Australian landscapes

Landscapes, Soils & Surface Environments - Workshop 2a

Raphael Viscarra Rossel, Lewis Walden

2026-02-17

Recap from Workshop 1

  • Landscapes are integrated systems: environment → landforms → soil → water → vegetation
  • Components don’t operate independently - continuous feedbacks
  • Processes operate across multiple scales (regional → catchment → hillslope → site)
  • Soil and water are the connecting threads

Today: apply this framework to Australian landscapes.

Why focus on Australia?

Australia is a exemplary “lab” for landscape science:

  • Very old, mostly stable continent
  • Long isolation from other land masses
  • Large arid and semi-arid interior
  • Strong gradients in climate, soils, and vegetation

We’ll start at continental scale, then next hour will zoom in to Western Australia.

Why Australia is distinctive

Key features shaping Australian landscapes:

  • Ancient geology - Some of the oldest continental crust
  • Long isolation - ~45M+ yrs separated from other land
  • Arid dominance - ~70% of continent arid or semi-arid
  • Low relief - Average elevation ~330 m (global ~840 m)

Note

These set the environmental constraints on soils and ecosystems.

Australian physiographic units or landforms

Australia can be divided into four broad physiographic (landform) regions:

  • Western Plateau

  • Central Lowlands

  • Eastern Highlands

  • Coastal Plains

We can link these to soil orders, vegetation types, and landforms.

Western Plateau

  • Ancient shield, mostly high, flat to undulating
  • Large areas of very old, weathered surfaces
  • Common features:
    • Extensive lateritic profiles
    • Sandy and gravely soils
    • Sparse to open vegetation in arid areas

Note

“Very old, often nutrient-poor, but diverse.”

Central Lowlands

  • Large sedimentary basins
  • Low-relief alluvial and aeolian plains
  • Common features:
    • Alluvial clays and loams
    • Floodplains and ephemeral lakes
    • Vertosols and Sodosols in many areas

Note

Include key agricultural regions e.g. Murray–Darling Basin.

Eastern Highlands

  • Great Dividing Range and associated uplands
  • Higher relief and, in many places, higher rainfall
  • Common features:
    • Steeper slopes, dissected plateaus
    • Younger or less weathered soils in some areas
    • Higher biodiversity in many subregions

Note

Topography, climate, and geology combine to give strong gradients.

Coastal Plains

  • Relatively narrow belts along the coast of Australia
  • Low-lying, often gently sloping
  • Common features:
    • Marine, estuarine, and fluvial sediments
    • Coastal dunes, wetlands…, shallow groundwater

Note

These areas host many major cities and high population densities.

Australian soil broad characteristics

  • Many soils ancient and strongly weathered

  • Nutrient status is variable:

    • Extensive areas with very low in P, N
    • Localised fertile alluvial and basalt-derived

  • Very diverse soils spanning most of the 15 soil orders

Note

Soil diversity closely reflects the underlying diversity in landscape and climate.

Soils across physiographic units (examples, not exhaustive)

Western Plateau: Tenosols, Kandosols (weakly developed, sandy-earthy, deeply weathered, low fertility)

Central Lowlands: Vertosols, Sodosols, Chromosols (cracking clays, texture‑contrast, more fertile on plains)

Eastern Highlands: Ferrosols, Dermosols (iron‑rich, well‑structured on uplands, younger and more fertile)

Coastal Plains: Podosols, Hydrosols, Organosols (sandy, leached, wetlands, organic/peaty, poorly drained)

Note

Different regions bring different soil constraints and management opportunities.

How landscape position affects soil

Drainage lines: Seasonally or permanently wet, distinct soils and vegetation

Catena and toposequence

A sequence of related soils down a single hillslope

Activity (10 min): hillslopes and catenas

Consider a typical hillslope catena in the Western Plateau or Eastern Highlands:

Summit ➡ shoulder ➡ backslope ➡ footslope ➡ drainage line

Discuss: Along this catena:

  • How do soil depth, texture and drainage change from summit to drainage line?
  • Where along the slope would you expect more organic matter to accumulate, and why?
  • How might vegetation composition and productivity respond to these soil changes downslope?

Discussion: hillslope catena

Share your observations:

  • One example of how soil properties change downslope (depth, texture, drainage, organic matter).
  • One example of how vegetation responds to those soil and water changes.

Important

Soil and vegetation patterns along hillslopes are not random – they reflect systematic water and sediment redistribution from summit to footslope, creating predictable catenary sequences.

Australian vegetation: climate and position

Vegetation reflects the soil–water–landscape template:

  • Climate gradient
    • Tropical north: rainforests, savannas
    • Temperate south: eucalypt forests, woodlands
    • Arid interior: mulga, spinifex, chenopod shrublands
  • Landscape position
    • Ridges: more drought-tolerant, sclerophyll species
    • Valleys/drainage: taller or denser vegetation, riparian species

Important

Vegetation is both a response and a driver of ongoing landscape processes.

Vegetation of the Western Plateau

  • Dominated by arid and semi-arid vegetation:
    • Mulga (Acacia aneura) woodlands and shrublands
    • Spinifex (Triodia) hummock grasslands
    • Chenopod shrublands (saltbush)
  • Vegetation is sparse, open and low
    • Deep-rooted, drought-adapted
    • Sclerophyllous leaves, fire-adapted
    • Episodic recruitment after rain

Mulga woodlands Spinifex grasslands

Vegetation of the Central Lowlands

  • Alluvial plains support:
    • Mitchell grass tussock grasslands
    • Brigalow/Gidgee (Acacia) woodlands
    • Open eucalypt woodlands on cracking clays
  • Floodplains and ephemeral lakes:
    • Chenopod shrublands (saltbush, bluebush)
    • Samphire shrublands in saline/sodic clay areas
    • Riparian woodlands along rivers and drainage lines

Mitchell grasslands Brigalow woodlands

Soil–vegetation linksof the Central Lowlands

  • Vertosols and Sodosols provide fertile, cracking clays that support productive grasslands, woodlands and croplands
  • Subtle changes in flooding, waterlogging, salinity and shrink–swell behaviour create strong soil–moisture contrasts over short distances, driving sharp boundaries between grasslands, woodlands, shrublands and samphire communities.

Note

Small differences in soil moisture, salinity and texture sort vegetation: chenopod shrublands on saline clays, tussock grasslands on cracking Vertosols, and eucalypt or acacia woodlands on better‑drained, less saline soils.

Vegetation of the Eastern Highlands & Coastal Plains

Eastern Highlands

  • High‑rainfall eucalypt forests and woodlands, some temperate rainforest and wet sclerophyll.
  • Basalt soils → tall forests; older leached soils → heath and dry sclerophyll.

Coastal Plains

  • Banksia woodlands, heaths, dunes shrublands and mangroves on low nutrient, sandy soils.
  • Dunes support Banksia and heath; low flats support paperbark (Melaleuca) wetlands and sedgelands.

Important

Vegetation reflects rainfall, soil age and position along the landscape.

WA scarp–plain–coast

We now move from continental scale to a region of WA, where the Western Plateau meets the Coastal Plain

  • With clear contrast between:
    • The Darling Scarp and dissected plateau
    • The Swan Coastal Plain and its coastal dune systems

Note

This area lies on Whadjuk Noongar Country

Key takeaways

  1. Australia offers diverse examples of how environment shapes landscapes, soils and vegetation.
  2. Four broad physiographic units (major landforms) dominate the continent: Western Plateau, Central Lowlands, Eastern Highlands, Coastal Plains—each with distinctive soil–vegetation relationships.
  3. Soils are highly diverse: many are ancient and strongly weathered, but some are younger and relatively fertile.
  4. Hillslope position and catena/toposequence concepts help explain systematic downslope changes in soils and vegetation.
  5. Next, we zoom into a Western Australian landscape, from Perth across the Swan Coastal Plain to the Darling Scarp

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