The Hydrology and Biogeochemistry of Australian and African Peatlands

Peatlands cover only 3% of the world’s land area while storing ~30% of the global soil carbon (C) stock. This C stored in peatlands is threatened by climate change and other anthropogenic disturbances such as drainage, land use change, and grazing and trampling by feral animals. Despite the importance of these ecosystems, there remain key knowledge gaps on the biogeochemical and hydrological controls of peatland functioning. The objective of this interdisciplinary study was to contribute new scientific knowledge on peatland functioning by exploring the complex interactions between peat biogeochemistry and hydrology, as well as identifying innovative peatland condition monitoring and assessment techniques. To examine the link between peat hydrology and biogeochemistry, the movement of the water table depth (WTD) of an Australian Alpine Sphagnum peatland was monitored over four years. WTD was used to identify the boundaries of the peatland ecohydrologic layers: the acrotelm, mesotelm and catotelm. Additionally, the C chemistry, protein content and amino acid composition of peats within each of these ecohydrologic layers were quantified. The results from this study revealed a strong positive correlation between the extent of peat decomposition and protein content, suggesting selective preservation of proteinaceous materials during peat decomposition. Each ecohydrologic layer displayed a distinct amino acid composition and C functional group composition, suggesting differences in microbial activity and decomposition dynamics between these three layers. Building upon these findings, the links between WTD, C chemistry, and the microbial community composition of degraded and intact Australian Alpine Sphagnum peats were then further examined. To do so, the WTD data was compared with peat samples analysed using High-Throughput Sequencing (HTS) and solid-state 13C Cross Polarisation Magic Angle Spinning Nuclear Magnetic Resonance (13C CP/MAS NMR) spectroscopy from three peat areas (two intact and one degraded). The results of this study demonstrated that the microbial communities of the three peat areas differed significantly, and that WTD, peat chemistry, and depth in the peat profile all influenced microbial community structure. Significant interactions between the microbial communities of these three peat areas and the WTD, as well as with depth in the profile, were observed. While C content and C:N ratios explained most of the variability in fungal and prokaryotic community structure of the two intact peat areas, the C functional groups explained the variations in these microbial communities in degraded peat areas. These findings imply that disturbance-induced changes to WTD, microbial communities, and/or C chemical composition of peats may affect the ecosystem function and C storage dynamics of these C-rich ecosystems. The utility of near infrared (NIR) spectroscopy as an innovative technique for monitoring peatland condition was explored by assessing spectra from the intact and degraded Australian Alpine Sphagnum peat areas. The results of this study showed that in situ scanning of fresh peat at the peatland surface was the most effective strategy for using the microNIR spectrometer to measure peatland condition. This study demonstrated the efficacy of the microNIR spectrometer for rapid and cost-effective peatland assessment, which could enable early detection of changes in condition to inform management actions to prevent and/or mitigate further peatland degradation. The further development and application of this technology may foster the preservation of peatlands and the invaluable ecosystem services they provide over broader geographic scales than explored here, including regions where peatland research is currently critically lacking. Finally, a systematic quantitative literature review and analysis of primary scientific peer-reviewed journal publications on the ‘ecosystem’ (i.e. socio-academic context) of African peatland research revealed a number of research gaps and imbalances in the human dimensions of this field. This systematic quantitative literature review found only 32 primary, peer-reviewed journal articles published between 1992 and 2021 on African peatlands. Although peatlands play a major role in the global C cycle, only nine studies measured the C content of peat, and there were no primary scientific peer-reviewed journal articles reporting peat GHG emissions. This study also revealed the underrepresentation of African peatlands in scholarly research, coupled with a skewed demographic overrepresentation of male and non-African authors. This study highlights the urgent need for increased attention to African peatlands, both in biophysical research and in conservation efforts. Overall, this thesis advances our understanding of peatlands in Australia and Africa, by providing valuable insights into the key drivers of C storage and peat degradation, as well as identifying a novel technique for effective peatland monitoring. The management implications of this research for Australian Alpine Sphagnum peatlands are discussed. The findings of this thesis contribute new knowledge for policy makers, researchers, and land managers working to preserve these critical C-rich ecosystems for climate change mitigation and environmental conservation.