title: A Life-strategy Classification of Grassland Soil Prokaryotes and Its Applications in Interpreting Alpine Meadow Responses to Environmental Changes
Creators: name: Che, Rongxiao
Publisher: name: Griffith University
Year: 2018
Subjects: subject: Grassland soil
subject: Prokaryotes
subject: Alpine meadow
subject: Environmental changes

description: The extensive applications of high-throughput sequencing have remarkably improved our abilities to analyze soil microbial community profiles. However, due to the paucity of knowledge on characterizing most of the microbial lineages, the predominant challenge in investigating soil microbes has shifted from community composition descriptions to the interpretations for their ecological implications. Currently, assessing the relative abundances of microbial lineages with different life strategies (i.e., copiotrophs and oligotrophs, analogous to r- and K- specialists, respectively) is the most widely used approach to explore the ecological implications of microbial community profiles. Moreover, the relative abundance of copiotrophs and oligotrophs is usually closely correlated with soil microbial respiration rates. Collectively, identifying the life- strategies of soil microbial lineages is not only essential to interpreting the ecological implications of microbial community profiles, but also crucial to understanding the links between microbial communities and their ecological functions. Nonetheless, with almost all of the life-strategy classification efforts being made at the phylum level, the life strategies of microbial lineages at finer taxonomy levels remain largely unknown. Although the majority (&gt; 90%) of soil microbes are dormant and contribute little to the ecosystem functioning, the life-strategy classifications are seldom conducted targeting the active microbial populations. Furthermore, grasslands cover around one-third of the global terrestrial surface, providing essential services for maintaining our planetary health. However, the life-strategies of grassland soil microbial lineages were far less identified than those of forests and farmlands. Therefore, my thesis aimed to determine the life strategies of total and active prokaryotic lineages in grassland soils, and then tried to apply them to interpret the responses of alpine meadow soil prokaryotes to environmental changes. Briefly, in Chapter 2, I assessed the possibilities of using the methods based on 16S rRNA to identify the prokaryotic life strategies. Subsequently, in Chapter 3, I classified grassland soil prokaryotic lineages (from kingdom to genus) into copiotroph-oligotroph categories, using methods based on 16S rDNA and rRNA. Finally, in Chapters 3 and 4, I tried to interpret the responses of prokaryotic communities to litter amendments, phosphorus fertilization, livestock grazing, and experimental warming based on the proportional changes of copiotrophic and oligotrophic microbial lineages. In Chapter 2, soil samples collected from a Tibetan alpine meadow were amended with different amounts of glutamate. The 16S rDNA and rRNA copies, as well as community structures based on 16S rDNA and rRNA were analyzed using real-time PCR and terminal-restriction fragment length polymorphism, respectively. Except for 16S rRNA copies and rRNA-rDNA ratios, all of the indices based on rDNA and rRNA were significantly correlated with the soil microbial respiration rates. However, the 16S rRNA-based bacterial community structure could explain 72.7% of the soil microbial respiration variations, which far outperformed the other indices. These findings indicate that the 16S rRNA-based community structure is a sensitive indicator for soil microbial respiration activity, and also highlight its potential for identifying microbial life strategies (i.e., copiotrophs and oligotrophs). This study provides the basis for the 16S rRNA-based life strategy classifications of prokaryotic lineages in Chapter 3. In Chapter 3...