Can urban tree re-inventories inform future species selection? : diameter at breast height as an indicator for tree performance in Malmö municipality’s tree database

Abstract: Using the inventory database of trees for Malmö municipality, Sweden, this study explored the potential of using the diameter at breast height (DBH) measurement in re-inventories, as a decision-making tool for species selection and management in urban forests. With the escalating pressures of urbanization and unpredictable climate change effects, there is an urgent need for urban forest managers to possess reliable tools that can facilitate the selection of resilient tree species capable of thriving in diverse and changing urban contexts. A series of discussion graphs were used in this study’s analysis to effectively illustrate the relationship between DBH, growth rates, and the provision of ecosystem services. DBH, acknowledged as a significant inventory parameter, was found to be an effective proxy for crown diameter, which serves as a vital indicator of the extent of ecosystem services provided by urban forests. The study found species-dependent differences in relative performance, as indicated by growth rate, across various planting environments and groundcover types. One method of categorizing trees into age groups was explored to assess any age-dependent performance differences. However, the analysis revealed little variation within species between the selected age groups. Future research could adopt more sophisticated analyses, focusing specifically on speciesspecific growth curves and performance in younger trees. This study demonstrates that DBH measurements are a valuable tool for guiding species selection. Continued study of this data can help urban tree managers make informed decisions about species likely to perform well in the future. Specifically, understanding species performance in more restrictive environments, such as hardscapes or street environments, can provide predictive insights into species' resilience in increasingly challenging conditions induced by climate change. It is strongly recommended that future re-inventory efforts continue to prioritize the inclusion of DBH measurements in re-inventories to increase the available data for analysis. The continuous incorporation of this parameter will yield a more comprehensive understanding of tree populations, ultimately enabling informed decision-making and facilitating the formulation of effective management strategies for urban forests in the future.