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Biotic Disturance Agents VS Forest Health

Outline​

  • Forest disturbances abiotic versus biotic
  • "Forest health" in the headlines
  • Forest health: what it really means

"Healthy" forests require change or disturbance

  • Insects and diseases have much greater impacts than wildfire
  • Disturbance annually affects many thousands of hectares
  • High public profile
    • "Forest Health"

Biotic disturbances and "forest health" in the news:​

  • the emerald ash borer
  • Forest diseases in the news: Dutch elm disease
  • Sirex Wood Wasp
    • Lays eggs and a packet of fungi and enzymes in sapwood
  • Sudden oak death
    • Fungi pathogen
  • Spruce beetle
    • Massive impacts to Alaska nad the Yukon
  • Chestnut Blight
    • Geneticists have been trying to fix this issue by introducing genes from Asian Chestnut
  • Mountain Pine Beetle

Forest health: A closer look​

  • One of the most widely used terms in ecosystem management
  • Often in the news
  • Associated with:
    • Air pollution
    • Invasive species
    • Wildfires
    • Insect outbreaks
    • Powerful personal imagery
    • Connects fragility of "health" with ecosystems
    • Misused and abused

Healthy or unhealthy: Natural Forest:

  • In Timber supply area...
    • Pest (unhealthy)
  • In protected area...
    • natural disturbance (healthy)
  • Intensively managed forest:
    • No pest impacts
    • Meets management objectives, but...
    • Limited in all aspects of ecological function

FRST-307/Forest-health-A-functional-definition

Pathogens​

  • Can cause disturbances by disrupting tree physiological processes which can result in reduced growth or mortality
  • They can attack tree roots, stems, branches, foliage, and the vascular system

Dont always kill trees, they can also reduce tree growth​

  • Pathogens can reduce tree growth by reducing leaf area and decreasing photosynthesis
  • Also steal resources from the host
  • Cause tree deformities, which weakens host

50 WAYS TO KILL A TREE​

  • Disurpting water transport by blocking vascular system
  • Kill roots and cause major structural damage
  • Girdle stems, killing the living tissues of trees

Forest Health: A Functional Definition

  • Values create conflicts!
  • Need a definition without human expectations: A working definition:
  • Forest ecosystems are healthy when their underlying ecological processes operate within a natural range of variability, so that on any temporal or spatial scale, they are dynamic and resilient* to disturbance
  • If an ecosystem is resistant to disturbance and returns to a similar pre-disturbance state, it is considered resilient

Warming and forests: The conundrum​

Increased productivity but increased biotic and abiotic disturbances

Disturbance vs C dynamics in Canada's forests​

  • large insect impacts in recent years
  • Insects greater than fire + harvesting
  • Significant impacts on C dynamics
  • Biotic disturbance creates carbon source

Disturbance vs C dynamics: The Mountain Pine Beetle Example​

Modelling C dynamics in forests through time as a result of disturbance

  • Harvesting
  • Fire-caused mortality, fuel consumption
  • MPB-caused mortality Project growth of forests in western Canada post disturbance to assess changes in C balance

Mountain Pine Beetle

  • 270 Mt C to atmosphere
  • Equilavent to 5 yrs of emissions from Canadian transportation sector
  • Conversion of BC forests from C sink to source
  • Unprecedented outbreak: potential feedback to global climate system

Mitigation options in the forest sector​

  • Increase or maintain forest area
    • Reduce deforestation and mitigate disturbance, increase afforestation
  • Increase stand-level carbon density
    • Increase use of partial harvest systems, eliminate residue burning, reduce regeneration delays, species selection, mitigate disturbance
  • Increase stored carbon in products, reduce emissions through product substitution and bioenergy
    • Promote longer-lived products, building materials, recycling, biofuels from residues, salvage, plantations
  • Increase landscape-level carbon density
    • Lengthen rotations (where appropriate), increase conservation areas, protect against disturbance