Relating the climate envelopes of urban tree species to their drought and thermal tolerance

Wide climatic niche breadth and traits associated with climatic tolerance facilitate eucalypt occurrence in cities worldwide

“…Cities like Ado Etiki (Nigeria), Antalya (Turkey), Barcelona and Bella Vista (Panama) harbour species with broad climatic niches (~13°C) and none of the species planted in those cities exceeded the upper or lower limit of their climatic niche breadth neither for MTWM or for PDM. Eucalyptus camaldulensis, for example, has a broad natural distribution across the Australian continent, is well-adapted to arid and semi-arid lands and has a wide climatic envelope (Booth & Pryor, 1991;Hanley et al, 2021;Teulières et al, 2007); here, E. camaldulensis had the broadest climatic niche breadth for MTWM of all the species. This species is also the most commonly planted eucalypt species in cities worldwide (32 cities; 48%) had the highest thermal and precipitation safety margins and only exceeded its realized climatic niche breadth in four cities (6%) for MTWM (Bhopal, India; El Centro, Las Vegas and Phoenix, USA) and in seven cities TA B L E 1 Outputs from the generalized linear mixed-effects models of traits associated with heat and water deficit tolerance (leaf δ 13 C, leaf dry mass, leaf length, leaf N per dry mass and wood density), species' climate niche breadths (estimated as the difference between the 95th and the 5th percentiles of MTWM and PDM), and thermal and precipitation safety margins, for maximum temperature of the warmest month (MTWM) and precipitation of the driest month (PDM), respectively.…”

“…Functional traits have proved to be useful determinants of the likely tolerance of a large panel of urban tree species to heat and drought stresses (Esperon‐Rodriguez et al., 2020; Hanley et al., 2021; Ibsen et al., 2023; Marchin et al., 2022; Sjöman et al., 2018). Here we found evidence that species with small leaves, high δ 13 C, high leaf N per dry mass and high wood density—which are typical characteristics of heat and drought tolerant species—are planted in cities experiencing warmer and drier conditions than in their native range in Australia.…”

“…Functional traits such as leaf turgor loss point, stomatal conductance and the Huber value can determine species' tolerance in cities (Esperon-Rodriguez et al, 2020Hanley et al, 2021;Hirons et al, 2021;Marchin et al, 2022;Sjöman et al, 2018).…”

“…To date, several studies have been conducted on a local or regional scale, focusing on few species or common garden experiments (e.g. Esperon‐Rodriguez et al., 2020, 2021; Hanley et al., 2021; Ibsen et al., 2023; Ilyas et al., 2021), which limits their broad applicability and capacity to describe global patterns of urban tree distribution.…”

Can Trait-Based Schemes Be Used to Select Species in Urban Forestry?

“…An increasing diversity of species are proposed for use in urban forestry in response to existential threats such as biosecurity risks and climate change (Kim et al, 2019;Hanley et al, 2021). To test whether trait schemes can aid selection of novel species or identify species that are currently used but that are likely to be inappropriate under climate change, we selected species that are discussed in current industry guidance (see Supplementary Table 1) and used a case study genus (Magnolia L.) to explore the potential of different schemes to identify species (shown in Table 2) that would be appropriate for different urban forestry purposes such as street trees, parks, or swales.…”