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Carlos collecting Quercus ×alentejana (Q. faginea × Q. pyrenaica) in northeastern Portugal for his PhD thesis © Carlos Vila-Viçosa
An interview with Portuguese oak conservationist Dr. Carlos...
Amy Byrne | Apr 19, 2024
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It was a great pleasure for me to be able to write about my...
Gert Fortgens | Feb 15, 2024

Plant Focus

Quercus crassipes acorns with inrolled cupule margin
One of the more well-known Mexican oaks in cultivation.

California’s Oak Habitat for Endangered, Threatened, and Candidate Species

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Individual articles can be purchased for U$S 10. If you would like to purchase an article, email a request to website@internationaloaksociety.org

Angela Moskow

Published May 2023 in International Oaks No. 34: 165–180


California Wildlife Foundation’s California Oaks (CWF/CO) program issued a 2021 report that demonstrates the importance of oaks for California’s biodiversity, with a focus on species, subspecies, varieties, populations, distinct population segments, evolutionarily significant units, and clades that are federally and/or state designated as endangered or threatened (listed), or are candidates for federal or state designation.

California Department of Fish and Wildlife provided spreadsheets of sensitive species associated with oaks. Vertebrate data were derived from the California Wildlife Habitat Relationship (CWHR) information system, from which a list of 34 oak-dependent species, subspecies, distinct population segments, evolutionarily significant units, and clades was generated.

The plant and invertebrate tables were created utilizing two databases: California Natural Diversity Database (CNDDB), which is an inventory of the status and locations of rare plants and animals in California, and the oak woodlands layer of the Areas of Conservation Emphasis (ACE) system, which provides course-level spatial data on wildlife and vegetation, which is synthesized into thematic maps to help inform discussions on the conservation of biodiversity, habitat connectivity, and climate change resiliency. A 5% overlap threshold was established to exclude species, subspecies, varieties, and populations with a low average percentage overlap of all CNDDB occurrences with the oak woodlands layer in ACE. One hundred and thirty-four listed and/or candidate plant species, subspecies, and varieties, and twenty-six listed and/or candidate invertebrate species, subspecies, and populations were found to be associated with oaks.


endangered, threatened, listed, Quercus, Notholithocarpus


California  Natural  Diversity  Database  (CNDDB).  2021.  Special  Animals  List.  California  Department  of  Fish  and  Wildlife. Sacramento, CA. (https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=109406&inline).

California  Natural  Diversity  Database  (CNDDB).  2020.  State  and  Federally  Listed  Endangered  and  Threatened  Animals of California. California Department of Fish and Wildlife. Sacramento, CA. (https://nrm.dfg.ca.gov/FileHandler. ashx?DocumentID=109405&inline)

California Oaks. Oaks. 2021. Berkeley, CA: California Wildlife Foundation/California Oaks (www.californiaoaks.org).

Hamilton, H., R.L. Smyth, B.E. Young, T.G. Howard, C. Tracey, S. Breyer, D.R. Cameron, A. Chazal, A.K. Conley, C. Frye, and C.

Schloss. 2022. Increasing taxonomic diversity and spatial resolution clarifies opportunities for protecting US imperiled species. Ecological Applications 32(3): e2534. doi.org/10.1002/eap.2534.

Slauson, K.M., G.A. Schmidt, W.J. Zielinski, P.J. Detrich, R.L. Callas, J. Thrailkill, B. Devlin-Craig, D.A. Early, K.A. Hamm, K.N. Schmidt, A. Transou, C.J. West. 2019. A conservation assessment and strategy for the Humboldt marten in California and Oregon. Gen. Tech. Rep. PSW-GTR-260. U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. 121. Arcata,

University of California Integrated Hardwood Range Management Program, California Department of Fish & Game, and California Department of Forestry and Fire Protection. 1996. Guidelines for Managing California’s Rangelands 1996. University of California Division of Agriculture and Natural Resources (Publication 3368) (Appendix B, 146-157).

Wu, W.X., R.B. Siegel, H.L. Loffland, M.W. Tingley, S.H. Stock, K.N. Roberts, J.J. Keane, J.R. Medley, R. Bridgman, and C.

Stermer. 2015. Diversity of great gray owl nest sites and nesting habitats in California. The Journal of Wildlife Management 79(6): 937-947. doi.org/10.1002/JWMNG.910.