Lecture Fourteen - Australian phytogeography Flashcards
How does climate effect plant and animal distribution in Australia?
Currently the Aus climate is between 10-43 degrees C and across 40 degrees latitude, resulting in large climatic variations.
Subject to mid-latitude high pressure cells - defending, dry masses of air - primarily cause of extent of aridity.
How does rainfall effect climate in Australia?
Rainfall:
Driest of the worlds inhabited continents.
Lowest effective precipitation of any continent - due to variable and low precipitation, and high evapotranspiration.
Average annual rainfall 451mm -> strong gradients from wet to dry.
High seasonality, with sumer rainfall in North, winter rainfall in the South.
Local effects of rain shadows, which are mountains where winds sweep rain in precipitated out of the ocean.
Climate exerts a major control over plant distribution.
E.g. river red gum seeds germinate after flooding.
Floods determine geographical range -> important for inhabitant fauna.
Flooding important regeneration requirement for may plant species - lack of flooding = serious implications for many species.
What is insolation?
Insolation:
Clear skies and lack of cloud firing conditions - very high insolation. Insolation is the amount of sunlight hitting the ground.
Hoe does temperature effect climate in Australia?
Generally very high daytime temperatures.
Lack of extensive alpine areas - mild winter temps.
Mean annual temperature 21.5 degrees C - with large variations.
Temperature important determinant of plant distribution, but rarely limiting to plant growth.
What is El Nino?
El Nino Southern Oscillation (ENSO).
Disruption of Walker circulation, with warming of Eastern Pacific Ocean, formation of high pressure systems in Asia and northern Australia, resulting in drougb in eastern Australia.
Walker circulation (the normal circulation between Indonesia and South America) is reversed into ENSO circulation. This brings the top warm water layer towards South America rather than towards Indonesia. It also means that the way the wind and water are traveling, there is deeper ocean in this direction.
Explain the physiography, geology and soils of Australia.
Australia is divided unequally by the Great Dividing Range - a watershed rather than a mountain range.
Small areas of alpine environment in the southeast.
Major physiographical barriers to biota Nullabor Plain and Great Victoria Desert - Separate reasonable well watered regions of southeast and southwest.
Soils:
Australia’s land surface is very old geographically with some variation.
Some the oldest rocks and land surfaces on Earth.
Current status a result of weathering processes on stable, dry landscape for much of the past 400my.
Generally leached and infertile (amongst most nutrient poor on Earth), with low P and N - ranging to more recent fertile soils.
Consequently, of great importance for interrelationships between climate, soils and vegetation.
How is the nature of vegetation communities in Australia determined?
Their genotypes - inherit requirements for growth. These are the characteristic/adaptations required for the environment in which they live.
Their environment - climate and soils, disturbance regimes, competition and biotic factors.
What geospatial scales do vegetation composition and structure operate at?
Vegetation composition and structure operate at many geospatial scales.
Micro(local) - affected by local aspects (water table effects, soil nutrients, patch sizes etc.
Regional - broadly shaped by upstream/catchment dynamics, effects of fire, flooding etc.
Continental - tectonics, wind and water currents etc.
E.g. Southern oscillation Index/ El Nino, evolution.
What is typical Australian flora characterised by?
High degree of endemism.
Many sclerophyllous species.
Close relationships among biotic elements.
No cacti, few conifer species, few deciduous taxa.
Adaptations such as sclerophylly, carnivore and epiphytic species (plants that live on trees but are not parasites).
Paradoxically, nutrient poor soils often support high species diversity due to combinations of climate, topography, soils and fire.
What are the major categories of climate in Australia?
1) Tropical/subtropical evergreen wooded vegetation.
Tropical eucalyptus woodlands ( 70-100% fc.
Mangrove forests.
2) Arid and Semiarid grass lands and shrub lands.
Triodia grass lands of central Australia.
Mulga (acacia aneura) shrub lands to the south.
Most extensive vegetation communities in Aus, and together encompass bulk of arid and semiarid regions.
Also includes:
Other grassland communities, mallee communities and chenopod shrub lands on naturally saline soils.
3) Temperature forests, grasslands and shrub lands.
Southweat Aus (including Jarrah, Karri forests = in WA, have been largely cleared for agriculture and logging).
Southeastern Aus and Tasmania (mountain alpine ash, stringy barks and box-ironbarks = wet and fry sclerophyll forests).
Largely woodlands of Eucalyptus species with a shrubby or grassy understory.
In both areas, these forests and woodlands have been largely cleared from cropping and grazing.
Also warm and cool temperate rain forests are fire sensitive.
What events can cause disturbances to flora and fauna.
Climate:
Unpredictable, rapid perturbation in disturbance reflected in dramatic changes in landscape patterns.
Cyclones:
Northern Aus.
Drought:
Frequent and unpredictable.
Fire:
Dry, low nutrients, high volatile oils in some species - increasing incidence of fire.
Cycles of fire and brought/wet operated for thousands of yeas -> minting vegetation in dynamic state = spatial and temporal heterogeneity.
How does fire effect flora and fauna?
Sclerophyllous nature of the vegetation - high fuel content and high concentration of flammable oils and terpenes.
Common feature of open forests, woodlands and savannah.
Important dynamic in vegetation succession, and in maintenance of the flux between different vegetation communities in specific regions.
Important for:
- Nutrition recycling.
- Seed release and germination for many Australian plant species.
In fire-prone heathlands of south east Aus, >70% of species are capable of surviving fire.
Adaptations include:
- Below ground lignotubers (mallee eucalyptus).
- Thick bark (Angophora spp.).
- Epicormic buds (Many eukalyptus ssp.).
Obligate seed regeneration (E. regnas).
Thick, protective seed capsules that open after optimum temperature is reached (callistemon, melaleuca).
