Abstract:

In order to investigate the status of arbuscular mycorrhizae (AM) in

tropical dipterocarpaceae forest, rhizospheric soil with roots of seventeen species

of dipterocarpaceae plants grown in both native forests and plantations in tropical

region Xishuangbanna, Yunnan Province, were sampled to determine their mycorrhizal

colonization, spore density, isolation frequency, relative abundance and species

richness of AM fungi. The mycorrhizal colonization rate of host plants were measured

under a BX50 Olympus Microscope with Automatic Photo Micrographic System (320-640

×) after staining with 0.5% acid fuchsin. Spores of AM fungi in aliquots (20 ml)

of each soil were isolated by wet-sieving decanting and cane sugar centrifugal method,

hich were used to identify according to the newest taxonomic system described by

Morton and Redecker (2001). Species richness was measured as the number of species

compared with the number of individuals in the community. Results showed that most

roots collected were colonized by AM fungi, typical arbuscules and vesicles were

formed with various colonization rates (up to 40%, grade VIII), and 0-1.86 vesicles

per mm root length. Species richness on Parashorea chinensis was the highest

(4.31),while Shorea assamica showed the lowest (1.63). Hopea mollissima gave

the maximum spore density (7.76), Vatica astrotricha the minimal (3.09).

Thirty_two AM fungal species belonging to the genera Acaulospora, Glomus,

Paraglomus, Achaeospora and Scutellospora were identified. The frequencies

and relative abundances of AM fungi varied. Acaulospora and Glomus were

likely the dominant proportion in the rhizospheric soil of dipterocarpus plants in

the tropical region. It was suggested that most dipterocarpus plants can form typical

AM and there was high species diversity of AM fungi in tropical dipterocarpaceae

forest. The functional role of these AM fungi in the physiology of dipterocarpus

plants needs further research.