Researchers at Los Alamos National Laboratory in New Mexico have joined members of the National Park Service in an attempt to find out if air pollution is a possible culprit in the declining saguaro cactus forests of Arizona.

The saguaro is the tall cactus with upraised arms that is almost the living symbol of southern Arizona and the neighboring desert of Sonora, Mexico.But recent studies show that emissions from copper smelting and smog from the Tucson metropolitan area may be playing a role in the cactus' decline.

Researchers are taking soil samplles from the Saguaro National Monument near Tucson to see if such nutrients as nitrogen and potassium are becoming less available to the cacti and to test for the presence of pollutants in the ground.

They are also testing the role of pollution in the saguaro decline by taking samples of trees in the region to study the biological record of air pollution in all plant life in the area over the past century.

Saguaros, rarely found outside southern Arizona or Mexico, grow as tall as 30 feet.