Monday, 10 July 2006

Microbial Dversity of the Soil and Leaf Litters in an Exotic Pine Plantation of Subtropical Australia.

Li Zhang1, Bharat Patel1, and Zhihong Xu2. (1) School of Biomolecular and Biomedical Sciences, Griffith Univ, 170 Kessels Road, Brisbane, Australia, (2) School of Environmental Studies, Griffith Univ, 170 Kessels Road, Brisbane, Australia

Slash pine is a species of choice for reforestation in infertile sandy soil in southeast Queensland, Australia. These exotic pine plantations have gained recognition as a complex environmental system and they are of great value for studying soil microbial community diversity. Examination of microbial diversity is not only important for basic scientific research, but also necessary for improving the understanding of the relationship between diversity and community structure and function. Although extensive works have been done on soil chemistry and microbiology, the phylogenetic relationship between soil and leaf litters remain elusive represented. This study presented one of few attempts to discover the phylogenetic structures of the different fractions of soil and leaf litters in the exotic pine plantation. To assess the phylogenetic community of an exotic pine plantation in subtropical Australia, the molecular based approaches were performed. Three sub-samples at different depth (designated E1= L layer leaf litter, E2= F layer leaf litter and E3= soil 0-10 cm) were selected and total genomic DNA was extracted. The highly purified DNA was successfully amplified by bacteria universal primer Fd1 and R6, producing products of 1500 bp. PCR-amplified 16S rDNA genes were subsequently cloned and a total of 194 clones from leaf litters and soil were sequenced. 194 partial 16S rDNA sequences were obtained and the sequences from each of the sample having a similarity > 98 % were regarded as phylogenetic identical and grouped as a phylogroup. A representative from each group was selected and completely sequenced. Five bacterial divisions were identified from the forest soil clone library by the sequences. The distribution of clones among different bacteria divisions was uneven. Three divisions - the Acidobacterium, the Proteobacteria and the Verrucomicrobiales, accounted for 81% of the clones examined. The Acidobacterium division was the most abundant phylogenetic group in terms of the number of clones. Members of this division accounted for 42 % of the 194 clones. The Verrucomicrobiales and the Proteobacteria were the second and third most abundant divisions found in the clone libraries, accounting for 11 % and 12 % of the clones, respectively. About 27 % of the clones were phylogenetically unidentified. When individual leaf litter samples were compared, Firmicutes was the only division presented in the L layer leaf litter clone library. Similarly, Firmicutes dominated the F layer leaf litter (79 % of the library), which was followed by Proteobacteria (21 %). The most significant results were the observation that, the bacteria diversity present in the leaf litters was greatly different from the community of the soil. The information provided by assessing the different depths of leaf litters and forest soil improved our understanding of the phylogenetic relationship between soil and above-leaf litters. It is suggested, in this study, to perform molecular based methods to characterize the bacteria structure and diversity in forest litters and soil samples, particularly in response to different forest management practices and global change. This study also provides the basis for the further functional studies of the forest soil and leaf litters of exotic pine plantation in subtropical Australia.

Back to SCE Evaluating Management Impacts on Forest Soils - Theater
Back to WCSS

Back to The 18th World Congress of Soil Science (July 9-15, 2006)