Lesson 6: Fire effects part 1

this unit of s 244 field observer and

fire effects monitor presents an

introduction to fire effects monitoring

the unit builds on your knowledge of the

fire environment gained in s 290

intermediate fire behavior and in the

previous environmental observations unit

of this course this unit has three parts

lesson 1 general concepts of fire

effects lesson two methods for measuring

fire effects and lesson three plots and

protocols upon completion of this unit

students will be able to one describe

common fire effects and methods by which

to measure and document these effects to

implement fuel loading and photo

monitoring protocols three list sources

of other protocols available for fire

effects monitoring and for characterize

and report the range of variability of

first-order fire effects due to changes

in fire behavior and the plant community

these objectives are directly related to

task number 11 in the fire effects

monitor and field observer position task

book in lesson 1 will cover some general

concepts so you can understand what

causes specific fire effects and which

aspects are important to observe and

document when you are assigned to

monitor a fire these concepts include 1

the difference between first-order fire

effects and second-order fire effects

and how this difference relates to the

positions of fire effects monitor and

field observer to how fire behavior

interacts with a species adaptations to

fire to produce fire effects three fire

regimes and how fire adaptations are

influenced by fire regimes and for how

and why fire effects vary over space and

time the first concept is the difference

between what are referred to as first

order and second order fire effects

first order fire effects are those

effects caused by the direct and

immediate result of a fire they are the

effects observable within a short time

after the fire has passed such as crown

scorch top kill fuel consumption and

animal mortality due to burns

second order effects are the indirect

effects that occur later as a result of

the first order effects you might think

of a second order effect as the effects

of the effect for example the first

order fire effect of native grass

mortality may provide the opportunity

for non-native invasive plants such as

cheatgrass to invade a site which would

be a second order fire effect other

examples of second order fire effects

include increased germination of fire

dependent species delayed plant

mortality due to root damage and animal

mortality due to loss of habitat animals

are often able to escape the direct

effects of fire due to their mobility

but can be impacted by the effects of

fire on vegetation such as the

short-term loss of their habitat

wildlife mortality due to loss of forage

is a second order fire effect for

example during the 1988 Yellowstone

fires around one percent of the parks

elk were killed by burning or smoke

inhalation a first order fire effect but

loss of Forge due to drought and Fire

combined with a severe winter caused

forty percent mortality in the elk

population during the following winter a

second order fire effect on the other

hand wildlife habitat can also be

enhanced through burning increased

wildlife habitat is often a land

management goal and fire may be used to

achieve this goal for example a

prescribed fire management objective in

support of this goal might be to top

kill sixty to eighty percent of the

understory shrubs in order to increase

sprouting of red stem ceanothus a second

order fire effect which would enhance

the forage for mule deer notice that

fire effects whether first order or

second order can be beneficial to some

species and detrimental to others fire

effects are neither good nor bad by

themselves they are considered desirable

or undesirable based on land management

objectives as a fire effects monitor or

field observer on a prescribed fire or a

wildfire assignment your task is to

observe and document the immediate post

fire or first order fire effects the

second order fire effects are generally

not apparent until weeks months or even

years after the fire and monitoring them

is generally part of a larger more

comprehensive land management plan if

you see a need to follow up with

additional future monitoring be sure to

note that as part of your monitoring

report most of the first order fire

effects you'll be observing and

documenting are related to fires effect

on vegetation because first order fire

effects on vegetation usually determine

second order fire effects on other

elements of the ecosystem for instance

the loss of ground cover vegetation a

first order fire effect can lead to soil

erosion a second order fire effect in

the future so in the next section we'll

look at how fire behavior interacts with

plants adaptations to fire to produce

fire effects understanding this concept

will help you determine whether the

predicted fire behavior will have the

desired effect on vegetation and meat

management objectives for the fire

standard terminology exists for

describing the behavior of wildland

fires it is important to understand the

different properties a wildland fire can

have how they can be described and how

the various aspects of fire behavior can

be related to fire effects monitoring

and documenting fire behavior and

characteristics according to these

standard terms can increase

understanding of the relationship

between a specific fires behavior and

heat characteristics and the effect of

that fire will start our review of fire

behavior by looking at the nature of

heat exposure and how it relates to fire

behavior then we'll briefly review the

fire behavior terms residence time

burnout time fire line intensity and

flame length as they relate to

documenting heat exposure the effects of

fire on vegetation are caused by

exposure to heat and exposure to heat is

a function of both temperature and time

the hotter the temperature and the

longer the exposure to it the more

intense the effects of the fire will be

the lower the temperature the longer the

plant tissue must be exposed to be

affected one effective exposure to heat

is plant mortality lethal temperatures

can vary by species but a general

guideline in plants is 60 degrees

Celsius or 140 degrees Fahrenheit

for 60 seconds the lowest temperature at

which plant cells die is between

approximately 50 to 55 degrees Celsius

or 122 to 131 degrees Fahrenheit plant

tissue can sustain higher temperatures

for greatly decreasing periods of time

as shown in this graph depicting lethal

heat exposure for Douglas fir needles

exposure to heat can also have a

beneficial effect on plants that have

adaptations requiring heat to stimulate

vital functions for example some pines

such as jack pine and lodgepole pine

have serratus cones meaning that the

cones remain closed until heat causes it

to open and release its seeds so in

order to understand and document fire

effects fire effects monitors and field

observers need to be able to describe

heat exposure in terms of both time and

temperature will use standard fire

behavior terminology to accurately

characterize these components of heat

exposure two terms are useful in

describing fire behavior in terms of

time residence time and burnout time the

residence time is the length of time the

flaming front of the fire is present in

terms of the three phases of combustion

it's the time period when the fire is in

the flaming phase at the point you are

monitoring burnout time that presents

the total time for all phases of

combustion flaming glowing and

smoldering and is often a more important

unit of measurement for monitoring some

fire effects than residence time for

monitoring that will later be related to

fire effects an estimate of the total

combustion duration of large diameter

fuels and the surface layers is

important while it is not important to

document the burnout time to the exact

minute it is important to note whether

smoldering combustion lasts for only a

few minutes a few hours or several days

burnout time is sometimes called fire

duration now we'll look at how we

document the temperature component of

heat exposure in research projects a

fires temperature can be measured

directly by heat sensors but in fire

effects monitoring temperature is

usually inferred from fire line

intensity which is the rate of heat and

released per unit time per unit length

of the fire front an example of fire

line intensity would be 100 BTUs per

second per foot fire line intensity is

an output of the fire behavior

prediction system and can be calculated

using the fire behavior prediction

program behave or fire behavior noma

graphs but in the field a more common

method of estimating fire line intensity

and therefore temperature is to use

flame length Richard Rothermel who

developed many of the mathematical

equations used by the fire behavior

prediction system cautioned that flame

length is an elusive parameter that

exists in the eye of the beholder it is

a poor quantity to use in a scientific

or engineering sense but it is so

readily apparent to fire line personnel

and so readily conveys a sense of fire

intensity that it is worth featuring as

a primary fire variable this is the

reason many prescribed fire or wildfire

management objectives specify a flame

length it's an easily observable

indication of the fire line intensity

and temperature that can be used to

predict fire effects or determine which

suppression resources might be effective

even if it can be challenging to

estimate accurately however this method

of estimating temperature applies only

to the flaming front and the heat above

ground it does not measure the heat

pulse downward into the soil therefore

it is useful only for predicting fire

effects above ground such as crown

scorch and tree mortality due to bowl

damage so in order to understand and

document fire effects fire effects

monitors and field observers need to be

able to describe heat exposure both in

terms of the temperature indicators of

the fire and the amount of time it

burned in the area they were monitoring

we can determine the time using

residence time and burn out time and use

flame length as a rough indicator of

temperature next we'll discuss how the

time and temperature components of heat

exposure combined to produce severity

and how we can properly describe

severity in fire effects monitoring the

term severity has no single definition

in fire management it is a broad concept

that is applied in various ways

sometimes it is used incorrectly

as a synonym for intensity it is

important to remember that intensity

refers to a physical property of fire

regarding how much heat is produced

severity on the other hand refers to the

results or impacts of the fire in terms

of environmental change because severity

has a broad definition and is used to

describe different aspects of fire if

the term severity is used in the

management objectives of the fire you

are assigned to monitor it's critical

that you understand how the term is

being used for that specific project for

the purposes of this unit we will define

fire severity and burn severity and

describe how these terms will be used

but be aware that you will encounter

other definitions for these terms in the

course of your work more specifically

the National wildfire coordinating group

or nwcg defines fire severity as the

degree to which a site has been altered

or disrupted by fire it's traditionally

expressed by classifying the magnitude

of a fires impact on a particular

resource into qualitative classes

ranging from low to medium to high fire

severity 'he's a general classification

of fire severity defines low moderate

and high severity in terms of overall

effects to the vegetation surface fuels

and soil in a low severity fire there is

only slight modification to the

structure of the vegetation and nearly

all mature woody plants survive there

may be some consumption of fine fuels in

litter but the Duff remains intact and

there's little or no soil heating in a

moderate or mixed severity fire some

Stan structure change occurs through

limited mortality of mature woody plants

the foliage of trees and shrubs may be

scorched there is higher consumption of

fine fuels and litter and the Duff layer

is partially consumed some surface soil

heating occurs in a high severity fire

most or all of the small plants litter

and Duff are consumed significant soil

heating occurs sometimes impacting the

subsurface layer there is high mortality

of mature plants including overstory

trees this type of severity is often

referred to as a stand replacing fire

the most obvious and common way to

measure severity

through impacts on forested overstory a

specific classification of fire severity

targets this impact low severity is

defined as less than twenty five percent

mortality of the dominant overstory

species moderate severity is 25 to 75

percent mortality of the overstory

species and high severity is greater

than 75 percent mortality in the

overstory the important point in

understanding and documenting fire

severity is to identify the particular

resource of interest and the

classification criteria to be used we'll

discuss classification protocols in

detail in lesson 3 of this unit burn

severity is a type of fire severity

measurement it specifically targets the

fire's impact on the ground due to

surface and subsurface heating nwcg

defines burn severity as a qualitative

assessment of the heat pulse directed

toward the ground during a fire burn

severity relates to soil heating large

fuel and duff consumption consumption of

the litter and organic layer beneath

trees and isolated shrubs and mortality

of buried plant parts it can be

classified into categories of low medium

and high based on established criteria

that we'll cover in lesson 3 burn

severity is a function of fire line

intensity and burnout time so even

though burn severity is related to fire

line intensity a low intensity fire does

not always produce a low severity fire

in fact there can be many combinations

of fire line intensity and burn severity

on any site depending on fuel loading

and distribution and site weather and

moisture conditions at the time of the

fire for example any of the combinations

of fire line intensity and burn severity

on the following slides can occur in the

example on this slide both the carrier

fuels and the organic layer are dry the

result is a fire with high fire line

intensity exhibit extreme fire behavior

and that is also a deep burning high

severity fire flame lengths are long

large fuels are removed soil organic

layers are consumed and a significant

amount of subsurface heating occurs in

this video of grass fire winds increase

the flame lengths and rate of

bread causing high fire line intensity

and low residence time the lack of

coarser fuels also decreases burnout

time and results in little subsurface

heating and minimal impact to the soil

and organic layers in this example a

fire with low fire line intensity

ignites ground fuels and the Duff and

litter layer which smolder for many days

before burning out the amount of heat is

relatively low but the long burn out

time causes high consumption of the

organic layer and lethal heating of the

underground and surface plant parts here

the fuels are moist and the litter and

Duff layer is wet the result is a fire

with low fire line intensity that also

has low severity that is there is little

heating of the surface or subsurface and

minimal consumption of the organic layer

in summary fire behavior observation and

documentation are important to fire

effects monitoring because fire behavior

is an indication of the amount and

duration of heat plants are exposed to

by the fire as a fire effects monitor or

field observer your understanding of

fire behavior terminology and ability to

apply it accurately is critical to

documenting fire effects next we'll

discuss the second part of the fire

effects equation adaptations to fire

plants have evolved strategies to

survive or take advantage of exposure to

heat from fire these adaptations

interact with the heat created by the

fire to create fire effects these

strategies can be divided into two types

structural adaptations that allow an

individual plant to survive exposure to

fire and reproductive adaptations that

allow a population of plants to survive

fire even if the individual plants don't

survive the fire structural adaptations

those allowing an individual plant to

survive exposure to fire are generally

related to the characteristics of the

stand the crown the bud structures or

the bark resisting the carrying of fire

or insulating critical plant structures

from the fires heat the structure of a

stand affects the way a fire will burn

through it open stands with some

distance between crowns minimize the

exchange of heat between crowns during a


and allow heat and gases to rise through

the canopy reducing Crown mortality and

crown fire potential stands of widely

spaced trees with light ground fuels

tend to experience frequent low

intensity fire and denser stands with

greater contact between Crown's

considerable mutual heating as possible

and there is higher crown fire potential

than in an open stand some lodgepole

pine forests typically burn at high

intensity due to their naturally close

spacing characteristics of individual

tree crown that decrease the impact of

fire include low crown density high

crown base height and the ability to

self prune dead branches conversely a

dense crown that extends down near

surface fuels will increase the

probability of crown fire in this

picture the engelmann spruce on the left

is highly susceptible to torching while

the whitebark pine in the middle may be

spared due to its high crown base height

sparse crown density and lack of lower

branches the large buds of some fire

resistant pine species such as long leaf

pine can absorb more heat before

incurring damage than the smaller buds

of spruces and firs and the longer

needles provide some insulation from the

heat the seasonality of fire can affect

buds as well actively growing buds are

more sensitive to heat than buds that

are dormant cambium is the thin layer of

living plant tissue that produces the

critical plant structures necessary to

transport nutrients and water for thick

barked trees such as ponderosa pine

western larch Douglas fir and Jeffrey

pine the heat sensitive cambium is well

protected from the fires heat by the

insulating layer of bark thin marked

trees such as lodgepole pine subalpine

fir and most of the spruces are highly

susceptible to cambium damage from the

fires heat on these thin barked tree

species the cambium is probably dead

beneath any charred bark so bark

thickness varies by species with the

thickest bark providing the most

effective insulation against heat in

addition larger diameter trees of any

species generally have the thickest bark

and I'm

more resistant to cambial damaged by

fire as mentioned reproductive

adaptations to fire allow a population

to survive exposure to fire even if the

individual plant does not reproductive

adaptations to fire include post fire

sprouting and fire enhanced seedling

establishment sprouting is a means by

which many plants recover after fire

surface plant parts produce a plant

hormone that inhibits the growth of

dormant buds fire initiates regeneration

from buds by killing the surface plant

parts that produce this hormone allowing

the buds to sprout the buds that become

shoots are usually those nearest to the

part of the plant killed by the fire

shoots can originate from dormant buds

located on plant parts above the ground

surface or from various levels within

the litter Duff and mineral soil layers

the type of plant parts that support

dormant buds and where they are located

in or above the soil are species

specific characteristics post-fire

seedling establishment is the other

strategy employed by plants to

regenerate after fire this survival

strategy involves using the environment

created by fire to favor the

distribution or germination of seeds

we'll discuss the creation of favorable

seed beds by fire the strategy of

serratus seed cones and how germination

of seeds can be enhanced by fire fire

creates significant changes in site

conditions which can vary substantially

within the burned area depending on the

severity and pattern of the fire

consumption of fuel especially the

forest floor is an important determinant

of post-fire conditions because it

controls the amount and distribution of

good seed bed conditions nutrients may

be more readily available in ash and the

mineral soil does not dry out as quickly

as organic material the blackened

surface causes warmer soil temperatures

that enhance nutrient cycling and can

favour growth particularly in cold

limited environments such as boreal

forests after a severe fire there's less

competition from sprouting plants

seedlings and trees if feeder roots and

seeds stored in the Duff and soil were

killed there may be little shade

in the first few post-fire years because

of plant mortality the physiological

requirements of individual species

determine whether post fire conditions

are favorable for seedling establishment

for most species that develop from seeds

dispersed after fire the best seed beds

are micro sites where most or all the

organic layer has been removed by fire

because they provide the greatest chance

for seedling survival for some shade

intolerant species this is the only time

that seedlings can establish but these

conditions can result in abundant

regeneration notably of western larch

and many species of pine the serratus

cones of species such as lodgepole jack

pitch table mountain and pond pines

retained some of their seeds because of

the presence of a resin bond between

scales on some of their cones serratus

cones slowly open and release their

seeds after they are heated to at least

45 to 50 degrees Celsius or 113 to 122

degrees Fahrenheit a temperature that

melts the resin bond cones protect a

significant portion of pitch pine seeds

from the high temperatures reached

during fire lodgepole pine seeds can

survive in cones heated in flames for

length of time typical of crown fires

numerous viable lodgepole pine seeds are

dispersed even after a long duration

crown fire fire can induce germination

of dormant seeds of some species

germination of some hard seeds can occur

only after heat from the fire causes

cracks to form in the seed coat allowing

water to enter requirements for optimum

germination maybe species-specific fire

stimulated germination has been

documented from any hard seated general

including wild hollyhock blackberries

and raspberries gooseberry current

Western chokecherry Mountain hollyhock

geranium Muhly grass and mountain big

sagebrush so regarding the interaction

between fire behavior and adaptations to

fire the knowledge of plant response to

fire can be critical to successful

application of prescribed fire and fire

for resource benefit to ensure that a

desirable range of plant species estab

is after a fire it is important to

understand how different prescriptions

can produce different fire and plant

responses designing fire prescriptions

and evaluating management objectives

requires knowledge of fire behavior fire

severity species survival mechanisms and

methods of post-fire vegetation recovery

properly conducted the fire treatment

will result in the desired amount of

mortality injury re sprouting and

seedling establishment from the target

species one of the responsibilities of

the fire effects monitor or field

observer is to report whether the fire

behavior produced the desired fire

effects for the resources targeted in

the management objectives next we'll

discuss fire regimes and how they

influence plant adaptations and fire

effects fire regimes are patterns of

fire occurrence frequency size severity

and sometimes vegetation and fire

effects in a given area or ecosystem

ecosystems evolved with and adapted to

specific fire regimes in a particular

ecosystem natural fires occurred with

fairly regular frequency and a typical

season of occurrence with characteristic

fire line intensity and severity and

characteristically did or did not

involve the Crown's of trees or shrubs

large differences in fire regimes

occurred between ecosystems for example

frequent low intensity surface fires

were common in many ponderosa pine

ecosystems whereas fires in big

sagebrush were probably less frequent of

higher intensity and killed much of the

sagebrush overstory high intensity stand

replacement fires at long intervals were

characteristic of some conifer forest

types while annual fires may have been

common on some great plains grasslands a

fire regime is a generalization based on

fire histories at individual sites fire

regimes can often be described as cycles

because parts of the histories are

usually repeated and the repetitions can

be counted and measured fire regimes

have been described by factors such as

fire frequency size of fire pattern on

the landscape season of burn and depth

of burn the more detailed

classifications are useful to fireman

ecologists and fire effect specialists

interested in the intricate aspects of

fire effects the simpler classifications

are useful for broad scale assessments

and non-technical audiences some of the

simplest and most common classification

systems use frequency and severity to

classify fire regimes frequency is

defined as the reoccurrence of fire in a

given area over time it is related to

the terms mean fire return interval fire

return interval fire cycle and fire

rotation severity as defined earlier in

this lesson is the degree to which a

site has been altered or disrupted by

fire in this context it usually refers

to the effect of fire on the dominant

overstory species fire regime condition

class or FRC see is an interagency

classification system used to describe

the departure of an area from its

natural condition one of the first steps

in determining departure is to establish

what the naturally occurring fire regime

is fr CC classifies naturally occurring

fire regimes into five groups based on

frequency in severity this table defines

the classification scheme for each of

the five fire regimes used in fr CC

although frequency and severity are

useful for broad classifications

understanding other aspects of the

naturally occurring fire regime can be

useful for evaluating an eco systems

response to fire and the effect it will

have on the vegetation the season

pattern and size of the naturally

occurring fires in an ecosystem

influence the native plants adaptations

to fire for example many ponderosa pine

stands historically experienced frequent

low severity fires that were patchy and

limited in size the seed of the

ponderosa is high in the crown where low

flame lengths do not damage it and the C

does not disperse far from the parent

tree when uncharacteristically extensive

crown fires burned through Ponderosa

forests ponderosa seed is destroyed and

the burned area may be too large to be

reseeded by surviving poderosas on the

edge of the burn this may cause the

burned area to regrow as another

forest type or convert to another

vegetation type such as shrubland

natural fire regimes cannot be

maintained in unnatural communities

timber harvest practices grazing

patterns the accidental or deliberate

introduction of exotic plants and

animals and the modification of

historical fire patterns through active

suppression have changed many plant

communities interruption of fuel

continuity by livestock grazing road

construction and other developments has

resulted in fires that are less frequent

smaller and of lower fire line intensity

in some ecosystems the introduction of

exotic plants such as cheatgrass coupled

with anthropogenic ignition sources has

greatly increased fire size and

frequency in other ecosystems in summary

fire regimes influence adaptations to

fire that is plants have adaptations

that allow them to survive under the

characteristic fire regime fire that is

uncharacteristic of the natural fire

regime may defeat the native species

ability to survive exposure to fire and

cause irreversible changes to the

ecosystem next we'll look at how and why

fire effects can vary over time and

space in monitoring fire effects as a

fire effects monitor or field observer

you will find that the effects you

observed and documented on one part of a

fire may differ significantly from what

you observed on another part of the same

fire or you may reburn an area that you

burned before only to find that you

produce different fire effects the

second time around to begin our

discussion of how and why fire effects

vary over time and space will go back to

an earlier concept fire behavior

interacts with organisms and their

adaptations to fire to produce fire

effects therefore variability and fire

behavior and in the plant community will

interact to create variability and fire

effects you'll remember from unit 6 that

fire behavior is the manner in which a

fire reacts to the influences of fuel

weather and topography fuels can vary a

great deal over small areas in terms of

quantity arrangement moisture content

and continuity and topography can vary

spatially over even short distance

the weather can change by the minute and

interact with topography to create micro

climates these varying conditions

interact to cause the sometimes rapid

changes in fire behavior that you have

observed in the past as we've discussed

the changes in fire behavior change the

amount of heat plants and other

components of the ecosystem are exposed

to by the fire and cause the lethal heat

zone created by fire to vary

significantly in time and space changing

the fire affects the plant community

also changes over time and space

different soils and micro climates

within a small area can support

different plant communities which in

turn may have varying degrees of fire

resistance the structure and fire

tolerance of a plant community may be

altered by past disturbances such as

previous fires wind storms or human

activities such as timber harvest

livestock grazing or fuel treatments

seasonal differences in plant

development reproductive stage

flammability and curing and exposure of

heat sensitive structures leads to

differences in plant responses to fire

for example grasses are more susceptible

to heat damage during their active

growing period than when they are

dormant in summary of lesson 1 let's

review the most important points fire

behavior is an indication of the amount

and duration of heat the plant is

exposed to by the fire fire effects on

vegetation are the result of an

interaction between the heat exposure

created by the fire and the plants

adaptations to fire fire regimes

influence adaptations to fire that is

plants have adaptations that allow them

to survive under the characteristic fire

regime the fire environment and plant

communities Theory spatially and

temporally therefore fire effects can be

expected to vary widely over space and

time next are a few comprehension check

questions note that these questions are

not graded select an answer for the

question and click Submit to check your

answer click Next to move to the next

question or previous to review or redo a

question if you are finished with the

lesson one material close the entire

window the video is displayed in and

proceed to lesson 2

this unit where we'll cover specific

techniques for measuring and documenting

these fire effects