Evaluating the role of biotic and chemical components of plant-soil feedback of primary successional plants

During primary succession, vegetation and soil form important feedbacks that enhance plant species turnover. However, the mechanisms underlying such plant-soil feedbacks (PSFs) remain unclear. We studied PSFs among 12 species from different successional stages in a limestone quarry. We explored the changes in abiotic and biotic soil conditions induced by individual species, and the effects of these changes on further plant germination and biomass production. We performed a two-phase PSF experiment. Firstly, we conditioned the quarry soil by three early- and three mid-successional species. Secondly, we planted the conditioned soils, as well as unconditioned control, by the same early- and mid-successional species, and by three late-successional grassland and three invasive species. We recorded seedling establishment and total biomass of all plants. The conditioned soils were analysed for pH, nutrient content and composition of bacterial and fungal communities. Soils conditioned by early-successionals were characterized by higher proportion of pathogenic fungi than soils conditioned by mid-successionals. Bacterial communities were rather species- (14.6% of variation) than guild-specific (7%). From the individual properties, the most frequent predictors of plant performance were the changes in soil chemical properties and the biomass of conditioning plants (5 species out of 12). In case of two species, we found significant links between seedling establishment but not plant growth and changes in fungal communities (2 species), suggesting that biotic feedbacks might be more important in the initial stages of plant life.