Testing Predictions of a Three-Species Plant-Soil Feedback Model

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Journal of Ecology



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1. A growing number of experiments measure plant growth on soils cultivated by different species. Models show that the resulting plant–soil feedbacks (PSFs) can determine plant abundance and persistence; yet, quantitative tests of their importance in community dynamics are lacking.

2. Here, we use the growth of eight plant species on ‘self’ and ‘other’ soils to parameterize a three-species PSF model. Predictions from the parameterized model were compared to plant growth observed in a 3-month glasshouse experiment. Four types of three-species communities were simulated: native, non-native, nitrogen-fixing and non-nitrogen-fixing. Because the PSF model is founded on a competition model, removing PSF effects from the model allowed us to compare PSF model predictions to competition model predictions.

3. Mean plant biomass differed among soil types by 20% and differed among plant species by 101%.

4. The PSF model correctly predicted rank abundance in the four communities tested while the competition model correctly predicted rank abundance in the two communities with nitrogen-fixing plants. Furthermore, PSF model predictions of species abundances were closer to observed values than competition model predictions. Despite consistently improving upon the competition model, predictions from the PSF model were significantly different from observed values for three of four communities. Competition model predictions were different from observed values for all four communities.

5. Our three-species model described the plant and soil conditions that allow coexistence and competitive exclusion, but when parameterized with experimental data, no communities were predicted to result in long-term coexistence.

6. Synthesis. Results suggest that PSFs captured a mechanism of plant community development. However, because improvements in model predictions were consistently small, either PSFs were not a dominant mechanism determining plant community development or PSFs were underestimated by our experimental or modelling approaches. Further testing of PSFs and development of improved methods to measure PSFs are suggested.