Native California Shade Trees--East S.F. Bay Area

Can anyone recommend types of shade trees native to the Livermore, Calif. area region with hot summer days in the East S.F. Bay area? Sunset Magazine identifies this area as Climate Zone #14. The trees would provide shade to livestock in a sheep pasture and should be drought-resistant which a native species presumably would be.</p>

Shade trees? Hmmmm I`m not sure if either of the California black walnuts are native in the Livermore Valley, but they make great shade trees. Then there are the live oaks - Quercus agrifolia, Q. chrysolepis my favorite - called interior live oak, Q. wizlezenii. If you wanted more sun in the winter, you could go with a deciduous oak like valley oak - Q. lobata. Fall is the best time to plant these trees! Lori</p>