Underpinnings of fire management for biodiversity conservation in ...

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Fire and adaptive management 42 Chapter 3 Prescribed burning as a fuel-modification measure Introduction In chapter two, the value of tracks in fire suppression was examined in the context of biodiversity conservation. From the point of view of stopping a fire, the fire property examined in grasslands (without trees and other significant sources of brands) was the length of flames in relation to the width of the track in the fire’s path. In eucalypt forests in which the production and spread of fire brands is significant, tracks were useful for stopping fires, but only over a limited range of intensities. Therefore, the modification of the fuel array throughout a significant proportion of a forest area, to minimise the production and dissemination of airborne burning materials, may be advocated. With reduced fuel loads and modified fuel structure, the potential for spread by fire brands can be reduced for a number of years. A common cost-effective way to reduce fuel loads and modify fuel structure, especially where woody fuels are predominant, is to use fire under defined and low-risk conditions – prescribed burning (Text Box 3.1; Plate 3.1). Prescribed burning reduces the fuel load, fuel continuity, loose lower bark of trees and, initially at least, the proportion of dead-to-live fuel contained within the fuel array. Therefore, by definition (see Chapter 1), the potential fire intensity is reduced. It may then be argued that this in turn increases the chance of controlling the fire, and therefore decreases the chance of the loss of human life and economic assets. Another broad-area technique is the use of grazing animals to reduce fuels, especially where grassy fuels predominate – even in forests. This will be examined in the next chapter. In this chapter, prescribed burning as a fuel-reduction measure is considered in light of conservation objectives. Plate 3.1 Prescribed low-intensity fire for fuel reduction (Graham 2004).
Underpinnings of fire management for biodiversity conservation in reserves Text Box 3.1. Prescribed burning The term prescribed burning can be used in a number of ways. In Australia, the definition can be expressed as: the deliberate and safe use of fire to achieve an explicit outcome under specified conditions of fuel, weather and ignition in a designated area. Therefore, it does not include a fire that is unplanned (wild), even a low intensity one that fits a prescription – as is used in the USA (Bunnell 1995). It is also not ad hoc burning off; however, it does include a number of diverse circumstances, which include: • The burning of woody debris (slash) after logging, often at high intensity, to remove as much woody material as possible (Plate 3.2) and create a seed bed for the regeneration of trees • The burning out of fuels during suppression of an unplanned fire • The application of fire to achieve a particular ecological purpose • Broad-area treatment under mild weather conditions to reduce the quantity, arrangement and continuity of forest litter or shrubby/grassy fuels in an area (Plate 3.1). In this chapter, the emphasis is on the last of these, sometimes called fuel-reduction burning, but given that fuel is what burns, this term is a tautology (Esplin et al. 2003, p. 74). Fuel reduction by low-intensity fire is a better description. Fuel modification may be preferred by some as the arrangement of the fuel can be important. Note that if a low-intensity fire kills, but does not consume, the green component of a grassy sward, shrubs, lower canopies of trees or green bracken, fuel available for future fires may be generated as well as reduced (see also Gould et al. 2007, p. 79). If the prescribed fire enhances shrub germination or the growth of bracken, for example, then fuel conditions also change. Both prescribed burning and grazing will affect biodiversity, as both affect fuels in some way. Fuels may be partly seen as species or habitat – elements of biodiversity. Invertebrates may have at least part of their life cycle in habitats that are associated with live or dead plant or animal parts that are found above or below ground, exposed or concealed and in or out of water of various types. Nonvascular plants – including lichens, fungi, bacteria and algae – have a similar wide range of habitats. Fuel management always involves habitat, whether this be grass, bark, foliage of woody plants, standing or fallen logs or litter. In this chapter, the links between vegetation, fuels and habitat are briefly considered before a discussion of aspects of fuel dynamics, the efficacy of prescribed burning for fuel modification and fire control, and the effects of fires on the environment. Plate 3.2 Burning of woody debris (slash) after logging (Fisher 2005). Fire and adaptive management 43
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