Data from: Spatial heterogeneity in plant-soil feedbacks alters competitive interactions between two grassland plant species

1. The effects of plants on soil vary greatly between plant species and in
mixed plant communities this can lead to spatial variation in plant-soil
feedback (PSF) effects. Such spatial effects are thought to influence
plant species coexistence, but the empirical evidence for this hypothesis
is limited. 2. Here, we investigate how spatial heterogeneity in PSFs
influences plant growth and competition. The experiment was carried out
with high and low nutrient soils to examine how these effects depend on
soil fertility. We collected soil from field plots planted for three years
with monocultures of Anthoxanthum odoratum and Centaurea jacea and tested
the performance of the two species in a greenhouse experiment in
heterogeneous soils consisting of patches of “own” and “foreign” soils and
in soils where the “own” and “foreign” soils were mixed homogeneously. In
the test phase, plants were grown in monocultures and in 1:1 mixtures in
live or sterilized soils. 3. Overall, A. odoratum in monocultures produced
less aboveground biomass in heterogeneous soils than in homogeneous soils.
Centaurea jacea produced less belowground biomass in live heterogeneous
soils than in live homogeneous soils, but there was no difference between
sterile heterogeneous and homogeneous soils. The belowground biomass per
patch varied more in pots with live heterogeneous soils than in pots with
live homogeneous soils for both plant species, but there was no difference
between pots with sterile heterogeneous and homogeneous soils. In pots
with plant mixtures, the difference in aboveground biomass between the two
competing species tended to be smaller in heterogeneous than in
homogeneous soils. In pots with heterogeneous soils, both plant species
grown in mixtures produced more aboveground biomass in “foreign” soil
patches than in “own” soil patches. The responses of plants to
heterogeneous PSFs were not different between low and high nutrient soils.
4. Our results show that spatially heterogeneous PSFs can influence plant
performance and competition via reducing the growth inequality between the
two competing species by allowing selective growth in foreign soil
patches, independent of initial soil nutrient availability. Such effect
may slow down exclusion processes and thus promote the coexistence of
competing species at the local scale in mixed plant communities.