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''Quercus lobata'', commonly called the valley oak or roble, grows into the largest of North American oaks. It is endemic to California, growing in interior valleys and foothills from Siskiyou County to San Diego County.〔(CalFlora taxon report, University of California: ''Quercus lobata'' (valley oak) )〕 Mature specimens may attain an age of up to 600 years. This deciduous oak requires year-round access to groundwater.〔Pavlik, B. M., Muick, P., Johnson, S., & Popper, M. (1992). Oaks of California. Cachuma Press ISBN 0-9628505-1-9〕〔Sawyer, John O., & Keeler-Wolf, Todd. (1995) A manual of California Vegetation. California Native Plant Society, page 312.〕 Its thick, ridged bark is characteristic and resembles alligator hide. The valley oak's deeply lobed leaves assist in identification. ==Description and ecology== The sturdy trunk of the Valley oak may exceed three meters (10 feet) in diameter and its stature may surpass 30 meters (100 feet) in height. The "Henley Oak", in Covelo, California, is the tallest known North American hardwood, at .〔(【引用サイトリンク】title=Largest North American Hardwoods )〕〔(Flora of North America: ''Quercus lobata'' )〕 The branches have an irregular, spreading and arching appearance that produce a profound leafless silhouette in the clear winter sky. During Autumn leaves turn a yellow to light orange color but become brown during mid to late fall. In advancing age the branches assume a drooping characteristic. Its pewter-colored rippled bark adds to the attractive aesthetic of this species.〔 Typically, leaves are five to ten centimeters (2-4 inches) long and are roundly and deeply lobed. The leaf width is approximately one half its length. Each leaf is matte green with an underneath pale green appearance; moreover, the leaf is covered with abundant soft fuzz, yielding an almost velvety feeling. When a fresh leaf is rubbed or broken, an aromatic scent is exuded, evoking a forest odor. The wood is a dull brown approaching yellow, and it has not been used extensively for milling.〔 Over most of the range, acorns fall in October. A variety of mammals and birds eat them, including the acorn woodpecker, western scrub jay, yellow-billed magpie, and California ground squirrel.〔(US Forest Service Fire Ecology )〕 The acorns are also attacked by bruchid beetles, but can survive moderate levels of infestation. Surviving acorns all germinate in their first winter, and none remain by mid-winter. The acorns are medium to dark brown and range from two to three centimeters (0.8-1.2 inches) in length. The caps have deep stippling and are found most often as singlets, but occasionally as doublets. The Concow tribe call the acorns lō-ē’ (Konkow language). Globular galls up to several centimeters in diameter are frequently attached to twigs of mature specimens of valley oak. These house the larval stage of small indigenous wasps ''Andricus quercuscalifornicus''. A related wasp species, ''A. kingi'', produces small galls shaped like Hershey's kisses on leaf surfaces. The valley oak is the only known food plant of ''Chionodes petalumensis'' caterpillars. Like many oaks, valley oaks can tolerate wild fires. Although smaller individuals may be top-killed, most resprout from the root crown 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Quercus lobata」の詳細全文を読む スポンサード リンク
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