Data from: Plant competition alters the temporal dynamics of plant-soil feedbacks

1. Most studies on plant-soil feedback (PSF) and plant competition measure
the feedback response at one moment only. However, PSFs and competition
may both change over time, and how PSF and competition interact over time
is unclear. 2. We tested the temporal dynamics of PSF and interspecific
competition for the forb Jacobaea vulgaris and the grass Holcus lanatus.
We grew both species individually and in interspecific competition in soil
that was first conditioned in the greenhouse by J. vulgaris, by H. lanatus
or without plant growth. For a period of 11 weeks, we harvested plants
twice a week and analyzed the fungal and chemical composition of the
different soils at the end of the first and second growth phase. 3. During
the second growth phase, when grown in isolation, both species produced
more biomass in heterospecific conditioned soil than in conspecific
conditioned soil. Young J. vulgaris exhibited a strong negative
conspecific feedback, but this effect diminished over time and became
neutral in older plants. In contrast, when grown in competition, the
negative conspecific feedback of J. vulgaris exacerbated over time. Older
H. lanatus plants benefited more from heterospecific conditioning when
competing with J. vulgaris, then when grown isolated. 4. Fungal community
composition and soil chemistry differed significantly between soils but
this was mainly driven by differences between plant-conditioned and
unconditioned soils. Remarkably, at the end of the second growth phase,
fungal community composition was not explained by the legacy of the
species that had been grown in the soil most recently, but still reflected
the legacy of the first growth phase. We reexamined plant growth during a
third growth phase. Biomass of J. vulgaris was still influenced by the
treatments imposed during the first phase, while H. lanatus responded only
to the plant growth treatments imposed during the second phase. 5.
Synthesis: Our study shows that the direction and magnitude of PSF depends
on plant age and competition but also on soil legacy effects of earlier
plant growth. These results highlight the need to incorporate dynamic PSFs
in research on plant populations and communities.