Data from: Long-term effects of host-specific soil microbiota on plant interactions

It is increasingly recognised that resource competition and plant-soil
feedback (PSF) effects can jointly determine outcomes of plant
interactions. However, it is less clear whether PSF modulates
intraspecific or interspecific competition, or intrinsic growth rate.
Thus, it remains to be answered whether PSF alters coexistence predictions
by changing competitive ability of interacting species (fitness
differences) or rather by altering self-limitation (niche differences).
Here, I examined the effects of host-specific soil inoculum, including
target and competitor species inoculum, and non-specific inoculum on
pairwise interactions of four pairs of grassland perennials. To explore
whether the effects of PSF were persistent and dependent on resource
availability, interactions were studied over a two-year period under
control and fertilized conditions. These data were then used to estimate
fitness differences and niche differences and to predict species
coexistence. I found that a host-specific inoculum can promote the
coexistence of competing plants in two ways. First, it increased niche
differences due to less intense interspecific competition in the inoculum
of a competitor. Second, a competitively inferior species was more likely
to be found in the conspecific inoculum due to its negative effect on the
intrinsic growth rate. These effects persisted throughout the experimental
period but were absent after nutrient addition. In conclusion, PSF can
promote plant coexistence by increasing niche differences and reversing
competitive dominance. Although PSF effects can have long-term effects on
competitive plant interactions, they depend on abiotic (nutrient)
contexts. Therefore, they are less likely to mitigate competitive
inequality and prevent competitive exclusion after anthropogenic
fertilization.