Quercus lobata Woodland Alliance
Valley oak woodland and forest

USDA Ecological Section Map

Summary Information

  • Primary Life FormTree
  • Elevation0-775 m
  • State RarityS3
  • Global RarityG3
  • DistributionUSA: CA (NatureServe) (FEIS)
  • Endemic to CaliforniaYes
  • Endemic to California Floristic Province and DesertsYes
  • Date Added2025/02/27

Characteristic Species

Quercus lobata is dominant or co-dominant in the tree canopy with Aesculus californica, Quercus agrifolia, Quercus douglasii, Quercus kelloggii, Quercus wislizeni and/or Umbellularia californica. Shrubs are sparse and may include Toxicodendron diversilobum. Understory herbs include Bromus diandrus and/or Bromus hordeaceus.

Vegetation Layers

Trees < 30 m tall; canopy is open (greater than 10%) to continuous, or savanna-like (less than 10%, but evenly distributed). Shrub layer is sparse to open. Herbaceous layer may be grassy.

Membership Rules

  • Quercus lobata > 50% relative cover in the tree canopy or > 30% relative cover when other tree species, such as Q. agrifolia or Quercus douglasii are present (Allen et al. 1989, Keeler-Wolf and Evens 2006).
  • Quercus lobata > 50% relative cover in the tree canopy, or > 30% relative cover with Quercus agrifolia and/or Umbellularia californica in upland habitat (Buck-Diaz et al. 2021, Sikes et al. 2021).
  • Quercus lobata > 50% relative cover in the tree canopy, or > 30% relative cover with Quercus agrifolia, Q. douglasii, Q. kelloggii, and/or Umbellularia californica in upland habitat (Sikes et al. 2023, Sikes et al. 2025).

Habitats

Valley bottoms; summit valleys; gentle to somewhat steep, lower to upper slopes and ridgetops. Soil textures are various, including loams and clays. Soils are alluvial or residual. The USACE Wetland Inventory (2018 national list) recognizes Quercus lobata as a FACU plant.

Other Habitat, Alliance and Community Groupings

MCV (1995) Valley oak series
NVCS (2009) Quercus lobata woodland alliance
Calveg Valley oak
Holland Valley oak woodland
Munz Northern oak woodland
WHR Valley oak woodland
CDFW CA Code 71.035.00

National Vegetation Classification Hierarchy

Formation Class Mesomorphic Tree Vegetation (Forest and Woodland)
Formation Subclass Temperate Forest
Formation Warm Temperate Forest
Division Madrean Forest and Woodland
Macro Group California Forest and Woodland
Group Californian broadleaf forest and woodland