48 Plant and Kendal: Resident Tolerance for Mixtures of Tree Species Within Streets Brisbane, where early street tree plantings along wide verges consisting of monocultures of fashionable spe- cies (Plant 1996) have persisted to provide both mature and less diverse streetscapes. Though others have found that higher education and income levels can be strong predictors of species richness (Escobedo et al. 2015b) and support for street tree planting (Conway and Bang 2014), at the neighbourhood scale, there are clearly complex interactions between existing species diversity, socio-economics, patterns of development, and other factors (Rosiers et al. 2007; Kirkpatrick et al. 2011; Lowry et al. 2012; Flint et al. 2013; Ives and Kendal 2014; Shakeel and Conway 2014) that can influence resident tolerance to streetscape diversity at the finer scale of nearby streets, reinforcing the need for local assessments (Williams 2002). Given education level was a stronger predictor of sensitivity to species richness than income, targeted knowledge sharing may be effective when increases to species richness are being considered. Changes from monocultures of existing street species to varia- tions from block to block along major residential streets in precincts of Melbourne have been supported by community stakeholders following information sharing and engagement about the vulnerability of existing species to changing climate (City of Melbourne 2015). Similar “information interventions” about the role of green infrastructure in mitigating the impacts of heat waves and flooding have been found to shift preferences in streetscape composition toward more trees, rather than shrubs or grass (Derkzen et al. 2017) The importance of consultative approaches in Austra- lian cities where councils/municipalities are responsi- ble for street trees, but residents are highly involved, cannot be underestimated. Equally important is build- ing awareness across the range of decision makers and stakeholders. Recent studies in Canadian cities credit both improved availability of native tree nurs- ery stock, urban forest practitioner awareness of the importance of species diversity, and species diversifi- cation goals in urban forest management plans for increased street tree diversity in newer versus older neighbourhoods (Almas and Conway 2016; Nitoslawski and Duinker 2016). In managing resident sensitivity to mixtures of tree species in streets there is scope for achieving both species richness and visual homogeneity and order through the use of different species of similar forms and textures (Trowbridge and Bassuk 2004; ©2019 International Society of Arboriculture Gerstenberg and Hofmann 2016). While our study used inventory survey measures of species richness and diversity, residents are unlikely to detect species differences in the same way (Fischer et al. 2014). People often express their street tree preferences through traits such as size, growth rate, shape, and foliage type and densities (Williams 2002; Schroeder et al. 2006) rather than species identity, although some particular species have been identified as least pre- ferred by “hazard minimisers” and “native wildlife enthusiasts” (Kirkpatrick et al. 2012). Achieving greater perceived coherence in tree traits could allow for an increase in tree species richness without greatly changing perceived diversity. Promoting greater genetic diversity within species, such as various prov- enance sources or cultivars, may also provide greater ecological resilience while maintaining some visual orderliness, but further studies are required (Botzat et al. 2016; MacIvor et al. 2016). Exploring contextual and temporal gradients in species diversity tolerance in streetscapes across other types of residential land-uses and cities elsewhere are also important directions for future research. For example, mixtures of tree forms and uneven street tree placement, rather than closed, continuous street tree canopies in narrow, deep street canyons, can deliver greater air quality improvement (Vos et al. 2013). Residents in highly compact dwelling forms such as Hong Kong have already indicated greater receptive- ness to functional over aesthetic benefits of nearby greenspace, especially air purification (Lo and Jim 2012), and may consequently be less sensitive to mixtures of species in streets that contribute to cleaner air. Under- standing how people’s values for different kinds of urban landscapes can be incorporated into urban for- est planning will also help balance needs for diversity and people’s diverse needs from the urban forest (Ordóñez and Duinker 2014). The approach used in this study demonstrates the advantages of integrating street tree inventory data into hedonic price modelling to reveal resident preferences. Such techniques are valuable in comparing urban for- est needs, in relation to optimising and sustaining ecosystem services, to community needs and preferences at fine scales such as local streetscapes. Advancing such techniques also provides tools for policy evaluation and can assist in developing business cases for strate- gic investment in shared outcomes. An earlier study, using a similar approach, found that municipal goals
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