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Like many peat wetlands around the world, Temperate Highland Peat Swamps on Sandstone (THPSS), located in the Sydney Basin, Australia, have been impacted by urban development. In this paper, we used Illumina 16S rRNA DNA amplicon sequencing to characterise and compare the bacterial communities of surface (top 0–2 cm) and deep (50 cm) sediments in peat swamps that occur in both urbanised and non-urbanised catchments. Proteobacteria (32.2% of reads), Acidobacteria (23.6%) and Chloroflexi (10.7%) were the most common phyla of the dataset. There were significant differences in the bacterial community structure between catchment types and depths apparent at the phyla level. Proteobacteria, Bacteroidetes, Actinobacteria and Verrucomicrobia made up a greater proportion of the reads in the surface sediments than the deeper sediments, while Chloroflexi and Nitrospirae were relatively more common in the deeper than the surface sediment. By catchment type, Acidobacteria were more common in swamps occurring in non-urbanised catchments, while Nitrospirae, Bacteroidetes and Actinobacteria were more common in those in urbanised catchments. Microbial community structure was significantly correlated with sediment pH, as was the relative abundance of several phyla, including Acidobacteria (negative correlation) and Bacteroidetes (positive correlation). As an indicator of trophic shift from oligotrophic to copiotrophic conditions associated with urbanised catchment, we found significant differences ratios of β-Proteobacteria to Acidobacteria and Bacteriodetes to Acidobacteria between the catchment types. Based on SIMPER results we suggest the relative abundance of Nitrosomonadaceae family as a potential indicator of urban degradation. As the first study to analyse the bacterial community structure of THPSS using sequencing of 16S rDNA, we reveal the utility of such analyses and show that urbanisation in the Blue Mountains is impacting the microbial ecology of these important peatland ecosystems. [ABSTRACT FROM AUTHOR]

The devastating bushfires of the 2019-20 summer are arguably the most costly natural disaster in Australian recorded history.What is little known is that these fires severely affected the temperate highland peat swamps on sandstone (THPSS), a form of upland wetland that occurs in the water supply catchments of Sydney in the Greater Blue Mountains WorldHeritageArea and National Park.During the fires, 59%of THPSS was burnt and 72% of those by a high severity burn. Uplandswamps atNewneswere themost affected, with 96%of swamps burnt and 84%of these experiencing a very high burn severity.We present an analysis of the spatial extent and severity of the bushfire on the THPSS and discuss some of the likely consequences on their geomorphological, hydrological and ecological structure, function and recovery potential. [ABSTRACT FROM AUTHOR]

Fire in wetlands is poorly understood, yet hazard reduction burns are a common management practice and bushfires are becoming increasingly prevalent because of climate change. Fire may have long-lasting implications for the microbial component of these wetland ecosystems that regulate carbon and nutrient cycling. The extremely fire-prone Blue Mountains World Heritage Area in south-eastern Australia contains hundreds of endangered peat-forming upland swamps that regularly experience both bushfires and hazard reduction burns. In a before–after control–-impact study, we surveyed the sediment microbial community of these swamps to test the impact of a low-intensity hazard reduction burn. Along with sediment pH, moisture and organic content, we measured gene abundances including those relating to carbon cycling (quantitative PCR (qPCR) of pmoA , mcrA , bacterial 16S rRNA and archaeal 16S rRNA), and bacteria community fingerprint (terminal restriction fragment length polymorphism (T-RFLP)). One year after the hazard reduction burn, there were no significant differences in the gene abundances or microbial community fingerprint that could be attributed to the fire, suggesting that the hazard reduction burn did not have a long-term impact on these microbial communities. A hazard reduction burn in an endangered upland peat-forming swamp in eastern Australia did not cause ongoing changes to sediment microbial community or sediment properties 1 year after the fire. [ABSTRACT FROM AUTHOR]

Temperate Highland Peat Swamps on Sandstone (THPSS) are located at the headwaters of streams on low relief plateaus of Eastern Australia. Swamp sediment structure has a direct link to the high water tables, element cycling and carbon sequestration that are the characteristic functions of these systems. By comparing the sediment structure of intact swamps and channelised fills, we can gain an understanding of how changes in swamp geomorphology change both swamp structure and function. We examined the sedimentology of six intact and six channelised fill swamps in the Blue Mountains NSW, Australia. There were significant differences in texture, unit thickness, Carbon: Nitrogen (C:N) ratios and moisture content between intact swamps and channelised fills. The presence and thickness of unmodified contemporary sand layers in almost all channelised fills and its absence in almost all intact swamps was a distinctive structural difference. The two functional swamp layers, in terms of water and carbon storage were almost double the mean thickness in intact swamps than in channelised fills. Moisture content was 30% higher in intact swamps than in channelised fills. Mean C: N ratios for channelised fills were 25% lower than that of intact swamps. Peat forming potential, as defined by C:N ratios > 27, started at a greater depth in the sediment profile (0.9 m lower) in channelised fills than in intact swamps. It is clear from this study that these structural and functional indicators are important for assessing swamp condition and can also be useful in designing monitoring programs for management and rehabilitation that target key structural attributes that produce and maintain swamp function. [ABSTRACT FROM AUTHOR]

Temperate Highland Peat Swamps on Sandstone (THPSS) are a form of topogenous mire found on the plateau areas of eastern Australia. They are well recognised for their ecological value, but our understanding of their geomorphic structure, function and evolution remains limited. Across 19 sites, the valley fills of THPSS comprise sequences of mineral-rich sand and loam deposits. Basal sand and gravel sediments have low organic content and low carbon to nitrogen (C:N) ratios (a measure of peat formation) and are dated between 15.3 and 9 kyr cal. BP, with outliers back to 44 kyr cal. BP. These units reflect mineral-sediment trapping and accumulation on the valley floor. The transition to ‘swamp’ conditions through paludification occurred between 15.2 and 10.3 kyr cal. BP in some systems, and between 7.6 and 1.4 kyr cal. BP in other, adjacent valleys. These ‘swamp’ sediments comprise a package of units, progressing upward from fine cohesive sands, through assemblages of alternating organic sands to surface organic fines. These beds vary in texture from loams to sands and have a range of organic matter content (from 7.6% to 79.9%) and C:N ratios (from 15 to 58). The surface organic fines at 0 and 100 cm depth range in age from 13.1 to 0.7 kyr cal. BP. The composition and age structure of the valley fill suggest a mix of allogenic and autogenic controls are responsible for the formation of these swamps, but a regional model of THPSS evolution is emerging. Given these ‘peatlands’ have formed under a climate that experiences significant inter-annual variability in rainfall, conditions for peat formation are localised and not directly equivalent to those documented internationally. [ABSTRACT FROM PUBLISHER]