Arbuscular mycorrhizal fungi of northern white cedar ( Thuja occidentalis L.): Habitat effects on fungal communities and inoculum effects on plant growth on acid peat soils.

摘要

The relationship of arbuscular mycorrhizal (AM) fungi with northern white cedar (NWC) was examined from the perspective of both fundamental questions about habitat specificity in the root fungal community, as well as applied questions regarding AM fungal efficacy in NWC restoration in peat soils. I performed two experiments testing the effects of AM fungi on survival, growth, and nutrition of NWC seedlings; and one molecular study to determine the habitat effects on community composition of NWC root-associated fungi. First, a greenhouse AM inoculation experiment was conducted in factorial combination with fertilization and liming to examine conditional effectiveness of AM fungal inoculation. Second, a field experiment in a poor fen was conducted to determine effectiveness of AM fungal inoculation, AM plant proximity, and environmental factors on survival, growth, and nutrition of NWC seedlings. Third, an observational study employed Illumina sequencing to determine habitat effects on diversity and composition of NWC root-associated fungal communities in mine tailings, peatlands, and uplands. AM inoculation of NWC had different outcomes in the greenhouse and field experiments. In the greenhouse AM fungi significantly increased all plant growth and many nutrient metrics, whereas in the field there were no significant inoculum effects. This might be due to the differences in several experimental conditions. Seedlings in the greenhouse grew under high environmental control, higher pH, using commercial inoculum, and with no competition. In contrast, the field experiment was conducted without environmental controls, with native inoculum under more acidic and competitive conditions. However, in addition to pH and light effects, we observed positive AM plant proximity effects on growth and nutrition, perhaps indicating a mycorrhizal role in NWC seedling success in poor fens. In the fungal community analysis, unidentified Glomeraceae were the dominant AM fungi across all habitats. Total fungal and AM fungal community richness was higher in bog and upland than in stamp sands. Fungal community composition within Glomeromycota and all fungal taxa were both significantly different between the mine tailing and the other two habitats. There were taxa with both broad and narrow habitat associations that are potential targets for general vs habitat-specific AM inoculum.