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.