Barbed-wire pitch posts preserve forest history

At old ranches and on some remaining farms near the foothills, one can see old barbed-wire-fence "pitch posts." These relics of a bygone era artistically reveal some Colorado history and provide an interesting forestry lesson. Pitch posts were cut and split from the dense and heavy wood of live pitchy trees. Pitch is a resin found in evergreen trees and it forms when trees are injured. When the injury is caused by heat from ground-surface, low-intensity forest fires, and the fire has not killed the tree, more sap is made. This resin then concentrates in outer layers of sap-wood. Long ago, forest fires were started from lightning and often times by indigenous people. Native Americans knew that a flush of new and tender vegetation that sprouts after fire meant well-nourished game and thus better hunting. With no human effort to suppress forest fires, they were frequent, and trees were often injured by fire. In those conditions, a "relatively young," 150-year-old tree may have received fire damage three, four, five or more times in its lifetime. A living tree exposed to that many fires accumulates high concentrations of pitch all the way from its heartwood center out to the bark. Many fire-injured trees had a portion of their lower bark burned off. Exposed and charcoaled wood made inverted V-shaped black areas called "cat faces," usually on the uphill side. Often, the cat-faced trees healed over the charred surface with new wood, which can be seen in cross-sections of old pitch posts. Fire events can sometimes be dated by annual tree rings of wood that grew over the black fire scar or surround it...more