Effects of rainfall exclosure on the ectomycorrhizal fungi of a canopy tree in a tropical rainforest

We expected ectomycorrhizal (ECM) fungal community structure on mature tree to be affected by drought. A rainfall exclosure treatment was conducted to study changes in the ECM community of a single tree at Lambir Hills National Park, Malaysia. A vinyl sheet of conical shape covered the entire rooting area of a Dryobalanops aromatica from 22 November 2008 until 7 December 2008. Three root samples each were collected from both the tree that was treated with rainfall exclosure sheet and a control tree nearby before and after the treatment. ECM samples were identified using molecular technique. The ECM species abundance (mean number of species per sample) on the rainfall exclosure tree decreased from 8.0 ± 1.0 to 4.7 ± 0.6, whereas species abundance on the control tree was similar. Non-metric multidimensional scaling (NMDS) showed that the species composition of ectomycorrhizas differed between samples collected before and after treatment. Changes in species composition before and after treatment were caused by difference in tolerance to reduction in rainfall among fungal species and by spatiotemporal variation in species composition of ectomycorrhizas.