Flora and Fauna News

Sonoran Desert Edition

Wednesday, July 30, 2003
Vol. 5 No. 13


Monsoon Moisture Reaches Southwest Deserts


By Michael Plagens
Sonoran Desert Sciences


PHOENIX ----- Humid air from the tropics pushed into southwestern Arizona on July 18 but it took almost two weeks before any significant rainfall could be squeazed from it. Winged ants and termites have emerged from their deep soil retreats ready to swing into action and plants will green up within days.

Just last weekend most desert areas were brown and lifeless looking. Of course the desert wasn't truly lifeless, just dormant and waiting. Crickets and moths also emerged at once with the rainfall and are busy laying their eggs on the tender new foliage. The roller coaster boom and bust of the desert environment makes survival and successful reproduction all the more challenging.

The cicadas that laid their eggs recently will find favorable burrowing conditions in the moistened soil. But the seeds of Saguaro Cactus and many other plants that germinate now in response to the rain will face a gauntlet of hungry creatures wishing to dine on sprouts. House Finches, Black-throated Sparrows, and Gambel's Quail were already engaged in eating as many sprouts as fast as possible. Once the germinated seeds become established in a week or so they will begin producing compounds (esp. lignin and cellulose) that drastically reduce their palatability to birds and other animals. But because so many seeds have germinated all at once, and because populations of sprout eaters are down because of years of drought, many seedlings will survive this initial phase. Daily temperatures will likely bounce back to 40+ºC and without additional rain within the next two weeks most if not all of the new seedlings will wither and die.

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Photo by Mike Plagens
Creosote after months without rain.


Photo by Mike Plagens
Rejuvenated Creosote a few days after rain.

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Flora and Fauna News appears several times
per month and provides current information about the birds, insects and plants
(natural history) living in the Arizona Sonoran Desert.
Copyright Michael J. Plagens, 2008
Send questions or comments to mjplagens@arizonensis.org