Biology Reference
In-Depth Information
Altered fire regimes and fire management
Fires are generally rare events on rocky outcrops; however, frequent, high severity
fires can alter vegetation structure and change plant species composition (see
Figure 5.12). Many plants growing in rocky areas are unable to resprout after fire.
These species are called obligate seeders and can be eliminated by frequent, high
intensity wildfires. Changes to vegetation structure and plant species composition
also can have negative impacts on wildlife such as by altering the amount of
sunlight reaching the basking sites of reptiles.
Lightning strikes are the most common cause of fire on rocky outcrops, but
human-induced fires are becoming increasingly common in agricultural areas.
Responses to controlling fire on rock outcrops often involve lighting a perimeter
back-burn. The use of very high severity back-burns can have major negative
environmental effects and their use is to be avoided wherever possible. Perimeter
back-burns can have at least five kinds of detrimental effects on rocky outcrops
and their associated plants and animals:
Perimeter fires are usually ignited at the base of the outcrop causing the fire to
travel uphill and burn with greater severity than a fire travelling downhill.
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Native animals can become trapped and killed by high severity, fast-moving
perimeter back-burns.
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The amount of heat generated during back-burning can completely consume
hollow logs, and large standing dead trees.
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High severity perimeter back-burns can kill seed stored in the soil. Subsequent
widespread removal of native vegetation allows agricultural weeds to colonise
bare ground. Loss of native vegetation also increases soil erosion and nutrient
runoff.
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Fragile rock formations (vertical flakes and exfoliations) can be destroyed by
high-severity perimeter back-burns and it may take several hundred years for
them to be replaced.
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Grazing regimes and livestock management
In recent years, there has been a focus on developing grazing management
strategies to enhance biodiversity conservation outcomes in production
landscapes.
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Too much grazing can degrade outcrop environments. Too little
grazing can lead to regrowth vegetation significantly altering light penetration to
the ground with corresponding effects on reptile basking sites.
Two kinds of grazing strategies may be useful in managing the fringing
vegetation on the flared slopes of an outcrop. These are: (1) crash grazing, involving
high stocking levels for a short period of time to reduce biomass and minimise the
