Browsing by Author "Larsen, JR"
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- ItemDistribution and temporal variations in palaeo-groundwater on the Australian continent(International Association of Hydrogeologists in Canada, 2012-09-16) Cendón, DI; Markowska, M; Chen, JY; Van der Ley, M; Hughes, CE; Larsen, JRNot available
- ItemEffect of two types of tree guards (with and without weed control) on tree seedling establishment(Ecological Society of Australia, 2010-04-01) Ladd, B; Larsen, JR; Bonser, SPThere are many potential problems that can limit the success of revegetation efforts (Close & Davidson 2002; Close et al. 2007), many products available for revegetation, and little independent research on the efficacy of those products. For example tree guards are commonly used to establish native woody plants in ecological restoration projects yet the effectiveness of tree guards in promoting seedling establishment is uncertain (Lai & Wong 2005; Close et al. 2007). Tree guards may protect seedlings from vertebrate herbivores, and/or protect seedlings from desiccating hot wind and/or frost (Corr 2003; Gould 2005). In Aldinga, South Australia the summers are hot and dry and it is possible that tree guards could aggravate this heat stress (Close et al. 2007). However, due to the Mediterranean climate, winters are cold and tree guards may be beneficial because they limit seedling exposure to cold stress during the early establishment phase. Here we present the results of a trial in which we evaluated the microclimate amelioration effect of two types of tree guard, with and without weed control, on seedling establishment in Pink Gum (Eucalyptus fasciculosa) in South Australia. © 2010, Ecological Society of Australia
- ItemExceptional datolite crystals from Albion Park, New South Wales: morphology, chemistry and likely origin(Mineralogical Society of Victoria, 2018) Graham, IT; Colchester, DM; Cendón, DI; Lay, A; Hergt, JM; Greig, A; Larsen, JRLarge, well-formed, semi-transparent yellow–green crystals up to 5.6 cm were found in cavities within the Late Permian Bumbo Latite Member of the Gerringong Volcanics in the now abandoned Cleary Brothers Quarry, Albion Park, New South Wales. Although labelled by the collector as calcite, these were later identified as datolite, with two distinct habits, occurring on a matrix of crystallized quartz and prehnite. The datolite contains very low concentrations of elements other than the essential calcium, silicon, oxygen and boron. Its distinctive chondrite-normalized, positive europium anomaly, when compared with datolite data from elsewhere, suggests crystallization from postdiagenetic hydrothermal fluids in the temperature range of 200–250°C. These datolite crystals are the finest ever found in Australia and rank highly with those found elsewhere in the world. © 2018 Mineralogical Society of Victoria
- ItemThe floodplain sedimentology of Cooper Creek. Why billabongs (waterholes) in the Channel Country start and stop(Universidad Nacional de Tucumán, Fundación Miguel Lillo, 2009-08-24) Nanson, GC; Larsen, JR; Cendón, DI; Fagan, SD; Jones, BRThe Channel Country of western Queensland consists of a low gradient anastomosing channels inset in muddy floodplains in a desert climate. Annual transmission losses are large, averaging 75-80% of total volume along a ~400 km reach of Cooper Creek. Billabongs (waterholes) are common and consist of local channel expansions in the mud-lined anastomosing network, as well as isolated scour-channels on a floodplain that is formed of 2-3m of clay-rich mud. Both the primary anabranching and overbank flood channels carry water during large floods but only the billabongs store water for long periods of drought, making them vital to the ecology and agriculture of the region. Despite penetrating a very extensive underlying Pleistocene-age sand body, they are impermeable much of the time. However, transects away from several billabongs reveal marked increases in salinity and provide compelling evidence that they act as fresh-water ‘entry valves’ through an otherwise impermeable muddy floodplain. The base of each billabong is scoured during floods, enabling large volumes of surface water to be dumped into the 10 m deep saline aquifer. As flows decline the billabongs self-seal with mud such that fresh water can be stored for a year or more. Transmission losses along Cooper Creek were initially believed to be due to evaporation, however, the lack of any solute concentration between gauging stations along the ~400 study reach, suggests that of the ~1.8 km3 of surface flow lost from the ~3.0 km3 entering the upper end of the study reach, most leaks through the base of the billabongs. Such massive losses also account for why the billabongs in the form of large and efficient channels, terminate after just a few kilometres. They reform repeatedly at locations where conditions are suitable, but their numbers decline downstream in accordance with the loss of total flow-volume.
- ItemFreshwater recharge into a shallow saline groundwater system, Cooper Creek floodplain, Queensland, Australia(Elsevier, 2010-10-15) Cendón, DI; Larsen, JR; Jones, BG; Nanson, GC; Rickleman, D; Hankin, SI; Pueyo, JJ; Maroulis, JFreshwater lenses have been identified as having penetrated the shallow regional saline groundwater beneath the Cooper Creek floodplain near Ballera (south-west Queensland). Piezometers were installed to evaluate the major-element chemistry along a floodplain transect from a major waterhole (Goonbabinna) to a smaller waterhole (Chookoo) associated with a sand dune complex. The floodplain consists of 2–7 m of impermeable mud underlain by unconsolidated fluvial sands with a saline watertable. Waterholes have in places scoured into the floodplain. The transect reveals that groundwater recharge takes place through the base of the waterholes at times of flood scour, but not through the floodplain mud. Total dissolved solids rise with distance from the waterhole and independently of the presence of sand dunes. Stable water isotopes (δ2H and δ18O) confirm that recharge is consistent with, and dependant on, monsoonal flooding events. Following floods, the waterholes self-seal and retain water for extended periods, with sulfate-δ34S and δ18O isotopes suggesting bacterial reduction processes within the hyporheic zone, and limited interaction between the surface water and groundwater during no-flow conditions. The area occupied by the freshwater lenses (TDS < 5000 mg/L) is locally asymmetrical with respect to the channel flow direction, extending down gradient along distances of 300 m. © 2010, Elsevier Ltd.
- ItemGeomorphic controls on groundwater evolution in the arid Cooper Creek system, SW Queensland, Australia: inferences from element and stable isotope hydrogeochemistry(International Association of Hydrogeologists, 2007-09-17) Cendón, DI; Larsen, JR; Jones, BG; Rickleman, D; Nanson, GCQuaternary climatic changes have had a remarkable impact on the biological and geomorphological evolution of the Australian continent, and in turn can exhibit considerable control on the current hydrological cycle. In the absence of glaciation, changes in precipitation and wind strength have resulted in alternating fluvial, aeolian and lacustrine deposits over much of inland Australia. In the currently arid anabranching floodplain-channel system of Cooper Creek (SW-Queensland), this is manifest as extensive late Pleistocene fluvial and aeolian sand bodies overlain by floodplain and channel mud deposits. The alluvial muds are the result of the much reduced Holocene transport capacity of the Cooper Creek system, and are punctuated at the surface by remnant aeolian sand dunes which are stratigraphically connected to the underlying sand bodies. These Quaternary sand bodies (Chookoo dune-floodplain complex) have in turn become the main aquifers for the region, where the water table is ~10-12m below the floodplain surface. The presence of shallow groundwater is especially crucial for ecosystems in arid environments because evaporation quickly removes any available surface waters. Considering the importance of this resource, and the fragility of the hydrological cycle in arid zones, the shallow groundwaters in this region have received surprisingly little attention. This study aims to determine the basic recharge/evaporation processes of the Chookoo dune-floodplain-channel system using major and minor element chemistry together with water stable isotopes (δ18O, δ2H) and dissolved sulfate isotopes (sulfate-δ34S and δ18O). We hypothesise that groundwater recharge predominately occurs as diffuse rainfall infiltration via the dunes while chemical variations also occur through the dunes, modifying the original chemistry of the recharged water. Presented chemical data suggests that the main channel of the creek has little or no hydraulic connectivity with the shallow aquifers except during large flood events when the mud seal over their base is scoured and fresh water temporarily recharged. Major-element chemistry: All waters are Na-Cl-rich with appreciable amounts of Ca and SO4. All major elements increase along a transect from the sand dunes to the floodplain within the same aquifer. In general, major element ratios show a marine derived signal for groundwater, while a few surface water samples deviate from marine ratios (Fig. 1A). This difference is interpreted as an event based signature, with most solutes incorporated from dissolution of surfaces salts. Evaporation models also provide evidence of major element evolution (Fig. 1B). Simple evaporation of surface waters cannot reproduce the concentrations found in the groundwater. Only when a mixture of surface and groundwater and/or dissolution of previously precipitated salts along the recharge path are considered, do the evaporation models match with the observed concentrations.
- ItemThe hydrological legacy of deforestation on global wetlands(American Association for the Advancement of Science (AAAS), 2014-11-14) Woodward, C; Shulmeister, J; Larsen, JR; Jacobsen, GE; Zawadzki, AIncreased catchment erosion and nutrient loading are commonly recognized impacts of deforestation on global wetlands. In contrast, an increase in water availability in deforested catchments is well known in modern studies but is rarely considered when evaluating past human impacts. We used a Budyko water balance approach, a meta-analysis of global wetland response to deforestation, and paleoecological studies from Australasia to explore this issue. After complete deforestation, we demonstrated that water available to wetlands increases by up to 15% of annual precipitation. This can convert ephemeral swamps to permanent lakes or even create new wetlands. This effect is globally significant, with 9 to 12% of wetlands affected, including 20 to 40% of Ramsar wetlands, but is widely unrecognized because human impact studies rarely test for it. © 2014, American Association for the Advancement of Science.
- ItemThe hydrological legacy of deforestation on global wetlands(Australasian Quaternary Association Inc., 2014-06-29) Woodward, C; Shulmeister, J; Larsen, JR; Jacobsen, GE; Zawadzki, ACatchment erosion and increased nutrient loading are commonly recognised impacts of deforestation on global wetlands. Forest clearance can increase water availability in wetland catchments, but globally, the hydrological effect of deforestation has received little attention. We provide the first unequivocal evidence that historic and prehistoric forest clearance in dryland areas in Australasia increased catchment water yield; creating new wetlands and converting existing wetlands into shallow lakes. We developed a hydrological model to predict the location of global wetland catchments that are susceptible to this effect and demonstrate that hydrological alteration of wetland catchments is a previously overlooked dimension of the cultural landscape. We used a meta-analysis of published papers to demonstrate that the effect is widespread but under-appreciated in the literature. We conclude that artificially enhanced wetlands may be common even in regions with short histories of human settlement. Restoring them to their pre-human impact state may be difficult or even undesirable if we want to protect biodiversity and wetland ecosystem services.
- ItemLake Quaternary mega-lakes fed by the northern and southern river systems of central Australia: varying moisture sources and increased continental aridity(Elsevier Science BV, 2012-10-15) Cohen, TJ; Nanson, GC; Jansen, JD; Jones, BG; Jacobs, Z; Larsen, JR; May, JH; Treble, PC; Price, DM; Smith, AMOptically stimulated and thermoluminescence ages from relict shorelines, along with accelerator mass spectrometer C-14 ages from freshwater molluscs reveal a record of variable moisture sources supplied by northern and southern river systems to Lake Mega-frome in southern central Australia during the late Quaternary. Additional lacustrine, palynological and terrestrial proxies are used to reconstruct a record that extends back to 105 ka, confirming that Lakes Mega-frome and Mega-Eyre were joined to create the largest system of palaeolakes on the Australian continent as recently as 50-47 ka. The palaeohydrological record indicates a progressive shift to more arid conditions, with marked drying after 45 ka. Subsequently, lake Mega-Frome has filled independently at 33-31 ka and at the termination of the Last Glacial Maximum to volumes some 40 times those of today. Further sequentially declining filling episodes (to volumes 25-10 those of today) occurred immediately prior to the Younger Dryas stadial, in the mid Holocene and during the medieval climatic anomaly. Southern hemisphere summer insolation maxima are a poor predictor of palaeolake-filling episodes. An examination of multiple active moisture sources suggests that palaeolake phases were driven independently of insolation and at times by some combination of enhanced Southern Ocean circulation and strengthened tropical moisture sources. © 2012, Elsevier Ltd.
- ItemLand-atmosphere coupling during the last glacial maximum: an Australian perspective(International Union For Quaternary Research (INQUA), 2011-07-21) Larsen, JR; Nanson, GC; Cendón, DIThe last glacial climate experienced extreme variability, however during the peak of the glacial conditions, the last glacial maximum (LGM), many areas of the Southern Hemisphere do not appear to experience corresponding minima in temperature and precipitation. This presents a considerable conundrum for our understanding of glacial climates, and more specifically for the land-atmosphere energy balance. In an effort to gain further insight, we examine potential scenarios for the water budget on the Australian continent during the LGM, and compare these with a variety of direct and proxy evidence for temperature, evaporation, and precipitation. Current research suggests some areas of Australia were wetter than expected during the LGM, however many researchers have also suggested precipitation in most areas was lower than the present. Thus in order to rectify the water balance, lower global surface air temperatures have been used to infer correspondingly lower evaporation rates. We examine both the theoretical and the palaeoclimatic evidence for lower evaporation, and find that in many cases, the relationship between lower temperature and evaporation is not straightforward. If the global hydrological cycle was slowed by lower global temperatures, then reduced overall actual evaporation could potentially increase atmospheric capacity depending on the vapour pressure deficit. Furthermore, atmospheric demand strongly depends on whether the environment is water limited or energy limited, and since much of the Australian continent is water limited, we expect actual evaporation to be much more sensitive to other external forcings such as wind speed and solar irradiance than temperature. These results have significant implications for the continental water balance, and alterative scenarios for precipitation, runoff, evaporation, vegetation and atmospheric feedback are proposed.
- ItemLate quaternary aeolian and fluvial interactions on the Cooper Creek Fan and the association between linear and source-bordering dunes, Strzelecki Desert, Australia(Elsevier, 2010-02) Cohen, TJ; Nanson, GC; Larsen, JR; Jones, BG; Price, DM; Coleman, M; Pietsch, TJThe Innamincka Dome and associated low-gradient fan in the Strzelecki Desert is the product of Cenozoic crustal warping that has aided formation of an extensive array of palaeochannels, source-bordering transverse dunes and superimposed linear dunes. These dunes have impeded the course of Cooper Creek and provided a repository of evidence for Quaternary climate change as well as the interactive processes between transverse and linear dune formation. At Turra, Gidgealpa and sites nearby are extensive fluvial and aeolian sand bodies that date from marine isotope stages (MIS) 8–3 and the Last Glacial Maximum (LGM) and are now surrounded or buried by overbank mud. The sandy alluvium was deposited on the downstream slope of the dome by large channels transporting abundant bedload, subsequently blown northward to form transverse dunes from what were probably seasonally-exposed bars in a palaeo-Cooper system. Thermoluminescence (TL) and optically stimulated luminescence (OSL) ages demonstrate that the base of the dune complex is at least MIS 7 in age (~250 ka) but that it has been subsequently reworked by wind with additional sand blown from the river. Source-bordering dunes formed during a period of enhanced river flow and sand supply from ~120 to 100 ka, with another short episode of the same at ~85–80 ka and from ~68 to 53. The LGM was associated with enhanced flows and the supply of dune sediment, from 28 to 18 ka. Pronounced river flow and dune activity occurred in the early to mid Holocene, but there is no evidence of dunes being supplied from Cooper Creek since the LGM. The dunes forming the oldest basal sand units appear to be largely transverse in form and are aligned roughly parallel to adjacent east–west trending palaeochannels. Linear dunes have formed from and over these, and yield basal ages ranging from MIS 5 or MIS 4 but continuing to accrete and rework through to the Holocene. The study results in one of the few detailed chronological investigations of the interaction between transverse and linear dunes. It is apparent that long-distance sand transport has played no significant role in dune formation here for the linear dunes show no significant downwind decline in ages. Linear dunes appear to have accreted vertically from underlying transverse dunes. A wind-rift vertical accretion model with only minor lengthwise extension is the dominant mode of linear dune formation in this section of the Strzelecki Desert, the bulk of dune sediment being sourced from adjacent swales since the LGM. © 2010, Elsevier Ltd.
- ItemLate quaternary palaeoenvironmental change in the Australian drylands(Elsevier, 2013-08-15) Fitzsimmons, KE; Cohen, TJ; Hesse, PP; Jansen, JD; Nanson, GC; May, JH; Barrows, TT; Haberlah, D; Hilgers, A; Kelly, T; Larsen, JR; Lomax, J; Treble, PCIn this paper we synthesise existing palaeoenvironmental data from the arid and semi-arid interior of the Australian continent for the period 40–0 ka. Moisture is the predominant variable controlling environmental change in the arid zone. Landscapes in this region respond more noticeably to changes in precipitation than to temperature. Depending on their location, arid zone records broadly respond to tropical monsoon-influenced climate regimes, the temperate latitude westerly systems, or a combination of both. The timing and extent of relatively arid and humid phases vary across the continent, in particular between the westerly wind-controlled temperate latitudes, and the interior and north which are influenced by tropically sourced precipitation. Relatively humid phases in the Murray-Darling Basin on the semi-arid margins, which were characterised by large rivers most likely fed by snow melt, prevailed from 40 ka to the Last Glacial Maximum (LGM), and from the deglacial to the mid Holocene. By contrast, the Lake Eyre basin in central Australia remained relatively dry throughout the last 40 ka, with lake high stands at Lake Frome around 35–30 ka, and parts of the deglacial period and the mid-Holocene. The LGM was characterised by widespread relative aridity and colder conditions, as evidenced by extensive desert dune activity and dust transport, lake level fall, and reduced but episodic fluvial activity. The climate of the deglacial period was spatially divergent. The southern part of the continent experienced a brief humid phase around ∼17–15 ka, followed by increased dune activity around ∼14–10 ka. This contrasts with the post-LGM persistence of arid conditions in the north, associated with a lapsed monsoon and reflected in lake level lows and reduced fluvial activity, followed by intensification of the monsoon and increasingly effective precipitation from ∼14 ka. Palaeoenvironmental change during the Holocene was also spatially variable. The early to mid-Holocene was, however, generally characterised by moderately humid conditions, demonstrated by lake level rise, source-bordering dune activity, and speleothem growth, persisting at different times across the continent. Increasingly arid conditions developed into the late Holocene, particularly in the central arid zone. © 2012 Elsevier Ltd.
- ItemLowland river responses to intraplate tectonism and climate forcing quantified with luminescence and cosmogenic 10Be(Elesevier Science BV, 2013-03-15) Jansen, JD; Nanson, GC; Cohen, TJ; Fujioka, T; Fabel, D; Larsen, JR; Codilean, AT; Price, DM; Bowman, HH; May, JH; Gliganic, LAIntraplate tectonism has produced large-scale folding that steers regional drainage systems, such as the 1600 km-long Cooper Ck, en route to Australia's continental depocentre at Lake Eyre. We apply cosmogenic Be-10 exposure dating in bedrock, and luminescence dating in sediment, to quantify the erosional and depositional response of Cooper Ck where it incises the rising Innamincka Dome. The detachment of bedrock joint-blocks during extreme floods governs the minimum rate of incision (17.4 +/- 6.5 mm/ky) estimated using a numerical model of episodic erosion calibrated with our 10Be measurements. The last big-flood phase occurred no earlier than similar to 112-121 ka. Upstream of the Innamincka Dome long-term rates of alluvial deposition, partly reflecting synclinal-basin subsidence, are estimated from 47 luminescence dates in sediments accumulated since similar to 270 ka. Sequestration of sediment in subsiding basins such as these may account for the lack of Quaternary accumulation in Lake Eyre, and moreover suggests that notions of a single primary depocentre at base-level may poorly represent lowland, arid-zone rivers. Over the period similar to 75-55 ka Cooper Ck changed from a bedload-dominant, laterally-active meandering river to a muddy anabranching channel network up to 60 km wide. We propose that this shift in river pattern was a product of base-level rise linked with the slowly deforming syncline-anticline structure, coupled with a climate-forced reduction in discharge. The uniform valley slope along this subsiding alluvial and rising bedrock system represents an adjustment between the relative rates of deformation and the ability of greatly enhanced flows at times during the Quaternary to incise the rising anticline. Hence, tectonic and climate controls are balanced in the long term. © 2013, Elsevier Ltd.
- ItemRadiocarbon and geochemical constraints on shallow groundwater recharge in a large arid zone river, Cooper Creek, SW Queensland, Australia(Copernicus Publications, 2010-05-02) Larsen, JR; Cendón, DI; Nanson, GC; Jones, BIn the arid and semi-arid internally drained Lake Eyre Basin of central Australia, large mud dominated anabranching river systems transport monsoon derived floodwaters into the centre of the continent during the summer months, and subsequently spend much of the year under low to no flow conditions. Cooper Creek has the largest catchment in this basin, and in south west Queensland has a wide (20-60km) floodplain and multiple channel system. Enlarged channel segments, known as waterholes or billabongs, can retain water throughout much of the dry season, and their mud base can often be scoured during floods into the underlying sandy alluvium where the shallow groundwater table exists 3-5m below the base of the waterholes. Little is known of the groundwater recharge mechanisms in this ecologically important and hydrologically unregulated river system, thus a number of piezometer transects were construct across the floodplain between two waterholes to investigate groundwater recharge processes in further detail. Samples recovered from all piezometers were analysed for major-trace element, water stable isotopes (δ2H and δ180), 3H and 14C. Water stable isotopes reveal shallow groundwater is recharged by high magnitude, low frequency monsoonal flood events, with minor evaporative enrichment probably linked to recent smaller flooding events. 14C dating of dissolved inorganic carbon reveals recharge is most effective beneath the deepest channel segments of the waterholes, and that residence time of the shallow groundwater increases with distance from major waterholes, with the post 1950’s 14C bomb pulse signature present only in close proximity to the channels. 3H allows further refinement of the shallow groundwater residence times, with no 3H detected in groundwater over ~500m from the waterholes, indicating groundwater recharge is slow and restricted to major flooding events. The increase in groundwater residence time with distance from waterholes, is also accompanied by an abrupt increase in salinity, and suggests recent recharge has formed local freshwater lenses above the regional, more saline groundwater. This increase in salinity with increasing distance from the waterholes is not accompanied by an increase on the evaporative signal of water stable isotopes, suggesting evapotranspiration is the dominant mechanism of salinisation within the shallow groundwater beneath the floodplains and minor channels. This study demonstrates that detailed chemical analysis of groundwaters from arid and semi arid areas can provide a useful estimate of recharge where the remote location makes traditional detailed borehole monitoring difficult or impossible to achieve.
- ItemShallow groundwater recharge and residence time in two separate flood plains along an aridity gradient in South Queensland, Australia(National Centre for Groundwater Research And Training, 2015-11-03) Cendón, DI; Kelly, BFJ; Larsen, JR; Hankin, SI; Hughes, CE; Meredith, KT; Hollins, SE; Iverach, CPFertile floodplains in headwater Darling-Murray catchments like the Condamine have endured profound physiographic changes over the last ~150 years, including the onset of intensive agriculture and groundwater abstraction since the 1960s. This has placed groundwater within alluvial aquifers under stress, raising allocation concerns and triggering salinity problems in some areas. Approximately 1,000 km west, across a decreasing rainfall gradient (659 mm/yr at Dalby to 198 mm/yr at Ballera), the Cooper Ck floodplain (near Ballera) is still in pristine condition and provides an ideal example of arid zone hydrological processes. This study compares groundwater from two alluvial systems with an emphasis on understanding groundwater recharge processes under various climatic conditions. Groundwater was collected from the Condamine alluvium in 2014 from 30 irrigation and monitoring wells. Groundwater was collected from the Cooper Ck alluvium between 2008 and 2011, from piezometers installed along a transect between major waterholes. All bores were sampled for major, minor/trace elements, water stable isotopes (δ18O and δ2H), δ13C in dissolved inorganic carbon, 3H, 14C and sulfate isotopes (δ34S δ18O) in selected samples for both study areas. The groundwater dataset was complemented with available long term rainfall data. Both locations showed that groundwater had depleted isotopic signatures consistent with recharge associated with large floods. Also in both locations groundwater defined well-correlated evaporation lines (R2>0.95), consistent with mixing with other sources. Groundwater near main channels contained 3H and 14C consistent with modern recharge, however, in the Cooper Ck modern recharge appeared restricted to areas like channel confluences. This study has implications for understanding how to sustainably use groundwater resources and the role of floods in recharging floodplain aquifers. Comparing the two sites provides a snapshot of how the Condamine could respond to increased aridity.
- ItemSurface and groundwater hydrology of arid-zone billabongs (waterholes) in Queensland, Australia(International Association of Geomorphologists, 2009-07-06) Larsen, JR; Cendón, DI; Nanson, GC; Jones, BGNot available
- ItemTowards a physical description of habitat: quantifying environmental adversity (abiotic stress) in temperate forest and woodland ecosystems(Wiley-Blackwell, 2009-09) Ladd, B; Bonser, SP; Peri, PL; Larsen, JR; Laffan, SW; Pepper, DA; Cendón, DI1. Our aim was to develop a quantitative proxy for environmental adversity (abiotic stress) in temperate Eucalyptus and Nothofagus forest and woodland ecosystems. 2. Samples and measurements were collected at 42 sites across a rainfall gradient in southern Australia, an elevation gradient in south-eastern Australia, and a longitudinal transect (temperature gradient) in Patagonia, Argentina. 3. We compared the ability of (a) abiotic variables (14 soil and 21 climatic variables) and (b) the stable carbon isotope (δ13C) values of soil organic matter (SOM), to predict variation in leaf area index (LAI; a forest productivity variable). 4. The δ13C of SOM (soil aggregates) explained more variation (57%) in LAI than multivariate statistical models that integrated information on many abiotic variables. W* (a climatic water balance model) was also a powerful predictor variable, explaining 37% of the variability in LAI. 5. Synthesis. The stable carbon isotopic signature of soil aggregates is a powerful explanatory variable that may help us to quantify environmental adversity (abiotic stress) in temperate forest and woodland ecosystems. © 2009, Wiley-Blackwell. The definitive version is available at www3.interscience.wiley.com