Human land use creates long-term legacies in ecosystems, including significant effects on soil ecology by altering soil structure, reducing organic matter content, and changing nutrient availability. Although changes in physical and chemical properties of soil alone affect biota, changes to soil microbial communities can also have important impacts, particularly on plants, through synergistic interactions. Soil fungi, including mycorrhizal fungi, are important plant mutualists and their presence or absence can affect plant establishment, persistence and community composition. The impacts of former agricultural activities on soil fungi, however, is still poorly described and we propose that altered fungal communities following agricultural land abandonment can affect restoration efforts. In this study, we planted 360 individuals of two native wildflower species into both high quality and mid-successional mixed-mesophytic forests used for agriculture until the 1930s. In a factorial design, we amended soils in plantings with a) soil from high quality sites b) commercial inoculum and c) no amendment. We did not move soil from mid-successional plots to high quality plots. We used high throughput sequencing to “unpack the black box” and explore changes in fungal communities across forest types.
Results/Conclusions
We found substantial differences in fungal communities between high quality, mature forest sites and low quality, mid-successional forests but we saw no differences in species richness or diversity between sites. We observed approximately 800 operational taxa in soil from both high quality and low quality sites with communities dominated by taxa in the Ascomycota, Basidiomycota, and Mortierellomycota. Community differences between high and low quality sites were driven by changes within the phyla; there were more potentially ericoid mycorrhizal fungi in the low quality sites and a trend toward increased abundance of ectomycorrhizal taxa (e.g. Sebacinaceae, Thelephoraceae) in the high quality sites. Short-term herbaceous plant growth responded to site quality but not soil origin. Maianthemum racemosum had significantly larger leaves whereas Arisaema triphyllum grew significantly taller in high quality sites 8 months after planting. But soil origin had no effects on growth. Inoculation with a commercial mycorrhizal inoculant also had no effect on plant growth. Our data suggest that soil fungal communities change in substantial ways between high and low quality forests, but transplanted herbaceous plants may respond in the short-term to other site differences (e.g. light availability, soil moisture).