Deserts, wildfires, shrubby species, amazing finds: such is the life of Arizona Big Tree Coordinator.

By Bob Zahner

As a kid growing up in the Southern Appalachians I loved the forests and was interested in their conservation. This interest was expressed eventually as I became a professional forester and university professor of forest ecology.

On retirement from teaching in the eastern forests at the University of Michigan and at Clemson University, my wife Glenda and I discovered the wonders of dry climate trees in the deserts and mountains of southern Arizona. From our home near Tucson we hiked many wildland trails, learning all we could about plants and their habitats. This activity soon led me to the Arizona Register of Big Trees (ARBT), newly organized in 1991 by horticulturist Richard Harris.

Through my forest research I had become fully aware of American Forests' Big Tree Program. When I first joined the ARBT group, the National Register listed 16 champion trees for this state, most of them nominated by people just passing through Arizona. And most locations were in or near urban areas and along highways. There were also an amazing number of "species without champs" that occur in Arizona. It seemed to me that the potential for new champions was great.

In 1993 I volunteered to be our state coordinator. I knew we needed to get out of the urban areas, into the mountains, canyons, and deserts. But I had to adjust my sights to the small sizes of these dry climate "trees." Even the champions of most desert species don't grow very large, and many of these are endemic to just the Southwest. On the other hand, the streamside and mountain forests are different; there we have discovered champion sycamore, cottonwood, ash, cypress, pine, oak, maple, and juniper, all trees any state would be proud to boast.

Within two years Glenda (a botanist) and I had added 10 new national champions to the Arizona tally. Our technique was simple. We already knew many field botanists, birders, federal and state forest and park rangers, and passed the word to them to be on the lookout for large specimens of any tree species. Then I consulted herbarium specimens, species range maps, and notes from trail guides. Suggestions soon began pouring in. We now have many big tree hunters from all over the state, and coordinating their discoveries has become a major job.

By 1996 we had 48 national champions, and published our first "Arizona Register of Big Trees," with full-color photographs. In the year 2000 we published our second big tree register, then with 72 national champions. In 2002 my health began to fail for fieldwork, and I knew I'd soon have to retire from my job as the ARBT coordinator. I wanted to publish one more state register, which we did in 2005 with 88 national champions (2006 total: 82 national champs).

Of all of my nominations, the most exciting was the national champion Torrey vauquelinia. Like so many of our southwestern tree species, the vauquelinia is normally a large shrub, with a few stems reaching minimum tree size. Glenda and I had heard from a park ranger that there were some nice vauquelinia trees far up a remote canyon in Organ Pipe Cactus National Monument, down near the Mexican border. After backpacking several miles up the canyon, we began to pass a few tree-sized vauquelinias, and then suddenly, there it was, its huge crown emerging from giant boulders, towering 47 feet over all surrounding vegetation. We couldn't believe it, that this desert species could grow into a tall single bole tree over 2 feet in diameter!

A big tree coordinator's job is a roller coaster of expectations and disappointments. Arizona is a state with frequent severe wildfires, which keeps us on the alert monitoring our many champions out there. We have lost to wildfire an average of one a year, which the ARBT must try to replace. On the other hand, it is a thrill to find that a champion tree has in fact survived a holocaust. In the desert, lightning strikes are tree killers, and our giant saguaro cacti are the tallest things out there. Three times over the past 10 years it has been devastating to find our champion saguaro splattered on the ground.

"This has got to be the largest cottonwood tree in the world," I shouted. We had just rediscovered the gigantic Fremont cottonwood that used to be the national champion decades ago, but had been bested by a somewhat larger tree in New Mexico. We remeasured it, and sure enough it had grown significantly in the years since it had been dethroned. We re-instated it not only to national champion, but at 42 feet in girth and 623 points it turned out to be largest specimen of any cottonwood species in the U.S., and possibly in the world.

I (often with Glenda) have nominated probably 20 or more trees that have become national champions, but many of them have subsequently been dethroned. There were still 12 listed on the 2004 National Register (10 for 2006). The amazing record of the ARBT is due in large part to the zealous fieldwork of three very motivated men and their very understanding wives: Ken and Kathy Morrow of Patagonia (Morrow has taken over as Arizona's state coordinator), Mike and Sylvia Hallen of Chandler, and David and Judy Thornburg of Cottonwood. Each of these couples has more than a dozen champions listed on the current National Register. And they are still out there scouring the state to ensure that Arizona (currently #3 in number of national champs) stays among the champions of champion trees. AF

American Forests salutes Bob Zahner, who recently retired as our Arizona state Big Tree Coordinator. The National Register of Big Trees is better off because of you, Bob; we'll miss you.[TOP]