February 2, 2012
The North Campus is the proud parent of some baby oak trees!
Baby coast live oak sheltered by wallCarol Bornstein, our new Director of the North Campus Gardens, discovered a couple of oak saplings on one of her recent outdoor forays. The babies are coast live oaks, Quercus agrifolia, of which we recently planted several trees. We've also planted another species of oak, the Engelmann oak, Quercus engelmanni (we planted only three of this species). Both species reside in the section of the garden called the urban wilderness which is composed of several kinds of California native trees and shrubs.
This might be the mother oak!Oak trees provide amazing habitat value, and this is the main reason we planted them. By putting in such a sizable stand of oaks we're hoping our created wilderness will provide habitat for a whole slough of organisms rarely, if ever, seen before in Exposition Park. In just one oak tree it would be easy to find hundreds of species of associated plants and animals and thousands of individuals (think how many birds, ants, or squirrels you find in an oak tree). One species that has already shown up with our oaks, is a tiny insect called a whitefly.
Crown whitefly nymphs on oak leaf(each nymph is only 1 millimeter long)It was once again thanks to Carol, who was out inspecting our lovely oaks, that we discovered these small insects. At first we thought they might be a scale insect, but Brian Brown, the Museum's Curator of Entomology, identified them as crown whiteflies, Aleuroplatus coronata. As adults these small white homopterous insects (group of insects consisting of aphids, cicadas, scales, etc) fly around to find a suitable location to lay their eggs. For the crown whiteflies their plant of choice is oak. What you see in the image above are the nymphs (immature forms) of the whitefly, they have no wings but are covered with white waxy secretions that make them look like little crowns. The nymphs feed on the leaf's juices by piercing and inserting their mouthparts into the leaf. They can cause damage to the plant's health if their numbers are high enough, and they can also transmit disease organisms from one tree to another (not unlike mosquitos transmit malaria).Go check out your local oaks and see what animals live on them!