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Dead trees are a fire hazard. While live trees often contain a large amount of water in their tissues, dead tree tissues, particularly the leaves and small branches, have moisture levels that are generally in equilibrium with the moisture in the air. As a result, they are readily ignited and can burn under conditions where green vegetation would not. Most significantly concerning are recently dead trees with a full crown of dead leaves or needles since these dead leaves readily ignite, spreading fire into the tree crown and producing many embers. Dead public trees are a transitory phenomenon because these trees are likely to fall into a public right of way or park; the City makes removing these trees a priority. For this reason, the number of dead trees in the city changes annually, but they are always a minor component of the city’s trees. At the time of the inventory, dead trees comprised 0.5% of City trees. Maintenance of individual trees and groups of trees is as important as species or species characteristics. Well- maintained trees, with minimal deadwood or leaf litter accumulation and adequate clearance between the crown and surface vegetation, are less likely to ignite and burn. The City regularly maintains public trees for safety and clearance above roadways and sidewalks (pers comms G. Damonte July 2023), so public trees are generally maintained in a condition that reduces the risk of fire spreading into the tree crowns. Private Trees Pleasanton’s privately owned trees are dispersed throughout private lots and along privately maintained streets throughout the WUI area. Whereas the public trees primarily occur as single rows of individual trees along roadways, trees on private properties form a more uniform, although rarely dense, canopy. Tree densities vary significantly from property to property, with some lots devoid of trees and others heavily populated. Private property is assumed to contain more trees than public property because there is a greater area of private property than public property in the WUI areas. Most urbanized landscapes are more fire-resistant than native landscapes since they are maintained and irrigated to some degree, although they do not always focus on minimizing wildfire risk. Ornamental irrigated landscapes that receive maintenance (removal of dead and dying plants, trimming, thinning) are generally less receptive fuel beds than an unmaintained native landscape. No inventory was made of trees on private property, and the exact composition of tree species on private property in the WUI areas is unknown. However, based on observations made during the inventory of city trees and field visits with City staff, the variety of tree species on private property in the WUI area is similar to that on city property. A large portion of the urban forest canopy on private property in the WUI areas is composed of trees that do not have undesirable fire characteristics, including native trees such as oaks and ornamentals such as fruit trees and broadleaf shade trees. Trees with undesirable fire characteristics are more prevalent on private properties than public properties in the WUI areas. Dead trees on private property have the same fire potential as those on public property. However, where public trees are generally removed from buildings (more than 30 feet of separation) dead trees on private property can be much closer to a building. Therefore they can be considered a greater fire hazard, particularly when they are within 10 feet of a structure because of the risk of a fire transitioning from the tree to the building. Like dead public trees, dead trees on private property are a transitory phenomenon because property owners remove them as they are unsightly and are at risk of falling onto a home or improvement. The maintenance of trees on private property varies. However, most of the properties observed during the field visits for the preparation of this section were maintained to some degree, though not always with an emphasis on fire safety. Because private trees are more likely than public trees to be close to a building, it is much more common to see private trees with inadequate clearance from a building, which is less than 10 feet of space between tree branches and a chimney. 11