Plant Ecology of the Sonoran Desert Region - Design with the Desert: Conservation and Sustainable Development - page 166

8.7 Invisible Larder
I conducted a wildlife survey in the Lower Colorado River Valley in the 1970s. The site had
received almost no biologically effective rainfall for 3 years. Creosote bushes were almost
the only plants present; they were widely spaced and had shed most of their leaves. Yet
in the kilometer-long by 50-m-wide transect, I trapped one pocket mouse overnight, and
in the morning observed a whiptail lizard, a rock wren, and two black-throated sparrows.
These are all resident species; not transitory migrants. What were they living on?
The soil seed bank is a phenomenon unique to arid habitats. It provides an unseen
(by humans) food source for desert animals as well as survival insurance for plant species.
The greater density of seed-eating animals and the abundance of decomposing microbes in
the moist soils of wetter regions greatly shortens the viability of seeds. In deserts viable—
and nutritious—seeds persist in large numbers through decades of drought. After a wet
year there may be 200,000 seeds per square meter (square yard) of soil. Even after several
dry years with little or no additional seed production there are still several thousand seeds
per square meter, enough to sustain low populations of seed-eaters such as harvester ants,
kangaroo rats, and sparrows. The whiptail was foraging for insects that fed on the seeds
or plant detritus (partially decomposed organic matter) in the soil.
Further Readings
Bowers, J.E., A Full Life in a Small Place and Other Essays from a Desert Garden (Tucson, AZ: University
of Arizona Press, 1993).
Dykinga, J.W. and C. Bowden, The Sonoran Desert (New York: Harry N. Abrams, 1992).
Hanson, R.B. and J. Hanson, Southern Arizona Nature Almanac (Boulder, CO: Pruett Publishing, 1996).
Hartmann, W.K., Desert Heart: Chronicles of the Sonoran Desert (Lady Lake, FL: Fisher Books, 1989).
Imes, R., The Practical Botanist: An Essential Field Guide to Studying, Classifying, and Collecting Plants
(New York: Fireside Books/Simon and Schuster, 1990).
Larson, G., There's a Hair in My Dirt! A Worm's Story (New York: Harper-Collins Press, 1998).
Nabhan, G.P., The Desert Smells Like Rain (San Francisco, CA: North Point Press, 1982).
Nabhan, G.P., Gathering the Desert (Tucson, AZ: University of Arizona Press, 1985).
Nabhan, G.P. and S.L. Buchmann, The Forgotten Pollinators (Washington, DC: Island Press, 1996).
Seuss, Dr., The Lorax (New York: Random House, 1971*).
* This topic can be found in the children's and humor sections of bookshops, it conveys the essence of ecology
better than any scientific treatise I have encountered. The Lorax should be required reading for every citizen
of planet Earth.