SLE317 – Australian Vegetation and it’s Management
DEFINITIONS Vegetation
A collective term for plants – individual species and their structure – at a particular site or landscape.
Obligate seeders
Species that recruit only from seed after fire (only produce seedlings, no resprouting capacity).
Obligate resprouters
Regenerates after fire only by resprouting. Lack fire-resistant seedbank or post-fire seeding.
May produce seed/seedlings in inter-fire periods.
Facultative resprouters
Recruits either from seed or from resprouting after fire.
AUSTRALIA’S NATIVE VEGETATION AND ITS CLASSIFICATION
- High endemicity – 85%
- Two large tree and shrub groups: eucalypts and wattles
- Includes sclerophyll forest, mallee woodland and hummock grassland – doesn’t fit global veg classification
- Deciduous habit is rare
- Woody scleromorphic forms feature in many communities Element of our natural heritage
Many Ecosystem functions/services
Plants account for 70% of Australia’s national threatened species list Vegetation classification is important:
1. Communication
2. Comparison of composition
3. Making generalisations about compositional variation 4. Correlation of vegetation with environment
5. Assessment of resource potential 6. Prediction of future changes
7. Critical to planning for improved management 8. Facilities priority setting for investment
9. Provides basis for monitoring effects of interventions (e.g. restoration/pest-plant eradication)
National View of Native Vegetation
- All state and territory governments o Assess
SLE317 – Australian Vegetation and it’s Management
o Classify
o Map native vegetation
2001 – Native Veg Information System (NVIS)
2007 – recognises 23 Major Vegetation Groups (MVGs) MVGs:
- Based on typical aggregations of the structure o Height and cover
o Growth form
o Floristic composition (vascular plant species)
- In the dominant stratum of each vegetation type in the NVIS database - Dominant MVGs:
o Hummock Grasslands – 18%
o Eucalypt Woodlands – 12%
o Acacia Shrublands – 11%
- Most restricted MVGs
o Rainforests and vine thickets o Eucalypt tall open forests o Callitris forests and woodlands
o Low closed forests and tall closed shrublands o Mangroves
o Heathlands
o Eucalypt low open forests Key threats
- Loss, fragmentation and degradation of habitat - Unsustainable use of natural resources
- Invasive species
- Changes to the aquatic environment and water flows - Inappropriate fire regimes
- Urban development
- Lack of valuation of the environment - Climate change
ARID AND SEMI-ARID VEGETATION
Mallee woodlands and shrublands (MVG14) Distribution
Semi-arid southern Australian o South-western NSW o North-western Vic o Southern SA
o South-Western WA Pre 1750 extent: 318,217 km2
Present extent: 213,763 km2 (33% cleared)
SLE317 – Australian Vegetation and it’s Management
Area protected: 87,391 km2 Characteristics:
o Tall stratum 2 – 6 m high
o Typically dominated by multi-stemmed Eucalyptus spp. (mallee) o Projected foliage cover (PFC) ~ 10-30%
- Rainfall 150-600 mm (semi-arid) - Species include:
o Eucalyptus Dumosa (white mallee) o E. socialis (red mallee)
o E. gracillis (yorrell)
o E. oleosa (glossy-leaved red mallee) o E. incrassate (ridge-fruited mallee) o E. diversifolia (soap mallee)
- Co-dominants Acacia, Melaleuca, Hakea
- With open to dense shrubby understorey OR tussock grass/hummock grass understorey
Floristics of Mallee regions
- Infertile soils in wettest regions
o dense, species rich understorey of sclerophyllous shrubs, which are less than 2 m high, classed as mallee heath.
- Infertile soils with intermediate rainfall
o dense understorey of sclerophyllous shrubs with branched stems usually more than 2 m.
o i.e. Melaleuca (e.g. uncinata) classed as mallee broombush.
- Infertile soils in the driest area hummock grasses (Triodia spp.) with or without shrubs.
- Continental-scale decline in diversity of understorey as environment becomes more arid
Edaphic controls on distribution
o Soil texture: most important factor affecting plant distribution in eastern Australian mallee
▪ increasing levels of macronutrients with increasing clay content
▪ the inverse texture effect
o In arid environments, soil water supply to plants decreases with increasing clay content.
1) Less depth of penetration of rainfall into soils with higher clay contents and subsequent increased evaporative loss.
2) A larger amount of rainfall is needed to bring the clayier soils from air-dry condition up to the ‘available water’ range of soil water potential. i.e. light showers can make water available on dry sandy soils but not on dry clayey ones.
Seesaw between nutrient and water availability The inverse texture effect
o Sandy soils