The range can be thought of as a sky island , as it contains numerous species of flora and fauna that can not tolerate the triple-digit-Fahrenheit heat of the surrounding valleys . Vegetation found on the mountain flanks is strongly influenced by elevation and climate . Near the valley floor , conditions are often arid and hot , limiting the vegetative palette to species that are adapted to such conditions . At lower elevations forestation of the San Jacinto Mountains includes considerable California black oak associated with Coulter pine . At higher elevations , forests include Ponderosa pine , Jeffrey pine , Lodgepole pine , Incense cedar , White fir , Red fir , and deciduous oak . There is also a grove of over 150 Giant Sequoia Trees on the northeast facing slope . The sequoias ( native to the Sierra Nevada Mountains ) were planted by the U.S. Forest Service in the 1970s , and are now apparently healthy and producing seedlings . As in many other western U.S areas , bark beetle infestations have caused loss of some of the forest trees in recent years , especially during droughts . Wildfires , such as the Mountain Fire and the Cranston Fire , have also temporarily denuded some areas
Mountain Fire
Mountain Fire
San Jacinto Mountains