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Plant Focus

Quercus peninsularis
A Red Oak (Section Lobatae) endemic to inland ranges of northern Baja California, Mexico

The Oaks of Silicon Valley from the 1850s to Today

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Erica Spotswood, Robin Grossinger, Steve Hagerty, Erin Beller, April Robinson, and Letitia Grenier

Published May 2019 in International Oaks No. 30: 85–92


Many cities in California have been established in areas that were historically dominated by native oaks. In these landscapes, dramatic transformation has often occurred, leading to the replacement of native oaks with many non-native trees. While these transformations are well known, relatively few efforts have been made to quantify the extent of change. Here, we draw on historical and contemporary datasets from the cities in what is known today as Silicon Valley to compare the composition and structure of the modern urban forest to the historical landscape. We show that there have been dramatic shifts in forest structure and composition, including large increases in the species richness of trees, a near total loss of understory herbaceous vegetation, and a loss of large trees. These changes suggest that a reintroduction of native oaks could help to increase the ecological functions of the urban forest.


California oaks, historical ecology, urban forestry, Quercus lobata, Quercus agrifolia


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