if trees could talk: the tree ring story

A tree's age can be easily determined by counting its annual growth rings. The width of the annual rings can tell us about conditions of each growing season. Trees also may record other events, such as fires. Pines with thicker bark, such as Spruce Pine and western Ponderosa Pine, normally record fire scars. Because of their thick, fire-protective bark, most of Florida's slash and longleaf pines will not record fire scars. The exception, however, occurs when a tree is injured so that the cambium is exposed to fire — the tree will then record fire scars until the injury completely heals, a process that may take many decades. Some injuries are from unknown sources, but many injuries on southern pines are from scrapings, or "catfaces," made for the collection of tree gum for the production of turpentine and rosin. This was called the Naval Stores industry because it supplied essential materials for ship repair. Most catfaces were made in the first half of the 20th century.

The tree rings provided with the Fire in Florida's Ecosystems package are digital photographs of southern trees that show fire scars. A brief history and description of each tree is provided below. Your students may need to use a magnifier to "read" the tree rings and fire scars in the photos. You may want to share background information with your students and tell them the outer date on the tree, then let them measure the fire scars and guess the ages of the trees. Salt water intrusion shows up on some of the trees as grey areas. All of these trees were collected after they had died.

Cape St. George, Florida

Cape St. George is a barrier island in the Florida panhandle region. It is also know as Little St. George Island. The island was burned in a lightning fire during the early dry part of the 1999 growing season (April-July). Many of the older tress on the island were killed in the 1999 fire. Most of the other fires recorded in the tree rings also were started by lightning during the growing season, which is the most common time for fires in Florida.

Humans have tried to influence fire frequency on Cape St. George for the entire history of these trees. Naval stores operators either tried to prevent fire or burned frequently to lower fuel levels around the vulnerable trees. Throughout the second half of the 20th century, humans tried to exclude fire from Cape St. George -- first with cattle grazing, then during military operations in the 1960s and 1970s. The State of Florida Park Service took over management of Cape St. George in the 1980s and conducted prescribed fires to enhance the natural ecosystem. The Apalachicola National Estuarine Research Reserve assumed management of Cape St. George in the 1990s and has put out some fires and has let other fires burn. The current policy is to let lightning fires burn if they can be kept away from historic structures on the island.