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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    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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    Trading Water for Carbon: Maintaining Photosynthesis at the Cost of Increased Water Loss During High Temperatures in a Temperate Forest
    Griebel, A ; Bennett, LT ; Metzen, D ; Pendall, E ; Lane, PNJ ; Arndt, SK (American Geophysical Union, 2020-01-01)
    Carbon and water fluxes are often assumed to be coupled as a result of stomatal regulation during dry conditions. However, recent observations evidenced increased transpiration rates during isolated heatwaves across a range of eucalypt species under experimental and natural conditions, with inconsistent effects on photosynthesis (ranging from increases to stark declines). To improve the empirical basis for understanding carbon and water fluxes in forests under hotter and drier climates, we measured the water use of dominant trees and ecosystem‐scale carbon and water exchange in a temperate eucalypt forest over three summer seasons. The forest maintained photosynthesis within 16% of baseline rates during hot and dry conditions, despite ~70% reductions in canopy conductance during a 5‐day heatwave. While carbon and water fluxes both decreased by 16% on exceptionally dry days, gross primary productivity only decreased by 5% during the hottest days and increased by 2% during the heatwave. However, evapotranspiration increased by 43% (hottest days) and 74% (heatwave), leading to ~40% variation in traditional water use efficiency (water use efficiency = gross primary productivity/evapotranspiration) across conditions and approximately two‐fold differences between traditional and underlying or intrinsic water use efficiency on the same days. Furthermore, the forest became a net source of carbon following a 137% increase in ecosystem respiration during the heatwave, highlighting that the potential for temperate eucalypt forests to act as net carbon sinks under hotter and drier climates will depend not only on the responses of photosynthesis to higher temperatures and changes in water availability, but also on the concomitant responses of ecosystem respiration.
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    Exploring the Potential of DSCOVR EPIC Data to Retrieve Clumping Index in Australian Terrestrial Ecosystem Research Network Observing Sites
    Pisek, J ; Arndt, SK ; Erb, A ; Pendall, E ; Schaaf, C ; Wardlaw, TJ ; Woodgate, W ; Knyazikhin, Y (FRONTIERS MEDIA SA, 2021-03-16)
    Vegetation foliage clumping significantly alters the radiation environment and affects vegetation growth as well as water, carbon cycles. The clumping index (CI) is useful in ecological and meteorological models because it provides new structural information in addition to the effective leaf area index. Previously generated CI maps using a diverse set of Earth Observation multi-angle datasets across a wide range of scales have all relied on the single approach of using the normalized difference hotspot and darkspot (NDHD) method. We explore an alternative approach to estimate CI from space using the unique observing configuration of the Deep Space Climate Observatory Earth Polychromatic Imaging Camera (DSCOVR EPIC) and associated products at 10 km resolution. The performance was evaluated with in situ measurements in five sites of the Australian Terrestrial Ecosystem Research Network comprising a diverse range of canopy structure from short and sparse to dense and tall forest. The DSCOVR EPIC data can provide meaningful CI retrievals at the given spatial resolution. Independent but comparable CI retrievals obtained with a completely different sensor and new approach were encouraging for the general validity and compatibility of the foliage clumping information retrievals from space. We also assessed the spatial representativeness of the five TERN sites with respect to a particular point in time (field campaigns) for satellite retrieval validation. Our results improve our understanding of product uncertainty both in terms of the representativeness of the field data collected over the TERN sites and its relationship to Earth Observation data at different spatial resolutions.
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    Bark-dwelling methanotrophic bacteria decrease methane emissions from trees
    Jeffrey, LC ; Maher, DT ; Chiri, E ; Leung, PM ; Nauer, PA ; Arndt, SK ; Tait, DR ; Greening, C ; Johnston, SG (NATURE PORTFOLIO, 2021-04-09)
    Tree stems are an important and unconstrained source of methane, yet it is uncertain whether internal microbial controls (i.e. methanotrophy) within tree bark may reduce methane emissions. Here we demonstrate that unique microbial communities dominated by methane-oxidising bacteria (MOB) dwell within bark of Melaleuca quinquenervia, a common, invasive and globally distributed lowland species. In laboratory incubations, methane-inoculated M. quinquenervia bark mediated methane consumption (up to 96.3 µmol m-2 bark d-1) and reveal distinct isotopic δ13C-CH4 enrichment characteristic of MOB. Molecular analysis indicates unique microbial communities reside within the bark, with MOB primarily from the genus Methylomonas comprising up to 25 % of the total microbial community. Methanotroph abundance was linearly correlated to methane uptake rates (R2 = 0.76, p = 0.006). Finally, field-based methane oxidation inhibition experiments demonstrate that bark-dwelling MOB reduce methane emissions by 36 ± 5 %. These multiple complementary lines of evidence indicate that bark-dwelling MOB represent a potentially significant methane sink, and an important frontier for further research.