Fire History from Tree Rings Introduction
The massive and devastating wildfires of the late 1800’s and early 1900’s contributed to a nationwide movement that identified wildfire as being an undesirable, destructive force that must be prevented and controlled Other events helped strengthen the Smokey Bear message during the mid-20th century. In 1942, a Japanese submarine surfaced near southern California and fired shells that landed close to Los Padres National Forest. This raised concerns that the timber resources of the Pacific Coast could easily be set ablaze and lost. All able bodied men who could serve as firefighters were at war, so the Cooperative Forest Fire Prevention Campaign and Wartime Advertising Council decided to use propaganda to prevent wildfires. By convincing people to be more careful with fire, they could save America’s vital timber resources and thereby help win the war. US Fire History
US Fire History • More help came from the Walt Disney movie Bambi in 1944. This movie depicts the evils of wildfires through the eyes of adorable, fluffy little animals. People identified with these animals, so Smokey Bear, who was also adorable and fluffy, was chosen to be the nation’s number one firefighter. • Started in 1944, the Smokey Bear campaign is the longest running public service campaign in United States history. His message remained unchanged for 50 years until 2001, when it was updated • Today Smokey is working to educate people that wildfire is a destructive natural force that is usually caused by human carelessness. Smokey also explains that the current devastating wildfires are caused by fire suppression, climate change, and increased residential encroachment on wildland areas.
Fire regimes: • Fire frequency: how often • Fire seasonality: when fires occur throughout the year • Fire severity: effects on forests – not a measure of fire temperature • Fire intensity: a measure of fire temperature • Fire extent: spatial aspects • Patchy fires versus landscape level fires • Fire variability: changes in fire over time and space • Climatic or human-driven?
Fire Regimes • A natural fire regime is a general classification of the role fire would play across a landscape in the absence of modern human intervention, but including the influence of aboriginal burning. • In the southeastern US, there have been 4 different fire regimes
Southeastern Fire Regimes • The first fire regime existed prior to Euro-American settlement • Characterized by periodic, low-intensity fires set by lightning and by Native Americans, who augmented the natural fire regime • Wildfire acted as an intermediate-scale disturbance agent that promoted a mosaic of different vegetation types • The abundant distribution of fire-tolerant species during the pre-settlement era indicates that fire was an important force in North American forests before Euro-American settlement
Southeastern Fire Regimes • Fire-tolerant species – species that are able to survive fire events • Examples – most pines (excluding white pine) and several species of oak • Fire-intolerant species – species that are not able to survive fire events • Examples – maples, tulip poplars, sycamores, gums
Southeastern Fire Regimes • The second type of fire regime began when Euro-American settlers arrived and adopted Native American burning techniques to manage vegetation. • Euro-Americans continued the equivalent of prescribed burning and considered occasional wildfires part of the natural world • Burning during this period increased as a result of the increase in Euro-American population density
Southeastern Fire Regimes • The third type of fire regime began with the Industrial Revolution when widespread timber harvesting used steam-driven locomotives that also provided the ignition source for an era of high-severity fires • Intensive logging created vast areas of dried slash that were easily ignited by stray sparks from the steam power used in lumber transportation and processing • Fires that burned during this period were generally of much greater severity than during the pre-settlement and early-settlement periods and were deleterious to soils, waterways, and adjacent uncut forests • A nationwide conservation movement identifying wildfire as a destructive force was initiated after the massive wildfires of the late 1800s and early 1900s
Southeastern Fire Regimes • Finally, the fourth type of fire regime is marked by fire suppression during the 20th century, which allowed forests to recover, but also allowed fire-intolerant species to increase in dominance and hinder regeneration of yellow pines and xeric oaks • Fire was viewed as a threat to the nation’s timber supply during this time with paper companies in the southeast leading the call against fire. • Even though early Forest Service leaders understood the dangers of fire suppression, particularly in pine stands the Forest Service still opposed the use of prescribed fire • Forest Service promotional campaigns (such as Smokey Bear) taught Americans to be careful with fire, but also that fire had no place in maintaining American forests • This last change in fire regimes is considered responsible for the decrease in regeneration of fire-adapted species • Elimination of low-intensity surface fires has increased the density of stands with mid-stories and understories now consisting of fire-intolerant, shade-tolerant shrubs and trees
Southeastern Fire Regimes • The current period in fire history is one of fire management, where the historic role of fire is increasingly studied and integrated into forest management, mainly through the use of prescribed burns • A prescribed burn is fire that is applied in a knowledgeable manner to forest fuels in a specific area under specific weather conditions to accomplish predetermined, well-defined management objectives • The first approved prescribed burn took place in 1943 in Osceola National Forest, Florida, but the use of prescribed fire did not become common in the Southeast until after World War II
The Problem • The urban-wildland interface can be defined as an elevated human population living in a natural setting adjacent to population centers • As the urban-wildland interface shrinks, suppression costs, damage to public lands, rehabilitation, emergency aid for business and unemployment and reimbursements for firefighting effort will add to wildfire costs in future • These wildlands that are associated with the urban-wildland interface depend on fire to maintain health and biodiversity. In the absence of fire, vegetation grows quickly creating the fuel load necessary for intense wildfires. • In many wildlands, fire has become inevitable because of lightning or human-caused ignitions. The more people living in this interface, the more costly and intense fires will become.
Low severity wildfires … stays on the ground. Kills grass, shrubs, seedlings, saplings, dead and decayed trees, and diseased trees.
The fire-scar record from tree rings. Fire scars Catface on Table Mountain pine log, Reddish Knob, Virginia
The fire-scar record from tree rings. Fire scars on ponderosa pine, El Malpais National Monument, New Mexico
Seasonality of past fires from tree rings. This scar appears almost in the middle of the ring, so the fire occurred in the middle of the growing season Fire scar One Year Detail of fire scar on ponderosa pine, El Malpais National Monument, New Mexico
Notice how the tree tries to compartmentalize the fire scar wound by growing succeeding years around the wound. Detail of fire scar on ponderosa pine, El Malpais National Monument, New Mexico