BushfireConf2015 - 7. Fire as a tool for maintaining diversity and influencing vegetation structure

Fire as a tool for maintaining diversity and

influencing vegetation structure

The managementof GGRP sites

1. Protection of life

2. Protection of assets

Biomass reduction

Weed control

Biodiversity attributes

Cultural connections

Why do we burn?

Roadside burns in western Victoria maintain strategic fire breaks for human and asset protection

Burns also play an important role in preserving remnant roadside communities

Ground layer Fire response in remnant vegetation

Why do we burn GGRP sites?

• Reduce biomass and inhibit grassy dominants• Restrict undesired tree regrowth• Rejuvenate vegetation (grasses and forbs)• Allow for persistence of sub-dominants (forbs)• Maintain canopy gaps for recruitment• Cost (?)• Ease (?)• Effectiveness (?)• Competing objectives (?)

Restricting biomass and opening grassy canopy

Grass dropping seed into gaps after fire

Restricting tree regrowth

Rejuvenating vegetation

Allowing sub-dominants to persist

Opening niches for species to move to in adjoining vegetation

Issues with fire in current-day Australia

Can these goals be achieved by other means?

• Cut and bale• Slashing• Grazing

– Deferred– Rotational

• Herbicides• Combinations of the above

Grazing• Grazing can be effective in maintaining or increasing native

cover in semi-natural grasslands, but as a management tool requires good stock management skills

• Deferred (short or long term) or rotational grazing aims to graze pasture intensively (crash or cell grazing) at the point where annual grasses have raised (but not ripened) seed heads (early spring), and then remove stock over summer when natives are setting and dropping seed

• Conversely, set-stocking has been shown to have negative effects including selective grazing of native herbs, trampling, soil compaction, importation of weed seed, localised deposition and return to the soil of dung and urine

Mowing/baling

• Slashing/mowing of grass biomass (native and exotic) on public roads is a common practice due to the ready access of machinery and relatively low cost

• In native grasslands mowing is ideally followed by raking and baling to remove fallen biomass as herbage can return unwanted nutrients to soils, smother vegetation or restrict seedling recruitment

• Mowing and baling of built up grass canopy (autumn through winter) can reduce competition on wildflower species and provide recruitment gaps for seedlings

• Drawbacks of mowing include the possible introduction of weed seeds on equipment, soil compaction, and physical damage to plant structure by the tires of mowing equipment

Cut & Baling

Seed Hay

GGRP burns

Burn cues – > 70% vegetative cover

Burn cues – Dry material above 150 mm

Chepstowe

Patch burns

Hamilton

Is burning always best?

Probably not always but it is a very effective tool for grassland management in many situations