- Wood Decay
- Wood
- Components
- cellulose ~40% (glucose chains - 10,000)
- hemicellulose ~30% (sugars - 1,000)
- lignin ~30% (3D, amorphous polymer)
- extractives (phenolics & other compounds)
- Structure
- lignin & cellulose
- lignin more resistant to breakdown ...
- ... protects cellulose ...
- ... only a few fungi can decay wood (a most abundant energy source)
- Mechanism of Decay
- Enzymes
- cellulase (endo & 2 exo)
- lignase
- H2O2 & Fe
- enzyme production & sugar
- short half life
- lotsa sugar ... stop endo-cellulase prod'n
- Decay by Infection Mode
- Heart Rots
- True Heart Rots
- no wound necessary (tertiary stubs)
- heartwood only
- conks on live trees
- never invade slash
- dies soon after tree dies
- true heartrots in BC
- Echinodontium tinctorium
- Phellinus pini
- P. tremulae (P. ignarius)
- Wound Invaders
- requires a wound
- primary
- require sterile surface
- e.g. Annosus
- secondary
- altered surface is OK
- e.g. the rest
- mainly heartwood (sometimes sapwood)
- conk seldom on live tree
- some can invade slash
- lives after tree dies
- ~38 species in BC
- Sap Rots (=saprophyte)
- decay dead sapwood
- a.k.a. slash rots
- so ...
- live trees decay from the inside out
- dead trees decay from the outside in
- Decay by Digestion
- Asco - soft rots
- ascomycetes
- decay of wood-in-service
- Basidio
- white rots
- decay
- lignase, endo-cellulase & exo-cellulase
- selective delignification=bio-pulping (lignase)
- then cellulose exposed & decayed
- ... pocket rot or laminated rot
- result
- white b/c some "bleaching" & brown lignin gone
- localized decay
- surrounding wood still in tact
- maintains strength & pulp yield longer
- trees
- conifers
- hardwoods
- brown rots
- decay
- exo-cellulases
- no lignase ... lignin "protects" cellulose
- H2O2 & Fe - small enough to fit thru' pores ...
- ... and breakdown cellulose chains
- wood structure is altered, bigger pores ...
- enzymes can now enter and eat cellulose
- result
- early in decay: cellulose chains broken thru-out
- quick loss of strength
- quick loss of pulp yield
- brown & cubical b/c only lignin left
- trees
- primarily conifers
- seldom on hardwoods
- Decay by Location
- top rot
- stem rot
- butt rot
- root rot
- Rate of Decay
- Antagonism
- heartwood is not sterile ...
- ... endophytic fungi (non-decay)
- ... antagonistic to decay fungi
- e.g. Ascocoryne sarcoides in B, H & S
- pot'l to protect wood-in-service (not yet)
- Toxins
- when parenchyma cells die ... toxins
- heartwood (dead) contains toxins
- phenolics & thujaplicin (in Cw)
- Cw has MORE rot in live trees than any other BC conifer!
- succession of micro organisms invade from base ("cones")
- Cedar example
- unaffected heartwood is straw coloured
- Sporothrix fungus ("agent S") ... detox the thujaplicin -> non-toxic dimer (pink-purple)
- Kirschteiniella thujina ("special agent K")... detox the phenols (tan-brown)
- further invasion of others ... (darker brown)
- then the decay fungi appear
- animations :o)
- O2
- wetwood - saturated with water
- anaerobic condition
- also, N-fixing bacteria (uses O2), high pH & methane
- scar drains water ... decay
- trees: cottonwood/ aspen, willow, elm, H & B
- peeing tree example
- N
- wood low in N
- fungi "recycle" their own hypha
- set-up conditions for N-fixing bac.
- Alder??
- Host Defences
- bark
- dead bark: toxins
- live bark: cork cambium
- callous over
- to block future invasion
- may block O2 & limit decay of new infection
- wounded sapwood
- kamkasi reaction just behind wound
- barrier formed
- impervious to gases, liquids ... & fungus
- can have toxins
- blocks advance of decay
- "saucer shaped" if shallow wound - heartwood protected
- "pipe shaped" if deep wound - heartwood vulnerable
- isolates wounded area
- resin
- pumped to wound
- has toxic compounds
- attempts to "seal off" wound area
- CODIT
- hardwoods
- "special ring" of wood laid down after scar
- if complete = shape of tree
- how does this help?
- Management Considerations
- Cull Factors
- destructive sampling
- provides a "net down" for damaged trees
- broad factors - location (FIZ), age, spp.
- replaced with CGNF - tree based
- Decay & Tree Age
- interior
- At 50, Cw-Hw-B 100, Pl 150, Sx 175
- coast
- B 150, H 200, F 300
- mgmt
- timber supply ... west: young Pl, east: older Sx
- H - interior ... crap?
- but ...
- advanced regen
- rotation age
- Decay of Dead Standing
- factors - spp, moist & temp.
- rate 2-4 cm/yr
- small trees decay very quickly
- decay ... outside -> in or visa versa
- larger trees do have a brief shelf life ... BB??
- Decay & Other Resources
- Wildlife - habitat ... good
- Parks - safety ... bad
- UNacceptable Damage
- FG trees
- wound >1/3 circumference
- wound >20% length of stem
- but a scar is OK
- Partial Harvest consider ...
- Retention Period (short vs. long)
- Tree Species (susceptibility to decay)
- broadleaf (most susceptible)
- B, H, Ss, Cw <60 yr
- Cy, Sx, Cw >60 yr
- F, Pw
- Pl, Py (least susceptible)
- simplified version
- broadleaf (most susc.)
- the rest
- Douglas-fir & Pines (most resistant)
- Severity of damage
- small vs large (>400cm2)
- % circumference of wound: 2 thresholds: 50% - F&P & 33%-the rest
- wound vs gouge
