School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemNo Preview AvailableCan we integrate ecological approaches to improve plant selection for green infrastructure?(ELSEVIER GMBH, 2022-10)
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ItemNo Preview AvailableSelecting tree species with high transpiration and drought avoidance to optimise runoff reduction in passive irrigation systems(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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ItemNo Preview AvailableInfluence of water storage and plant crop factor on green roof retention and plant drought stress(Public Library of Science (PLoS), 2022-03-02)Green roofs can reduce stormwater runoff with deeper substrates providing greater storage for water retention and evapotranspiration (ET) regenerating storage capacity between rainfall events. In green roof models, ET can be estimated using species-specific plant crop factors (Kc), which characterize water use under non-limiting conditions. We manipulated Kc by altering plant density in a glasshouse experiment under well-watered conditions. We determined Kc of green roof plants growing in pots with different substrate depths (150 mm and 300 mm) and plant densities (0, 1, 2 and 4 plants per pot). We then analyzed the influence of storage and Kc on retention and drought stress using a water-balance model, with a 30-year climate scenario for Melbourne, Australia. We hypothesized that greater planting density and substrate depth would result in proportionally greater ET and therefore higher Kc (glasshouse experiment) and that this would improve retention and reduce drought stress (rainfall simulation). Contrary to our hypotheses, cumulative ET increased by only 38–48% with increased substrate depth and by only 28–38% with increased plant density, despite large increases in plant biomass (67–150%) and growth. Kc values ranged from 1.9–2.2 and 2.7–3.8 for shallower and deeper substrates, respectively. Due to these very high crop factors, our water balance model showed very high annual rainfall retention (97.5%). However, higher Kc and storage only increased rainfall retention by 3–5% and resulted greater drought stress. Plants in deeper substrates experienced 14–29 more days of drought stress, as these plants depleted substrate moisture more efficiently (i.e., had a higher Kc) compared with shallow substrates. These findings suggest that improvements in rainfall retention for green roofs with deeper substrates or higher plant densities are small relative to the increased risk of plant drought stress. The lowest planting density was optimal for improving rainfall retention and reducing plant drought stress.
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ItemAusTraits, a curated plant trait database for the Australian flora(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.