Plant-soil feedback (PSF), where plant performance is influenced by whether seedlings are grown in soil conditioned by conspecifics, is commonly theorized as a mechanism of plant coexistence and abundance. Yet, very few PSF experiments have been performed in the field. In addition, even in greenhouse settings the strength and sometimes direction of PSF can vary widely, presumably not only due to the plant species within the community but also due to environmental context. We hypothesized that light availability will influence the direction and strength of plant-soil feedback experienced by tree seedlings. We conducted a 17-week field transplant experiment where we assessed seedling survivorship twice a week of five temperate tree species that varied in local adult abundance and shade tolerance, to non-sterile intact soil cores collected under the canopy of conspecific vs. heterospecific adult trees. Soil cores, were then grown in transplant plots that spanned a light gradient (from 5 - 15% light available) in Alma College's Ecological Preserve, Michigan, USA.
Results/Conclusions
Three species (Prunus serotina, Quercus alba, and Quercus rubra) experienced negative PSF with reduced survival (9, 11 and 19%, respectively) in conspecific soil relative to soils cultured by Acer rubrum. Acer saccharum experienced positive PSF with increased survival (19, 14 and 15%, respectively) in conspecific relative to soils cultured by P. serotina, Q. alba, and Q. rubra. Populus grandidentata seedlings did not experience PSF. Contrary to our expectations, light availability did not influence the direction or strength of PSF a species experienced. In addition, for all species (except P. grandidentata) seeding survival in conspecific soil was the same regardless of light. For P. grandidentata, seedling survival was 10% higher in low relative to high light plots. Across all species with PSF, differences in survival based on soil source appeared at week 3 and for A. saccharum and P. serotina peaked at week 8 and for Q. alba and Q. rubra were still getting stronger at week 17. Our results in the field suggest that plant-soil feedback can influence plant community dynamics but contrary to our past work these feedbacks can occur across a light gradient.