Ectomycorrhizal fungal communities of Shorea robusta along an elevation gradient.

Shorea robusta (Sal) is an ecologically and economically important hardwood tree species growing in the plains and lower foothills of the Himalayan region. It is a dual-mycorrhizal tree associated with both arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi. To understand how ECM communities associated with Sal roots are structured, we studied their diversity, composition, and root colonisation in four tropical forests along an elevation gradient (82 to 950 m a.s.l.). The ECM community was not found to be very diverse: we obtained 155 ECM operational taxonomic units (OTUs) belonging to 13 ECM genera in 8 families of Basidiomycota. The genus Tomentella was the most dominant, followed by Russula and Inocybe. Elevation explained 10.2% of variability in ECM composition, and significant effects of forest type, geographic position, soil temperature and moisture were confirmed. The forest at the highest elevation had ECM communities whose community structure was divergent from those at lower elevation. ECM root colonisation significantly decreased with increasing elevation and decreasing available P content. Whereas a low number of ECM species produced a high ECM colonisation of Shorea roots in low-elevation forests, a more diverse ECM community formed a low ECM colonization in high-elevation forests. The identified dominant species may be potentially used as inoculum for Sal forest restoration.