Browsing by Author "English, NB"
Now showing 1 - 8 of 8
Results Per Page
- ItemAge-growth relationships, temperature sensitivity and palaeoclimate-archive potential of the threatened Altiplano cactus Echinopsis atacamensis(Oxford University Press & the Society for Experimental Biology, 2021-01-27) English, NB; Dettman, DL; Hua, Q; Mendoza, JM; Muir, D; Hultine, KR; Williams, DGThe tall (>4 m), charismatic and threatened columnar cacti, pasacana [Echinopsis atacamensis (Vaupel) Friedrich & G.D. Rowley)], grows on the Bolivian Altiplano and provides environmental and economic value to these extremely cold, arid and high-elevation (~4000 m) ecosystems. Yet very little is known about their growth rates, ages, demography and climate sensitivity. Using radiocarbon in spine dating time series, we quantitatively estimate the growth rate (5.8 and 8.3 cm yr−1) and age of these cacti (up to 430 years). These data and our field measurements yield a survivorship curve that suggests precipitation on the Altiplano is important for this species’ recruitment. Our results also reveal a relationship between night-time temperatures on the Altiplano and the variation in oxygen isotope values in spines (δ18O). The annual δ18O minimums from 58 years of in-series spine tissue from pasacana on the Altiplano provides at least decadal proxy records of temperature (r = 0.58; P < 0.0001), and evidence suggests that there are longer records connecting modern Altiplano temperatures to sea-surface temperatures (SSTs) in the Atlantic Ocean. While the role of Atlantic SSTs on the South American Summer Monsoon (SASM) and precipitation on the Bolivian Altiplano is well described, the impact of SSTs on Altiplano temperatures is disputed. Understanding the modern impact of SSTs on temperature on the Altiplano is important to both understand the impact of future climate change on pasacana cactus and to understand past climate changes on the Altiplano. This is the best quantitative evidence to date of one of the oldest known cactus in the world, although there are likely many older cacti on the Altiplano, or elsewhere, that have not yet been sampled. Together with growth, isotope and age data, this information should lead to better management and conservation outcomes for this threatened species and the Altiplano ecosystem. © The Author(s) 2021
- ItemAnomalous tree-ring identification facilitated by AMS 14C analysis in subtropical and tropical Australian Araucariaceae samples enables development of a long-term, high-resolution climate reconstruction(Australian Nuclear Science and Technology Organisation, 2021-11-17) Haines, HA; Palmer, JG; Hua, Q; English, NB; Hiscock, W; Turney, CSM; Marjo, CE; Gadd, PS; Kemp, J; Olley, JMIn Australia the majority of tropical and subtropical regions lack long-term instrumental climate records. Paleoclimate reconstructions from tree rings provide one alternative but very few dendrochronological investigations have so far been undertaken. Early assessments of mainland Australian tree species were discouraging due to the high prevalence of anomalous ring boundaries. Some species, however, were seen as more favourable than others including those in the Araucariaceae family which is common along the subtropical-tropical Australian east coast. These trees are longer lived than many other species in the region and contain growth rings known to be annual in nature and responsive to climatic conditions. There is however, a heavy prevalence of anomalous ring boundaries in species from this family which must be accounted for when dating these species. Here we describe the tree-ring characteristics and growth response from two stands of Hoop pine (Araucaria cunninghamii) trees located in subtropical and tropical Queensland, Australia (regions known for experiencing extreme hydroclimatic events). Confirmation of annual growth driven by moisture sensitivity was determined using radius dendrometers on four trees in Lamington National Park (c. 28º S). Tree cores were collected from both the Lamington stand as well as a stand at Hidden Valley near Paluma, Queensland (c. 19º S). Ring-width assessment showed the presence of false, faint, locally absent, and wedging rings in both sites. Results of bomb-pulse radiocarbon dating of selected single tree rings demonstrated that trees from this species can fall into one of three categories: A – those with locally-absent rings around the circumference of the trees, B – those where false rings were observed, and C – those with many wedging and locally-absent rings. Only trees in the first two categories were able to be included in the master chronologies. Traditional dendrochronological analysis with age validation by bomb-pulse radiocarbon dating allowed for a robust ring-width chronology from 1805-2014 CE to be developed for the Lamington National Park site. Growth-climate analysis of the master tree-ring chronology determined that the strongest environmental correlation was to wet season drought conditions. The strength of this response was compared to local and regional drought indices as well as to a long-term drought reconstruction. The combined analysis led to the development of a 200-year drought reconstruction for the region which shows influences from both the El Niño Southern Oscillation and the Interdecadal Pacific Oscillation. © The Authors
- ItemThe climate reconstruction potential of Acacia cambagei (gidgee) for semi-arid regions of Australia using stable isotopes and elemental abundances(Elsevier B.V., 2017-01-01) Witt, GB; English, NB; Balanzategui, D; Hua, Q; Gadd, PS; Heijnis, H; Bird, MITo provide multi-centennial, annually-resolved records of climate for arid and semi-arid areas of Australia it is necessary to investigate the potential climate signals in tree species in this large region. Using a stable isotope and x-ray fluorescence approach to dendrochronology in Acacia cambagei, this study demonstrates short (10 years) proxies of temperature and precipitation are possible. Because rings in A. cambagei are difficult to see, precluding traditional dendrochronology, we used elemental abundances of Ca and Sr as an annual chronometer back to 1962. Radiocarbon analysis confirmed that our dating of wood from two trees. We compared δ13C and δ18O from the α-cellulose of the dated wood over the most recent 10 years (n = 10) to local climate records demonstrating significant relationships between δ18O and precipitation (r = −0.85, p < 0.002); mean monthly maximum temperature (r = 0.69, p < 0.03); and drought indexes (CRU scPDSI 0.5°, r = −0.89, p < 0.001) for February and March. Acacia cambagei may be useful in developing regional networks of climate proxies for drought. Using modern trees, in combination with architectural timbers, it may be possible to construct a multi-century, annually-resolved proxy-record of rainfall and temperature for semi-arid north-eastern Australia. © 2016 Elsevier Ltd.
- ItemDeveloping tree-ring chronologies and climate reconstructions from moisture sensitive Araucariaceae trees in tropical and subtropical Australia(Australasian Quaternary Association Inc., 2018-12-10) Haines, HA; English, NB; Hua, Q; Olley, JM; Gadd, PS; Palmer, JG; Kemp, JMany parts of tropical and subtropical Australia lack both annually-resolved long-term instrumental climate data and proxy climate records. This limits our understanding of past climate patterns and impacts. There are however, remnant forest stands where dendroclimatology could be applied to extend the climate record. Tree species in these regions are known to be compromised by numerous ring anomalies and as such are understudied resulting in indistinct tree growth-climate relationships. Recent research of trees in the Araucariaceae family has attempted to address these issues with the goal being to develop long-term climate reconstructions across tropical and subtropical Australia. Araucariaceae trees are commonly found across northern and eastern Australia and are longer lived than many other local non-temperate species. They are known to produce growth rings that are mostly annual and their growth appears sensitive to climate, specifically to moisture conditions. Three Araucariaceae species, hoop pine (Araucaria cunninghamii), bunya pine (Araucaria bidwillii) and purple kauri pine (Agathis atropurpurea) have been studied at five locations within the rainforests of eastern Queensland. Ring anomalies including false, faint, locally absent, and pinching or wedging rings, were identified. This was done by applying bomb-pulse radiocarbon dating and Itrax radiographic analysis to hoop pine trees from subtropical Lamington and D’Aguilar National Parks respectively. Additionally, dendrometers were installed on trees of all three species so that the climate variables influencing seasonal growth could be identified. It was found that moisture conditions drive annual growth in Araucariaceae trees but that the onset and cessation of the growth season is dependent on temperature. Forest elevation also needs to be considered as the growth season length is longer at lower elevation and there is an influence of cloud cover seen in the north Queensland rainforest, which is close to a cloud forest classification. Annual growth was confirmed for all species through this analysis and the suitability for their use in climate reconstruction proven. Following this, a 164-year drought reconstruction for Southeast Queensland was developed using hoop pine trees from the subtropical rainforest of Lamington National Park. Additional work is continuing to further develop a network of long-term Queensland tree-ring climate records. © The Authors
- ItemHydroclimate proxies for eastern Australia using stable isotopes in grey mangroves (Avicennia marina)(Elsevier, 2022-01) Goodwin, MJ; Verdon-Kidd, DC; Hua, Q; English, NB; Haines, HA; Allen, KJThe development of high-resolution terrestrial palaeoclimate records in Australia is hindered by the scarcity of tree species suitable for conventional dendrochronology. However, novel analytical techniques have made it possible to obtain climate information from tree species that do not reliably form annual growth rings. In this paper we assess the potential of stable carbon and oxygen isotopes in the xylem wood of grey mangroves (Avicennia marina (Forssk.) Vierh.) as hydroclimate proxies for eastern Australia. Bomb-pulse radiocarbon dating and simple age models were used to estimate the age of the growth layers in radial sequence in stems from four grey mangrove trees in two adjacent estuaries in New South Wales, Australia. Stable isotope data measured from the xylem wood of the four stems were composited to yield mean δ18O and δ13C series for the 1962–2016 period. Significant negative Spearman correlations were found between δ18O and rainfall, sea level, instrumental Palmer Drought Severity Index (scPDSI) and the El Niño Southern Oscillation (ENSO), while δ13C was positively correlated with temperature, vapour pressure and evapotranspiration. The results demonstrate that stable oxygen isotopes in grey mangroves have the potential to yield valuable information about pre-instrumental hydroclimate. Grey mangroves can survive with intact centres for an estimate of >250 years based on observed growth rates, are widespread along northern Australian and tropical coastlines and could provide important information regarding pre-instrumental climate in regions currently lacking high-resolution (i.e., near annual) centennial scale climate proxy records. © 2021 Elsevier B.V.
- ItemIdentifying flood and drought events using a 500-year reconstruction of rainfall in the Australian subtropics as determined from hoop pine (Araucaria cunninghamii) tree rings(Science Council of Japan, Japan Association for Quaternary Research, and International Union for Quaternary Research, 2015-07-01) Haines, HA; English, NB; Olley, JM; Hua, Q; Heijnis, H; Palmer, JGSubtropical Australia is highly susceptible to extreme events like the catastrophic floods that occurred in Southeast Queensland (SEQ) in 2011. This event was suggested to be a 1 in 1000 year flood, however, preliminary research of past flood deposits has indicated that a similar sized event occurred about 200 years ago. Our understanding of the past frequency of these types of events is limited because there are few long-term climate records available for this region. Historical precipitation records extend back to the 19th century, which is not of a sufficient duration to understand extreme event frequencies. Other annual proxy methods of rainfall reconstruction are needed to better understand the flood and drought history of this area. Tree rings provide an annual record of past conditions based on a single environmental variable that is limiting tree growth. Here we present the first long-term (>150 years) Australian subtropical tree ring reconstruction of rainfall from Lamington National Park, a natural area of rainforest on the southern boundary of SEQ. Hoop Pine (Araucaria cunninghamii) trees were used as they are one of the longest lived tree species in subtropical Australia, they grow in response to precipitation conditions, and they put on a visible annual ring that can be measured. This record was developed using a multi-technique approach where traditional ring width measuring, X-ray densitrometry, and radiocarbon dating were combined to create a robust chronology that was then used to reconstruct rainfall. Years with major rainfall events are confirmed through Calcium and Strontium signals identified in the tree rings using ITRAX XRF trace elements. Climate conditions for years with known flood and drought events were then compared to our reconstruction to identify potential extreme events in SEQ beyond the period of instrumental record. The methodology, results, and future directions of this research will be discussed.
- ItemThe use of multiple dendrochronological techniques to develop a 200-year drought record for subtropical Southeast Queensland, Australia(European Geosciences Union (EGU), 2020-05-04) Haines, HA; Palmer, JG; English, NB; Hua, Q; Gadd, PS; Kemp, J; Olley, JMIn Australia the majority of tropical and subtropical regions lack any long-term (multi-decadal to centennial scale) instrumental climate records highlighting a need for alternatives such as proxy climate reconstructions. Despite this need, only a limited number of terrestrial proxy sources are available. Tree-rings provide one of the few options for climate reconstructions yet very little dendrochronological investigation has been undertaken as early assessments of tropical Australian species in the 1970s and 1980s indicated most species had short life-spans, poorly preserved timbers, or were compromised by having many ring anomalies. There has also been limited effort into understanding the growth-climate relationships of these trees with only a few studies undertaken targeting specific species that have unfortunately been heavily cleared from the region (eg. Toona ciliata). One exception noted in the early species assessment suggested that trees in the Araucariaceae family, a common tree family along the tropical Australian east coast, is longer lived than many other species in the region, contains growth rings which are annual in nature, and grows in response to climatic conditions. Here we describe the results from a stand of Araucaria cunninghamii trees located in Lamington National Park, a World Heritage listed rainforest in subtropical Southeast Queensland, Australia (a region known for experiencing extreme hydroclimatic events). Our assessment discovered the presence of false, faint, locally absent, and pinching rings. By combining traditional dendrochronological analysis (eg. crossdating) with more recent techniques such as age validation by bomb-pulse radiocarbon dating and tree-ring density analysis, a robust ring-width chronology from 1805-2014 was developed. Dendrometers installed on four trees at the Lamington site confirmed that tree growth was annual and that moisture sensitivity was driving growth. Further growth-climate analysis indicated that the strongest correlation to the tree-ring chronology was specifically related to drought conditions in the region. The strength of this response was compared to both local and regional spatial areas and to drought indices such as the self-calibrating Palmer Drought Severity Index (scPDSI), the Standardized Precipitation Evaporation Index (SPEI), and the long-term drought conditions shown by the Australian and New Zealand Drought Atlas (ANZDA). The combined analysis led to the development of a 200-year drought reconstruction for the region and demonstrates influences from both the El Niño Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO). © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.
- ItemUsing stable isotopes and radiocarbon to extract climate information from grey mangroves with non-annual growth rings(Australian Nuclear Science and Technology Organisation, 2021-11-17) Goodwin, MJ; Verdon-Kidd, DC; Hua, Q; English, NB; Haines, HA; Allen, KJHydroclimate variability in Australia is not well understood prior to the commencement of instrumental climate records in the mid-20th Century. Instrumental climate records can be extended further back in time using proxy data obtained from annual ring forming trees using dendrochronology. However, aside from several exceptions (e.g., Callitris spp.), suitable trees are rare in mainland Australia. Novel techniques such as bomb-pulse radiocarbon dating and stable isotope analysis have made it possible to obtain climate information from trees that do not form annual growth rings. Grey mangroves (Avicennia marina) are the most common mangrove species in NSW, but their growth layers are non-annual. However, grey mangroves are highly sensitive to climate-related variation in freshwater availability and soil salinity. In this study we demonstrate that radiocarbon-based time series of δ18O and δ13C measured from grey mangroves can be used as hydroclimate proxies. Four grey mangrove stem sections were sampled from dead mangrove trees in the Myall and Hunter River estuaries in NSW, Australia in 2018 and analysed layer-by-layer for δ18O and δ13C using isotope ratio mass spectrometry. Four of the growth layers in each stem including the pith, the outermost layer and two other layers spaced evenly along the selected measurement radius were dated using bomb-pulse radiocarbon dating. A simple age / growth model was prepared for each stem assuming linear growth between the dated layers. Age estimates for all growth layers were truncated to integer calendar years allowing isotope data from the four stems to be averaged into composite δ18O and δ13C series covering the 1962-2016 period. The composite δ18O and δ13C time series were then assessed for similarity with a range of relevant climate variables using Spearman correlation analysis. Significant correlations were found between δ18O and rainfall, days rain, sea level, vapour pressure, Palmer Drought Severity Index (PDSI) and the El Niño Southern Oscillation (ENSO). Grey mangrove δ18O values appear to reflect the relative proportions of assimilated sea water (δ18O ≈ 0‰ VSMOW) and 18O-depleted fresh water entering mangrove wetlands as rainfall and runoff. Higher δ18O values were observed during known droughts in the 1960’s and during the millennium drought, whilst lower δ18O values occurred at the same time as La Niña events in 2010-12, 2007-08, 1998-2001, 1988-89 and 1973-76. The composite δ13C series was positively correlated with temperature, vapour pressure and evapotranspiration, suggesting that grey mangrove δ13C values were primarily influenced by atmospheric moisture demand. The most significant positive δ13C peak occurred at the same time as the intense El Niño drought of 1982/83, and the most significant negative δ13C peak occurred at the same time as the La Niña of 2010-12 that was the wettest 24-month period on record in Australia. These results demonstrate that stable carbon and oxygen isotope ratios in grey mangroves yield valuable hydroclimate information. Grey mangroves can live for up to 800 years, are widespread along northern Australian and tropical coastlines and could provide important information regarding pre-instrumental climate in regions currently lacking highresolution centennial scale climate proxy records. © The Authors