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1.4.2 Tree Inventory The City of Pleasanton's most recent tree inventory was collected between 2023 and 2024 by Dudek. The current inventory was updated from an older inventory, originally collected by West Coast Arborists, Inc. (WCA), and includes 23,722 trees and 3,976 plantable vacant sites (three feet wide and greater in size) in streets and parks. Vacant sites were considered plantable if they were labeled as a vacant site or stump by inventory collection field staff and had a tree well or parkway size equal to or greater than three feet. The City's current stocking rate, which is calculated by dividing the total number of existing trees by the total number of plantable sites on public land is 85.6%. The stocking rate does not include potential sites that need modification to be viable or sites that are not captured in current inventory data. The variety of different tree species within the urban forest is known as species diversity. Another important related factor is species evenness, which is the relative abundances of each species. Species diversity and evenness help provide resiliency to pest and pathogen infestations through the variety of different biological and physiological characteristics of each tree species. If one tree species is especially susceptible to a particular pest, having a variation of species in the city that are more resistant or unaffected by the pest ensures that the overall urban forest will survive. Pleasanton's 23,722 trees are composed of 113 genera STATUS OF THE URBAN FOREST and 250 species. According to a recent study looking at the diversity of urban forests across multiple California cities, 250 is a typical number of species for a City with a size and climate similar to Pleasanton's (Love et al., 2022). The top 10 genera and species in Pleasanton are shown in Figures 1-5 and 1-6. The species diversity sustainability goals are as follows: ■ Sustainability Goal (Genus): No genus represents more than 20% of inventory. ■ Sustainability Goal (Species): No species represents more than 10% of inventory. An exception to the genus and species goals above are for native species such as oaks, which may exceed the recommended sustainability goals. The City and community have put a high value on native species for the additional benefits they provide, including supporting local ecosystems, requiring less maintenance and promoting biodiversity. The oak genus Quercus currently makes up just over 20% of the inventory and the two most common oak species (coast live oak and valley oak) within the City make up 9.4% and 7.2%, respectively, of the overall species in the inventory. Another exception to consider for the City are tree species that already have a proven history of resiliency in Pleasanton's urban landscape, which might include species that have already survived extreme heat and drought periods, recovered from pest infestations, or that have held up to root pruning for pavement repairs. CITY OF PLEASANTON URBAN FOREST MASTER PLAN i 23