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Mapping Microbial Biomass Over Changing Land-use in Relation to Environmental Perturbance in the Karst Region of Southwest China Using Lipid Membrane Biomarkers

Bristol student theses: Master's ThesisMaster of Science (MSc)

Authors

  • Simon James Hawkes

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Abstract

A comparison of soil bacteria, fungi, and archaea were estimated across changing land-use within the karst region of southwest China, a newly instated critical zone observatory. The site was divided, and samples taken to represent 3 different and comparable stages; agricultural, abandoned agricultural, and secondary forest, used to represent degraded, recovering, and recovered land respectively. Using lipid membrane analysis, namely phospholipid fatty acids and glycerol diether glycerol tetraether a quantitative analysis and comparison across the changing land-use was enabled; also analysed were the soil physical and chemical properties including soil organic carbon, soil bulk density, pH, dissolved organic/inorganic carbon, ammonium-N, nitrate-N, total nitrogen, total/available phosphorus and water content.
The bacterial groups Gram positive, Gram negative, Actinobacteria, alongside the bacterial stress indexes were identified using specific PLFAs, alongside a general fungal, and an arbuscular mycorrhizal fungi biomarker. The archaeal groups were less specific, with identification of GDGTs 0-3 as general lipids for archaea, and the crenarchaeal lipid specific to the Thaumarchaeota phylum. Identification of relatively novel compounds in the form of glycerol dialkanol diethers was also undertaken, with analysis identifying it as a potential biosynthetic compound, or potentially a standalone membrane lipid.
A statistically significant difference in concentrations across land-use was observed for bacteria, fungi and archaea, with lowest overall concentrations of bacteria and fungi PLFAs located within the agricultural sites, with the highest bacteria concentrations located in the abandoned and secondary forest. Archaeal concentrations showed the opposite trend with highest concentrations located within the agricultural sites and lowest in the secondary forest. Correlations with soil chemical and physical properties varied between groups, with pH influencing the distribution of bacteria, potentially inhibiting growth. It is also evident that plant succession across the recovering sites may play a large role in determining the distribution and abundance of soil microbial communities.

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Original languageEnglish
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Award date23 Jan 2019

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