Abstract
The soil microbiome provides large amounts of taxonomic and functional diversity to ecosystems and is considered one of the most diverse natural environments on earth. The functions associated with the soil microbiome are closely linked to the taxa that make up the microbial community. Understanding how environmental factors influence the structure of soil microbial communities through space and time can provide key information for biogeochemical processes such as nutrient cycling and also provide insights into how the soil microbiome might respond to changes in climate. To understand how a soil microbial community will respond to changes in its environment, it is necessary to first understand the structure and composition of a baseline soil microbial community. This work assessed the baseline soil microbial communities of subantarctic Campbell Island and two tussock grassland sites in alpine Takahē Valley, one site dominated by Chionochloa rubra and the other dominated by Chionochloa teretifolia. These locations are isolated sites, Campbell Island in terms of geographic location and Takahē Valley in terms of minimal disturbance of a grassland site. This will provide useful baseline data for both bacterial and fungal soil communities. Environmental conditions including temperature and nutrient levels in Takahē Valley were also manipulated to simulate the effects of climate change to provide insights into how the soil bacterial and fungal communities in Takahē Valley would respond to changes in abiotic conditions. High-throughput sequencing of the 16S rRNA and ITS2 genes identified significant differences in the bacterial and fungal communities associated with different vegetation types of Campbell Island and also significant differences in the bacterial and fungal communities associated with the two Chionochloa species in Takahē Valley. Furthermore, differences were also seen in the bacterial and fungal communities exposed to increased temperatures and nutrient levels. Statistically significant findings include a higher observed diversity in the bacterial community of C. rubra samples exposed to higher temperatures and an increase of several bacterial and fungal Orders when exposed to higher levels of sugar at either Takahē Valley site. The findings in this thesis contribute to our understanding of the structure of soil microbial communities and the factors that influence them. Additionally, characterising the structure and composition of microbial communities subjected to changes in climatic conditions provides a useful starting point for investigating the functional potential of soil microbial communities through time and space.