Cunninghamia lanceolata(Lamb.)Hook. (Chinese fir) is one of the most important industrial timber species in China, the area of Chinese fir plantation accounts for 21.35% of the total plantation area in China. At present, the Chinese fir plantation has some problems such as continuous planting, single tree species, mismatch tree species with site and so on, this contributed to productivity decline and soil degradation. Remarkable changes caused by soil degradation, for instance, soil microorganism, soil physic-chemistry characteristics, soil enzyme activity and undergrowth vegetation, etc.
Soils represent a huge reservoir of biodiversity with several billion prokaryotic and eukaryotic microorganisms, corresponding to numerous different taxa, inhabiting a single gram of soil. Fungi are the dominant eukaryotic lineage in terms of biomass in soil, where they play key roles as decomposers, pathogens, and mycorrhizal mutualists. Due to their large number of species, specialization, and important ecological functions, fungi are also excellent bioindicators. Investigating the fungal diversity becomes crucial for the ecological characterization of any given site.
Traditionally, diversity was assessed using selective plating and direct viable counts. Limitations include uncultivable microorganisms not detected, bias towards fast growing individuals, and bias towards fungal species that produce large quantities of spores. High-throughput tag-encoded FLX amplicon pyrosequencing has been used to study fungal diversity and allows identification of fungal as well as the prediction of phylogenetic relationships. This method avoided the limitations of plate count.
This study aims to provide an overview of soil fungal diversity in soils of Chinese fir plantations and examine the relationship between soil fungal diversity and environmental factors. To achieve the objectives, we employed high-throughput tag-encoded FLX amplicon pyrosequencing to analyze fifteen soil samples from the Chinese fir plantation forests at the Huangfengqiao farm. Our analyses showed that there were significant differences in soil physical-chemical characteristics and undergrowth vegetation among the sites that differed in forest age. Specifically, the soil from the first generation Chinese fir plantation had higher organic matter, total N, and available K than those from the second generation and the third generation Chinese fir soils. Similarly, the 454 pyrosequencing results showed that the fungal Ace index, Chao index and fungal genetic diversity of the first generation young Chinese fir soil were all higher than those in the soils from the second generation and the third generation Chinese fir plantations. The dominant phylogentic group was Sordariomycetes. Interestingly, fungi in family Tuberaceae were found only in soils of the second and third generation Chinese fir plantations. The RDA analyses identified that moisture content, organic matter, available P, and available K in the Chinese fir plantation forest all contributed to differences in the distributions of dominant soil fungi. The diversity of soil fungi was positively correlated with undergrowth vegetation diversity and total N. Similarly, the Chao index was correlated with Shannon-Weaver index and total N. In conclusion, our analysis of fungal 18S rRNA-based datasets revealed differences in soil fungal community structure among the different plantations of the Chinese fir and that the differences were correlated with the soil physical-chemical characteristics as well as undergrowth vegetations. Further research is needed to understand the detailed mechanisms responsible for the observed differences.