Abstract: [Objective] Pinus armandii distributes widely in the Erlang Mountain and is one of the dominant species in the community. The Erlang Mountain Forest Farm is located in Sichuan Province and it contains rich microbial resources. This article was intended to study the fungal diversity and analyze the relationship between fungal structure and their functions at the beginning of the P. armandii litter decomposition period. [Method] The grinding method was used in this paper to isolate fungi on the P. armandii litter from the altitude of 2 750, 2 650, 2 510, and 2 460 m. The isolates were further indentified according to the morphology combined with PCR amplification and sequencing using the universal primers based on the ITS sequence of fungi. In addition, the Rhizosphaera was for the first time isolated from P. armandii, and the relevant research on the fungi is still insufficient. There remains controversy on the fungal role as a pathogen or weak parasitic fungus in foreign reports. The fungus was reported to cause disease on P. sylvestris var. mongolica in China in 2013. In this study, 12 strains of Rhizosphaera were isolated from the four elevations. To study the saprophytic performance, three strains of Rhizosphaera sp. with different morphological features, namely R. sp.1, R. sp.2 and R. sp.3, and one strain of Lophodermium erlangshanense were selected for decomposition test in vitro, in which the P. armandii litter is the sole substrate. [Result] The isolation results showed that 23 fungi taxa were obtained. The imperfecti and ascomycetes were the major components that occupy 15 taxa and 5 taxa, respectively. All of the fungi belonged to 15 genera. Mucor, Trichoderma, Rhizosphaera, Penicillium and Talaromyces were isolated from the plots over the four different elevations, and were the abundant species. The filamentous fungi, such as Trichoderma, and Penicillium, which had the quantitative superiority and diversity, undoubtedly would play an important role in the process of litter decomposition. However, basidiomycete fungi, without abundant amount and species, might not participate in the decomposition at the early stage. The basidiomycete fungi originated from the environment may participate in the further lignin decomposition at the late stage. Through the determination of cellulose enzyme produced by the fungi, the activities of endoglucanase and β-glucosidase reach the maximum at the 13th day. The activities of Cellobiohydrolase reach the maximum at the 17th day. In general, there was no significant difference in the enzyme activities as well as the mass loss among the four strains. Those results indicated that Rhizosphaera sp. and L. erlangshanense could decompose the cellulose components, and there was a synergistic effect from the different cellulase enzymes (endoglucanase, cellobiohydrolase, β-glucosidase). The mass loss decomposed by L. erlangshanense was 15.74%, while the loss caused by Rhizosphaera sp. ranged from 12.00% to 13.40%. According to the previous researches, L. erlangshanense was usually found in the litter and rarely in alive needles, suggesting that it may not cause the needle disease. [Conclusion] The results indicated that filamentous fungi, such as Trichoderma, and Penicillium, played an important role at the beginning of the litter decomposition period. They were both the dominant species in the four different altitudes. Rhizosphaera sp. and L. erlangshanense were weak saprotrophic fungi in the P. armandii litter. However, it needs to be further verified that whether the capacity of cellulose decomposing enzyme is related to their pathogenicity.

Key words: Pinus armandii, litter, fungal diversity, Rhizosphaera sp., Lophodermium erlangshanense, decomposition