Effects of coastal embankments on ectomycorrhizal fungal communities and enzymatic activities of Pinus thunbergii in tsunami-affected areas in Japan

The 2011 earthquake off the Pacific coast of Tohoku and the subsequent tsunami eradicated coastal forests. To restore forests, Pinus thunbergii seedlings were planted on embankments made of various substrates. This study aimed to determine the effects of embankments on ectomycorrhizal (ECM) fungal communities and enzymatic activities associated with P. thunbergii seedlings. ECM roots were collected from planted seedlings and adjacent, surviving mature trees of P. thunbergii at two coastal sites in northern Japan. Mycorrhization was calculated by dissection microscopy based on the gross morphology and color of the ECM root tips. Representative colors of different ECM root tips were applied for the estimation of eight enzymatic activities using a microplate reader and of the fungal taxa involved using DNA barcoding. The rate of mycorrhization ranged from 75.8% to 100% and mature trees were almost 100% at both sites. For seedlings, the highest mycorrhization rate was 99.1% on soils from inland forested areas, whereas the lowest was 75.8% on substrates of crushed concrete fragments. The community composition of ECM fungi significantly differed among sites. The enzymatic activity of ECM root tips in Gls, Leu and Nag differed significantly between the Coast and other soil substrates. These results suggest that soil substrates may affect ECM fungal communities and their extracellular enzymatic activities.