Claire Farrell

Can the turgor loss point be used to assess drought response to select plants for green roofs in hot and dry climates?

Publisher: Springer Science and Business Media LLC

Date: 25-05-2019

DOI: 10.1007/S11104-019-04133-7

Biochar makes green roof substrates lighter and improves water supply to plants

Publisher: Elsevier BV

Date: 10-2014

DOI: 10.1016/J.ECOLENG.2014.06.017

Response of Spontaneous Plant Communities to Sedum mexicanum Cover and Water Availability in Green Roof Microcosms

Publisher: MDPI AG

Date: 16-06-2023

DOI: 10.3390/LAND12061239

Abstract: Lack of maintenance can lead to ‘weedy’ spontaneous vegetation on green roofs. Aspects of green roof design, including substrate depth and roof height, have been shown to influence the composition of spontaneous vegetation. In drier climates, Sedum species are often planted on shallow substrate ‘extensive’ green roofs and irrigated during summer to maintain cover. However, the response of spontaneous vegetation to Sedum cover and water availability is unclear. Understanding this relationship could help minimise maintenance and maintain Sedum vegetation cover. We hypothesised that increasing Sedum (Sedum mexicanum) cover and reduced water availability would reduce the abundance, biomass, species and functional richness, and the community weighted mean specific leaf area (SLA CWM by abundance) of spontaneous plant communities. We conducted a 10-month experiment in green roof microcosms planted with S. mexicanum (0%, 25%, 50%, 75% and 100% total cover), subjected to a well-watered or water-deficit irrigation treatment, and sown with a mix of 14 plant species that commonly occur as spontaneous on green roofs. We measured spontaneous species abundance, community biomass, and functional traits (specific leaf area, leaf dry matter content, and relative growth rate), and calculated species and functional richness. Increasing S. mexicanum cover reduced spontaneous species abundance and species and functional richness but did not affect community biomass. Species richness was affected by the interaction of S. mexicanum cover and watering treatment and was greatest in well-watered microcosms with 0% S. mexicanum cover. Increased water availability increased spontaneous plant biomass but did not affect functional richness. The SLA of spontaneous communities was affected by the interaction of S. mexicanum cover and watering and was significantly greater in well-watered treatments where S. mexicanum cover was %. Therefore, maximising Sedum cover and limiting water availability on green roofs will likely limit the abundance, biomass, and ersity of spontaneous vegetation. Conversely, for green roofs where substrate is left to be naturally colonised, increasing water availability could encourage establishment and increase functional richness of spontaneous vegetation.

Green roof substrate physical properties differ between standard laboratory tests due to differences in compaction

Publisher: Elsevier BV

Date: 05-2020

DOI: 10.1016/J.JENVMAN.2020.110206

Ten years of greening a wide brown land: A synthesis of Australian green roof research and roadmap forward

Publisher: Elsevier BV

Date: 07-2021

DOI: 10.1016/J.UFUG.2021.127179

Green roof storage capacity can be more important than evapotranspiration for retention performance

Publisher: Elsevier BV

Date: 02-2019

DOI: 10.1016/J.JENVMAN.2018.11.070

Abstract: Green roofs can significantly reduce stormwater runoff volumes. Plant selection is crucial to retention performance, as it is influenced by how well plants dry out substrates between rainfall events. While the role of plants in evapotranspiration (ET) on green roofs is well-studied, their potential influence on retention via their impacts on water movement through substrates is poorly understood. We used a simulated rainfall experiment with plant species with different water use strategies to determine the key drivers of green roof retention performance. Overall per-event retention was very high (89-95%) and similar for all plant species and unplanted modules for small events. However, for larger events, some species showed lower retention than unplanted modules or low-water using succulent species. Despite the fact that these species were more effective at replenishing storage between rainfall events due to their higher ET, they reduced the maximum storage capacity of the substrate, likely due to their root systems creating preferential flow paths. This finding has important implications for green roofs, as although ET represents the primary means by which the storage capacity of green roofs can be regenerated, if species with high ET also reduce the maximum storage capacity, effective retention performance is reduced. Therefore, we suggest that species selection must first focus on how plants affect storage capacity in the first instance and consider water use strategies as a secondary objective.

Biochar made from low density wood has greater plant available water than biochar made from high density wood

Publisher: Elsevier BV

Date: 02-2020

DOI: 10.1016/J.SCITOTENV.2019.135856

Abstract: Soil water limitations often restrict plant growth in unirrigated agricultural, forestry and urban systems. Biochar amendment to soils can increase water retention, but not all of this additional water is necessarily available to plants. Differences in the effectiveness of biochar in ameliorating soil water limitations may be a result of differences in feedstock cell structure. Previous research has shown that feedstock cell structure influences the pore structure of biochar and consequently the volume available for water storage. The availability of this water for plant uptake will be determined by biochar pore diameters, given its role in determining capillary forces which plants must overcome to access pore water. Therefore, we hypothesized that differences in hardwood feedstock cell structure would result in differences in the plant available water holding capacity of biochar. Before pyrolysis, we measured the wood morphology of 18 Eucalyptus species on three replicates of equal age on a gradient of wood density (572-960 kg m

Fast plants have water-use and drought strategies that balance rainfall retention and drought survival on green roofs.

Publisher: Wiley

Date: 09-12-2022

DOI: 10.1002/EAP.2486

Abstract: Green roofs can improve ecosystem services in cities however, this depends on appropriate plant selection. For stormwater management, plants should have high water use to maximize retention and also survive dry periods. Plants adapted to wetter habitats develop "fast" traits for growth, whereas plants from drier habitats develop "slow" traits to conserve water use and survive drought. Therefore, we hypothesized that (1) plants with fast traits would have greater water use, (2) plants with slow traits would have greater drought tolerance, (3) fast-slow traits would be consistent across the plant, and (4) fast plants with greater water use could avoid drought stress. We evaluated 14 green roof species in a glasshouse experiment under well-watered (WW) and water-deficit (WD) conditions to determine relationships between fast-slow traits, water use, and drought resistance. Traits measured were shoot dry mass, specific leaf area (SLA), root mass fraction (RMF), and specific root length (SRL). Daily evapotranspiration per shoot dry mass was used to describe water use. Drought resistance was represented by (1) days to stomatal closure (2) cumulative ET before stomatal closure and (3) degree of iso-anisohydry (difference between midday leaf water potential (Ψ

Relationships between plant drought response, traits, and climate of origin for green roof plant selection

Publisher: Wiley

Date: 30-08-2018

DOI: 10.1002/EAP.1782

Abstract: The ideal species for green or vegetated roofs should have high water use after rainfall to maximize stormwater retention but also survive periods with low water availability in dry substrates. Shrubs have great potential for green roofs because they have higher rates of water use, and many species are also drought tolerant. However, not all shrub species will be suitable and there may be a trade-off between water use and drought tolerance. We conducted a glasshouse experiment to determine the possible trade-offs between shrub water use for stormwater management and their response to drought conditions. We selected 20 shrubs from a wide range of climates of origin, represented by heat moisture index (HMI) and mean annual precipitation (MAP). Under well-watered (WW) and water-deficit (WD) conditions, we assessed morphological responses to water availability evapotranspiration rate (ET) and midday water potential (Ψ

Biochar and compost equally improve urban soil physical and biological properties and tree growth, with no added benefit in combination

Publisher: Elsevier BV

Date: 03-2020

DOI: 10.1016/J.SCITOTENV.2019.135736

Abstract: Soil compaction can be a major impediment to tree growth as it damages soil physical and biological properties and reduces plant available water. This may result in trees that are more vulnerable to seasonal water stress. Improving soil physical and biological properties by increasing soil organic matter content may lead to improved tree establishment. Organic matter (OM), in the form of municipal green waste compost (MGWC) or biochar was incorporated into compacted urban soils at two sites. We established six soil treatments: 1) unamended, 2) tillage only, 3) tillage with MGWC (20% v/v), 4) tillage with biochar (10% v/v), 5) tillage with MGWC + biochar (10% & 5% v/v - low), and 6) tillage with MGWC + biochar (20% & 10% v/v - high) (one site only). The treatments were established to a depth of 0.5 m in 2 × 2 m plots. One Corymbia maculata sapling was planted into each plot. Bulk density, hydraulic conductivity, stem diameter growth and tree water status were measured during tree establishment. At the end of the 30-month experiment, development of water stable aggregates, the rate of microbiological decomposition of OM, and tree size (diameter at breast height DBH, and canopy growth index) were measured. All OM amended treatments improved soil physical and biological properties. There were no significant differences among the OM treatments. At the end of the experiment, tree DBH and canopy growth index were greater in the OM treatments than tillage only and unamended. As such, we recommend using local and sustainable forms of OM to improve soils and assist tree establishment in challenging sites where soil water is limited, or evapotranspiration demand is high.

Is plant survival on green roofs related to their drought response, water use or climate of origin?

Publisher: Elsevier BV

Date: 06-2019

DOI: 10.1016/J.SCITOTENV.2019.02.349

Abstract: Green roofs are novel urban ecosystems with shallow substrate depths and low water availability. Hence, it is critical to select green roof plants that can survive water-deficits, particularly in climates with hot and dry summers. Shrubs are perennial plants which can be drought resistant and may be suitable for green roofs. However, studies about survival and health of shrubs are limited. The aim of this study was to determine whether plant climate of origin aridity, drought response and water use strategies could be used to select shrubs which can survive on green roofs that experience water-deficit. We selected 15 shrub species from a range of climates (dry, mesic and wet) and planted them together in 20 replicate green roof modules with 130 mm deep substrate. We monitored substrate water contents, plant minimum water potentials (ψ

Greywater irrigation can support climbing plant growth on building green façades

Publisher: Elsevier BV

Date: 07-2021

DOI: 10.1016/J.UFUG.2021.127119

Does the turgor loss point characterize drought response in dryland plants?

Publisher: Wiley

Date: 27-04-2017

DOI: 10.1111/PCE.12948

Abstract: The water potential at turgor loss point (Ψ

Linkage Projects - Grant ID: LP190100536

Start Date: 02-2021

End Date: 02-2025

Amount: $629,570.00

Funder: Australian Research Council

Linkage Projects - Grant ID: LP130100731

Start Date: 05-2014

End Date: 07-2018

Amount: $265,000.00

Funder: Australian Research Council