School of Agriculture, Food and Ecosystem Sciences - Research Publications

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    Can we integrate ecological approaches to improve plant selection for green infrastructure?
    Farrell, C ; Livesley, SJ ; Arndt, SK ; Beaumont, L ; Burley, H ; Ellsworth, D ; Esperon-Rodriguez, M ; Fletcher, TD ; Gallagher, R ; Ossola, A ; Power, SA ; Marchin, R ; Rayner, JP ; Rymer, PD ; Staas, L ; Szota, C ; Williams, NSG ; Leishman, M (ELSEVIER GMBH, 2022-10)
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    Selecting tree species with high transpiration and drought avoidance to optimise runoff reduction in passive irrigation systems
    Thom, JK ; Livesley, SJ ; Fletcher, TD ; Farrell, C ; Arndt, SK ; Konarska, J ; Szota, C (ELSEVIER, 2022-03-15)
    Rainfall in cities can generate large volumes of stormwater runoff which degrades receiving waterways. Irrigating trees with runoff (passive irrigation) has the potential to increase transpiration and contribute to stormwater management by reducing runoff received by downstream waterways, but the stochastic nature of rainfall may expose trees with high transpiration to drought stress. We hypothesized that for success in passive irrigation systems, tree species should exhibit i) high maximum transpiration rates under well-watered conditions, ii) drought avoidance between rainfall events, and iii) high recovery of transpiration with rainfall following a drought. We assessed 13 commonly planted urban tree species in Melbourne, Australia against three metrics representing these behaviours (crop factor, hydroscape area, and transpiration recovery, respectively) in a glasshouse experiment. To aid species selection, we also investigated the relationships between these three metrics and commonly measured plant traits, including leaf turgor loss point, wood density, and sapwood to leaf area ratio (Huber value). Only one species (Tristaniopsis laurina) exhibited a combination of high crop factor (>1.1 mm mm-1 d-1) indicating high transpiration, small hydroscape area (<3 MPa2) indicating drought avoidance, and high transpiration recovery (>85%) following water deficit. Hence, of the species measured, it had the greatest potential to reduce runoff from passive irrigation systems while avoiding drought stress. Nevertheless, several other species showed moderate transpiration, hydroscape areas and transpiration recovery, indicating a balanced strategy likely suitable for passive irrigation systems. Huber values were negatively related to crop factor and transpiration recovery and may therefore be a useful tool to aid species selection. We propose that selecting tree species with high transpiration rates that can avoid drought and recover well could greatly reduce stormwater runoff, while supporting broader environmental benefits such as urban cooling in cities.
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    Termite mounds mitigate half of termite methane emissions (vol 115, pg 13306, 2018)
    Nauer, PA ; Hutley, LB ; Arndt, SK (NATL ACAD SCIENCES, 2022-04-12)
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    Tree water-use strategies to improve stormwater retention performance of biofiltration systems
    Szota, C ; McCarthy, MJ ; Sanders, GJ ; Farrell, C ; Fletcher, TD ; Arndt, SK ; Livesley, SJ (PERGAMON-ELSEVIER SCIENCE LTD, 2018-11-01)
    Biofiltration systems are highly valued in urban landscapes as they remove pollutants from stormwater runoff whilst contributing to a reduction in runoff volumes. Integrating trees in biofilters may improve their runoff retention performance, as trees have greater transpiration than commonly used sedge or herb species. High transpiration rates will rapidly deplete retained water, creating storage capacity prior to the next runoff event. However, a tree with high transpiration rates in a biofilter system will likely be frequently exposed to drought stress. Selecting appropriate tree species therefore requires an understanding of how different trees use water and how they respond to substrate drying. We selected 20 tree species and quantified evapotranspiration (ET) and drought stress (leaf water potential; Ψ) in relation to substrate water content. To compare species, we developed metrics which describe: (i) maximum rates of ET under well-watered conditions, (ii) the sensitivity of ET and (iii) the response of Ψ to declining substrate water content. Using these three metrics, we classified species into three groups: risky, balanced or conservative. Risky and balanced species showed high maximum ET, whereas conservative species always had low ET. As substrates dried, the balanced species down-regulated ET to delay the onset of drought stress; whereas risky species did not. Therefore, balanced species with high ET are more likely to improve the retention performance of biofiltration systems without introducing significant drought risk. This classification of tree water use strategies can be easily integrated into water balance models and improve tree species selection for biofiltration systems.
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    Bridge to the future: Important lessons from 20 years of ecosystem observations made by the OzFlux network
    Beringer, J ; Moore, CE ; Cleverly, J ; Campbell, D ; Cleugh, H ; De Kauwe, MG ; Kirschbaum, MUF ; Griebel, A ; Grover, S ; Huete, A ; Hutley, LB ; Laubach, J ; Van Niel, T ; Arndt, SK ; Bennett, AC ; Cernusak, LA ; Eamus, D ; Ewenz, CM ; Goodrich, JP ; Jiang, M ; Hinko-Najera, N ; Isaac, P ; Hobeichi, S ; Knauer, J ; Koerber, GR ; Liddell, M ; Ma, X ; Macfarlane, C ; McHugh, ID ; Medlyn, BE ; Meyer, WS ; Norton, AJ ; Owens, J ; Pitman, A ; Pendall, E ; Prober, SM ; Ray, RL ; Restrepo-Coupe, N ; Rifai, SW ; Rowlings, D ; Schipper, L ; Silberstein, RP ; Teckentrup, L ; Thompson, SE ; Ukkola, AM ; Wall, A ; Wang, Y-P ; Wardlaw, TJ ; Woodgate, W (WILEY, 2022-06)
    In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those 'next users' of the knowledge, information and data that such networks provide. Here, we focus on eight lessons across topics of climate change and variability, disturbance and resilience, drought and heat stress and synergies with remote sensing and modelling. In distilling the key lessons learned, we also identify where further research is needed to fill knowledge gaps and improve the utility and relevance of the outputs from OzFlux. Extreme climate variability across Australia and New Zealand (droughts and flooding rains) provides a natural laboratory for a global understanding of ecosystems in this time of accelerating climate change. As evidence of worsening global fire risk emerges, the natural ability of these ecosystems to recover from disturbances, such as fire and cyclones, provides lessons on adaptation and resilience to disturbance. Drought and heatwaves are common occurrences across large parts of the region and can tip an ecosystem's carbon budget from a net CO2 sink to a net CO2 source. Despite such responses to stress, ecosystems at OzFlux sites show their resilience to climate variability by rapidly pivoting back to a strong carbon sink upon the return of favourable conditions. Located in under-represented areas, OzFlux data have the potential for reducing uncertainties in global remote sensing products, and these data provide several opportunities to develop new theories and improve our ecosystem models. The accumulated impacts of these lessons over the last 20 years highlights the value of long-term flux observations for natural and managed systems. A future vision for OzFlux includes ongoing and newly developed synergies with ecophysiologists, ecologists, geologists, remote sensors and modellers.
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    Riparian trees resprout regardless of timing and severity of disturbance by coppicing
    Fischer, S ; Greet, J ; Walsh, CJ ; Catford, JA ; Arndt, SK (ELSEVIER, 2022-03-01)
    Human modification of waterways has reduced flooding in many river systems, leading to the decline of riparian forests, which rely on flooding for their regeneration. Coppicing may help to promote the persistence of riparian trees by triggering resprouting and vegetative regeneration. The vigour of resprouting plants can vary with timing and height of coppicing and may depend on stored non-structural carbohydrate reserves like starch, the availability of which can vary seasonally. However, starch storage dynamics and the resprouting potential of broad-leafed evergreen riparian trees is not well understood. We coppiced two riparian tree species, Eucalyptus camphora and Melaleuca squarrosa, at two different times (autumn, spring) and at two different heights (0 cm and 90 cm). Over 52 weeks, we regularly quantified shoot growth and changes in the starch storage pool size, compared to uncoppiced control trees, in different tree organs (root and stem) and estimated the final shoot volume. The final shoot volume did not differ significantly between coppice treatments. Trees coppiced in autumn had a greater reliance on stored starch while they remained leafless (without shoots) over winter. Trees cut at 90 cm had more starch reserves due to remaining stems but also had higher biomass maintenance costs. Starch storage varied seasonally only in E. camphora, with starch concentrations in control trees increasing over winter and decreasing over summer. Although coppice timing and height affected use of stored starch, resprouting in our study species was not limited by starch availability - both species regenerated vegetatively to recover from physical disturbance. Thus, coppicing may be an efficient means to promote rejuvenation and persistence of tree species where site and tree condition are degraded and no longer support recruitment.
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    AusTraits, a curated plant trait database for the Australian flora
    Falster, D ; Gallagher, R ; Wenk, EH ; Wright, IJ ; Indiarto, D ; Andrew, SC ; Baxter, C ; Lawson, J ; Allen, S ; Fuchs, A ; Monro, A ; Kar, F ; Adams, MA ; Ahrens, CW ; Alfonzetti, M ; Angevin, T ; Apgaua, DMG ; Arndt, S ; Atkin, OK ; Atkinson, J ; Auld, T ; Baker, A ; von Balthazar, M ; Bean, A ; Blackman, CJ ; Bloomfeld, K ; Bowman, DMJS ; Bragg, J ; Brodribb, TJ ; Buckton, G ; Burrows, G ; Caldwell, E ; Camac, J ; Carpenter, R ; Catford, J ; Cawthray, GR ; Cernusak, LA ; Chandler, G ; Chapman, AR ; Cheal, D ; Cheesman, AW ; Chen, S-C ; Choat, B ; Clinton, B ; Clode, PL ; Coleman, H ; Cornwell, WK ; Cosgrove, M ; Crisp, M ; Cross, E ; Crous, KY ; Cunningham, S ; Curran, T ; Curtis, E ; Daws, M ; DeGabriel, JL ; Denton, MD ; Dong, N ; Du, P ; Duan, H ; Duncan, DH ; Duncan, RP ; Duretto, M ; Dwyer, JM ; Edwards, C ; Esperon-Rodriguez, M ; Evans, JR ; Everingham, SE ; Farrell, C ; Firn, J ; Fonseca, CR ; French, BJ ; Frood, D ; Funk, JL ; Geange, SR ; Ghannoum, O ; Gleason, SM ; Gosper, CR ; Gray, E ; Groom, PK ; Grootemaat, S ; Gross, C ; Guerin, G ; Guja, L ; Hahs, AK ; Harrison, MT ; Hayes, PE ; Henery, M ; Hochuli, D ; Howell, J ; Huang, G ; Hughes, L ; Huisman, J ; Ilic, J ; Jagdish, A ; Jin, D ; Jordan, G ; Jurado, E ; Kanowski, J ; Kasel, S ; Kellermann, J ; Kenny, B ; Kohout, M ; Kooyman, RM ; Kotowska, MM ; Lai, HR ; Laliberte, E ; Lambers, H ; Lamont, BB ; Lanfear, R ; van Langevelde, F ; Laughlin, DC ; Laugier-kitchener, B-A ; Laurance, S ; Lehmann, CER ; Leigh, A ; Leishman, MR ; Lenz, T ; Lepschi, B ; Lewis, JD ; Lim, F ; Liu, U ; Lord, J ; Lusk, CH ; Macinnis-Ng, C ; McPherson, H ; Magallon, S ; Manea, A ; Lopez-Martinez, A ; Mayfeld, M ; McCarthy, JK ; Meers, T ; van der Merwe, M ; Metcalfe, DJ ; Milberg, P ; Mokany, K ; Moles, AT ; Moore, BD ; Moore, N ; Morgan, JW ; Morris, W ; Muir, A ; Munroe, S ; Nicholson, A ; Nicolle, D ; Nicotra, AB ; Niinemets, U ; North, T ; O'Reilly-Nugent, A ; O'Sullivan, OS ; Oberle, B ; Onoda, Y ; Ooi, MKJ ; Osborne, CP ; Paczkowska, G ; Pekin, B ; Pereira, CG ; Pickering, C ; Pickup, M ; Pollock, LJ ; Poot, P ; Powell, JR ; Power, S ; Prentice, IC ; Prior, L ; Prober, SM ; Read, J ; Reynolds, V ; Richards, AE ; Richardson, B ; Roderick, ML ; Rosell, JA ; Rossetto, M ; Rye, B ; Rymer, PD ; Sams, M ; Sanson, G ; Sauquet, H ; Schmidt, S ; Schoenenberger, J ; Schulze, E-D ; Sendall, K ; Sinclair, S ; Smith, B ; Smith, R ; Soper, F ; Sparrow, B ; Standish, RJ ; Staples, TL ; Stephens, R ; Szota, C ; Taseski, G ; Tasker, E ; Thomas, F ; Tissue, DT ; Tjoelker, MG ; Tng, DYP ; de Tombeur, F ; Tomlinson, K ; Turner, NC ; Veneklaas, EJ ; Venn, S ; Vesk, P ; Vlasveld, C ; Vorontsova, MS ; Warren, CA ; Warwick, N ; Weerasinghe, LK ; Wells, J ; Westoby, M ; White, M ; Williams, NSG ; Wills, J ; Wilson, PG ; Yates, C ; Zanne, AE ; Zemunik, G ; Zieminska, K (NATURE PORTFOLIO, 2021-09-30)
    We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge.
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    Concurrent Measurements of Soil and Ecosystem Respiration in a Mature Eucalypt Woodland: Advantages, Lessons, and Questions
    Renchon, AA ; Drake, JE ; Macdonald, CA ; Sihi, D ; Hinko-Najera, N ; Tjoelker, MG ; Arndt, SK ; Noh, NJ ; Davidson, E ; Pendall, E (AMER GEOPHYSICAL UNION, 2021-03)
    Abstract Understanding seasonal and diurnal dynamics of ecosystem respiration (Reco) in forests is challenging, because Reco can only be measured directly during night‐time by eddy‐covariance flux towers. Reco is the sum of soil respiration (Rsoil) and above‐ground respiration (in theory, RAG = Reco − Rsoil). Rsoil can be measured day and night and can provide a check of consistency on Reco, as the difference in magnitude and time dynamic between Reco and Rsoil should be explained by RAG. We assessed the temporal patterns and climatic drivers of Rsoil and Reco in a mature eucalypt woodland, using continuous measurements (only at night for Reco) at half‐hourly resolution over 4 years (2014–2017). Our data showed large seasonal and diurnal (overnight) variation of Reco, while Rsoil had a low diurnal amplitude and their difference (Reco − Rsoil, or RAG) had a low seasonal amplitude. This result implies at first glance that seasonal variation of Reco was mainly influenced by Rsoil while its diurnal variation was mainly influenced by RAG. However, our analysis suggests that the night‐time Reco decline cannot realistically be explained by a decline of RAG. Chamber measurements of autotrophic components at half‐hourly time resolution are needed to quantify how much of the Reco decline overnight is due to declines in leaf or stem respiration, and how much is due to missing storage or advection, which may create a systematic bias in Reco measurements. Our findings emphasize the need for reconciling bottom‐up (via components measured with chambers) and direct estimates of Reco (via eddy‐covariance method).
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    Does the turgor loss point characterize drought response in dryland plants?
    Farrell, C ; Szota, C ; Arndt, SK (WILEY, 2017-08)
    The water potential at turgor loss point (Ψtlp ) has been suggested as a key functional trait for determining plant drought tolerance, because of its close relationship with stomatal closure. Ψtlp may indicate drought tolerance as plants, which maintain gas exchange at lower midday water potentials as soil water availability declines also have lower Ψtlp . We evaluated 17 species from seasonally dry habitats, representing a range of life-forms, under well-watered and drought conditions, to determine how Ψtlp relates to stomatal sensitivity (pre-dawn water potential at stomatal closure: Ψgs0 ) and drought strategy (degree of isohydry or anisohydry; ΔΨMD between well-watered conditions and stomatal closure). Although Ψgs0 was related to Ψtlp , Ψgs0 was better related to drought strategy (ΔΨMD ). Drought avoiders (isohydric) closed stomata at water potentials higher than their Ψtlp ; whereas, drought tolerant (anisohydric) species maintained stomatal conductance at lower water potentials than their Ψtlp and were more dehydration tolerant. There was no significant relationship between Ψtlp and ΔΨMD . While Ψtlp has been related to biome water availability, we found that Ψtlp did not relate strongly to stomatal closure or drought strategy, for either drought avoiders or tolerators. We therefore suggest caution in using Ψtlp to predict vulnerability to drought.
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    Stable isotopes in leaf water of terrestrial plants
    Cernusak, LA ; Barbour, MM ; Arndt, SK ; Cheesman, AW ; English, NB ; Feild, TS ; Helliker, BR ; Holloway-Phillips, MM ; Holtum, JAM ; Kahmen, A ; McInerney, FA ; Munksgaard, NC ; Simonin, KA ; Song, X ; Stuart-Williams, H ; West, JB ; Farquhar, GD (WILEY, 2016-05)
    Leaf water contains naturally occurring stable isotopes of oxygen and hydrogen in abundances that vary spatially and temporally. When sufficiently understood, these can be harnessed for a wide range of applications. Here, we review the current state of knowledge of stable isotope enrichment of leaf water, and its relevance for isotopic signals incorporated into plant organic matter and atmospheric gases. Models describing evaporative enrichment of leaf water have become increasingly complex over time, reflecting enhanced spatial and temporal resolution. We recommend that practitioners choose a model with a level of complexity suited to their application, and provide guidance. At the same time, there exists some lingering uncertainty about the biophysical processes relevant to patterns of isotopic enrichment in leaf water. An important goal for future research is to link observed variations in isotopic composition to specific anatomical and physiological features of leaves that reflect differences in hydraulic design. New measurement techniques are developing rapidly, enabling determinations of both transpired and leaf water δ(18) O and δ(2) H to be made more easily and at higher temporal resolution than previously possible. We expect these technological advances to spur new developments in our understanding of patterns of stable isotope fractionation in leaf water.