DOI: 10.5061/dryad.c4g76
title: Data from: Plant-soil feedbacks mediate shrub expansion in declining forests, but only in the right light

description: 1. Contemporary global change, including the widespread mortality of
 foundation tree species, is altering ecosystems and plant communities at
 unprecedented rates. Plant-soil interactions drive myriad community
 dynamics, and we hypothesized such interactions may be an important driver
 of succession following the loss of foundation tree species. 2. We
 examined whether plant-soil biota interactions, in the context of a
 putatively important light gradient associated with foundation tree
 decline, mediate the expansion of Rhododendron maximum in southeastern US
 forests where Tsuga canadensis (eastern hemlock), a dominant foundation
 tree species, is in decline. Using an 11-month, controlled inoculation
 experiment paired with Illumina sequencing, we tested the following
 hypotheses: (1) Relative to conspecific (R. maximum-conditioned) soils, R.
 maximum seedlings have higher performance in soils conditioned by T.
 canadensis and lower performance in interspace soils (conditioned by
 neither T. canadensis nor R. maximum) due to variation in soil fungal
 biota, and (2) seedling performance is greater in high light versus low
 light environments (matching environments under infested versus uninfested
 T. canadensis crowns, respectively). 3. In partial support of the first
 hypothesis, we found that R. maximum seedling performance was highest in
 T. canadensis-conditioned and R. maximum-conditioned soils and lowest in
 interspace soils. Mechanistically, soils conditioned by T. canadensis and
 R. maximum had more ericoid and ectomycorrhizal fungi, less saprotrophic
 fungi, and were less species-rich than interspace soils, and variation in
 these community traits predicted substantial variation in R. maximum
 seedling biomass. However, in support of our second hypothesis, soil
 effects on plant performance were evident in high light only; in low
 light, soil inoculation did not affect plant performance and plants
 performed worse. 4. Synthesis. Our findings suggest interactions with soil
 biota act synergistically with altered abiotic environments to mediate
 species responses to widespread foundation tree mortality, providing
 evidence for a novel mechanism of plant response to large-scale
 disturbance. Examining plant-soil interactions in the context of relevant
 abiotic gradients can therefore enhance our understanding, predictions,
 and management of community development processes following forest
 disturbance.
description: Pfennigwerth_plant_traitsThis file contains data on the following plant traits measured on Rhododendron maximum seedlings in an 11-month plant-soil feedback experiment: leaf budbreak phenology, aboveground biomass, belowground biomass, total biomass, root-to-shoot ratio, and specific leaf area.Pfennigwerth_feedback_calculationsThis file contains data on two types of plant-soil feedback calculations analyzed from an 11-month greenhouse experiment with Rhododendron maximum seedlings. Feedbacks were calculated as ln(biomass.home/biomass.away), where home is Rhododendron-conditioned soil, and away is either hemlock-conditioned soil or interspace soil.Pfennigwerth_FUNguild_L7This file contains a relative abundance matrix and ecological guild status (FUNGuild) of 63 fungal OTUs sequenced from 48 soil samples from an 11-month greenhouse plant-soil feedback experiment. Soil samples are collected from either T. canadensis-conditioned (hem), R. maximum-conditioned (rhma), or interspace (is) soil treatments.