Soil preparation methods promoting ectomycorrhizal colonization and American chestnut Castanea dentata establishment in coal mine restoration.
The objective of this research was to evaluate soil subsurface methods that may aid in seedling establishment and encourage root colonization from a diverse group of ectomycorrhizal (ECM) fungi during restoration projects. American chestnut Castanea dentata Marsh. Borkh. and backcrossed chestnuts seedlings were planted on a reclaimed coal mine site in central Ohio, USA. Roots from chestnut seedlings planted in the plots that were cross-ripped, plowed and disked, or a combination of treatments were sampled for ECM fungi and compared with control plots. The presence and identification of native ECM were determined by fungal DNA sequencing of the internal-transcribed (ITS) region. After two growing seasons, mechanical soil treatments resulted in seedlings with significantly more ECM species when compared to seedlings grown in the control plots (P<0.0001). A nonmetric multidimensional scaling ordination followed by a permutational MANOVA confirmed significant dissimilarities in community composition between the control and mechanically treated plots (F=0.24, P=0.015). Ectomycorrhizal root colonization was significantly higher on the chestnut seedlings sampled from the mechanically treated plots when compared to the control plots (F=10.63, P<0.0001). Differences did not exist among the three mechanical treatments. There was also a significant increase in above-ground seedling growth in the plots that were treated with a surface soil method (F=15.72, P<0.0001). It is not clear whether ECM activity was the driver of plant growth; regardless, both are strong indicators of healthy tree establishment. Synthesis and applications. This study illustrates that the use of soil subsurface methods increased ectomycorrhizal (ECM) activity and seedling growth. Employing methods that encourage the root colonization by beneficial ECM and promote healthy seedling establishment may aid the long-term survival of chestnuts in restoration projects. This can be applied to other hardwood seedlings used in reforestation in soils compacted after anthropogenic disturbances.