The burning of oil shale provides electricity for the people of Estonia.  The resulting ash hills are desolate, environmentally toxic, and prohibitive to potential plant colonizers.  Eventually, these sites undergo primary succession, and among the first colonizers are rare terrestrial orchids from the Orchis, Dactylorhiza, and Epipactis genera. These orchids are considered habitat specialists, yet they are capable of colonizing these new (<100 yr), unique locations.  Furthermore, successful orchid establishment is dependent upon the supply of organic carbon to the seedling from specific mycorrhizal fungi. Our research investigates the availability of suitable orchid mycorrhizal fungi in these extreme environments.   In order to assess the composition of the fungal community in the ash hill soils, we extracted DNA from the soil, PCR-amplified fungal ribosomal (ITS) and mitochondrial DNA, and sequenced the PCR products.  We compared our sequences to vouchers those in the NCBI database in order to identify fungal taxa.

Results/Conclusions

Fungi from the Cortinariaceae, Thelephoraceae, and Tulasnellaceae, all well established mycorrhizal families, are abundant and dominate the fungal community.  Saprotrophic fungi common to adjacent forest soils were absent from the majority of soil samples, likely due to very low levels of organic matter in the ash hill soils.  Although the initial carbon source for maintaining the mycorrhizal fungi in the soil remains unclear, once orchids have become established, the potential development of mycorrhizal networks may facilitate colonization by later arriving propagules. Importantly, the prevalence of symbiotic fungi in the ash hill soils enables orchids to populate this harsh, polluted environment.