprint for future investigations that aim to uncover the underlying process and test alternative mechanisms that explain patterns of interest in community ecology.