The positive relationship between diversity and productivity has been well established but the mechanisms explaining this relationship remain unresolved. Resource partitioning and sampling effects are known to be important, however they fail to explain the extent or variation of diversity-productivity relationships. In the past 10 years, plant-soil feedback (PSF) has gained attention as potential driver of plant community assembly and productivity. However, PSF studies are fairly new and most PSF experiments have been performed in greenhouse conditions. Further, few studies have used experimental PSF data to parameterize models of plant growth to provide explicit tests of the effects of PSFs in communities. Here we use field-measured PSF data to parameterize a newly developed spatially-explicit PSF model and compare model predictions to growth observed in plant communities. More specifically, nine species were grown for a two-year conditioning phase and a two-year response phase in a fully factorial PSF experiment, Jena, Germany. PSF values were used to parameterize a spatially-explicit model and model predictions were compared to plant growth in communities grown for three years in a separate diversity-productivity experiment.
Results/Conclusions
PSF values varied from negative to positive for different species. Consistent with theoretical predictions, the species with the most positive PSFs were underrepresented in communities (i.e., underyielded). However, the presence of the legume, Trifolium repens, mitigated this effect. Our PSF model based on only biomass production of monocultures on different soil types, predicted the dominant species, however the model was less successful at predicting the abundances of less productive species. Despite poor predictions for rare species, the spatial PSF model outperformed a null version of the same model that did not include PSF effects. The spatial model, however, did not outperform the non-spatial PSF model. Because the spatial model limited contact among species to several adjacent individuals, the spatial model tended to decrease PSF effects. We suggest that the exclusion of demographic factors, such as germination rate, survival and plant-plant interactions such as competition for light may explain this pattern. Including demographic characteristics and resource competition of each plant species and their variations among and within plant species, is an important direction for future research.