On-Line Activity

Over the years, the Ice Caves has allowed many universities to come and make detailed studies of the Geology, Botany, and Biology of the area. One of the most recent groups to do this was the University of Arizona Tree Ring Laboratory. From their research we have learned that one of the oldest douglas fir trees in the area is along the Ice Cave trail. The age of this tree was determined by taking a core sample of the tree. Other tree ring studies were done that give a very good account of the forest fires that occured in the area over time. One such set of tree rings is shown below. The information below was gained from this research.

This is a cross-section taken from a Douglas-fir tree that was killed by lightning sometime around 1952. This tree began its life on the slopes of Cerro Bandera, the cinder cone to the west of Bandera Crater, in the year 1640. During its 312 years, this tree would witness many events that changed the surrounding environment of the malpais. When the tree was only twenty years old, a forest fire swept through the area around the cinder cone, leaving a scar that provides tree-ring scientists the evidence needed to learn more about the history of past forest fires in the malpais. Many more forest fires followed. In all, this tree would record the occurrence of over 30 forest fires on the slopes of Cerro Bandera, or about one fire every ten years. Together with other trees collected, we now know that fire occurred on average about once every six years in this area of the malpais before white settlement began. Click the picture at left for a detailed image of the top section. Do you know what the arrows are pointing at?

Scientists now are aware that the forests of the American Southwest witnessed fire on a fairly regular basis during the last 400 years. However, because of grazing and fire suppression, the character of these forests changed during the last 100 years. Forest stands became unproductive and overstocked without fire to maintain the forest ecosystem, which also had a profound effect on wildlife. The type of information on fire frequency available from trees such as this Douglas-fir can be used by scientists to help reintroduce and restore fire in the forests of the Southwest. Without these low-intensity fires sweeping through and "cleaning" the forests, these stands become more and more susceptible to the high-intensity, catastrophic fires as forest fire "fuels," such as pine needles, twigs, large branches, and entire logs, build up to dangerous levels over time.

To try your hand at counting tree rings, we have provided slabs of Oak, Douglas Fir, and Ponderosa Pine below. Just click on each picture to bring up a virtual tree ring core. Counting begins at the left in each core image, just scroll your browser window to count the rings. Each of the slabs is approximately 3 to 3.5 inches in diamater, and grew within 50 feet of each other. How old is each tree?