Reciprocal interactions between plant and soil (i.e. plant–soil feedback, PSF) can generate priority effects in which the arrival sequence of plant species have long-term consequences on plant communities. Accordingly, the temporal development of the soil environment has important implications since the strength of priority effect that an early-arriving species imposes on a late-arriving species depends on how it had modified its surrounding environment before the arrival of the later. However, past studies often treat a species’ PSF strength as a fixed parameter and time required for significant changes in the soil environment to occur is rarely studied.
To understand species-specific changes in soil environment with increasing cultivation time, we utilized a series of aerial photos taken annually at the Bodega Dunes to estimate individual age for ice plant (Carpobrotus edulis) and yellow bush lupine (Lupinus arboreus), and sampled soils from individuals of different ages. Soils were analyzed for abiotic properties including: litter depth, pH, moisture, and temperature stability. Soil fungi and bacteria ribosomal DNA were amplified with taxon-specific primers and amplicons were sequenced with the Illumina Miseq platform. We used NMDS ordination to visualize microbial community similarity and its relationships with soil abiotic properties.
Results/Conclusions
We detected species-specific shifts in abiotic soil properties and microbial communities with increasing length of plant cultivation. The soil became more acidic with longer cultivation time, while litter depth and temperature stability showed species-specific nonlinear patterns that regressed back to bare sand state as old individuals became senescent. Such nonlinear changes were more pronounced for L. arboreu, potentially due to rapid breakdown of its thinner litter layer compared to C. edulis.
With time, both fungi and bacteria communities became progressively different from bare sand, and communities associated with different plant species became more diverged. Out of all abiotic properties, soil pH had the strongest effect on microbial community structure. With increasing cultivation length, microbial communities associated with the same plant species converged (i.e. decreased b-diversity) in structure but in different trajectories: b-diversity of fungi communities monotonically decreased through time while that of bacteria communities exhibited a hump-shaped pattern. The convergence of microbial communities, despite the retrogression of abiotic properties, might indicate the role of microbial interactions in structuring communities. This study provides a critical step to elucidate how a species’ PSF strength depends on the age of its neighbors, and the role of PSF in predicting plant community dynamics.