| Microbes play important roles in litter decomposition, nutrient cycling, and the accumulation of carbon of forest ecosystem. It is a fact that the global climate change(especially frequent extreme climate events) impacts on forest ecosystem. It was focusing on microbial dynamics and its function in the context of global climate change. In 2008, Southern China suffered serious rain and snow disaster, resulting in large area of forest damaged in Nanling region. Whether did microbial community structure chang after ice storm disaster? How about the microbial dynamics? In order to understand litter layer and soil fungal community diversity and their functions, the internal transcribed spacer(ITS) of the fungi in Yangdongshan Shierdushui Nature Reserve were amplified, cloned, sequenced and phylogenetic analyzed. It was also discussed the interaction and relationship between forest vegetation and microbes in the whole ecosystem. The main results are as follows:1. Russula vesca Fr. is the dominant population of soil fungi in sample No. 5. The 95 clones were divided into 25 operational taxonomic units(OTUs). The largest number of the OTU is Russula vesca Fr. with high sequence similarity(99%), which were detected 33 from 95 clones accounting for 34.7% of the total clones. In addition, some wood rotting fungi and mycorrhizal fungi in forest ecological system plays an extremely important role in degradation, decomposition of carbohydrate, lignin and cellulose, strengthening the soil ventilation and water retention ability, which is benificial to the nutrient circulation of the forest ecosystem.2. 1442 clones of the litter layer fungal samples were divided into 213 OTUs,were defined based on sequence similarity Searches(Fasta)and phylogenetic analyses.Among them,118 OTUs belong to Ascomycota(55.4%) and 61 OTUs(28.6%)to Basidiomycota.3. The temporal dynamic changes and community structure of litter layer fungi. From 2008 to 2011, the change of fungal species diversity showed in the shape of N curve. The species diversity of fungi significantly increased in 2009, sharply reduced in 2010 and rebounded in 2011. The species diversity in sample No. 3 is always the highest among the all samples in each year. Species diversity of fungi and community structure change with the composition and quantity of litter.4. After the rain and snow disaster, saprophytic fungi accounted for the ratio of fungi in the humus layer increased significantly in 2009-2010, and recovered in 2011, however, pathogenic fungi showed the opposite pattern, which decreased obviously in 2009-2010 and rise in 2011. Mycena sp. and Subramaniomyces sp. were the main populations in litter layer fungi. The trend of change were similar to those of saprophytic fungi and pathogenic fungi respectively. It indicated that Mycena sp. play an important role in degradation of litter.5. Improvement of the experimental methods. A pre-experiment indicated that the soil has high humic acid content. If DNA extracted with high humic acid content, it will affect the subsequent PCR amplification. We compared three different extraction methods. It shows that the DNA obtained by DNA extraction kit was in high purity, but the cost is relatively high. For its easy operating and high efficiency, it is suitable for less samples mircrobial diversity research. Comparison with the DNA extraction kit, the directly extraction of CTAB was cheaper and has larger molecular weigh. Therefore, an appropriate DNA extraction method should be selected according to different soil types and sample quantity. In order to eliminating negative effects of humic acid, the different concentration of BSA(bovine serum albumin) contents were experimented in the PCR amplification. It showed that suitable amount of BSA help to reduce the negative effect of humic acid in PCR amplification. |
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