Friday, October 16, 2009

Homogenous Eclecticism

Lantana from South America

15. What are the major plant associations in your region?

In my lifetime, I've lived in at least eight different major ecosystem types, from the Pacific northwest Douglas Fir forests to the mixed hardwood forests of northern Illinois, and now to the Sonoran Desert. Maps for the larger plant associations or communities can be found in any ecology or plant geography textbook. Here in Phoenix, we inhabit a transition zone between the hilly Arizona Uplands, dominated by saguaros and palo verde and the broad flats of the Lower Colorado River Valley division of the Sonoran Desert, which gives us miles and miles of creosote and bursage. Anywhere you venture in natural areas within 50 miles of where I live, you will find these plants. The thousand or so other species occur in pockets, arroyos, at springs and on special rock outcrops along with these four dominant species. Brittlebush is another I would name as ubiquitous, but mostly because it is a reliable drought tolerant pioneer, able to drop in almost anywhere there has been a disturbance, especially in the Uplands.

But the plant association of the suburbs has not been mapped. What is in the wild and what we have transplanted into our suburbs is an entirely different assemblage of plants than the natural areas that have accidentally or intentionally been preserved. The suburban plant association is an eclectic collection of species gathered and cultivated for landscaping from all over the globe. We have euphorbias, aloes and gazanias from Africa; giant cereus cacti, lantana and bougainvillea from South America; acacias, senna and eucalyptus from Australia; oleander, olives and chaste tree from southern Europe. From China we've imported rose vines and jasmine. From other regions in North America we bring Texas sage, red yucca and candelilla. We even have an endemic from Afghanistan, Pinus eldarica, or Afghan Pine.

In fact, if you thumb through a handy guide distributed by our regional Water Conservation Committee, Landscape Plants for the Arizona Desert: Guide to Growing More tThan 200 Low Water use Plants," nearly half of the recommended species are not native to the local region. And so we have created our own kind of plant association here in the suburbs. Although Sonoran natives are still included in the melieu...palo verde and mesquite are favorites in most parking lots...the dominant creosote and bursage that occupied the suburban landscape before they were bulldozed away are largely missing. Saguaros remain as occasional icons of the native landscape, but often don't survive the process of development.

I've often wondered what would become of the Suburban "division" of the Sonoran Desert flora if humans suddenly left, irrigation was ceased, and all of these species were left to fend for themselves in these foreign soils. Would they thrive or die off? Would they adapt and invade? Would they eventually mingle and reproduce well enough with the natives in the wild to create a whole new plant association?

Lilac Vine from Australia

Some have already shown their adaptability. We usually denigrate them by calling them "noxious weeds." Bermuda grass, fountain grass and African sumac are a few of the species that do quite well on their own here, to the bemusement of land managers whose predecessors may have brought them here. Others die off quickly without a drip. Our neighbors abandoned and foreclosed on house is surrounded by skeletons of lantana and ailing Queen palms.

Either way, I quite enjoy all of them, especially when I'm walking in the morning, and notice the also introduced swarms of honeybees (from Europe) feeding on daleas (from the Chihuahuan desert), and hummingbirds (native) slurping nectar from red yuccas (Chihuahuan), house sparrows (from Europe) congregating in fig trees (from Africa and China), and cottontails (native) feasting on Bermuda grass (African). The landscape changes slightly every fifty feet or so, depending on the preferences or inherited landscape of the current homeowner. Perhaps these variations could be called the Bermuda/Palo Verde/Lantana association; or the Texas sage/willow acacia association; or the senna/mesquite association. This wonderfully eclectic collection of plants is, however, uniquely homogenized into our own humanly assembled plant community, and it is spectacular!

1 comment:

Belladonna said...

Here's a question for you. I bought a bi-color lilac bush for Mother's day. It had a thin white line outlining each green leaf which I thought was very pretty. But when I looked at it recently the leaves were solid green. What happened to my white line? Will it come back in the spring?