Changes in biomass burning mark the onset of an ENSO-influenced climate regime at 42°S in southwest Tasmania, Australia

Fletcher, Michael Shawn; Benson, Alexa; Heijnis, Hendrik; Gadd, Patricia; Cwynar, Les C.; Rees, Andrew

doi:10.1016/j.quascirev.2015.05.002

Cited by 30 publications

(30 citation statements)

References 61 publications

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“…7.0 kcal bp during the mid‐Holocene thermal maximum (Rees et al ., ). Palaeoclimate reconstructions in Australia also suggest that enhanced ENSO activity in the mid‐Holocene resulted in oscillations between wet–dry and warm–cool intervals (Fletcher et al ., ). Speleothem records from Lynd's Cave Tasmania (Xia et al ., , ) and Holocene lake‐level fluctuations in Lakes Keilambete and Gnotuk, southern Australia (Wilkins et al ., ) concur with records of precipitation and effective moisture data from pollen, indicating the highest lake levels occurred c .…”

Section: Discussionmentioning

confidence: 97%

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Aboriginal impacts on fire and vegetation on a Tasmanian island

McWethy

Haberle

Hopf

et al. 2016

Journal of Biogeography

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Aim To evaluate the influence of climate and Aboriginal landscape management on Holocene vegetation and fire activity. Location Flinders Island, Bass Strait, Tasmania where archaeological data document extended periods of human presence and absence over the past 12,000 years. Methods We evaluated climate–human–fire interactions through high‐resolution pollen, charcoal and geochemical analyses of sediment cores from two wetland sites. Proxies for environmental change are qualitatively compared with archaeological data documenting Aboriginal occupation and later abandonment during the mid‐Holocene. Results Warm and dry conditions of the early Holocene combined with anthropogenic ignitions promoted frequent fires that sustained highly fire‐tolerant Eucalyptus savanna. During the mid‐Holocene, when both temperatures and precipitation reached Holocene maxima, archaeological data suggest Aboriginal populations abandoned Flinders Island. At this time, Eucalyptus savanna was replaced by Casuarinaceae and broadleaf forests and fire activity decreased. The late Holocene was marked by a transition to increased incidence of intense fires that was associated with a shift from Casuarinaceae forests to xerophytic scrub dominated by Callitris rhomboidea, a conifer that is sensitive to frequent fires but regenerates well following infrequent fires. Main conclusions Palaeoenvironmental analyses from Flinders Island document significant shifts in fire regimes and vegetation types through the Holocene. In the early Holocene, Aboriginal landscape management played a key role in maintaining open Eucalyptus savanna, a prime habitat for marsupial prey species. Increasing aridity and strengthening of the El Niño Southern Oscillation climate mode during the mid to late Holocene contributed to the cessation of permanent human occupation and concomitant reduction of ignitions. Infrequent fire activity led to the dominance of xerophytes, especially Callitris, a genus adapted to drought and infrequent high‐severity fires. This study highlights how climate change affects the persistence of human populations on islands and the capacity of human‐set fires to create savanna habitats.

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Section: Discussionmentioning

confidence: 97%

“…Fletcher et al . () suggest SWW were particularly important in regulating hydroclimatic conditions in Tasmania during the early Holocene when they were weak and the mid‐Holocene when they were strong. Contrastingly, ENSO became the dominant control on subregional hydroclimatic controls in the late Holocene.…”

Section: Discussionmentioning

confidence: 99%

Aboriginal impacts on fire and vegetation on a Tasmanian island

McWethy

Haberle

Hopf

et al. 2016

Journal of Biogeography

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“…5.5 ka (Fletcher & Moreno, ; Mariani & Fletcher, ) drove an increase in regional biomass burning and a replacement of areas of rainforest by fire‐promoting sclerophyll plant taxa, such as the fire‐adapted Eucalyptus (Beck et al, ; Beck, Fletcher, Kattel, et al, ; Fletcher et al, ; Mariani et al, ; Stahle et al, , ). Subsequently, during the late Holocene, a decrease in moisture availability and a synchronous phase of increased fire activity across western Tasmania (Fletcher et al, ; Mariani & Fletcher, ) resulted in a rainforest decline around Dove Lake (Mariani et al, ). These hydroclimatic changes are likely the long‐term (millennial scale) effect of increasingly frequent El Niño events in the tropical Pacific (Donders et al, ; McGlone et al, ; Moy et al, ), which would have resulted in overall cooler than normal waters over the western tropical Pacific and high pressure systems driving negative moisture anomalies in eastern Australia.…”

Section: Introductionmentioning

confidence: 99%

Biogeochemical Responses to Holocene Catchment‐Lake Dynamics in the Tasmanian World Heritage Area, Australia

et al. 2018

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Environmental changes such as climate, land use, and fire activity affect terrestrial and aquatic ecosystems at multiple scales of space and time. Due to the nature of the interactions between terrestrial and aquatic dynamics, an integrated study using multiple proxies is critical for a better understanding of climate‐ and fire‐driven impacts on environmental change. Here we present a synthesis of biological and geochemical data (pollen, spores, diatoms, micro X‐ray fluorescence scanning, CN content, and stable isotopes) from Dove Lake, Tasmania, allowing us to disentangle long‐term terrestrial‐aquatic dynamics through the last 12 kyear. We found that aquatic dynamics at Dove Lake are tightly linked to vegetation shifts dictated by regional hydroclimatic variability in western Tasmania. A major shift in the diatom composition was detected at ca. 6 ka, and it was likely mediated by changes in regional terrestrial vegetation, charcoal, and iron accumulation. High rainforest abundance prior ca. 6 ka is linked to increased terrestrially derived organic matter delivery into the lake, higher dystrophy, anoxic bottom conditions, and lower light penetration depths. The shift to a landscape with a higher proportion of sclerophyll species following the intensification of El Niño‐Southern Oscillation since ca. 6 ka corresponds to a decline in terrestrial organic matter input into Dove Lake, lower dystrophy levels, higher oxygen availability, and higher light availability for algae and littoral macrophytes. This record provides new insights on terrestrial‐aquatic dynamics that could contribute to the conservation management plans in the Tasmanian World Heritage Area and in temperate high‐altitude dystrophic systems elsewhere.

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“…Fogt and Bromwich (2006) have identified that SAM is modulated by interactions with ENSO, amplifying alterations in precipitation linked to complimentary trends in each phenomenon, with this variability observed in dramatic differences in the discharge rates of the Little Swanport River (DPIW, 2006). Over the Holocene period, Fletcher et al (2015) have demonstrated the influence of an increase in ENSO frequency and amplitude at a sub-millennial scale over the last 5000 years on fire activity (increased biomass burning) in South West Tasmania, which is also observed more broadly across the mid-to high-latitudes of the South Pacific region (McGlone et al, 1992;Shulmeister, 1999;Fletcher and Moreno, 2012).…”

Section: Study Sitementioning

confidence: 99%

“…In a general sense these impacts are well understood for the Australian environment, with significant land clearance for agriculture, forestry and mining; rapid introduction of exotic species; extinction of native taxa; and the imposition of new fire regimes (Adamson and Fox, 1982;Hobbs and Hopkins, 1990;Benson, 1991;Kirkpatrick, 1999;Bickford and Gell, 2005;Moss et al, 2007;Bickford et al, 2008;Romanin et al, 2016). However, at the regional scale, there are relatively few attempts to examine European impacts using palaeoecological proxies, due to the relatively low-resolution of existing Holocene reconstructions (Kershaw et al, 1994) that often attempt to provide insight into Holocene environments and/or focus on Aboriginal human-environment relationships (e.g., Colhoun and Shimeld, 2012;Ulm, 2013;Fletcher et al, 2014Fletcher et al, , 2015Rees et al, 2015;Mackenzie and Moss, in press for recent publications from Tasmania). Those records that do exist suggest that there is a great deal of regional variation in the timing and nature of ecosystem response to European settlement, with some alterations linked to obvious European impacts, such as land clearance (e.g., Moss et al, 2007), while other ecological alterations are linked to much more subtle changes in land management, particularly the imposition of new fire regimes (e.g., Fletcher et al, 2014).…”

Section: Introductionmentioning

confidence: 99%