Abstract
1. Plant-soil feedback (PSF) has gained attention as a mechanism
promoting plant growth and coexistence. However, because most PSF
research has measured monoculture growth in greenhouse conditions,
field-based PSF experiments remain an important frontier for PSF
research. 2. Using a four-year, factorial field experiment in Jena,
Germany, we measured the growth of nine grassland species on soils
conditioned by each of the target species (i.e., PSF). Plant community
models were parameterized with or without these PSF effects, and model
predictions were compared to plant biomass production in new and
existing diversity-productivity experiments. 3. Plants created soils
that changed subsequent plant biomass by 36%. However, because they
were both positive and negative, the net PSF effect was 14% less growth
on ‘home’ than ‘away’ soils. At the species level, seven of nine species
realized non-neutral PSFs, but the two dominant species grew only 2%
less on home than away soils. At the species*soil type level, 31 of 72
PSFs differed from zero. 4. In current and pre-existing
diversity-productivity experiments, nine-species plant communities
produced 37 to 29% more biomass than monocultures due primarily to
selection effects. Null and PSF models predicted 29 to 28% more biomass
for polycultures than monocultures, again due primarily to selection
effects. 5. Synthesis: In field conditions, PSFs were large enough to be
expected to cause roughly 14% overyielding due to complementarity,
however, in plant communities overyielding was caused by selections
effects, not complementarity effects. Further, large positive and large
negative PSFs were associated with subdominant species, suggesting there
may be selective pressure for plants to create neutral PSF. Broadly,
results highlighted the importance of testing PSF effects in communities
because there are several ways in which PSFs may be more or less
important to plant growth in communities than suggested from simple PSF
values.