- Forest Health
- What is a healthy forest (tree)?
- "normal" biological functions
- leaves photosynthesizing (making sugar)
- roots absorbing water & nutrients
- stem is translocating sugars & water to all parts
- growth (making fiber & wood)
- reproduce (cones/seeds)
- etc.
- resilient to short term stress
- able to adapt to long term changes (climate)
- * satisfies mgmt objectives
- habitat for fish & wildlife
- wilderness
- biodiversity
- sequester carbon
- water quality
- recreation & aesthetics
- products (timber, food, greenery)
- 3 levels of health
- individual tree
- forest stand - majority healthy (some sick, individuals die - new trees grow)
- forest ecosystem
- broad view ... "considers everything"
- interactions of all parts (plants, soils, animals, fungus, etc.)
- disturbances leave biological legacies
- landscape pattern (from disturbance) over time
- hydrology (water flow)
- carbon & ntrient cycling
- Damaging Agents
- Fire
- low intensity - kills in sporatic patches
- moderate intensity - kills most, but leaves "legacy trees"
- high intensity - "cleans the slate" compeltely
- Insects
- Disease
-
- Laminated Root Rot
- Biology
- fungus, decays wood
- Hosts: Douglas-fir & "balsam"
- restricted to roots (not in soil)
- spread by root-to-root contact
- occurs in centres
- damage
- mortality - girdles young, windthrow for old trees
- reduced growth
- rotted wood at the butt
- but
- creates openings
- horizontal and vertical structure more varied
- tree species diversity
- CWD (downed logs)
- symptoms
- windthrow - crisscross pattern
- "root balls"
- roots have laminated decay
- fungus
- root surface in dirt - white
- root surface in forest floor - brown & crusty
- in decayed wood - fuzzy brown
- Mgmt
- plant alternate species
- red cedar, pines, hardwoods
- need to be ecol. suited to the site
- often slower growing
- remove stumps/roots
- removes fungus ... plant Fir again
- $$, so needs to be a productive site
- steep ground not suitable
- sensitive soils not suitable
- live with the infection - if it is quite low
-
- Biology
- parasitic plant (yellowish, no leaves)
- requires a live host
- impact
- infected tree develops brooms, grows slower
- volume loss - can be 20-40%
- value - swollen stems, poor wood quality, large knots
- but provides resting/nesting platforms
- symptoms
- aerial shoots
- "moon craters" in bark
- brooms
- swellings - spindle shaped
- verical spread = 40 cm
- fast growing stand can "outgrow" mistletoe
- provided there are no overhead sources (infected residual trees)
- horizontal spread
- 15 (20)m "clear shot"
- 50-100cm in even-aged forest
- Mgmt
- Hawksworth infection rating
- divide crown into 3
- rate each section (0=none, 1=<1/2 branches infected, 2 >1/2)
- add the 3 ratings
- values: 0 - 6 (ratings of 2 or lower is OK)
- Harvest Time
- a few infected residuals can re-infect whole stand
- eliminate infected residuals
- 3 m knock down
- fire
- mechanical
- partial harvest??
- infected edges??
- planting
- mix species will slow spread
- alternate species around infected residuals
-
- Abiotic
- Scale of Disturbance
- low (endemic) level
- "natural"
- acts as a thinning agent ... good
- sporatic mortality provides diversity (structure, age, species)
- high (epidemic) level
- typically short-term, unusually high
- = major disturbance event
- stand replacement (i.e. kill existing and begin anew)
- can interfere with desired values (recreation, timber, etc.)
- introduced pests are a special case
-
- native trees have little/no defence against introduced pests
- Often "wipes out" the native species
- examples
- Why do we even care?
- look back at mgmt objectives
- Forest Health Mgmt
- we manage forest to minimize/ prevent negative impacts
- how
- consider forest health triangle
- damaging agent (insect, disease or fire)
- host tree
- environment
- essentially target one of the above
- "attack" the agent (e.g.sanitation)
- manage the host: use resistant species
- alter the environment (mainly in a nursery)
- short term ("target the pest")
- stumping for root rots
- pruning for stem rusts
- trapping for insects
- sanitation - removed diseased/ infested
- pesticides - mainly defoliators (Btk & NPV)
- long term ("grow a healthy forest")
- promote species mix within stand
- many diseases/insects are "host specific"
- also consider potential climate change at planting - considers long term resilience
- a diverse forest stand is more resilient
- silviculture - maintain vigour
- fertilization
- thinning
- a vigourous stand is more resilient
- harvesting "mimics" natural disturbance patterns
- "natural" patterns
- breaks-up the landscape
- mosaic of different aged forests
- many diseases/insects are age class specific
- a diverse landscape is more resilient
