Browsing by Author "Zwart, C"

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    Holocene climate–fire–vegetation feedbacks in tropical savannas: insights from the Marura sinkhole, East Arnhem Land, northern Australia
    (Wiley, 2022-11) Rowe, C; Rehn, E; Brand, M; Hutley, LB; Comley, R; Levchenko, VA; Zwart, C; Wurster, CM; Bird, MI
    Aims Informed management of savanna systems depends on understanding determinates of composition, structure and function, particularly in relation to woody‐plant components. This understanding needs to be regionally based, both past and present. In this study, Holocene plant patterns are explored at a site within the eucalypt savannas of northern Australia. Australian savannas are the least developed globally and uniquely placed to track ecological change. Location Northern Territory, Australia. Methods Palynological analyses were undertaken on a 5‐m sediment core, spanning the last 10,700 calendar years. Pollen was categorised to capture vegetation type, classified further according to plant function and/or environmental response. Detrended Correspondence Analysis was used to quantify ecological dissimilarities through time. Results At the Pleistocene transition, grasses were abundant then declined and remained low relative to increased woody cover from the mid‐late Holocene. Savanna composition gradually transitioned from Corymbia to Eucalyptus dominance until significantly disturbed by a phase of repeated, extreme climate events. Highest non‐savanna variability in terrestrial and wetland plant types formed mixed vegetation communities through the mid‐Holocene. Conclusions Savannas are not homogeneous but the product of plant changes in multiple dimensions. In the Northern Territory, dynamic though restricted non‐eucalypt shifts are embedded within larger, slower eucalypt change processes. Primary climate–vegetation relationships determine the long‐term fire regime. The role of large but infrequent disturbance events in maintaining savanna diversity are significant, in degrees of impact on tree–grass turnover, its form and the extent of vegetation recovery. People's landscape interactions were found to be interwoven within this feedback hierarchy. © 1999-2024 John Wiley & Sons, Inc or related companies. All rights reserved.
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    Indigenous impacts on north Australian savanna fire regimes over the Holocene
    (Springer Nature, 2021-12-01) Wurster, CM; Rowe, C; Zwart, C; Sachse, D; Levchenko, VA; Bird, MI
    Fire is an essential component of tropical savannas, driving key ecological feedbacks and functions. Indigenous manipulation of fire has been practiced for tens of millennia in Australian savannas, and there is a renewed interest in understanding the effects of anthropogenic burning on savanna systems. However, separating the impacts of natural and human fire regimes on millennial timescales remains difficult. Here we show using palynological and isotope geochemical proxy records from a rare permanent water body in Northern Australia that vegetation, climate, and fire dynamics were intimately linked over the early to mid-Holocene. As the El Niño/Southern Oscillation (ENSO) intensified during the late Holocene, a decoupling occurred between fire intensity and frequency, landscape vegetation, and the source of vegetation burnt. We infer from this decoupling, that indigenous fire management began or intensified at around 3 cal kyr BP, possibly as a response to ENSO related climate variability. Indigenous fire management reduced fire intensity and targeted understory tropical grasses, enabling woody thickening to continue in a drying climate. © 2024 Springer Nature Limited. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.