Arizona Public Radio | Your Source for NPR News
Play Live Radio
Next Up:
0:00
0:00
0:00 0:00
Available On Air Stations

Earth Notes: Juniper and Ash

Jim Harrigan

Nine hundred years ago the eruption of Sunset Crater volcano must have been a brilliant spectacle. Ultimately, nearly 750 square miles of northern Arizona were blanketed in cinders and ash. After the destruction, life slowly returned. 

The Sinagua people living in the area discovered that the ash acted as a mulch that helped crops grow. Now, a tree called one-seed juniper thrives at Sunset Crater and neighboring Wupatki National Monument, but on about five inches less precipitation than it normally needs.

How do these trees manage? Soil scientist Jim Harrigan of the USDA Natural  Resources Conservation Service tested the ash soils at Sunset and Wupatki and compared them to other soils, such as loam and sandy loam, considered to have superior water-holding and drainage properties.

He learned that the ash soils absorbed and retained rain water more quickly and efficiently than the others.

Ash and cinders are light and filled with air spaces that serve as miniature water-storage tanks. The hairlike roots of one-seed juniper seedlings penetrate the soil particles into these hidden stores of water. Apparently that’s enough to keep a young juniper going until it can grow larger, stronger roots to reach deeper water.

These hardy trees are adapting just as the early human dwellers of Sunset Crater and Wupatki did, in their land of little water.

Related Content