Seminars 1.“Plant Talk” – Thurs April 1 12:00 PM in FA 214. Giles Thelen: “ Insect herbivory stimulates allelopathic exudation by an invasive plant and the suppression of natives.” 2.EECB Colloquium OSN 102 at 4:00 PM Thursday April 1. Lonnie Aarsen, Queens University. “Ecology – less than a science or more than a science?”

Abstracts and assignments 1.Abstracts – Extention? Due April 4. 2.Grad Student lectures – April 13 lab period. What order? Anyone need handouts made? 3.“class conference” April Term papers due April 28.

Outline 1.Importance of fire in range and forest 2.Fire regimes 3.Types of fire and their effects 4.Species responses to fire 5.Effects on environment and soil 6.Fire as a management tool 7.Fire in sagebrush steppe ecosystems

Reading 1.Textbook Chapter 13 2.Chapter 12, Fire, and selected pages from chapter 16, Disturbance. Barnes et al Forest Ecology 4 th edition. J. Wiley and Sons, New York. (on reserve) 3.Chapter 22, Prescribed fire in rangeland management. From heady and Child Rangeland Ecology and Management. Westview press, Boulder. (on reserve).

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 >1000 years in northern hardwood to <5 years in tallgrass prairie.

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

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

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!

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

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”)

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

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

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)

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

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.

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 1870’s Almost ceased with fire suppression 1900.

Fire suppression Why was this policy implemented?

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?

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)

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

Fire in sagebrush steppe Should fire be suppressed here? Is there a role for prescribed burning? Historic fire regime – 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 (D’Antonio and Vitousek).

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.