House In Joshua Tree National Park, California, United States

The higher, drier, and slightly cooler Mojave Desert is the special habitat of Yucca brevifolia, the Joshua tree for which the park is named. It occurs in patterns from dense forests to distantly spaced specimens. In addition to Joshua tree forests, the western part of the park includes some of the most interesting geologic displays found in California's deserts. The dominant geologic features of this landscape are hills of bare rock, usually broken up into loose boulders. These hills are popular amongst rock climbing and scrambling enthusiasts. The flatland between these hills is sparsely forested with Joshua trees. Together with the boulder piles and Skull Rock, the trees make the landscape otherworldly.
Joshua trees dominate the open spaces of the park, but in among the rock outcroppings are piñon pine, California juniper (Juniperus californica) and scrub oak. These communities are under some stress, however. The climate was wetter until the 1930s. The same hot and dry conditions that provoked the Dust Bowl affected the local climate. These cycles were nothing new, but the original vegetation did not prosper when wetter cycles returned, however. The difference may have been human development. Cattle grazing took out some of the natural cover and made it less resistant to the changes. But the bigger problem seems to be invasive species, such as cheatgrass. These things deliver a double punch. During wetter periods, they fill in below and among the pines and oak. In drier times, they die back, but do not quickly decompose. This makes wildfires hotter and more destructive, which kills some of the trees that would have otherwise survived. When the area regenerates, these non-native grasses form a thick layer of turf that makes it harder for the pine and oak seedlings to get a roothold. This is not a very generous environment and there are not that many second chances.