PS 43-70 - Factors influencing tree resistance to tropical cyclone damage in urban environments: a review

Background/Question/Methods

Tropical cyclones, also called typhoons and hurricanes, can be a major disturbance driver in rural and urban coastal ecosystems, causing substantial damage to tree populations. Decades of observational and experimental biomechanical work in rural forests and tree plantations have shown that multiple biotic and abiotic factors impact the resistance of individual trees to damage by severe tropical cyclone-associated winds. However, since urban environments can create unique growing environments for trees (e.g., open growing conditions, close proximity to infrastructure, pruning practices), the applicability of rural forest-based frameworks of tree wind resistance to the urban forest remains unclear. This review examines the questions, what factors influence urban tree resistance to tropical cyclones, how do these factors compare to observations made in rural forests, and what are the gaps in knowledge on the subject? We systematically searched academic journals and databases in English, Chinese, French, Japanese, Portuguese, Spanish, and Chinese. We identified papers which had measured wind-related tropical cyclone damage to trees using ground-based observations within one year of the tropical cyclone and analyzed factors influencing tree resistance to wind damage. We then extracted information about the study site, methodologies, response variables (e.g. broken trunk), and predictor variables (e.g. tree height).

Results/Conclusions

From the preliminary search and screening, 44 research papers met our screening criteria. The studies come from 12 different countries and include 33 rural studies (large forests and plantations) and 11 urban studies (street trees, residential areas, and parkland). For both rural and urban trees, the most commonly studied response variables (in descending order) were mortality, uprooting, stem failure, and whole tree damage. The most commonly studied predictor variables (in descending order) were trunk diameter at standard height (~1.3-1.4 m), species, wood density, wind speed, and modulus of elasticity. Based on our literature review, we propose grouping tropical cyclone wind resistance factors for urban trees into three interacting themes: biotic (size, species, pathogens), abiotic (storm, soil, infrastructure, buildings), and management (pruning, planting location relative to other trees). Factors in need of additional research in urban contexts include infrastructure, buildings, pathogens, pruning, and the interactions between factors (e.g., the interaction between species and soil volume). Findings from this research can be used to inform management practices such as species selection, pruning, and planting designs to foster greater resistance to tropical cyclone damage in the urban forest.