1. USDA‐ARS U.S. Water Conservation Lab. 4331 E. Broadway Road Phoenix AZ 85040
2. Humbolt Univ. of Berlin Dep. of Soil Science Invalidenstrasse 42 10115 Berlin Germany
3. Potsdam Institute for Climate Impact Research Natural Systems Dep. P.O. Box 601203, 4412 Potsdam Germany
4. LI‐COR 4421 Superior St. Lincoln NE 68504
5. Lab. of Tree Ring Res. Univ. of Arizona Tucson AZ 85721