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.