English N. B., Dettman D. L., Sandquist D. R., Williams D. G., Daily to decadal patterns of precipitation, humidity, and photosynthetic physiology recorded in the spines of the columnar cactus, Carnegiea gigantea, Journal of Geophysical Research: Biogeosciences, 2010, 115(G2):G02013, doi: 10.1029/2009JG001008
A study of saguaro spine-growth chronology and carbon and oxygen isotope records. Marking and photography support a daily interpretation of tissue bands. Short series and one multidecadal record link isotope signals with rainfall, humidity and growth while retaining physiological limits to interpretation.