Environment or traits: what determines tree survival?

Tree species selection for ex situ conservation and urban planting mostly relies on climate matching, yet this approach may oversimplify species adaptability to local conditions. Climate range limits based on native distributions are a critical factor in determining suitability of trees. However, species with similar climatic range do not necessarily exhibit similar tolerance due to differing plant strategies. The research highlights this contrast by investigating the relative survival rates of selected ex situ species, Acer rubrum and Quercus rubra, from similar climatic ranges and linking their differing mortality with their hydraulic strategies. The research utilises records of living collections from three major UK botanic gardens – the Royal Botanic Gardens, Kew (KEW), Westonbirt, the National Arboretum (WESB), and the Royal Botanic Garden Edinburgh (RBGE). The observed difference in survival rates – higher in Q. rubra and lower in A. rubrum – was consistent with their hydraulic strategies, which was assessed using sap flow measurements from the SAPFLUXNET database. The study also demonstrates that the contrasting water use strategies and associated plant traits between Quercus and Acer genera, and their interactions with local conditions may explain their differing survival responses. While macro-environmental variables provide essential reference guidelines, they may be too coarse to capture the nuances of species relative tolerance. The study emphasises that future research should focus on integrating these aspects and identifying interrelated functional traits to enhance our understanding of species-specific responses to climate change.