School of Agriculture, Food and Ecosystem Sciences - Research Publications

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    Decision-making of municipal urban forest managers through the lens of governance
    Ordonez, C ; Threlfall, CG ; Livesley, SJ ; Kendal, D ; Fuller, RA ; Davern, M ; van der Ree, R ; Hochuli, DF (ELSEVIER SCI LTD, 2020-02)
    Awareness of the benefits of urban trees has led many cities to develop ambitious targets to increase tree numbers and canopy cover. Policy instruments that guide the planning of cities recognize the need for new governance arrangements to implement this agenda. Urban forests are greatly influenced by the decisions of municipal managers, but there is currently no clear understanding of how municipal managers find support to implement their decisions via new governance arrangements. To fill this knowledge gap, we collected empirical data through interviews with 23 urban forest municipal managers in 12 local governments in Greater Melbourne and regional Victoria, Australia, and analysed these data using qualitative interpretative methods through a governance lens. The goal of this was to understand the issues and challenges, stakeholders, resources, processes, and rules behind the decision-making of municipal managers. Municipal managers said that urban densification and expansion were making it difficult for them to implement their strategies to increase tree numbers and canopy cover. The coordination of stakeholders was more important for managers to find support to implement their decisions than having a bigger budget. The views of the public or wider community and a municipal government culture of risk aversion were also making it difficult for municipal managers to implement their strategies. Decision-making priorities and processes were not the same across urban centres. Lack of space to grow trees in new developments, excessive tree removal, and public consultation, were ideas more frequently raised in inner urban centres, while urban expansion, increased active use of greenspaces, and lack of data/information about tree assets were concerns for outer and regional centres. Nonetheless, inter-departmental coordination was a common theme shared among all cities. Strengthening coordination processes is an important way for local governments to overcome these barriers and effectively implement their urban forest strategies.
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    Quantifying the importance of urban trees to people and nature through tree removal experiments
    Ordonez, C ; Threlfall, CG ; Kendal, D ; Baumann, J ; Sonkkila, C ; Hochuli, DF ; van der Ree, R ; Fuller, RA ; Davern, M ; Herzog, K ; English, A ; Livesley, SJ (WILEY, 2023-08)
    Abstract Experimentally manipulating urban tree abundance and structure can help explore the complex and reciprocal interactions among people, biodiversity and the services urban forests provide to humans and wildlife. In this study we take advantage of scheduled urban tree removals to experimentally quantify the benefits that urban trees provide to humans and wildlife. Specifically, we aim to understand how trees affect: (1) bird and mammal abundance and diversity, as well as an ecological process (predation); and (2) people's perception responses, such as the importance that people assign to the trees, wildlife and the site. We designed two independent Before‐after‐control‐impact (BACI) experiments based on two sites where tree removals were occurring (impact sites): an urban park and a residential street, both located in the Greater Melbourne Area, Australia. We selected three control sites for each impact site, or four per experiment. Ecological data were collected through field surveys, and social data on people's perceptions through intercept questionnaires among park and street users. Data were analysed using a GLMMs to determine the combined effect of time (before and after) and treatment (impact and controls). At the urban park, the abundance of nectarivorous birds and possums both declined by 62% following tree removal, while invertebrate predation increased by 82.1%. The level of importance people assigned to the urban park and to the trees at the site decreased after tree removal, and people's attitudes towards tree planting became more positive, meaning more people wanted to plant more trees at the site. None of these changes were observed in the street experiment where fewer and smaller trees were removed, suggesting that effects may be highly specific to context, where factors such as tree volume, diversity and arrangement influence the magnitude of social–ecological effects observed. By demonstrating the social–ecological effect of removing urban trees, we provide evidence that urban trees provide critical habitat to urban wildlife and are perceived as an important aspect of the human experience of urban nature. Read the free Plain Language Summary for this article on the Journal blog.
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    Tree removals as socioecological experiments in cities
    Threlfall, CG ; Ordonez-Barona, C ; Livesley, SJ ; Baumann, J ; Callow, D ; Davern, M ; English, A ; Fuller, RA ; Hertzog, K ; Hochuli, DF ; van Der Ree, R ; Kendal, D (WILEY, 2024-02)
    As keystone structures in urban ecosystems, trees are critical to addressing many of the current livability, health, and environmental challenges facing cities. Every day, trees are removed from urban landscapes as part of routine management. These tree removals are an opportunity for implementing manipulative experiments to directly measure the social and ecological functions of trees. Here we review the kinds of tree removals that commonly occur in cities, assess the relevant opportunities that arise for research–practice partnerships, and discuss the challenges posed when implementing experiments of this nature. We argue that experimental studies on the routine removal of urban trees will improve and expand the mechanistic understanding of how trees support biodiversity and human well‐being in cities beyond current knowledge, which is largely based on correlative studies. Finally, we highlight the opportunity for experiments to be co‐designed by scientists and urban land managers, and how “learning while doing” can generate tangible research impacts and improve urban forest decision making.
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    Water use strategy determines the effectiveness of internal water storage for trees growing in biofilters subject to repeated droughts
    Hanley, PA ; Livesley, SJ ; Fletcher, TD ; Szota, C (ELSEVIER, 2023-10-10)
    Impervious surfaces create large volumes of stormwater which degrades receiving waterways. Incorporating trees into biofilters can increase evapotranspiration and therefore reduce stormwater runoff. Tree species with i) high water use, ii) drought tolerance and iii) rapid and full recovery after drought have been suggested for biofilters to maximise runoff reduction while minimising drought stress. Moisture availability fluctuates greatly in biofilter substrates and trees growing in biofilters will likely experience multiple, extended drought events that increase trade-offs between these traits. Providing an internal water storage has the potential to reduce tree drought stress and increase evapotranspiration. Two urban tree species (Agonis flexuosa and Callistemon viminalis) were grown in plastic drums with biofilter profiles. Three irrigation treatments were used: well-watered, drought with an internal water storage and drought without an internal water storage. Transpiration, leaf water potential and biomass were measured to determine the effect of biofilter internal water storage and repeated drought events on tree water use, drought stress and growth. Biofilter internal water storage improved water use and reduced drought stress for A. flexuosa, whereas C. viminalis reduced leaf loss but saw no change in water use or drought stress. A. flexuosa with biofilter internal water storage was able to recover transpiration to well-watered levels after repeated droughts, while C. viminalis experienced reduced recovery ability. It is recommended all biofilters planted with trees should have internal water storage. In systems with lower moisture availability a species with more stomatal control, such as A. flexuosa, is recommended. If selecting a species with less stomatal control, such as C. viminalis, the internal water storage volume needs to be increased to avoid drought stress.
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    Supporting Growth and Transpiration of Newly Planted Street Trees With Passive Irrigation Systems
    Thom, JK ; Fletcher, TD ; Livesley, SJ ; Grey, V ; Szota, C (Wiley Open Access, 2022-01)
    Solutions that use stormwater runoff to rapidly establish tree canopy cover in cities have received significant attention. Passive irrigation systems that direct stormwater to trees have the potential to increase growth and transpiration and may limit drought stress. However, little data from the field demonstrates this, and we lack robust and reliable designs which achieve it. Here, we quantified growth and transpiration for trees: (a) in infiltration pits receiving stormwater, with a raised underdrain and internal water storage (drained), (b) next to infiltration pits receiving stormwater but without an underdrain and internal water storage (adjacent), and (c) planted in standard pits, not receiving stormwater (control). Trees in drained pits grew twice as fast as control trees in the first 2 years, but fast initial growth rates were not sustained in years three and four. Trees outgrowing the small infiltration pits, rather than a lack of water, was most likely responsible for growth rates slowing down. Despite this, rapid initial growth for trees in drained pits meant trees were larger by year three and transpired more than twice as much (5.1 L d−1) as trees adjacent to pits (2.4 L d−1) or control trees (2.3 L d−1). No trees showed drought stress during the study. However, some trees planted adjacent to infiltration pits showed waterlogging stress, suggesting caution installing infiltration pits adjacent to establishing trees in fine‐textured soils. Overall, our results suggest passive irrigation systems can substantially increase initial tree growth, thereby facilitating greater cooling and runoff reduction through increased transpiration.
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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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    Daytime irrigation leads to significantly cooler private backyards in summer
    Cheung, PK ; Jim, CY ; Tapper, N ; Nice, KA ; Livesley, SJ (ELSEVIER, 2022-12)
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    Public satisfaction with urban trees and their management in Australia: The roles of values, beliefs, knowledge, and trust
    Kendal, D ; Ordonez, C ; Davern, M ; Fuller, RA ; Hochuli, DF ; van der Ree, R ; Livesley, SJ ; Threlfall, CG (ELSEVIER GMBH, 2022-07)
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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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    Editorial: Urban soil formation, properties, classification, management, and function
    Scharenbroch, BC ; Trammell, TL ; Paltseva, A ; Livesley, SJ ; Edmondson, J (FRONTIERS MEDIA SA, 2022-08-19)