Variation in the effectiveness of native microbial amendments for coastal dune restoration

Introduction Microbial amendments can improve restorations by increasing plant performance and decreasing soil erosion. Whole‐soil amendments collected from native ecosystems, in particular, can produce desirable outcomes; however, it is unclear if all native soil amendments produce equally positive effects. Instead, it is likely that donor locations differ in their microbial communities, which may change their efficacy for restoration. Objectives We tested whether soil amendments sourced from sites across the Texas Gulf Coast differed in their effects on aboveground and belowground responses, and whether donor site characteristics predicted the efficacy of the soil amendments. Methods In a greenhouse experiment, a community of five native plant species was grown in live or sterilized soil amendments collected from 11 sites. Results In comparison to sterile amendments, live amendments improved plant biomass, plant diversity, arbuscular mycorrhizal (AM) fungal colonization, and density of AM fungal extra‐radical hyphae (ERH), a metric strongly connected to soil stability. One soil amendment origin outperformed the others, with an almost three‐fold increase in total plant biomass and an almost six‐fold increase in ERH compared to other live treatments. The performance of amendments was positively correlated to plant species richness and ERH at the donor sites. Conclusions Where native soil amendments are sourced from could dramatically alter restoration outcomes. While amendments generally outperformed sterile soil, one location clearly outperformed the others by increasing plant biomass and soil stability, suggesting that careful selection of microbial amendments can be useful for optimizing restorations.