Biodiversity of arbuscular mycorrhizal fungi in a tropical rainforest of Xishuangbanna, southwest China

The tropical rainforests of Xishuangbanna in southwestern China are located at the northern margin of the tropical rainforests of Southeast Asia. They harbour a high diversity of animals and plants. We investigated the diversity of arbuscular mycorrhizal fungi in soil under trees in these forests in order to establish if these fungi are also highly diverse. One hundred and eighteen rhizosphere soil samples were collected from a tropical rainforest in Xishuangbanna, and 525 arbuscular mycorrhizal fungal spores (or sporocarp) samples were obtained using the wet-sieve method. Twenty-seven species of arbuscular mycorrhizal fungi were identified from the collections. The species of arbuscular mycorrhizal fungi were of the genera Acaulospora (9 species), Gigaspora (1 species), Glomus (13 species), Sclerocystis (3 species) and Scutellospora (1 species). Acaulospora and Glomus were dominant at the study site. The arbuscular mycorrhizal fungi spore density ranged from 25 to 2550 per 100 g soil (average 675), and the species richness of arbuscular mycorrhizal fungi ranged from1-7 (average 4.4). Although tropical rainforests support a high diversity of plants, their associated symbiotic fungi are not as diverse as we had expected, possibly because arbuscular mycorrhizal ftmgi are not specific to their host plants.