Quercus tomentella
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 Island Oak grove, Santa Rosa Island
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| Quercus tomentella Engelm. |
The Island Oak (Quercus tomentella), also known as Island Live Oak or Channel Islands Oak, is an oak in the section Protobalanus. Island Oak is endemic to six islands off the coast of California, Santa Rosa, Santa Cruz, Anacapa, Santa Catalina, San Clemente, and Guadalupe islands. The first five islands are Channel Islands of California; Guadalupe Island is located to the west of Baja California, Mexico.
Island Oak is a tree usually less than 20 meters in height. Its bark is usually gray and becomes furrowed with age. The specific name tomentella, Latin for "beset with tomentum (fuzz)", references the dense hairs found on the undersides of its leaves. Leaves, which are evergreen, are usually 5-8 cm in length, oblong to oblong-obvate in shape, with a toothed margin, deeply indented. Acorns take 2 years to mature and are saucer- to bowl-shaped with a rounded tip, and large in size (cup 20-30 mm wide, 6-8 mm deep, nut 20-35 mm).
Island Oak can hybridize with all other members of the section Protobalanus, although its natural range overlaps only with Q. chrysolepis, the Canyon Live Oak.
Fossils of Island Oak have been found in mainland California; the youngest known fossils are two to ten million years old and were found near St. Mary's College, somewhat near the Oakland hills. The oldest known fossils are 30 to 60 million years old and were found in the Mojave desert. Island Oak is no longer native to mainland California, and is thought to be a relict of a climate that was warmer and wetter than today's. However, it will grow readily in mainland California if planted and regularly watered.
The Island Oak is listed as Vulnerable (VU B1+2ce) by the IUCN. Many populations are in need of immediate restoration due to severe impacts of grazing by non-native herbivores. The National Park Service has classified Island Oak as a species of special environmental concern.
On Guadalupe, the local population is probably doomed. It has declined some 80-90% since the 1950s, and one or two dozen trees are all that remains. These do not seem to be reproducing any more.[1] While the Island Oak was once an important part of the local ecosystem, its decline was caused by tens of thousands of feral goats swarming the island since the mid-19th century. Removal of the goats was finally all but complete in 2005 and fenced enclosures have been built since 2001, permitting an amazing comeback of local flora.[2] Even if the local oaks should disappear, the population could probably be reestablished soon from Channel Islands stock.
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[edit] References
- Junak, S.; Keitt, B.; Tershy, B.; Croll, D. & Sánchez, J.A. (2003): Recent conservation efforts and current status of the flora of Guadalupe Island, Baja California, Mexico. Presentation at Taller sobre la Restauración y Conservación de Isla Guadalupe ["Workshop on restauration and conservation of Guadalupe Island"]. Instituto Nacional de Ecología, November 13-14, 2003. HTML abstract
- León de la Luz, José Luis; Rebman, Jon P. & Oberbauer, Thomas (2003): On the urgency of conservation on Guadalupe Island, Mexico: is it a lost paradise? Biodiversity and Conservation 12(5): 1073–1082. doi:10.1023/A:1022854211166 (HTML abstract)
- Nixon, Kevin C. (1997): 39. Quercus tomentella. In: Flora of North America Editorial Committee (eds.): Flora of North America North of Mexico vol. 3.
- Nixon, K. et al. (1998). Quercus tomentella. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006.
