In even-aged industrial plantations, fire protection is required on external plantation boundaries to protect Acacia, Eucalyptus, Pinus and other even-aged timber plantations, from wildfires originating from beyond these plantations’ property boundaries. Many lands outside plantations consist of some form of natural vegetation (such as woodland, indigenous forest or grassland), nature reserves or agricultural land used for grazing or growing of short-rotation crops. Industrial plantations can also border public roads or railway lines, rural or farming communities, urban-interface areas of cities, or industrial sites. What these different types of land-use along plantation borders have in common is that they all present varying degrees of wildfire hazard to plantation timber resources.
External fire protection, in the form of firebreaks, can be provided along plantation boundaries in various ways, such as:
• Regular burning of grassland or other bordering vegetation.
• By adding prescribed burned plantation stands.
• Ploughing of firebreaks.
• Scraping of firebreaks.
• Hand-cleaning (or fuel removal within) fire breaks.
• Maintaining (or scraping) of roads on external boundaries.
Dynamic grasslands (such as Australian or African montane and savannah grassland) are normally burned after grassland curing has commenced. Before curing starts, tracer lines are prepared by means of chemical surface sprays, so that the grass within these lines can die before curing takes place, and to ensure that they can be burned prior to grassland curing. This is done to make certain that these lines are in place before the prescribed burning season, so that they do not take up valuable burning time after grassland curing. The grassland between these tracer lines is then burned on days suitable for prescribed burning; as soon as possible after grassland curing is completed. The burning of static grasslands (such as the Pampas) is regulated by grazing intensity, yearly biomass production (normally related to climatic factors such as rainfall) and age, as there are no clear seasonal fuel changes.
It is equally important to reduce fire hazard within plantations, than to provide external fire protection. Fires can originate within plantation blocks, or external wildfires can spot or burn across external firebreaks. If this happens, internal fire breaks will have to ensure that the spread of these fires within “plantation areas at risk” is restricted to the smallest area possible, and the smaller (and better protected) these plantation units are, the better will be the chances to bring these internal fires under control, and to minimize damage. Clean roads within plantation blocks, regularly-burned wetlands, indigenous forests, steep (rocky) terrain with low fuel profiles, rivers with riverine forests and slash-burned compartments, are all examples of suitable internal protective barriers that can be incorporated into internal fire break systems. The more continuous these lines are, the better the chances will be to restrict wildfires within plantation boundaries.
Watershed lines - also acting as firebreaks - can also be utilised as “wildlife corridors” and even facilitate optimised water runoff, thus forming multi-purpose fire management systems. Alternative firebreak routes should be investigated, where these requirements cannot be met.
Because of the clearfelling regime applied in even-aged industrial plantations, slash is deposited in large quantities where mature trees are felled and exploited, prior to re-establishment. In many cases this litter-and-slash loading occurs in low quantities, which will not present tree re-establishment problems. However, in some areas, e.g. at some high altitude sites, the slash loading can be of such a nature that access and replanting is severely restricted. It is then that some degree of fuel reduction will be a required to make economical re-establishment of trees possible. Sometimes slash burning will have to be applied regardless whether the fuel loading is restricting access for replanting purposes or not, because the stand is either bordering a major fire protection bufferzone, or falls within a major bufferzone/fuel break area. It is important to evaluate slash features such as loading, spread and vertical distribution in clearfelled stands, to determine whether slash burning should be considered as a fuel reduction measure, or not. Slash burning should be avoided on sandy soils or other sites with low nitrogen levels. However, if slash burning cannot be avoided on these sites, the impact of these burns on nutrients should preferably be determined by means of the collection and analysis of surface soil samples (sampling to be applied before and after the burn). Slash burning on steep slopes should also be avoided to prevent erosion.
With regard to slash burning techniques to be used, broadcast burning of slash (after spreading the slash when timber removal is completed) is recommended in most cases because (a) it has proved to be the safest and cheapest method, and (b) stacking of slash in heaps and then burning the heaps has not only proved to be more expensive, but is also exposing the soil to high fire temperatures for longer periods of time, which can be detrimental to chemical and physical soil properties.
Selective use of prescribed burning inside stands can also be considered as a fuel reduction measure, particularly where a serious lack of decomposition of litter is experienced. This technique can also be used to combat certain weed problems, to eradicate insect pests and can even enhance nutritional availability. Specific species/age requirements and burning techniques are needed in this case.
Where natural heritage areas are situated within plantation boundaries, special care will be required when prescribed fire is to be applied. Where ancient rock paintings, prehistoric villages or other heritage sites are found, care should be taken to apply fire in such a manner that no damage (such as fire scorch) is caused. Preventative measures in the form of physical fuel removal around the site, or fire application only when the wind blows from a specific direction (away from the site), may be required, or will be stipulated in the form of written rules in the fire protection plan.
The creation of natural corridors through areas covered by plantations - many times making use of major wetland/river lines and mountain crests - should be considered where buffer zones (sensu fuel breaks) are placed and maintained. This will provide free access between forest and grassland sites for mammals such as grazers, within and outside plantation boundaries.
Other important issues to be considered are the protection of breeding areas for rare bird species within plantation boundaries, and to avoid any fire application too close to these nesting sites. Some species may prefer steep mountainous terrain for nesting platforms, while other species may prefer wetlands or marshes to breed. In each case it is important to identify and map these nesting sites, and to avoid any burning operations close to these sites during the breeding period.
Where nature walks and trails exist within plantation property boundaries, care should be taken to apply fire protection in such a way that the immediate area surrounding these routes is burned in a prescribed sequence, so that no large areas are blackened simultaneously, but rather burned in strips or blocks in rotation, with footpaths forming the fire break tracer lines, where possible.
In many cases fuel-break systems or buffer zones along specific lines - normally facing the direction of hazardous wildfire threat at an angle - are constructed, of a width of up to 500 m or even wider, to replace inadequate fire breaks. A qualified fire management specialist, who can identify optimum routes in the landscape and calculate minimum fire protection requirements, should preferably do the placing of buffer zones. It is also important to start fire protection evaluation by considering regional requirements before changing any within-plantation firebreaks, and to make sure that these zones comply with ecological and riparian zone specifications.
Many times buffer zones will follow natural fire barriers, such as steep terrain, existing indigenous forests or major rivers with riverine forests, but where these are not available, man-made lines such as public roads, railway lines or powerlines can also be used as a bufferzone base. In most cases a combination of natural and man-made fire protection areas, with some form of fuel restriction, will be used for buffer zones, which will bypass artificial boundaries. Where plantation stands have been identified as forming rather weak links in firebreak or bufferzone lines, incorporation of these stands as prescribed burned areas should be considered. Sometimes species and/or stand age may not yet be suitable for prescribed burning application, in which case (temporary) alternative routes should be investigated until such time that these stands have reached the correct age, or species have been changed.
Fire protection techniques (or fire break management procedures) other than regular vegetation burning - such as slashing, hoeing or some forms of soil preparation - may sometimes present viable alternative options for fuel reduction, if regular prescribed burning is not possible. However, it must be kept in mind that these may still present some fuel residue, and e.g. slashing of fuel still presents the same fuel loading, although the depth of the fuel bed has been reduced. Methods such as ploughing or scraping of roads can also be used effectively to create fuel-free fire protection lines when applied correctly.
