14: Wood Decay & Forest Disturbance Flashcards
How can wood decay affect a living tree?
It weakens structure (risk of breakage/windthrow) and root rot disrupts sap flow, potentially killing the tree.
Difference between brown rot and white rot in decomposition and wood appearance?
Brown rot breaks cellulose/hemicellulose (blocky, brown residue);
white rot breaks lignin too (stringy, whitish/yellow residue).
What is heart rot, and how do fungi initiate it?
Decay of heartwood in living stems/branches.
Fungi enter through wounds;
3 basidiospores germinate and hyphae grow into wood cells.
What is compartmentalisation and one mechanism involved?
Tree defense strategy that walls off infected areas. Tyloses block xylem to stop vertical spread of fungi.
How do soft rot fungi decay wood?
Hyphae enter through pits, penetrate S3 layer, secrete cellulase to degrade cellulose in S2 layer.
Key condition for soft rot, and where is it commonly found?
Needs moisture; found in wood in soil contact (e.g., fence posts, telephone poles).
Why is “dry rot” a misnomer?
Serpula lacrymans requires moisture initially but can sustain decay by producing moisture internally as it breaks down cellulose.
How do disturbance frequency and size affect forests?
Small/frequent disturbances → shade-tolerant species thrive. Large/rare disturbances → favour fast-growing, shade-intolerant species.
Alters age structure and diversity.
What is the plant trade-off related to sunlight and disturbance regimes?
Shade-tolerant plants grow slowly in low light;
shade-intolerant grow fast in full light but fail in shade.
Which fungal group is associated with soft rot decay?
Ascomycota
What compound do brown rot fungi primarily degrade?
Cellulose
What is a characteristic result of white rot in wood appearance?
Intact grain with whitish residue
How do fungi typically enter to cause heart rot?
Through wounds on the tree
Which structure helps a tree block vertical fungal movement?
Tyloses
Where are soft rot fungi most likely to be found?
In soil-contact structures like fence posts
What enables “dry rot” to persist after moisture is gone?
Moisture created by fungal metabolism
Large, infrequent forest disturbances favour:
Shade-intolerant, fast-growing species
Which of the following is not a chemical defense in heartwood?
A) Tannins
B) Stilbenes
C) Lignin
D) Terpenes
Lignin (it’s structural, not a chemical defense)
