Applying the concept of niche breadth to understand urban tree mortality in the UK

• Published in: The Science of the total environment Vol. 902; p. 166304
• Main Authors: Kim, Eun Hye, Hitchmough, James D., Cameron, Ross W., Schrodt, Franziska, Martin, Kevin W.E., Cubey, Robert
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2023
• Subjects: Drought stress; Heatwaves; Niche position; Tree inventory data; Urban gardens; Urban tree assessment; Drought stress; Niche position; Urban tree assessment; Tree inventory data; Heatwaves; Urban gardens
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.166304

Accelerated climate change has raised concerns about heightened vulnerability of urban trees, spurring the need to reevaluate their suitability. The urgency has also driven the widespread application of climatic niche-based models. In particular, the concept of niche breadth (NB), the range of environmental conditions that species can tolerate, is commonly estimated based on species occurrence data over the selected geographic range to predict species response to changing conditions. However, in urban environments where many species are cultivated out of the NB of their natural distributions, additional empirical evidence beyond presence and absence is needed not only to test the true tolerance limits but also to evaluate species' adaptive capacity to future climate. In this research, mortality trends of Acer and Quercus species spanning a 21-year period (2000–2021) from tree inventories of three major UK botanic gardens - the Royal Botanic Gardens, Kew (KEW), Westonbirt, the National Arboretum (WESB), and the Royal Botanic Garden Edinburgh (RBGE) - were analyzed in relation to their NB under long-term drought stress. As a result, Acer species were more responsive to drought and heat stress. For Acer, positioning below the lower limits of the precipitation of warmest quarter led to an increase in the probability of annual mortality by 1.2 and 1.3 % at KEW and RBGE respectively. In addition, the mean cumulative mortality rate increased corresponding to an increase in the number of niche positions below the lower limits of the selected bioclimatic variables. On the other hand, Quercus species in general exhibited comparable resilience regardless of their niche positions. Moreover, Mediterranean oaks were most tolerant, with cumulative mortality rates that were lower than those of native oaks in the UK. These findings further highlight the importance of incorporating ecological performance and recognizing species-specific adaptive strategies in climatic niche modeling. [Display omitted] •Cumulative water stress during growing seasons and heatwaves have continually exacerbated between 2000 and 2021 in the UK.•Acer species showed higher vulnerability to accumulated drought and heat stress than Quercus species.•Precipitation during warmest quarter (PWQ) was most influential in the mortality response of Acer.•Quercus species showed resilience beyond their known lower thresholds of climatic range.•Mediterranean oaks outperformed native oaks in the UK.