Friday, December 24, 2010

Joshua Tree

Joshua Tree National Park is located in southern California. It was declared a National Park in 1994 after being a National Monument since 1936.  It is named for the Joshua tree (Yucca brevifolia; right photo) forests native to the park. It covers an area that is slightly smaller than Rhode Island. The park includes parts of two deserts: the higher Mojave Desert and lower Colorado Desert.

I visited the park on my road trip to Truckee in May of 2006 and took these photos.  I recently found some cool facts about the park and the trees that I wanted to share.

The higher, drier, and slightly cooler Mojave Desert is where you can find the Joshua trees. The name Joshua tree was given by a group of Mormon settlers who crossed the Mojave Desert in the mid-19th century. The tree's unique shape reminded them of a Biblical story in which Joshua reaches his hands up to the sky in prayer.

Like most desert plants, Joshua tree blooming is dependent on rainfall. They also need a winter freeze before they will bloom. Once they bloom, the trees are pollinated by the yucca moth, which spreads pollen while laying eggs inside the flower. The moth larvae feed on the seeds of the tree, but enough seeds are left behind to produce more trees. The Joshua tree is also able to actively abort ovaries in which too many eggs have been laid.

There is some concern that climate change will eliminate Joshua trees from the park; which will damage and fundamentally transform the ecosystem of the park. The giant Shasta ground sloth (Nothrotheriops shastensi) went extinct 13,000 years ago; but their dung has been found to contain Joshua tree leaves, fruits, and seeds, suggesting that the sloths might have been key to the tree's dispersal.  Therefore, is concern about the ability of the trees to migrate to favorable climates.

The western part of the park also includes hills of bare rock, usually broken up into loose boulders like you see in some of the photos. I took a hike and found water and birds (of course).

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