Presettlement forest structure as a factor in urban forest development

Characteristics of presettlement forests at Menlo Park and South Lake Tahoe, CA were compared with the present characteristics of the urban forests in these cities. Urbanization of forest types in both cities led to decreased tree density (in Menlo Park from 279 to 43/ha; in South Lake Tahoe from 761 to 373/ha), decreased tree cover (in Menlo Park from 92 to 34%; in South Lake Tahoe from 57% to 19%). In contrast, urbanization of the oak savannas at Menlo Park has resulted in an increase in tree density (from 4 to 35/ha) crown cover (from 14 to 25%) and the number of species (from 3 to 130). The number of tree species has increased in both cities as a result of urbanization of presettlement forests (in Menlo Park from 5 to 145; in South Lake Tahoe from 1 to 6). The uneven-aged structure of presettlement oak savannas at Menlo Park has been modified to an all-aged structure as a result of tree planting and the mortality of older age classes. The all-aged structure of the presettlement oak forest at Menlo Park was not changed in the transition to the present urban forest. At South Lake Tahoe the even-aged structure of the presettlement Jeffrey pine forest has been modified into a uneven-aged structure by tree planting. Presettlement forest age structure is recognized as the most significant characteristic for the identification of possible management problems in the urban forest.