Urban trees can face a myriad of complex challenges including loss of green space and harm to the existence of urban dwellers and trees, along with domestic greenhouse gas (GHG) and air pollutant emissions. Understanding tree species diversity in cities is important for climate change regulations and can provide a characterized tree population for improved species structure, function, and value. Despite New Zealand being a biodiversity hotspot in terms of natural environments, there is less understanding about native trees’ species diversity assessment to utilize their regulating service (i.e., tree growth and physiological responses to low air quality, GHG, elevated air temperatures, and drought) in built-up environments such as cities. Therefore, we investigated the species abundance and ratio of municipal alien and native trees grow in streets/parks of Christchurch, New Zealand through Christchurch City Council (CCC) tree inventory and Microsoft Excel pivot table. This study described and updated current tree diversity and provided the newest information of native trees census planted on streets and in urban parks.
Results/Conclusions
By quantifying tree species diversity in Christchurch urban area, this research provides a basis for a better understanding of the current street trees’ abundance and basic assessment that it is needed to have more urban tree diversity fulfillment with native species which gives implication how that diversity can impact ecosystem resilience and the environmental regulating services.
Through 2020 CCC tree inventory, total abundance (i.e., number of trees) of street trees was 112,886 and some of the main species (i.e., more than 2200 per monospecies) were 31,339. Alien tree species (mainly Betula pendula, Fraxinus ornus, Quercus palustris, Prunus yedoensis, Liquidambar styraciflua, and Quercus robur) were more dominant than native trees (mainly Plagianthus regius, Sophora tetraptera, Cordyline australis, and Sophora microphylla) in parklands and on streets in Christchurch, by showing species ratio of [(alien): (native) = 66.45: 33.55]. We concluded this result can provide implication that is it required to be viewed in relation to how current species will grow and respond to urban abiotic extremes and climate change and to how diversity affects New Zealand’s native trees and alien species in urban environmental stress conditions.
