Site Soil-Fertility and Light Availability Influence Plant-Soil Feedback

Abstract

Negative plant-soil feedback (PSF), where plant performance is reduced in soils conditioned by conspecifics, is widely documented in plant communities. However, the strength and sometimes direction of PSF can vary widely, presumably not only due to the plant species within the community but also 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 Northern red oak (Quercus rubra) and 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. Q. rubra seedlings experienced neutral plant-soil feedback regardless of light level or site as only one seedling died during the course of the experiment. Prunus serotina seedlings experienced microbe-mediated negative PSF in low fertility sites 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 Fe 3+ and C:N ratios and decreased with NH4+. 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, particularly in P. serotina. Since Q. rubra experienced neutral microbial PSF, P. serotina has a relative disadvantage to Q. rubra under lower site fertility, but a relative advantage under higher site fertility. These results are consistent with these species relative abundances in the field and thus PSF could be an important driver of plant community dynamics.

Multi‐dimensionality as a path forward in plant‐soil feedback research

“…Subsequent research has since shown that soil pathogenicity can also drive variation in PSFs across environmental gradients (Bennett & Klironomos, 2018; Dominguez‐Begines et al., 2020; Hersh et al., 2012; Spear et al., 2015). There is now growing evidence that spatial variation in a wide range of environmental factors can alter the strength or direction of PSFs, including soil nutrients (Gustafson & Casper, 2004; Larios & Suding, 2015; McCarthy‐Neumann & Kobe, 2019), water (Rasmussen et al., 2020), light (McCarthy‐Neumann & Ibanez, 2013; Smith & Reynolds, 2015), elevation (Fry et al., 2018; Lynn et al., 2020; Van Nuland et al., 2017) and biotic factors including competition and herbivory (Kostenko et al., 2012; Lekberg et al., 2018). However, it is also important to note that not all studies have found PSFs to be responsive to these types of environmental factors (e.g.…”

Tree seedling functional traits mediate plant-soil feedback survival responses across a gradient of light availability

“…Both A. saccharum and P. serotina experienced lower survival in live than sterilized conspecific soils, indicating that soil-borne microbes have negative effects on seedling survival. For P. serotina, although soil-borne microbes cultured in conspecific soils may have a negative effect on survival, the net effect of PSFs (assessed as survivorship in conspecific versus pooled heterospecific soils) appeared to be neutral [but see [78][79][80].…”

Tree seedling shade tolerance arises from interactions with microbes and is mediated by functional traits

“…Future studies should consider teasing apart these mechanisms in the field, rather than the greenhouse, to provide more realistic seedling responses. Furthermore, although we were interested in light availability and shade tolerance, other environmental variables, such as nutrient or water availability, also could influence seedling survivorship (McCarthy-Neumann and Kobe, 2019).…”