Leda N. Kobziar School of Forest Resources and Conservation

University of Florida

Ecological Effects- short version

Chapter IX: Interagency Prescribed Fire Training

Ecological Effects - Outline

Objective: Understand the what and how of fire’s role in Florida’s ecosystems

Fire dependent ecosystems of Florida, their fire regimes

Fire’s effects on ecosystem components e.g. water, soil, vegetation, fauna

Relationship between timing/season of fire and ecosystem effects

How to manipulate fire regime attributes to encourage specific ecological responses

Fire in Florida

Objectives

1) Identify fire’s primary effects on the basic physical ecosystem components of water and soils.

2) Identify fire’s primary effects on floral (plants) and faunal (animal) components of ecosystems.

3) Identify common Florida fire-dependent ecosystems and frequency of fire return intervals that sustain them (IN YOUR BOOK)

4) Understand the relationship between season or timing of fire applications and certain ecosystem responses.

5) Understand the connection between burn prescription parameters and ecological effects.

What does fire ecology entail?

• Fire history (pyrodendrochronology, reconstructions, sediment and pollen charcoal analyses)

• Fire regimes• Fire dependence or

adaptations of plants and animals- AUTECOLOGY

• Fire effects on water, plants, animals, from individuals to populations, communities, ecosystems, landscapes.

• Fire effects on nutrient, energy, and carbon cycling

Why is fire ecology important in the south?

US Wildfires by Region: 2000-2010

Fire in Florida

# of Lightning Fires in Florida1986-1997

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Fire in Florida

# of Lightning Fire Acres1986-1997

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Florida’s Historical Fire Regime: May-June

Native Americans burned to stimulate grasses and forage, acorn production, reduce fuels and pests, clear land for agroforestry, increase access, herd game, etc.

Practices adopted by European Settlers (c. 1700s to mid 1900s)

12,000+ yrs of Lightning + Anthropogenic Fire Use

Thousands of yrs of repeated burning ecosystem structure & composition Selected for fire-resistant or

fire-dependent species (e.g. longleaf pine, red cockaded woodpecker) and communities

Resulted in 26 fire dependent and/or influenced communities in Florida alone (1/3rd of 81 total).

Legacy of anthropogenic and lightning fires

Chris Evans

The Florida Natural Areas Inventory lists 81 communities in Florida: 18 of these are considered FIRE DEPENDENT– will change significantly if any aspect of the fire regime is changed for a given length of time.

These ecosystems cover the majority of non-developed land area in Florida. Examples: Sandhill, Upland Pine Frequent, 1-3 yrs ScrubVariable, 5-30 yrs Dry Prairie Frequent, 1-2 yrs Mesic Flatwoods Frequent, 1-4 yrs Scrubby Flatwoods Variable, 5-15 yrs Wet Flatwoods Frequent, 3-10 yrs Glades Marsh approx. 2-5 yrs Marl Prairie Frequent, 1-6 yrs

Repercussions of long-term burning FL Fire Ecosystems

UNSUSTAINABLE HARVESTING & FIRE SUPPRESSION FOREST DEGRADATION:

~3% ORIGINAL FOREST REMAINING1) Lack of seed sources,

regeneration of fire adapted species

2) Altered soil fertility, pH, texture, mycorrhizae…

3) Loss of fire-structure dependent wildlife spp.

4) Closed communities with limited early successional species recruitment

5) Changes in flammability and fuels structure

6) Fuel load build-up larger, less predicable, higher severity, more costly wildfires

IN THE SOUTH, REVERSING THE LEGACY OF SUPPRESSION AND DEGRADATION MEANS USING

PRESCRIBED FIRE TO RESTORE AND MAINTAIN NATIVE ECOSYSTEMS

What’s in the prescribed burner’s “restoration toolbox”? FIRE REGIME ATTRIBUTES • Fire frequency• Seasonality• Extent of area burned/ landscape heterogeneity

• Type (crown, ground, surface)• Intensity• Severity• Synergy, interaction with other

disturbances• Includes using fire with mechanical

treatments, silviculture, CLIMATE

Longleaf pine Southeastern USFire 1-4 yearsLow intensity, understory, Spring/ summer

Florida Big Scrub (sand pine) Fire 30+ years,high intensity, crown, spring or summer, large areas

Basin swampFire > 5-150 years, small area, mixed severity, only burns during drought (peaty soils)

Randy Cyr

Frequent fire

Infrequent fire

Examples of Historical FL Fire Regimes

The South burns more than any other region of similar size in the world…but still doesn’t meet

fire rotation goals

Quiz

Southern Region: 354 M acres forest pre-settlement

How many acres would have burned historically to maintain a 10-yr average FRI across the forests?

200 M acres forest today 8 M burned…how much more should be

burned? Caveat: “forest” includes plantations, which are not

subject to the historical FRI…but you get the picture!

Dept

h to

Wat

er Ta

ble

(m)

Fire Interval

Pine Flatwoods

High Pine

Sand Pine

Scrub

Shrub Wetland

Sava

nna

Mar

sh Bay head Hydric Hammoc

k

Mesic Hammoc

k

Xeric Hammoc

k

Slash

pine scru

b Rosemary scrub

Low scrub

Oak scru

b

Rosemary scrub

Rosemary Bald

FIRE REGIMES CORRESPOND TO THE DISTRIBUTION OF FL NATIVE ECOSYSTEMS

Fire Regime

• 30+ year fire return interval• Late spring / early summer fires associated w/ drought, high winds, low RH and high temperature

• High-intensity, larges scale, stand-replacing crown fires

• Auto-successional (fire climax) ecosystem• Pinus clausa (sand pine) is serotinous

Without fire sand pine scrub will likely succeed to xeric oak/hickory scrub.

Example: sand pine scrub

Serotinous cones (Pinus clausa)Open after heating by fire, require bare mineral soil for germination

Quiz: What fire regime attributes would you “prescribe” to regenerate the stand?

Given this knowledge of fire ecology:

Sand pine doesn’t burn well unless it’s a drought, or around March-May when resin content is highest and MC is lowest

The cones require high heat; the crowns of the trees must be burned

The seeds require bare mineral soil

Younger trees don’t produce enough viable seeds to regenerate a stand, are killed by fire

a

a

bbb ba

a

adequate foroverstory restocking

Importance of fire severity: P. clausa seedling recruitment

Senescent

Mature

Severity and stand age/ frequency

Example: Reference Condition- savanna

Directly Fire Frequency Fire Season Area Burned

Indirectly Fire Type Fire Intensity Fire Severity

Fire regime attributes manipulated goalsSavanna Restoration

Low density, mature overstory (BA < 15 m2/ha)

Small regeneration gaps Grassy understory,

diverse herbaceous component

High C sequestration Low hardwood occupancy Wildlife habitat function

(imperiled species: red cockaded woodpecker, gopher tortoise, skink, etc.)

Wildfire mitigation function: reduce severity by reducing fuel loads

Successful Prescribed Fire Use = Applied Fire Ecology to Meet Management Objectives

Where to find information? Southern Fire Exchange: hub for

resources http://

southernfireexchange.org/index.html

Start with the basics: General Fire Effects on Plant Communities

Competition for moisture, nutrients & light are temporarily reduced

Species composition and successional stages are altered Earlier seral stage, but not always

Structure of community may change e.g. susceptibility to blowdown Fuel profiles may change fire effects

Certain species may be selectively eliminated or selected for based on their degree of fire adaptation This changes over the life cycle of a plant/ phenology

Plant Adaptations to Fire

Flower & seed production stimulated (e.g. wiregrass)

Seed germination stimulated (seed or soil conditions)

Rapid growth & development (e.g. longleaf pine)

Fire-resistant bark, self pruning of ladder fuels (most pines, mature hardwoods)

Adventitious buds (gallberry, pond pine)

Root/ tuber/ rhizome sprouting, and storing carbohydrates (oaks, saw palmetto, perennial grasses)

Serotinous cones (sand pine) Flammability (?)

Woody plant mortality: multiple mechanisms, time-dependent

Hiers et al. Final Report: JFSP 01-1-3-11

Foliage mortality

02468

1012

Temperature F

Tim

e (m

in)

Woody Plant Mortality- Crowns

Crown scorch (dead foliage) increases as air temperature

increases may not kill crowns of longleaf

and slash pines Crown mortality affected by:

stand & shrub density fuel concentrations at the base of

trees bud dormancy & heat resistance foliar moisture content presence of flammable

compounds Season!!! Resistance high when

dormant, lower in late summer

Woody Plant Mortality- stems

Stem & cambium mortality affected by: bark thickness & heat resistance stem diameter & degree of heat

girdling heat received during all stages

of combustion Damage to tree stems

managed by: controlling fire intensity,

flame length, and residence time

reducing duff & litter consumption where long unburned

Looks Severe…Will everything die?

Nope! That’s the beauty of fire adaptation.

Woody Plant Mortality- Roots

Root mortality affected by: depth of lateral and feeding

roots moisture content of duff/litter

and surface soils duration of fire heating

Damage to roots managed by: knowing where roots are

located regulating duff & litter

consumption by burning at specified moisture contents

Drought indices are important to consider Influence duff consumption

Hiers et al. Final Report: JFSP 01-1-3-11

Fire-Caused Plant Mortality- effects of fuel and structure

Fuel & stand characteristics affect lethal heating Heat disperses in open stands High fuel loads increase heat release High fuel moisture content decreases heat Litter and duff accumulations increase heating

at base of stem Therefore, burn prescriptions also affect

mortality: fire regime attributes: Frequency: Frequent fires reduce fuel loads Intensity: Ignition pattern (how so?) Season of burn

Woody Plant Mortality- Secondary effects

Mortality may develop slowly (even over a period of several years) Damage in one part

of plant stresses other parts

Secondary infection by insects or fungi

Post burn environment matters (drought/rain)

Bark beetle pitch tubes

Woody Plants: Post-Fire Recovery

Sprouting is the recovery mechanism in most hardwoods and shrubs:Roots, root crowns, dormant stem buds, rhizomesSurvival related to depth, locationdependent on season and fire severity

most sprouting: low intensity, dormant season burns least sprouting:

▪ high intensity, growing season fires▪ low soil moisture▪ High organic matter consumption

exceptions when reproductive parts deep in soil

Managing for Post-Fire Seedling Establishment

Reproduction by seed after a prescribed fire can be managed by: knowing the seed ecology of a species Burn prescription

size and/or intensity of burn- seeding species often require bare mineral soil. What does this suggest about desire litter/duff consumption/ severity?

season/timing of burn- post burn precipitation is important!

Schedule burns to take advantage of seasonal responses

SummaryEffects on Plants

Plants vary in adaptations to fire Fire effect is created by interaction of

weather, fuel conditions, fire behavior, & site moisture

Post-fire conditions significantly affect recovery & productivity

Plant community responses are predictable, if you learn about plant ecology

Landowner should monitor burning conditions and post-fire responses and make changes to subsequent prescriptions as necessary

Effects on Animals:General Principles

Many Florida species have evolved in a fire environment

Mortality levels are generally low (direct effects)

Indirect effects on cover and food sources can be substantial but vary across the landscape and diminish with time

• Animals with limited mobility (young, old, small animals) are more vulnerable to injury and mortality than animals with high mobility (mature or larger animals, flying species).

Smokey’s great grandson?

The principle way that fire affects fauna is by affecting HABITAT Cover is temporarily decreased Microclimate is modified Food sources & nutritional quality

increase plant species diversity increases foliage of new herbaceous plants and

shrub sprouts is more palatable and higher in nutrients (N,P) and crude protein

seed production of many species increases

abundance and diversity of insects may increase

prey are more visible for predators

For Wildlife in General, Create Habitat Diversity

Grant Steelman

Example: WILD TURKEY ROTATION PATTERNMixed burn rotations such as the one above with a three year rotation provide adequate nesting and escape habitat when the adjacent unit has been burned. Mix dormant/growing season burns (Grant

Slide: Grant Steelman

Putting it all together: when to burn, how?

Seasonal Effects: Dormant Season

Increase number of stems of many hardwoods and shrubs ***

Generally doesn’t kill larger diameter hardwoods (e.g. oaks)

Favors bird species that prefer shrubby - hardwood habitats

A few months makes a difference: Wiregrass seed production vs. shrubs (gallberry)

May Burn

August Burn

FIRE SEASON: EFFECTS ON UNDERSTORY, FIRE BEHAVIOR, SUMMER VS. WINTER

Saw palmetto: 80% annual growth in summer

10 mo. post burn

Seasonal Effects: Early Spring

Deciduous hardwoods most susceptible to damage Can be top killed after leafing out, don’t have

carbo. Reserves to respond Positive for hardwood control May be a negative for mast production for wildlife

May damage gamebird nests and brood, but food supplies probably not a problem, especially with patchy fires

Seasonal Effects: Growing Season

Stimulate flowering/seed production of many grasses and forbs increase number of original plants that flower increase number of flowering stems per

original plant Higher damage to shrubs and

hardwoods Top-kills larger, more stems than

dormant season burn reduces amount of resprouting increases percentage of individuals

completely killed

Seasonal Effects: Growing Season-2 If fire conducted during rainy, humid

weather, results may be more patchy than in dry weather a positive for wildlife habitat a negative for some other objectives

Small pines may be damaged by intense fire if ambient temperatures are high

Favor birds that prefer open woodlands & grasslands

Seasonal Effects: Fall

Evergreen trees (pines) & shrubs (including palmetto & gallberry) most susceptible to damage!!!!

Most hardwoods will not be affected

Crown damage, season in southern pines

Fire in Florida

How do we manipulate fire to achieve desired ecological effects? Burn

Prescription Parameters.

What will influence fire’s behavior that will result in specific ecological effects?

1) Weather parameters before, during, and after the burn (Air temp., RH, precipitation, wind)

2) Timing of the burn

3) Ignition patterns  

Fire in Florida

Firing Plans/Ignition Patterns

1) Slow moving fires of all types are hotter at the soil surface, and have more potential to heat and ignite ground (subsurface) fuels and affect roots and soil

2) To minimize the degree of fire severity, limit the fire residence time

3) The pattern of ignition (how the fire is applied, could be solid line, point source or a combination) will alter the intensity of the resultant fire ecological effects

Summary Major factors that influence ecosystems:

Depth to water table Fire frequency, fire regimes

Effects on animals include: Direct Mortality - MINOR Habitat changes – can be MAJOR (+)

Wildlife, plant diversity and numbers increase with a mosaic of successional stages created by a variety of fire prescriptions over time Pyrodiversity promotes habitat diversity

promotes species diversity

Smokey says, “Burn wisely!”