COS 182-1 - Woodland restoration age alters soil microbial communities and shapes interactions between microbiota and plant growth

Abstract: Soil microbial communities (SMC) can influence plant performance positively or negatively during restoration, depending on the presence or abundance of soil symbionts (e.g., AMF) and pathogens. Yet, how SMC might shift in response to restoration and, in turn, affect plant performance remains poorly understood in many ecosystems. In woodlands, restoration-associated changes in the relative abundance of tree species could influence SMC because different tree species may associate with distinctive fungal communities. The goals of this study are to: 1) quantify differences in soil abiotic properties, microbial communities, and vegetation across a Midwestern oak woodland restoration chronosequence, 2) test the growth responses of four forb species to whole-soil inoculum from sites with variable restoration ages, and 3) characterize changes in SMC in inoculated soils before and after soil conditioning by each forb species using DNA metabarcoding.

In a field study, we quantified ten soil abiotic properties and the relative abundances of AMF- and EMF-associating tree species in young, intermediate, and old restored oak woodlands that varied in the onset of a prescribed burning regime (7-29 years ago). In a glasshouse experiment, we grew four species of woodland forbs in a sterilized medium inoculated with small quantities of live whole-soil inoculum from the three restored woodlands and measured growth-responses of each individual after five months. We also used DNA metabarcoding to characterize SMC in each inoculum treatment, before and after soil conditioning by each species.

Young restored woodlands maintained greater relative abundance of AMF-associating tree species (primarily sugar maple, Acer saccharum) and lower soil phosphorous than intermediate or older restored woodlands. However, other soil abiotic properties differed little across the chronosequence. Bacterial and fungal soil communities varied significantly among sites (PERMANOVA, P < 0.03). Young restored woodlands had higher fungal richness and AMF abundance but lower fungal pathogen abundance compared to intermediate or older restored woodlands. Each forb species exhibited significantly greater (all P-values < 0.01) leaf size when grown in young (AMF-enriched) relative to intermediate or old restored woodland inoculum (pathogen-enriched and dominated by EMF-associating trees). Each forb species developed a unique core soil microbiome in each inoculum treatment, with minimal overlap between the core taxa of conspecific plants grown in conditioned and unconditioned soil.

Our results demonstrate how shifts in soil microbial community composition during restoration can affect plant performance, with the most suitable SMC’s for the reintroduction of perennial forbs occurring during the early stages of oak woodland restoration.