Mycorrhizal mediation of plant adaptation to coal mine soil

Adaptation of plants to harsh conditions may be mediated by their association with beneficial microbes that associate with plant roots. Most plants, for example, associate with arbuscular mycorrhizal fungi, a group of soil fungi that increase the availability of limiting soil nutrients. We performed a series of experiments to test the potential for arbuscular mycorrhizal fungi to mediate plant adaptation to mine soil conditions, and to test if utilizing adapted communities of mycorrhizal fungi might enhance or accelerate coal mine restoration. We utilized a full factorial design for all three experiments. Each experiment included two fungal communities, one derived from mine soil and one derived from non-mine soil, and two soil types, mine soil and non-mine soil. For two experiments we also had two populations of plants, those grown from seeds collected from mines, and those grown from seeds collected from non-mine sites.;Our expectations of finding heavy metal toxicity to be an important factor in adaptation to mine soils was not realized. There was no evidence that the plants suffered from aluminum toxicity; however, plants grown in coal tailings produced far less biomass than those grown in low-nutrient clay soil.;We found evidence of local adaptation to mine soil in Andropogon virginicus, Liquidambar styraciflua and Plantago lanceolata. Mine plants of A. virginicus and L. styraciflua grew more slowly than non-mine plants. P. lanceolata from mines had higher root-shoot ratios, when uninoculated, than their non-mine counterparts. This suggests the mine and non-mine populations were genetically different, and it is consistent with slower growth in mine soil being adaptive, perhaps because of correlated reduction in mortality. Moreover, for L. styraciflua we saw plant x soil interactions. Mine plants produced more biomass in mine soil and non-mine plants produced more biomass in non-mine soil.;In P. lanceolata and L. styraciflua root-shoot ratios were higher when plants were inoculated with arbuscular mycorrhizal (AM) fungi. AM fungi from the mine were better mutualists, increasing plant biomass when coupled with A. virginicus or P. lanceolata, supporting other research which has indicated that harsh conditions may reinforce mutualistic relationships.;There was evidence of local adaptation with fungi from the mine demonstrating sensitivity to mine soil when grown with A. virginicus or L. styraciflua. Percent root colonization was higher with both these plant species when they were grown in mine soil inoculated with fungal communities also derived from mine soil.;We have evidence of mycorrhizal mediation of plant adaptation to mine soil in L. styraciflua, as the mine ecotype derived the most benefits from inoculation when grown in the soil from which it was derived. In A. virginicus we saw interactions between soil and fungi with higher root-shoot ratios occurring when fungi were in their own soil types, mine fungi in mine soil and non-mine fungi in non-mine soil.;We tested Euonymus atropurpureus, Fagus grandifolia and Quercus rubra with fungal communities derived from mine soil and non-mine soil; however the responses observed could be explained by pH preference for those species to the two soil types.;We concluded that harsh edaphic conditions may help reinforce the symbiotic relationship between plants and AM fungi, resulting in more beneficial symbionts, and that using adapted plants and fungal communities may be helpful in restoring Indiana coal mines.