Professor University of Alberta Edmonton, Alberta, Canada
Abstract: Testing the role of plant-soil feedbacks in natural grassland communities
Plant-soil feedbacks have the potential to be an important structural force in plant communities, as they can either severely restrict or help plant growth through conspecific-induced changes in soil properties. Tests for feedback effects often only consider changes to the soil biota and are typically conducted under highly controlled conditions, isolating plants from their more natural community settings. Therefore, to further explore feedback effects, it is necessary to test them under more natural conditions. To determine the relative extent of soil feedback effects in a natural community setting, we conducted an outdoor mesocosm experiment where we grew 42 pairs of field collected grassland communities in soils of different origin. Communities grew in their own home soil and soil from another adjacent community. To differentiate between total soil effects (abiotic and biotic) and biotic effects in isolation, we grew communities with whole field soil or with field soil as inocula. We tested whether soil origin affected various aspects of community structure, including productivity, richness, and evenness.
Conclusion/Results
We found that productivity at both the species and community level was largely independent of soil origin, indicating limited relevance of plant soil feedback effects on productivity outside of controlled conditions. Interestingly, we also found that greater compositional dissimilarity between the communities from which the soils were collected was an important driver of the strength of our community productivity feedback responses. This effect was only present in whole soil. We also discovered that soil biota impacted community structure, with communities grown in foreign soil inocula exhibiting higher richness and evenness than those grown in their home soil inocula. However, no similar effect was present with whole soils, suggesting damping of soil biotic effects by abiotic soil properties.
Our results indicate that plant-soil feedback effects may have limited relevance in natural communities. However, if feedback effects are present, it is likely that changes to abiotic soil properties play a larger role than soil biota.
