Wildfire legacies on pyrogenic carbon stocks in Amazonian peatlands

Amazonian peatlands are carbon-rich ecosystems that act as long-term carbon sinks but have faced increasing fire risks in recent decades. As a legacy of past fires, the contribution of pyrogenic carbon (PyC) to carbon cycling in these peatlands remains poorly understood. Here, we assess PyC accumulation variability using six cores spanning peatlands in northwestern Amazonia using hydrogen pyrolysis. We also estimate the PyC stock for the entire Amazonian peatlands by combining our field dataset with published sources. The PyC to total organic carbon ratio averaged 1.2% across our sites and increased with peat age. We estimate a total peatland PyC stock of 0.73 ± 0.61 Pg for the Amazon Basin, representing 1.6% of their TOC stock. Due to the slower turnover of PyC in peatland ecosystems, our findings indicate the importance of PyC generated by past fires and highlight the potential long-term carbon sequestration role of PyC in the future carbon cycle.</p

Monsoon driven ecosystem and landscape change in the 'Top End' of Australia during the past 35 kyr

The Indo-Australian Summer Monsoon (IASM) is the dominant climate feature of northern Australia, affecting rainfall/runoff patterns over a large portion of the continent and exerting a major control on the ecosystems of Australia's Top End, including the viability of wetland ecosystems and the structure of the woody savanna. We examined the behaviour the IASM from 35 kyr using proxy data preserved in the sediments of Table Top Swamp, a small seasonal swamp in northern Australia. Elemental data, stable C and N isotopes, pollen and sedimentary data were combined to develop a picture of monsoon activity and landscape and ecosystem response. Results demonstrated that between 35 and 25 ka conditions were drier and more stable than present, with a more grass dominated savanna and limited wetland development, implying reduced IASM activity. After ~25 ka, there is evidence of increased moisture at the study site, but also increased IASM variability. However, despite evidence of at least periodic increases in moisture, including periods of wetland establishment, the IASM displayed a subdued response to peak precession insolation forcing by comparison to the other global monsoon systems. Instead, the greatest change occurred from ~10 ka when the continental shelf flooded, increasing moisture advection to the study site and resulting in establishment of a quasi-permeant wetland. Whereas the early Holocene was marked by both the onset of pollen preservation and a wetter vegetation mosaic, indicative of a consistently active IASM, the mid-late Holocene was marked by drier vegetation, increased fire, but also increased C3 vegetation and runoff, implying increased IASM variability. Holocene changes in ecosystem dynamics occur coincident with an expansion in human population, which likely also influenced vegetation and landscape response at the study site

A 47,000 year archaeological and palaeoenvironmental record from Juukan 2 rockshelter on the western Hamersley Plateau of the Pilbara region, Western Australia

Archaeological and palaeoenvironmental investigations at Juukan 2 rockshelter have yielded new information on the ancient Aboriginal occupation of the Pilbara uplands in northwest Australia. Using multiple lines of evidence, including lithic, faunal, pollen, ancient DNA, radiocarbon dating, optically stimulated luminescence, and Bayesian chronological modelling, we show that Aboriginal people occupied the western Hamersley Plateau as early as 47,000 years ago (47 ka). Late Pleistocene populations utilised a diverse range of tool technologies, including bone points, grindstones, and flaked stone artefacts. Palaeoclimatic conditions at Juukan 2 rockshelter varied greatly over the past 47 ka, with repeated site visits by people, including during the peak hyper-arid phase of the Last Glacial Maximum (LGM) c. 21 ± 2 ka. Ancient starch analyses of the ground stone artefacts show the processing of Ipomoea (Bush Potato) from around 42 ka to the present day. Pronounced increases in the discard of stone artefacts and bone in the last 3500 years are interpreted to be the result of increased frequency of site use. A braided hair fragment dated to this period has demonstrated genetic links between the earlier rockshelter occupants and contemporary Puutu Kunti Kurrama and Pinikura peoples, who have maintained strong cultural connections to the area

Correction to: Early human occupation of Australia’s eastern seaboard (Scientific Reports, (2024), 14, 1, (2579), 10.1038/s41598-024-52000-y)

Correction to: Scientific Reportshttps://doi.org/10.1038/s41598-024-52000-y, published online 31 January 2024. Thomas Dooley was omitted from the author list in the original version of this Article. The Acknowledgements now reads: “This research has been made possible by the extraordinary dedication of the Quandamooka People to ensuring their cultural heritage is appropriately recognised and protected. The Quandamooka Yoolooburrabee Aboriginal Corporation (QYAC) team who oversaw this research was led by Chairperson Prof. Valerie Cooms, Joint Management Coordinator Darren Burns and Senior Cultural Heritage Coordinator Michael Costelloe. The authors of this paper are both honoured and privileged to assist the Quandamooka People in documenting their remarkable heritage. These results are the culmination of decades of study by three pioneering researchers, Archaeologists Rob Neal, Dr Richard Robins and Geomorphologist Dr Errol Stock. Together, they have laid a foundation for the scientific understanding of what is a complex, dynamic and internationally significant environmental and cultural landscape. Vital financial support for this research was provided by QYAC, the University of Queensland Faculty of Humanities and Social Science, Everick Foundation and the Queensland Parks and Wildlife Service.” The Author contributions now reads: “RR and ES conceived the project. CC, KN and SA wrote the main text with specialist contributions from JK and ZJ. Figures by KN, CC, SA, PM and JK. CC, AF, KN, MC, DB, KM, TM and TS re-excavated WWC. SA, ZF, SL, MC, TS, KM and DB excavated MCA20. AF obtained funding for WWC and KM obtained funding for WWC and MCA20 excavation. TR contributed funding for WWC and MCA20 excavation and analyses. KN collected, prepared and measured the optical dating samples, and ZJ generated the optical ages at WWC. ZJ wrote the optical dating SI with assistance from KN. JK performed the optical dating at MCA20. CC analysed stone artefacts from WWC and MCA20. AF performed flotation and identified charcoal for radiocarbon dating from WWC. TM and TD conducted faunal analysis at WWC and MCA20. TS performed mollusc analysis from WWC and MCA20. KML performed GPR, magnetic gradiometry and magnetic susceptibility at WWC. MM identified heat treatment on silcretes from WWC and MCA20.” The original Article has been corrected

Early human occupation of Australia’s eastern seaboard

Secure archaeological evidence for human occupation on the eastern seaboard of Australia before ~ 25,000 years ago has proven elusive. This has prompted some researchers to argue that the coastal margins remained uninhabited prior to 25 ka. Here we show evidence for human occupation beginning between 30 ± 6 and 49 ± 8 ka at Wallen Wallen Creek (WWC), and at Middle Canalpin Creek (MCA20) between 38 ± 8 and 41 ± 8 ka. Both sites are located on the western side of Minjerribah (North Stradbroke Island), the second largest sand island in the world, isolated by rising sea levels in the early Holocene. The earliest occupation phase at both sites consists of charcoal and heavily retouched stone artefacts made from exotic raw materials. Heat-treatment of imported silcrete artefacts first appeared in sediment dated to ~ 30,000 years ago, making these amongst Australia’s oldest dated heat-treated artefacts. An early human presence on Minjerribah is further suggested by palaeoenvironmental records of anthropogenic burning beginning by 45,000 years ago. These new chronologies from sites on a remnant portion of the continental margin confirm early human occupation along Sahul’s now-drowned eastern continental shelf

OCTOPUS Database v.2.2: Sedimentary Charcoal Records Sahul & NZ

An open database of sedimentary charcoal and black carbon records from Australia, New Guinea, and New Zealand. The data uses the WGS84/Pseudo-Mercator (EPSG: 3857) projected coordinate reference system. Sample metadata is comprehensive and includes bibliographic, contextual, and sample preparation and measurement related information

OCTOPUS Database v.2.2: Sedimentary Charcoal Records Sahul & NZ (units only)

An open database of sedimentary charcoal and black carbon records from Australia, New Guinea, and New Zealand. This collection contains unit-level information only. The data uses the WGS84/Pseudo-Mercator (EPSG: 3857) projected coordinate reference system. Sample metadata is comprehensive and includes bibliographic, contextual, and sample preparation and measurement related information