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Title: Seminars


1
Seminars
  • Plant Talk Thurs April 1 1200 PM in FA 214.
    Giles Thelen Insect herbivory stimulates
    allelopathic exudation by an invasive plant and
    the suppression of natives.
  • EECB Colloquium OSN 102 at 400 PM Thursday April
    1. Lonnie Aarsen, Queens University. Ecology
    less than a science or more than a science?

2
Abstracts and assignments
  • Abstracts Extention? Due April 4.
  • Grad Student lectures April 13 lab period. What
    order? Anyone need handouts made?
  • class conference April 27.
  • Term papers due April 28.

3
Outline
  • Importance of fire in range and forest
  • Fire regimes
  • Types of fire and their effects
  • Species responses to fire
  • Effects on environment and soil
  • Fire as a management tool
  • Fire in sagebrush steppe ecosystems

4
Reading
  • Textbook Chapter 13
  • Chapter 12, Fire, and selected pages from chapter
    16, Disturbance. Barnes et al. 1998. Forest
    Ecology 4th edition. J. Wiley and Sons, New York.
    (on reserve)
  • Chapter 22, Prescribed fire in rangeland
    management. From heady and Child 1994. Rangeland
    Ecology and Management. Westview press, Boulder.
    (on reserve).

5
Extent of fire effects
  • Widespread, occurs in most ecosystems at some
    time.
  • Some systems adapted to frequent fire longleaf
    pine, ponderosa pine, chaparral
  • Table 16.1 textbook type, frequency, and
    intensity of fire in diverse ecosystems
  • Handout page 1 vegetation regions and
    generalized fire freqencies for North America
  • Range from gt1000 years in northern hardwood to lt5
    years in tallgrass prairie.

6
Fire Regime
  • Definition the kinds and immediate effects of
    fire characteristic for an area.
  • Includes type, frequency, size, intensity,
    severity and timing.

7
  • Ground Fire burns soil organic matter/litter.
  • Slow moving, not intense, but very destructive
  • Usually occurs in areas with thick organic layer
    forest, peat bogs etc.
  • Surface Fire burns along soil surface
  • Fast, intermediate intensity
  • Burns understory vegetation, removes above-ground
    biomass of herbaceous species but usually does
    not kill roots or perennating buds
  • Hot surface fires can generate ground or crown
    fires
  • HEADFIRES burn with wind. More intense
  • BACKFIRES burn against wind. Less intense.
  • Crown fire burns canopy of adult trees
  • Can be quite intense and destructive

8
Fire Behavior
  • Fire behavior includes buildup, rate of spread,
    type of spread, rate of combustion
  • Text figure 16.1 determinants of fire behavior
  • Ignition pattern
  • Fuel properties (physical properties,
    arrangement, quantity, moisture)
  • Weather (temperature, humidity, wind)
  • Topography (configuration, slope)
  • For prescribed burns, important to understand
    determinants and effects of fire behavior!

9
Role of fire
  • Acts as a disturbance clears space
  • Alters chemical and physical properties of soil
  • Releases some nutrients in ash (eg, P)
  • Volatilizes C and N
  • Resets cycling (burns accumulated biomass)
  • Affects species composition and diversity
  • Alters wildlife habitat
  • Affects presence and abundance of insects and
    pathogens

10
Fire as disturbance
  • Fire is one of the dominant disturbances in most
    forest ecosystems worldwide
  • In grassland, can increase production
    substantially IF during a wet year (response
    dependent on which resource limiting)
  • Removes biomass, provides substrate for
    establishment, increases light penetration,
    releases nutrients
  • Thins even-aged stands
  • Maintains diversity (intermediate disturbance
    hypothesis resets succession)

11
Effects on abiotic conditions
  • Burning of organic matter and heating of soil.
  • Can change soil chemistry
  • Increases pH
  • Decrease soil N and C but potential increase in
    fixation and mineralization rates
  • Increase soluble minerals (but susceptible to
    leaching)
  • Can create an unwettable layer below soil
    surface (especially if species burned has oily
    exudates). This can cause fire-flood situation
    e.g. chaparral burns landslides afterward.
  • Microclimate effects altered infiltration (may
    be reduced), greater irradiation temperature
    fluctuations

12
Pathogen outbreaks and sanitation
  • Dense, even aged stands following fire can be
    susceptible to disease or insect outbreaks
  • Diseased or infested stands create fuel
    conditions conducive to intense fire
  • Intense fire destroys pathogens allowing
    establishment of vigorous even aged stand
  • And so on
  • Ground fire can also control pathogens e.g.
    longleaf pine

13
Species responses to fire
  • Avoiding damage characteristics include
  • Thick bark (e.g. pines, oaks)
  • Buried buds or lignotuber (grasses, aspen,
    Eucalyptus)
  • grass stage longleaf pine.
  • Deep rooting and rapid growth
  • Self-pruning (prevents fire ladder)
  • Fire resistant foliage
  • Rapid decomposition (no fuel buildup)
  • Recovering from damage
  • Resprouting (rhizomes, root crown, lignotuber,
    epicormic shoots)
  • Deep rooting (allows rapid regrowth)

14
Species responses to fire
  • Recolonising after fire
  • Early flowering and seed production (esp. with
    short fire interval)
  • Asexual reproduction
  • Wind-borne seeds
  • Serotony
  • Promoting fire pyrogenic species
  • Flammable foliage and bark
  • Volatile compounds
  • Short stature
  • Retention of foliage near ground, retention of
    dead branches

15
Species persistence
  • Propagating by seed
  • Invaders copious short lived, wind dispersed
    seed. Pioneer species (fireweed)
  • Evaders store seed in canopy or soil. Seeds
    evade high temps, then germinate rapidly after
    fire. Serotinous pines.
  • Avoiders shade tolerant, arrive later in
    succession. Lack fire adaptation. Sugar maple.
  • Surviving fire
  • Resisters adult stages survive low intensity
    fire. Sequoia. Many members are also evaders.
  • Endurers resprout from perennial buds after
    fire. Include trees, shrubs, grasses.

16
Fire for management
  • prescribed burning is an ancient practice
  • Humans worldwide have used fire for numerous
    purposes
  • Clear space for safety
  • Create green pick for game
  • Encourage medicinal plants
  • Drive game
  • In western North America, fire frequency
    decreased around 1870s
  • Almost ceased with fire suppression 1900.

17
Fire suppression
  • Why was this policy implemented?

18
Fire suppression
  • Why was this policy implemented?
  • Based on observations of northern hardwood
    forests (rarely burn)
  • Misunderstanding of role of fire in west
  • Fear of fire, destruction of property etc.
  • Result?

19
Fire management and prescribed burning
  • Prescribed burning concentrates on setting of
    fire in a manner that will achieve desired
    purposes.
  • In rangeland and forest used to alter vegetation
    composition, increase forage quality and
    quantity, manage for wildlife, reduce wildfire
    risk, prevent catastrophic fires,control exotic
    species, maintain wilderness character,
    maintain particular communities (longleaf pine,
    tallgrass prairie)

20
Fire management and prescribed burning
  • How should fire be managed and used?
  • Is there a role for fire suppression where,
    how, why?

21
Fire in sagebrush steppe
  • Should fire be suppressed here? Is there a role
    for prescribed burning?
  • Historic fire regime 20-150 year fire return
    interval. Sage fire sensitive, recruits by seed.
    Perennial grasses, rabbit brush, more tolerant.
  • Current frequency (with cheatgrass) can be under
    10 years.
  • Fire creates vegetation type conversion after
    invasion of annual grasses (DAntonio and
    Vitousek).

22
Breaking the cycle?
  • Is there a way to re-establish natural fire
    regime
  • How could this be accomplished?
  • Tomorrow vegetation sampling in 30-year-old burn.
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