Greenhouse experiment data: Soil microbial legacies influence plant survival and growth in mine reclamation

Plants alter soil biological communities, generating ecosystem legacies
that affect the performance of successive plants, influencing plant
community assembly and successional trajectories. Yet, our understanding
of how microbe‐mediated soil legacies influence plant establishment is
limited for primary successional systems and forest ecosystems,
particularly for ectomycorrhizal plants. In a two‐phase greenhouse
experiment using primary successional mine reclamation materials with or
without forest soil additions, we conditioned soil with an early
successional shrub with low mycorrhizal dependence (willow, Salix
scouleriana) and a later‐successional ectomycorrhizal conifer (spruce,
Picea engelmannii × glauca). The same plant species and later‐successional
plants (spruce and/or redcedar, Thuja plicata, a mid‐ to late-successional
arbuscular mycorrhizal conifer) were grown as legacy‐phase seedlings in
conditioned soils and unconditioned control soils. Legacy effects were
evaluated based on seedling survival and biomass, and the abundance and
diversity of root fungal symbionts and pathogens. We found negative
intraspecific (same‐species) soil legacies for willow associated with
pathogen accumulation, but neutral to positive intraspecific legacies in
spruce associated with increased mycorrhizal fungal colonization and
diversity. Our findings support research showing that soil legacy effects
vary with plant nutrient acquisition strategy, with plants with low
mycorrhizal dependence experiencing negative feedbacks and ectomycorrhizal
plants experiencing positive feedbacks. Soil legacy effects of willow on
next‐stage successional species (spruce and redcedar) were negative,
potentially due to allelopathy, while ectomycorrhizal spruce had neutral
to negative legacy effects on arbuscular mycorrhizal redcedar, likely due
to the trees not associating with compatible mycorrhizae. Thus, positive
biological legacies may be limited to scenarios where
mycorrhizal‐dependent plants grow in soil containing legacies of
compatible mycorrhizae. We found that soil legacies influenced plant
performance in mine reclamation materials with and without forest soil
additions, indicating that initial restoration actions may potentially
exert long‐term effects on plant community composition, even in primary
successional soils with low microbial activity.