Placerita Canyon has an abundance of oaks, mostly coastal and canyon oaks. You can find them along many of the hiking trails next to the nature center. There is a hike that leads to a waterfall- you might find some rotting wood there. I haven't gone all the way out to the falls, so it's unknown what tree species are closest to the falls, but you can collect the dry wood further up the trails and just start a rotting process yourself.