Abstract
Negative plant-soil feedback (PSF) , where plant performance is reduced in soils conditioned by conspecifics, are widely documented in plant communities. However, the strength and sometimes direction of PSF can vary widely, presumably due to environmental context. We hypothesized that soil fertility and light availability influence the direction and strength of plant-soil feedback experienced by tree seedlings. We conducted a 10-week greenhouse experiment and assessed survivorship of black cherry (Prunus serotina) in low (~1% full sun) vs. high (~18% full sun) light availability and in non-sterile vs. sterile soils collected under the canopy of conspecific vs. heterospecific adult trees at five sites that vary in nutrient availability in Manistee National Forest, Michigan, USA. Northern red oak (Quercus rubra) also was included in the experiment, but no seedlings died and thus there are no survivorship responses to report. Prunus serotina seedlings experienced microbe-mediated negative plant-soil feedback in low fertility sites (higher C:N ratios and lower NH4+) but positive feedback at high fertility sites, but these feedbacks occurred only under high light availability. Consistent with these results, microbe-mediated negative PSF increased with soil Fe3+ and C:N ratios and decreased with NH4+. Thus lower fertility soils, characterized by high C:N and Fe3+availability and low NH4+, are associated with stronger negative conspecific feedback for P. serotina seedlings. Conversely, higher fertility soils flip the feedback to positive. Our results demonstrate the important role of environmental context, specifically light and soil nutrient availability, on the magnitude and direction of conspecific plant soil feedback. Thus, PSF is likely an important driver in plant community dynamics that may be either destabilizing (promote species coexistence) or stabilizing (promote monodominance) depending upon environmental context.
Highlights
A long-standing challenge in ecology is to identify factors regulating plant abundance, co-existence, and community composition
In general as soil fertility increased, biotic-mediated plant soil feedbacks in high light went from negative to positive; while effects were less pronounced in low light, there were consistent results with a negative biotic-mediated plant-soil feedback (PSF) at the intermediate fertility site and a positive PSF at the highest fertility site
In the non-sterile soil treatment, where biotic and abiotic effects both occurred, Prunus serotina seedlings grown at high light experienced negative PSF at low fertility sites, and positive PSF at the intermediate and one of the high fertility sites (Figure 2A)
Summary
A long-standing challenge in ecology is to identify factors regulating plant abundance, co-existence, and community composition. Nutrients and Light Affect Plant-Soil Feedback and/or seedling survivorship near conspecific adults and/or at high conspecific densities. Such NDD seedling mortality would favor establishment of heterospecific individuals under an adult tree, and promote species coexistence (Mangan et al, 2010; Alvarez-Loayza and Terborgh, 2011). Interactions between adult plants and juveniles that are mediated by root-associated fungi and other symbiotic microorganisms (“biotic-mediated plant soil feedback”) (Bever et al, 2012; Terborgh, 2012) is likely a prime mechanism creating these NDD patterns since plantsoil feedback can reduce seedling survival near conspecific adults while favoring heterospecific seedlings (Mangan et al, 2010; McCarthy-Neumann and Kobe, 2010; Alvarez-Loayza and Terborgh, 2011; McCarthy-Neumann and Ibáñez, 2012)
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