Conclusion

To affect species coexistence, or to have large effects on plant community productivity, PSFs must be large relative to differences in intrinsic growth rates among species (Crawford et al., 2019; Ke & Wan, 2020; Lekberg et al., 2018). While PSFs changed plant growth within plant species by 36%, this effect was smaller than differences in growth among species, and the dominant plant species demonstrated small PSFs in our experiment. The lack of an effect of PSFs of the magnitude observed were surprising, but appropriate because complementarity effects did not contribute to overyielding observed in the current diversity productivity experiment. Our results demonstrate that species identity and composition of the plant communities can determine whether PSFs are important to plant community growth: large PSFs for sub-dominant species and small PSFs for dominant species will cause small overall effects on plant community productivity. Our results also highlight a potential connection between PSFs and competitive ability (Lekberg et al., 2018; Petermann et al., 2008). More specifically, there may be selective pressure for species to produce both small PSFs and large competitive ability in order to dominate. Results provide an important but uncommon perspective on the role of PSF in plant communities in field conditions.