MCA: Plant-soil feedbacks and population dynamics of two arid system shrubs with contrasting spatial distributions and life histories

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Plant-soil interactions represent a burgeoning and impactful area of ecological inquiry that is improving understanding of plant-plant interactions within and between species, and controls on community structure. The complementary expertise included in this study offers a novel collaboration to integrate plant-soil feedbacks with plant population growth. This integration advances understanding of context-dependent population regulation and promises to advance future ecological research. Outcomes from this research will provide important understanding of plant-microbial feedbacks at the population level and permit long-term assessment of these feedbacks, which is increasingly important due to ongoing changes in the occurrence and severity of drought in the US Southwest. An integrated outreach component will support ongoing efforts to improve diverse participation in ecology and environmental biology. By recruiting underrepresented student participants from an existing project that examines the relationship between identity and ecology education, the current project provides a unique opportunity to assess student field experiences with cutting edge research that treats cultural influences on student retention, and pedagogy. This synthesis adds value to both research efforts.The project examines feedbacks between two common plant species and the soil microbial community of a well-studied arid plant system. These feedbacks will be studied at different life history stages of two dominant species in the US Southwest, Ambrosia dumosa (A. Gray) Payne Asteraceae, white bur-sage, and Larrea tridentata (DC.) Coville Zygophyllaceae, creosote bush. The study will occur in a field site at Joshua Tree National Park where more than 35 years of spatially-explicit demographic data have been collected within a permanently mapped plot. Observational and experimental studies of microbial respiration, microbial diversity, and microbial composition in response to 1) plant species, 2) plant size and 3) plant density will be conducted, and outcomes will be used to project future population growth. The researchers will use specialized population models to measure differences in population trajectories that differ by 1) exclusion of microbial activity, 2) inclusion of microbial respiration but not diversity or composition, 3) inclusion of microbial diversity and composition but not respiration, and 4) inclusion of microbial respiration, composition, and diversity. By including the influence of the soil microbiome on plant growth and survival, this project advances the ability to understand how plant immobility and variable habitat conditions interact to control the spatial structure and dynamics of populations and communities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.