South-West Australian Forests & Timber Species – Exam Notes

Four principal forest types repeatedly referenced by the teacher:
• Jarrah Forest
• Marri (often co-occurs with Jarrah but can form its own dominant canopy)
• Karri Forest
• Wandoo Forest
(A fifth, the Red-Tingle forest, is briefly mentioned as a "very special" SW corner type.)
Location pattern (visualise from coast inland and from north to south of WA):
• Forests hug the SW coastal fringe where rainfall and milder temperatures allow tall eucalypts.
• Inland transition → open woodland, then shrubland as rainfall declines.
Humans mostly occupy coasts → strongest socio-economic / environmental interactions with these forests occur along that same coastal rim.

Key criterion = canopy density (% cover + spacing of trees).
• Forest: high density, overlapping crowns, shade beneath; tall trees.
• Woodland: lower density, wider spacing, sunlight penetrates, more understory.
Rainforest (tropical or temperate) sits at the extreme: almost complete canopy closure, multi-layered strata.

Rainfall:
• Teacher shorthand: \text{>700\;mm yr^{-1}} → continuous forest (Karri belt).
• 600\;\text{mm yr^{-1}} \rightarrow Jarrah/Marri mixed forest margin.
• Decline below $600\;\text{mm}$ rapidly converts to Wandoo woodland.
Temperature gradient (north to south & altitude):
• Hot + wet (≈ $32\,^{\circ}\text{C}$ , high humidity) → tropical rainforest (QLD example).
• Temperate (≈ $20\,^{\circ}\text{C}$ peak, mild winters) + reliable rain → temperate rainforests / Karri.
• Hotter & drier interior → open woodland.

Jarrah Forest: lateritic gravels on the Darling Scarp.
• Easily mapped: gravel soil band ≈ Jarrah distribution.
Coastal plain (coloured sands) = poor nutrients → supports Banksia woodlands & low Jarrah in patches.
Karri: deep loams & red-brown earths in high-rainfall valleys.
Wandoo: pale clayey duplex soils slightly further inland (lower fertility, lower rain).

Dominant canopy where rainfall ≥ $600\,\text{mm}$ + gravel soils.
Timber traits: extremely hard, burns hot → historically fuel for glass-making furnaces (example: “need enough heat to melt silica for glass – Jarrah delivered”).
Nuts: very small, teacher compares to a student’s fingertip “gum-nut” demonstration.
Exploitation history: targeted for rail sleepers, flooring, high-temperature fuel → heavy selective logging.

Often co-dominant with Jarrah; can form pure stands.
Dark red kino (sap) exudes when cut → historically despised by sawyers:
• Sap clogged hand-saws & axes, blunted blades.
• Result: early settlers left many Marri standing while removing Jarrah (classic case of SELECTIVE LOGGING – choosing individual high-value trees, leaving others).
Ecological role: heavy-seeded gum-nuts (“honking outside”) important food for cockatoos & possums.

Restricted to very high rainfall corners around Pemberton / Southern Forests.
Physical description:
• Exceptionally tall (≈ $30$ m of straight trunk before first branch; total heights >60 m).
• Straight, light-coloured timber; low density relative to Jarrah → valued for long, continuous beams (bridges, wharves).
Forest appearance: tall, not as dense as rainforest but canopy still closes;
understory often lush tree-ferns.

Bark: less mottled, more stripy than Jarrah/Marri.
Occupies lower-rainfall margin east of Jarrah belt; canopy more open → woodland classification common.

Deforestation: clearing every tree – NOT what early WA loggers generally did.
Selective Logging: picking individual high-value trees (e.g., “I want that Jarrah”).
• Led to mixed stands today with disproportionate Marri / regrowth Jarrah.

Production: forest growth + harvesting (Jarrah fuel wood, Karri saw-logs, Marri historically ignored).
Consumption: domestic timber, export markets, industrial fuel (glassworks).
Distribution: along coastal transport corridors & ports; reflects coastal human settlement concentration.

Melting glass analogy: required temperature underscores Jarrah’s calorific value.
“Small gum-nut the size of your fingertip” to memorise Jarrah fruit ID.
Rainforest vs woodland comparison for canopy density (close eyes: rainforests dark; woodland bright gaps).

Rainfall thresholds: $700\;\text{mm}$ (Karri); $600\;\text{mm}$ (Jarrah margin).
Karri trunk lengths used as beams: ≈ $30\;\text{m}$ straight section.
Class temperature references: $32\,^{\circ}\text{C}$ (hot tropics) vs $20\,^{\circ}\text{C}$ (temperate south).
Classroom aside: charger “25 / 425” etc. appear social, not ecological – ignore for exam.

Draw WA outline + simple coastal/inland rainfall isohyets.
• Shade SW corner → Karri belt (high rain).
• Strip east of that (gravel soils) → Jarrah/Marri.
• Further inland band → Wandoo woodland.
Use blocking/colour chunks rather than intricate squiggles; must be doable in $\le 2$ minutes.
Overlay soil type (gravels vs coloured sands) or rainfall bands to demonstrate causal links.

Legacy of selective logging → uneven age-class stands, altered fire regimes.
High human-forest overlap along coast intensifies conflicts: conservation vs timber, recreation, urban sprawl.

Jarrah: rough fibrous bark, small nuts, gravels; test burn – high heat.
Marri: patchy bark, bleeding red kino, large “honky-nut” fruit.
Karri: pale smooth trunk shedding in ribbons, colossal height, cool damp gullies.
Wandoo: white/cream trunk with long vertical fissures, drier sites.
Red Tingle: massive buttressed base, found only near Walpole.

"J, M, K, W, T" = Jarrah, Marri, Karri, Wandoo, Tingle (north-to-south + moisture gradient).
"600 gets J, 700 grows K" – remember rainfall cut-offs.
"Gravel loves Jarrah" – soil link.