A new laser ablation IRMS facility for high resolution stable isotope analysis in Australia

A new laser ablation IRMS facility for high resolution stable isotope analysis in Australia | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 10 July 2025 V1 Latest version Share on A new laser ablation IRMS facility for high resolution stable isotope analysis in Australia Authors : Oliver M. Medd 0009-0000-6230-0592 [email protected] , Matthew T. Brookhouse , Peter Lanc , Andew Latimore , Hayden Miller , and Stewart Fallon 0000-0002-8064-5903 Authors Info & Affiliations https://doi.org/10.22541/au.175211835.56585086/v1 522 views 205 downloads Contents Abstract Abstract 1. Introduction 2. Methods 2.2 Sample Materials 2.3 LA-IRMS Analysis 2.4 Mass of Ablated Material 2.5 Micromill Sampling 2.6 Elemental Analysis Isotope Ratio Mass Spectrometer 2.7 Comparison of LA-IRMS and EA-IRMS Techniques 3. Results 3.2 Tree Ring δC series 3.3 Intra-annual Pattern in δC Ring Series 4. Discussion 5. Conclusion 6. Acknowledgements 7. Reference List Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Rationale: Laser ablation isotope ratio mass spectrometry is a technique that is increasingly being applied for high-resolution analysis of carbon stable isotopes in organic materials. Here we present a new LA-IRMS facility housed in the Research School of Earth Sciences, Australian National University, Canberra, following the development and implementation of similar facilities elsewhere. The LA-IRMS technique allows for the measurement of stable isotopes within incredibly challenging tree ring chronologies, of which rings may be only several cells wide. Methods: We tested two commonly used standard materials, including IAEA-C3 holocellulose and VWR gel blotting pads, in the new LA-IRMS system. Additionally, we analysed a 13-year tree ring sample of Eucalyptus pauciflora subsp . niphophila to test the intra-annual capability of the LA-IRMS. Results: IAEA-C3 holocellulose ( n = 35) and VWR gel blotting pads ( n = 27) produced δ 13 C ‰ (VPDB) values of -24.73 ± 0.08 ‰ and -26.56 ± 0.13 ‰, which agreed with published values (IAEA-C3: -24.72 ‰, VWR: -26.57 ‰). The LA-IRMS system produced a single-tree δ 13 C ring series with high intra- and inter-annual variability. Conclusions: Our results demonstrate the potential for ultra-high temporal resolution analysis of stable-isotope dendrochronological samples using the new LA-IRMS. This facility offers an avenue for the expansion of tree ring research in Australia, supporting a field that continues to face challenges associated with poor ring definition in much of the endemic flora. In addition to this, the LA-IRMS facility has the potential to expand into the measurement of other organic and inorganic for their stable isotopic signal, for example the calcareous material of molluscs. Oliver M. Medd 1 , Matthew T. Brookhouse 2 , Peter Lanc 1 , Andew Latimore 1 , Hayden Miller 1 , Stewart J. Fallon 1 1 Research School of Earth Sciences, Australian National University – Canberra, Australia 2 Fenner School for Environment and Society, Australian National University – Canberra, Australia Corresponding Author Email: [email protected] Keywords Carbon, Isotopes, Dendrochronology, Lasers, Ablation. Abstract Rationale: Laser ablation isotope ratio mass spectrometry is a technique that is increasingly being applied for high-resolution analysis of carbon stable isotopes in organic materials. Here we present a new LA-IRMS facility housed in the Research School of Earth Sciences, Australian National University, Canberra, following the development and implementation of similar facilities elsewhere. The LA-IRMS technique allows for the measurement of stable isotopes within incredibly challenging tree ring chronologies, of which rings may be only several cells wide. Methods: We tested two commonly used standard materials, including IAEA-C3 holocellulose and VWR gel blotting pads, in the new LA-IRMS system. Additionally, we analysed a 13-year tree ring sample of Eucalyptus pauciflora subsp . niphophila to test the intra-annual capability of the LA-IRMS. Results: IAEA-C3 holocellulose ( n = 35) and VWR gel blotting pads ( n = 27) produced δ 13 C ‰ (VPDB) values of -24.73 ± 0.08 ‰ and -26.56 ± 0.13 ‰, which agreed with published values (IAEA-C3: -24.72 ‰, VWR: -26.57 ‰). The LA-IRMS system produced a single-tree δ 13 C ring series with high intra- and inter-annual variability. Conclusions: Our results demonstrate the potential for ultra-high temporal resolution analysis of stable-isotope dendrochronological samples using the new LA-IRMS. This facility offers an avenue for the expansion of tree ring research in Australia, supporting a field that continues to face challenges associated with poor ring definition in much of the endemic flora. In addition to this, the LA-IRMS facility has the potential to expand into the measurement of other organic and inorganic for their stable isotopic signal, for example the calcareous material of molluscs. 1. Introduction Stable isotope analysis aids in palaeological interpretation of Earth’s biological, chemical and geological systems 1-4 . Tree rings offer a source of inter- and intra-annual palaeoclimatological data across local and global scales with unrivalled dating control. Although traditionally focussed on tree-ring width and wood-density data, dendroclimatological research is increasingly drawing upon ratios of stable isotopes, particularly those of carbon ( i.e. , 13 C/ 12 C) and oxygen ( i.e., 18 O/ 16 O), for climatological interpretation and paleoclimate reconstruction 5 . Trees respond to changes in environmental conditions, through morphological and physiological adaptations, to balance CO 2 uptake/assimilation and water loss 6 . These adaptations produce variability in the isotopic composition of plant tissues, including tree rings 7, 6, 8 . For isotopes of carbon, the process of fractionation and the effect of ecophysiological stressors is relatively well understood 9 . In tree rings, variability of δ 13 C time series has been shown to relate indirectly to temperature 10 , precipitation 11 and atmospheric vapour-pressure deficit (VPD), as well as other metrics of local climate 12, 13, 6, 14, 15 . In addition to their reconstructive capacity, tree-ring δ 13 C chronologies can facilitate prediction of tree-/forest-level vulnerability to non-analogue conditions, such as those associated with anthropogenic climate change 16 . Relative to those consisting of tree-ring widths, isotope chronologies are both more costly and time-consuming to produce. These hurdles are exacerbated when analyses are conducted at a sub-annual scale 17 . The advent of laser-ablation systems has vastly reduced analysis times and improved the resolution of stable-isotopic tree-ring records by permitting simultaneous sampling and analysis at sub-millimetre scales. Further, the technique also allows generation of tree-ring chronologies from species that lack clear annual boundaries 18, 19 . The laser-ablation-combustion-GC-IRMS method, now known commonly as laser-ablation isotope ratio mass spectrometry (LA-IRMS) 20-31, 18, 17, 32, 33 , involves ablation of the surface from intact samples within a sealed chamber, via a focused pulse from a UV laser. Ablated material is carried by a flow of helium from the sample chamber through a furnace (at ~700℃) containing chromium oxide (Cr 2 O 3 ), where the resulting ablated particles of wood and gaseous products are reacted to form carbon dioxide gas (CO 2 ). Staged loops within the gas line both trap and focus the sample of CO 2 into a concentrated pulse, passing through a Gas Chromatography (GC) column, before arriving at an isotope ratio mass spectrometer (IRMS). Although principally applied to analysis of carbon isotopes 18 , recent advances now permit application to isotopes of oxygen ( i.e ., 16 O and 18 O) 33 . A major advantage of LA-IRMS in dendroclimatological studies is the high resolution that the technique can yield. That is, narrow beam size and truncated sampling/analysis times permit measurement of multiple samples ( i.e., time points) within each ring. This allows for resolution at sub-seasonal intra-annual scales 18 , rivalling conventional microtome-based sampling 34, 35 . Furthermore, by permitting integration of spot-based ablations at small scales ~30 µm), complex ablation paths that follow the curvilinear shape of tree ring boundaries can be produced, which is a challenge using conventional manual-sampling methods 17 . In contrast to the northern hemisphere, the Australian landmass is relatively devoid of woody species that form objectively identifiable annual tree rings 36 . Annual tree rings are only reliably formed by the dominant tree taxon, Eucalyptus , in cool-temperate areas of the continent’s far south-west/-east and in Tasmania 37 . While recent examination of monsoonal and seasonally dry tropics has revealed dendrochronological opportunities more broadly 38-44 , the discipline remains relatively under-developed and moderately resourced in Australia. The addition of a local LA-IRMS facility would add substantially to that resourcing, allowing rapid investigation of native species, while also facilitating close collaboration with the global stable isotope dendrochronological community. This paper reports on a new LA-IRMS facility housed at the Research School of Earth Sciences, Australian National University (RSES-ANU). The system is an adapted form of those described by Schulze et al. , (2004) and Loader et al. , (2017), and is a hybrid of existing elemental analyser (EA) IRMS and High Temperature EA-IRMS within RSES-ANU. Here, we outline the structure of the RSES-ANU LA-IRMS and its analytical methodology. To test the system’s properties, we characterise the δ 13 C ‰ (VPDB) values of two reference materials commonly used in LA-IRMS studies; IAEA-C3 holocellulose (IAEA-C3) (IAEA, 2021) and VWR gel blotting pads (VWR) 17 . In addition, we report on a preliminary high-resolution intra-annual analysis of Eucalyptus pauciflora subsp. niphophila , an endemic species known to form clear annual tree-ring series that has been identified as a suitable climatological proxy 45, 37 . Using that material, we compare data derived from both LA- and EA-IRMS techniques to analyse a 13-year period in a single tree, assessing the ability of laser ablation to replicate results of more conventional methods. 2. Methods 2.1 The LA-IRMS System The LA-IRMS system consists of a bespoke laser-ablation unit, attached to a combustion unit, cryogenic trapping loop apparatus, and an isotope ratio mass spectrometer (Figure 1). The laser ablation system is built around a 193nm ArF EX5 Excimer Laser unit (GAM Laser, Inc.) (Figure 1; Laser Unit ). We selected the GAM EX5 ArF 193nm laser, over the more widely used solid-state 213nm Nd:YAG laser unit, due to the higher CO2 conversion efficiency (~70% 193nm vs. incorporate the ArF 193nm unit is also consistent with its use elsewhere ( e.g. , ETH, Zurich CH; see Welte et al. , (2016)) to perform in-situ laser ablation-based sampling of carbonate material for direct accelerator mass spectrometer (AMS) analysis of radiocarbon. We aim to utilize our system similarly in future, linking the LA-IRMS to the single-stage AMS at our facility, thus acquiring the same laser unit was appropriate. Our system carries the ablation beam through a slit drive, via a bespoke flight tube. The beam is reflected by three 45° mirrors, producing a total flight distance of 1.8 metres to ensure the correct demagnification for the ArF laser. The ablation beam passes through a focusing lens at the end of the flight tube to produce a precise beam spot on the sample surface. A two-axis (XY) sample stage positions an ablation cell (IsoSCell, TerraAnalitic) containing the samples and any standard/reference materials. Sample materials are viewed via a microscope camera apparatus consisting of camera unit (The Imaging Source, 33U Series DFK 33UX249) and microscope lens (Navitar 1-60135 coupled to a 2x Nira 1-60185) This microscope apparatus is positioned behind, and separate to, the ablation cell stage (Figure 1). Custom in-house control software developed in NI’s LabVIEW drives the stage to a predefined list of analytical sample positions in an automated fashion. Laser spot size can be customised for each location via motorised variable width and height slit. Both the laser and the mass spectrometer are triggered automatically as the software moves from spot to spot. Helium is used as a carrier gas, with flow through the cell controlled by a Bronkhorst EL-FLOW Select mass flow meter and controller. Ablated sample material and gases are delivered to a reaction chamber containing Chromium Oxide (Cr 2 O 3 ) at 700 °C where material is converted into CO 2 . The gas sample is then carried by the flow of helium (30ml min -1 ) to a CryoPrep (Sercon, Ltd.) device, where cryogenic trapping and focusing loops concentrate the sample CO 2 gas prior to sending to a 20-22 Stable Isotope Ratio Mass Spectrometer (Sercon, Ltd.) for analysis. The operation of the IRMS, as well as the collection of data, is controlled using Sercon supplied software. Figure 1: A) Diagram of LA-IRMS system components at the RSES – ANU. The system consists of four main parts: The laser ablation system, a furnace, the CryoPrep device (Sercon. Ltd) and a Stable Isotope IRMS (Sercon 20-22 IRMS, Sercon Ltd.). The laser ablation system shown above consists of a laser unit (purple box), gas control box, flight tube (black), slit drive (not shown), reflectors, and IsoScell sample box (blue box), 20-22 Stable Isotope Ratio Mass Spectrometer (Sercon. Ltd). B) Sample holder loaded with sample wood, and a range of standards, with IAEA-C3 and VWR Blotting Pad inserted in the bottom left of the holder. 2.2 Sample Materials We examined the performance of the laser-ablation unit on both reference and biological materials. We measured high-resolution isotopic composition with a stem section from E. pauciflora subsp. niphophila . The sample was collected in May 1978 (see Banks, (1982)) from a sub-alpine woodland at an elevation of southeast Australia. Tree-ring formation is reliably annual in the sample area and both earlywood (EW) and latewood (LW) fractions can be readily distinguished. Prior to mass spectrometry, the sample surface was sanded to a fine finish using 2000-grit sandpaper. To prevent contamination of the sample surface by wood-dust arising from sanding, the sample was cleaned with high-pressure water. The sample was then imaged using a Leica M80 Stereo Zoom microscope, coupled to a Leica FLEXACAM C1 microscope camera, using a single-axis manual traverse bench (Curt Zahn) to create overlapping images panning left to right. Individual microscope images were combined using PTGui (New House Internet Services B.V., Rotterdam, Netherlands) software to compose a panorama of the wood sample. Images were first calibrated using a Leica metric stage micrometer and the width of each ring was then measured along a 2mm wide path within WinDendro 2022 (Regent Instruments, Canada). The resulting ring-width series crossdated against an existing master ring-width chronology spanning 302 years (1702-2021CE). We used the ‘Schulman’ convention, which assigns tree rings formed in the southern hemisphere to the calendar year in which growth started 48 . For LA-IRMS analysis, a subsection spanning 1966-1978 CE was removed from the main sample block. This smaller whole-wood subsection, measuring 38✕5✕3.5mm, was cut to fit within the sample holder of the IsoSCell ablation cell (Figure 1b). The sample was then placed into the sample holder along with LA-IRMS reference materials IAEA-C3 and VWR (Figure 1b). The cell was sealed and locked into the two-axis stage. Helium gas-flow was initiated at 30ml min -1 and left to purge any remaining atmospheric gases that remained inside the cell for 24 hours. 2.3 LA-IRMS Analysis Ablation of IAEA-C3 and VWR reference materials was conducted prior to the ablation of tree-ring material, and subsequently every 8 measurements. Each ablation was conducted across a distance of 700µm for approximately 60 seconds. A 35µm spot with a repetition rate of 20Hz and a laser energy of ~6mJ (fluence of approximately 1250 j/cm 2 ) was used to produce the required material for LA-IRMS measurement. Ablations were spaced 200µm apart, adjusted where required to ensure none crossed the EW/LW boundary between rings, as this could produce δ 13 C values that averaged between two rings. Each sample was normalized to a pulse of CO 2 reference gas with the amount optimized to match the wood CO 2 . Sample and reference material measurements were presented on the Vienna Pee Dee Belemnite (VPDB) scale, as δ 13 C (‰): δ 13 C ‰ = (R (sample) /R (standard) - 1) x 1000 where R = 13 C/ 12 C, and R (sample) refers to the R value of the measured sample, and R (standard) refers to the VPDB R value (see Loader et al. , (1995)). Data from each analytical session was single-point corrected using laser measurements of IAEA-C3 holocellulose. Testing of additional materials for multi-point calibration for future analysis is in progress. 2.4 Mass of Ablated Material We used the Sercon Callisto software CO 2 beam area calculation to estimate the ablated wood mass to range between 20-30μg of carbon. This is consistent with a previous estimate of 2.5 Micromill Sampling A robotic, programmable micromill was used to remove fine whole-wood powder from the surface of the E. pauciflora subsp. niphophila sample block. This method has been utilized previously for a similar application by Dodd et al. , (2008). A 500μm mill bit was used to sample along the shape of each growth ring, following the contours of the LW of each ring first, followed by EW samples. Samples were spaced to limit overlap and maximise the number of samples per ring, with more samples achieved for wider rings. The mill was lowered to a depth of ~1200μm into the sample block, adjusted as required to produce the highest yield of powder. After each mill run, sample powder was removed from the surface of the block and stored within a 2ml centrifuge tube. Before the next mill run, the sample block and bit were cleaned of remaining powder from the previous sample using both vacuum and compressed air. The surface of the sample block can be seen pre- and post-sampling as the mill makes a pass (Figure 2). Figure 2: The robotic micromill device at the RSES, ANU, following mill runs across the block of E. pauciflora subsp. niphophila. Previous sampling channels with material removed can be seen on the left-hand side of the block. Unsampled rings are shown on the right of the block surface. 2.6 Elemental Analysis Isotope Ratio Mass Spectrometer The EA-IRMS method followed in this study is after Wood et al. , (2023). In short, wood powder was weighed to 500ug in a tin cup. Standard weights were adjusted to match to the percentage of carbon (%C) and isotope value expected within wood samples. A multipoint scaling process was used to correct the data 52 . For example, samples were measured against an in-house gelatine material and scaled using USGS-61 and USGS-65. Data accuracy was then assessed using IAEA-C3 and VWR cellulose pads. 2.7 Comparison of LA-IRMS and EA-IRMS Techniques Stable carbon isotope values for EA-IRMS analysis were used to perform a cross comparison to the LA-IRMS method, to assess the accuracy and reliability of the LA-IRMS system. The x-axis value of length (mm) was based on the distance of each LA-IRMS ablation from the bark edge (far-right edge of sample, Figure 3). The EA-IRMS measurements were normalised to LA-IRMS measurements by aligning EA-IRMS LW minimum δ 13 C values for each ring to the matching LA-IRMS measurement and evenly distributing the variable number of intra-annual samples between each LW value. This was deemed appropriate as both series prioritised LW sampling as close to the ring boundary as feasibly possible, and also because the ring widths varied slightly, making a pure distance-based comparison unreliable and unrepresentative. 3. Results 3.1 Reference Materials The LA-IRMS system produced values for IAEA-C3 and VWR standard materials consistent with their known values (Table 1). The standard material IAEA-C3, when measured as samples, produced an average δ 13 C value of -24.73 ± 0.09 ‰ from 35 measurements. This agrees with the published value of the re-homogenized material, now called IAEA-CH-3, of -24.72 + 0.04 ‰, as well as with measurements made by WSL, Switzerland and Luke, Finland of -24.71 + 0.07 ‰ and -24.61 + 0.13 ‰ respectively (See IAEA, (2021), Saurer et al. , (2023)). Samples of VWR Gel Blotting Cellulose Pads measured as unknowns produced an average δ 13 C value of -26.56 ± 0.13 ‰ from 27 measurements, which agreed with the LA-IRMS analysis value of -27.56 + 0.09 ‰, reported by Saurer et al. , (2023). >> Table 1 Location 3.2 Tree Ring δC series Figure 3: Intra-annual and annual measurements of δ 13 C from 1966 to 1978 in single tree ring series. The small, black triangles represent the high-resolution δ 13 C values (‰, VPDB) produced by the LA-IRMS technique. Values were plotted relative to their distance (millimeters) from the bark edge, as to align the data to the corresponding marks on the post-ablation scan of the wood core. The red circles represent δ 13 C values (‰, VPDB) produced by the EA-IRMS/Micromill technique. Above, a scan of the tree ring section that was analysed by LA-IRMS. The horizontal lines visible across the sample are the marks made by the ablation and are 30 x 700 microns. For scale, a ruler with 0.5mm increments is present at the base of the scan. In total, 192 ablations were made for the 13-year-long ring series in the sample block of E. pauciflora subsp. niphophila , with the number of ablations ranging between 10 and 21 per ring. (Figure 3). Values of δ 13 C (‰) in the sample whole-wood material show a high level of both inter- and intra-annual variability (Figure 3). Fifty-four milled samples were produced using the EA-IRMS technique within the same tree rings as the LA-IRMS analysis. The δ 13 C (‰) values from the milled samples were matched up to the LA-IRMS ring series by first aligning the last LW result of each technique, as these were distinct locations where signal reached its most negative for each year. Intra-annual EA-IRMS data-points were distributed evenly between these LW points to compare the overall ring data between the two techniques (Figure 3). The δ 13 C values of the EA- and LA-IRMS chronologies within E. pauciflora subsp. niphophila showed strong agreement, aligning with the findings of Loader et al. , (2017). However, there is a notable deviation in the data within some year rings between methods. The strongest example of this deviation pertains to the 1976-year ring, where the EW δ 13 C value peaks at a value of -25.98‰ in the EA-IRMS dataset, where in the LA-IRMS dataset, the peak EW value is at -24.92‰, approximately 1‰ less negative. 3.3 Intra-annual Pattern in δC Ring Series A yearly, intra-annual pattern can be observed within each tree ring of the E. pauciflora subsp. niphophila sample δ 13 C (‰) ring series. Firstly, a rise in δ 13 C value is evident in the first few measurements within each ring (indicated by arrow 1, Figure 4). Following this, EW values stabilise at a less negative value across much of each tree ring, with variability observable across the bulk of the ring (arrow 2, Figure 4). Finally, δ 13 C values become more negative again through the LW portion of each ring, with the most negative point coinciding with the LW value closest to the ring boundary (arrow 3, Figure 4). Figure 4: An observed intra-annual pattern in δ 13 C (‰) present in E. pauciflora subsp. niphophila. Data from three years, 1975, 1976 and 1977, sampled and analysed by the LA-IRMS method, illustrate this trend in three stages, outlined by numbered arrows as follows; 1) an initial δ 13 C increase into the growth ring, 2) a peak, variable plateau across the EW, and 3), a final decrease in δ 13 C through the LW portion of the ring, with the last measurement being most negative. 4. Discussion 4.1 Analysis of Reference Materials Our testing indicates that the ANU-RSES LA-IRMS consistently yields δ 13 C results from reference materials in agreement with published values (Table 1) (IAEA, (2021), Saurer et al. , (2023)). The system produces consistent values over numerous periods of analysis, supporting the use of the device in measuring the stable carbon isotopic composition in applicable materials, such as bulk wood or cellulose materials. 4.2 Laser Ablation IRMS versus Micromill-Elemental Analysis IRMS The LA-IRMS system has successfully demonstrated capability to generate δ 13 C values from the surface of whole wood samples in E. pauciflora subsp . niphophila. These results are consistent with the more common EA-IRMS based approach, albeit at a finer intra-annual scale. The minimum, maximum, and overall variation in δ 13 C values year-to-year appear to visually match well. However, where the number of micromilled EA-IRMS samples in a ring is restricted by ring width, peak EW δ 13 C values for the year are lower. That outcome is particularly evident in our data from ring years 1974 and 1976 (Figure 3). This is likely driven by a much wider sampling width within the ring material, as a 500-μm wide channel was created across the sample block to obtain the required mass for each EA-IRMS analysis. Because of this, the micromill/EA-IRMS technique integrates more wood into each measurement, compared to LA-IRMS. This effect likely averages variation in δ 13 C composition over a larger portion of each ring, producing a smoothing of annual peak values. The opposite to this restriction applies, with much greater agreement in δ 13 C values between techniques within thicker rings. This allows for more micromill samples to be achieved within a single ring, producing intra-annual values closer to the higher resolution LA-IRMS technique. A similar relationship between intra-annual δ 13 C values EA- and LA-IRMS and intra-annual pattern was reported by Schulze et al. , (2004). The benefits of LA or EA-IRMS lie in the finer resolution and simultaneous sampling and analysis of manual sampling 17 . We recognise that core microtomy has the capacity to yield yet higher resolution using an EA-IRMS 54 . However, the LA-IRMS is capable of ablating curvilinear shapes, such as those expressed by tree rings, particularly in slow-growing high-altitude/-latitude shrubs (e.g., Battipaglia et al. , (2010)); an aspect difficult to replicate using microtomy. Although not tested here, that attribute makes our system well suited to fine tree-ring series generated by species such as Podocarpus lawrencei , a long-lived (to ~600 yrs) Australian alpine conifer that often forms rings <100μm wide 56 . Our experience suggests that, when designing a sampling protocol for LA-IRMS analysis of tree-ring material, a greater number of samples taken within a ring will produce a greater isotopic sensitivity and resolution across a ring width. This presents a trade-off between resolution and analytical time when under a restriction of either time or funding for analysis, reducing the number of ablations per ring may make larger studies of long chronologies of isotope values, across multiple cores, trees and stands more achievable. However, a greater number of measurements may serve best in cases where a short time series is of interest. 4.3 Preliminary Interpretations - Intra-annual δC Pattern Interpretation of our LA-IRMS time series is limited by the analysis of only a single tree, within a short thirteen-year window of growth. Thus, we have refrained from attempting to relate our data to interpret the results in the context of climatic drivers. A dataset sourced from multiple trees spanning a longer period is needed to achieve that outcome and is currently in development. Nevertheless, we note that the intra-annual variability of δ 13 C within our LA-IRMS time-series forms a consistent pattern (Figure 4). That pattern is comparable to those reported for other taxa elsewhere 21, 28, 57, 58 , and may correspond with variation in evaporative stress and leaf-level CO 2 uptake, as well as seasonal variation in the use of stored non-structural carbohydrates 59 . Regardless of its source, the evidence of a clear intra-annual pattern in the high-resolution δ 13 C record, as well as inter-annual variation, is a prompt for further investigation of E. pauciflora subsp. niphophila. Coupling dendrometric monitoring and wood sampling aimed at revealing xylogenesis with high-resolution LA-IRMS, would likely offer insight to the species’ physiological responses to meteorological conditions. That insight would also inform climatological interpretation of a well-replicated longer time series, realising the apparent potential of the species as a paleoclimatic recorder. 5. Conclusion A new LA-IRMS system­­—housed at Research School of Earth Sciences, Australian National University, Canberra—has produced δ 13 C (‰) values from cellulose reference materials IAEA-C3 and VWR in agreement with published values on similar systems globally. This supports the accuracy of the LA-IRMS in determining stable carbon isotope values from wood-based materials. The LA-IRMS enables the analysis of tree-ring chronologies locally, expanding the potential for more stable-isotope-based research to be conducted on native species of tree - once thought to be too challenging to sample. Although this paper has focussed on the use of tree ring materials to test the system, the incorporation of a 193-nm laser unit means high resolution analysis of carbonate-based paleoclimate recorders such as corals, bivalves and brachiopods may also be achieved. A preliminary analysis of the δ 13 C composition of a section of E. pauciflora subsp . niphophila yielded high intra-annual δ 13 C variability, with a seasonal trend congruent with those shown in similar studies. The high intra-annual resolution achieved by the new LA-IRMS facility demonstrated strong agreement with the more conventional EA-IRMS approach. Future work will seek to determine whether E. pauciflora subsp . niphophila woody material requires cellulose extraction for LA-IRMS, or if whole wood is viable to produce representative isotope chronologies. Additionally, the viability of E. pauciflora subsp . niphophila for dendroclimatic reconstruction will be explored through the investigation of a potential limiting climatic factor driving variability in δ 13 C values. The expansion of stable isotope dendrochronology in Australia is supported through the addition of this facility, allowing for local analysis and research to equal and collaborate closely with the rapidly expanding global field. 6. Acknowledgements We would like to thank the ANU Major Equipment C grant, through Carl Were – Construction and Engineering. We would like to acknowledge the unwavering support of the teams running the existing LA-IRMS systems, who have aided us in the successful setup and running of our new facility. These include the team at Luke, Helsinki, Finland, including Katja Rinne-Garmston, Elina Sahlstedt, the team at WSL, Zurich, Switzerland including Mattias Saurer, and Neil Loader and team at Swansea University, Wales, UK. We would like to thank Garry Armstrong, Dave Harris and the entire team at Sercon, Crewe, UK. We would like to thank NSW Environmental Trust Grant (2020/RD/0002) and the Australian Government Research Training Program for personal funding. 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P-values (p) indicate non-significant differences between measured and known values for reference materials. Information & Authors Information Version history V1 Version 1 10 July 2025 Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords ablation carbon dendrochronology isotopes lasers Authors Affiliations Oliver M. Medd 0009-0000-6230-0592 [email protected] Australian National University Research School of Earth Sciences View all articles by this author Matthew T. Brookhouse Australian National University Fenner School of Environment and Society View all articles by this author Peter Lanc Australian National University Research School of Earth Sciences View all articles by this author Andew Latimore Australian National University Research School of Earth Sciences View all articles by this author Hayden Miller Australian National University Research School of Earth Sciences View all articles by this author Stewart Fallon 0000-0002-8064-5903 Australian National University Research School of Earth Sciences View all articles by this author Metrics & Citations Metrics Article Usage 522 views 205 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Oliver M. Medd, Matthew T. Brookhouse, Peter Lanc, et al. A new laser ablation IRMS facility for high resolution stable isotope analysis in Australia. Authorea . 10 July 2025. 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