Maintaining Forests to Prevent Fires

Forest fires are the archenemy of the trees and of the forest's ecosystem. A forest fire ignites when there is high temperature, oxygen and flammable material. A forest fire will spread when assisted by contiguous flammable material, both horizontal and vertical, by slopes and ravines and by weather conditions, primarily strong winds, low humidity and high temperatures.

The ability of foresters to be effectual in preventing forest fires and minimizing them is based mainly on reducing the amount of flammable substances in the area and breaking its contiguity vertically as well as horizontally. Good infrastructure also helps minimize the area a fire spreads to, such as access roads and water supply, above all, and early detection of the fire as well as availability of sufficient firefighters to reach the fire as soon as possible.

KKL-JNF rehabilitates forests damaged by an annual average of 600 wildfires that destroy 50,000 trees on an area of 800 hectares (2,000 acres).

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There are additional factors that can reduce the number of forest fires such as community participation in fire prevention through publicity and education, legislation, law enforcement and penalties.

Different trees and shrubs have different levels of flammability and rates of consumption. KKL JNF plants species that are relatively less flammable, which reduces the danger of fires. Research studies since the 1950s have examined the temperatures of fire ignition and the rates of fire consumption of standard species of forest trees and shrubs. In accordance with the findings, detailed charts were made for many kinds of trees and shrubs, and recommendations were made regarding planting and interface. The aim of the studies was to recommend planting trees and shrubs with low flammability rates and slow consumption rates, to reduce the probability of fire ignition and diffusion in places at a high risk for fires, and to plant along determined firebreak lines.

Research in Israel has shown that the Athel tamarisk, also known as the saltcedar, is the most suitable tree for preventing fires from spreading. There are also three shrubs with a low flammability rate - caper, mastic and oleander.

In addition, KKL JNF adopted a model developed for planting forests in Israel, according to which cypress and saltcedar trees, as well as shrubs with low flammability rates, are used as barriers and fire deterrents in planted forests, in accordance with the geographical region of the location of the forest.

The frequency of planted sapling rows varies in accordance with the surrounding conditions (incline, northern or southern slope, wind regime and so forth). In order to create firebreaks on summits and ridges, trees are planted sparsely with low, spreading shrubs planted among them.

In order to prevent forest fires, KKL-JNF distinguishes between young forests and mature forests with regard to their maintenance. A young forest is one that has been planted within the last six years and it is the most vulnerable to fires, since a fire will cause it total damage and prevent natural renewal. To prevent fires in a young forest, the area around it must be isolated. The area within it must have firebreaks, and the quantity of flammable substances must be reduced within the area (light and heavy flammable substances) along with controlled development of seedlings by spraying, grazing and so on.

Grazing in the forest is one of the methods for reducing the risk of forest fires, since it reduces the brush biomass, which serves as fuel for fires, and consequently assists in preventing fires from starting and from spreading.

fires start in low brush (leaves, twigs, grass), and their spreading to the treetops depends on the contiguity of flammable substances between the forest floor and the treetops. Proper grazing, which eliminates the low brush and the lower branches of the trees, will therefore considerably reduce the number of fires and also their magnitude. A young forest that is at least three years old can host a herd in the springtime without sustaining significant damage to its trees, and this can reduce brush biomass by at least 1,000kg dry material per hectare, a quantity that mitigates the danger of forest fires in the summertime.

Another issue involved in planting an area and opening it for grazing is the mixture of quick growing species, mainly conifers, and slow growing species, especially broadleaf. In forests where there are slow growing species, opening the area for grazing is delayed, and the time of year when the herds may enter is also prescribed.

 

Another operation that serves to protect the forest from fire is to spray the brush with herbicides. This requires a deep understanding of the types of chemicals, the way they work, and how resistant different plants are to them. The success of this treatment also depends a great deal on the spraying contractor’s level of expertise as well as on the fencing around the grove (the small unit of a forested area) in the young forest (preferably when it is being prepared for planting or for natural renewal), as a device for controlling the area.

The main operations for the tree interface of a mature forest include sanitation, thinning, pruning and removing the cuttings and the tree waste. Additional interface operations executed in order to reduce the quantity of flammable matter are the creation and maintenance of firebreaks and grazing lines. Treatment of the forest requires preparation of a program for the forest interface, which would include prioritization of the necessary tasks according to their level of urgency as dictated by the physical state of the forest, section or grove, primarily by considering the risk level of a fire starting and spreading.

This work includes creating barriers along principal roads that serve hikers and visitors (for example in recreation areas), along main ridge lines and, with especially high priority, where the forest borders on residential communities and other facilities.

 

The following are the details of the operations performed by KKL JNF in order to reduce fire damage in mature forests:

Sanitation – Continuous work done throughout the lifecycle of the forest, which includes removal of dead/desiccated/sick trees from the forest, whether they are upright or prone. Trees that cannot be removed due to problematic conditions are sawed into stumps around 1m long, which are left scattered in that section.

Thinning – Ideally, thinning should be done every seven to ten years. This entails removing the less developed trees and the withering trees. Thinning in conifer forests is done in accordance with the density charts that define the number of trees left while taking the age of the forest into consideration and the quality of the habitat. Some of the trees are removed by thinning, and the normal density level for proper development of the trees is thereby retained. In the process of thinning, a high enough level of shade is maintained for preventing massive development of sub-forest brush.

Pruning – Pruning includes the lower branches of a tree up to a third of its height, 2.5m from the ground at most. In recreation areas and along trails (where there is a higher risk for fires), pruning might be done as high as 4m. This is in order to remove the lower branches of the tree so that the treetop is separated from the ground. The lower branches tend to be very dry, and they conduct the fire upward. In the process of pruning, vines on the trees that could conduct fire up to the treetop are also removed.

Removing the Cuttings and the Tree Waste – The cuttings and waste are transported from the forest area to the side of the road, where they get chopped up and then removed from the forest for various uses or, alternatively, scattered on the ground. KKL JNF is careful about keeping a strip of forest along the roads free of cuttings and tree waste, for at least 30m from the roadside, and encourages the residents of nearby communities to use cuttings and tree waste for heating and other uses.

Burning the Cuttings – This is an interface operation of great importance for the management of cuttings, and it is customary in various forested countries as a routine treatment. After sanitation, thinning and pruning, the cuttings must be dealt with, and in places where the forest is on a steep slope or far from the road, the cuttings are burned in a glade. Spot treatments (such as felling a single tree) that do not justify or facilitate chopping up the cuttings, include burning.

Also, in order to respond quickly and effectively in the event of a fire, KKL JNF is responsible for the following checklist:

Water – Water supply infrastructure for providing fire trucks and firefighters with water in the event of a fire. Water is logistically the most important resource for extinguishing a fire.

Watchtowers – These watchtowers are intended for early detection of a forest fire and directing firefighters to its location. The watchtowers are positioned in a network so that any smoke rising above the forest will be visible from at least two watchtowers, which allows for precisely locating the fire that has been detected. The watchtowers are all at least 12m high.

Signposting – Destination signs and direction signs provide for quick and exact access to forest fires and assembly points. The forest fire direction signs on forest roads include the road number as determined by the Department of Public Works (DPW) as well as warnings about four wheel drive (ATV) limitations and dead ends. Forest fire destination signs are mobile signs intended for a specific fire as it is being extinguished that read: TO THE FIRE. In the event of a fire, these signs are placed in the area by foresters in order to direct the firefighting forces as they leave the main roads and follow routes leading directly to the fire.

*The information in this article was taken from a book called Forest Theory, which was written by KKL-JNF's professional staff.