Transcript Wildlife Management - Midlands State University

Wildlife Management
Habitats
HABITATS
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A habitat is a place where an organism lives.
Types of habitats
(a) Woodlands- They are characterized by crowns of wood
plants that may be continuous and forming 20-80% of
total cover.
(b) Shrub lands- These are intermediate between woodlands
and grasslands. They are generally dense and experience
low grazing.
(c) Grasslands- They vary from treeless to areas of up to 20%
woody cover.
(d) Urban and special- e.g.. Sewerage farms, dams and small
ponds.
(e) Agriculture habitat.
HABITATS
Habitat Management
This include fire control, bush clearing, game water supply
and population control.
Use of Fire
Objectives of Burning
- to alter vegetation composition by removal of undesirable
shrubs and herbaceous species.
- Promoting desirable species.
- To promote foliage quality by promoting sprouting of new
plants.
- To initiate early spring growth on grasses.
- To prepare a seedbed to facilitate new seed germination.
- To control pests and insects.
Fire Effects on Soil
All fires, regardless of whether they are natural or
human-caused, alter the cycling of nutrients and the
biotic, physical, moisture, and temperature
characteristics of soil. In many cases however, these
impacts are either negligible or short-lived and thus
have little, if any, impact on the overall ecosystem.
In some cases however, the impact of fire on soil
conditions can be moderate to severe. The overall
degree and longevity of this impact is determined by
numerous factors including fire severity, temperature,
fire frequency, soil type and moisture, vegetation type
and amount, topography, season of burning, and preand post-fire weather conditions.
Fire Effects on Soil
Past research has identified many fire-related
impacts on soil conditions. They have divided
them into the following categories: Physical and
Chemical Properties, Nutrient Properties, Soil
Temperature, Soil Moisture, and Soil Biota.
In general, when compared to the impacts felt by
other ecosystem components, fire effects on
soil are typically minor, are often short-lived and
can be either positive or negative, with degree
of impact increasing with increased fire severity.
PHYSICAL AND CHEMICAL
PROPERTIES
Fire can impact a variety of soil physical and chemical
properties including the loss or reduction of structure
and soil organic matter, reduced porosity, and
increased pH.
These changes can also result in various indirect
impacts including increased hydrophobicity (water
repellency), which results in decreased infiltration and
increased runoff which often results in increased
erosion.
Most of these changes to the soil, including a loss or reduction
of structure and reduced porosity, are caused by an
alteration in soil chemistry resulting from complex
interactions among geomorphic processes, climate,
vegetation, and landforms.
PHYSICAL AND CHEMICAL
PROPERTIES
Organic matter is also consumed or lost during a
fire. This is dependant on the soil moisture
content of the organic layer of the soil profile,
fire severity and the subsequent precipitation.
Any alteration in soil organic matter is
significant.
The degree of impact that reduced organic matter
has on a site is primarily dependant on the
ecological makeup of the site. For example,
reduced organic matter is especially critical on
nutrient deficient sites including arid and semiarid rangelands.
pH
During the combustion process, several previously
bound nutrients are released in their elemental or
radical form.
Certain positive ions, collectively called cations, are
stable at typical combustion temperatures, and remain
onsite after burning in the form of ash or uncombusted
hydrocarbons.
If in the ash form they are subsequently leached into the
soil where they exchange with H+ ions; the resulting
increase in H+ ions in solution increases the pH.
These changes are significant on low pH sites (e.g.cold,
wet, acidic sites) since a higher pH typically increases
the nutrient cycling of various elements critical for
plant growth, including nitrogen and phosphorus.
pH
In addition to the pre-fire pH of a site, the degree
of impact this process has on a site is
dependant on fuel loading, with the degree of
impact typically increasing with increased fuel
loading.
Ash deposited after a fire is composed mostly of
salts. If exchange sites are available, these
salts can effectively increase soil pH by
capturing the salt cations as they leach through
the soil profile.
Hydrophobicity
Changes in soil organic matter may also cause
hydrophobicity.
This phenomenon occurs during the combustion
process when distilled aliphatic hydrocarbons
migrate into the soil profile and condense on
soil particles to form a water repellent layer.
Hydrophobicity, which typically results in reduced
infiltration rates, appears to be most common in
dry, coarse textured soils that are heated from
176 to 204 OC.
These effects however, are usually short-lived,
generally disappearing after the first year.
Erosion
Vegetation removal, combined with the above changes
in soil physical properties, will typically result in
erosion following a fire.
Whether or not erosion occurs, is not only dependant on
fire-influenced changes (bare soil, soil structural
changes, altered hydrology etc.), but also on a variety
of topographical factors, including slope and aspect,
and climatic factors, such as rate and amount of
precipitation.
Since root systems of top-killed shrubs and trees assist
in maintaining soil stability, erosion may not occur
immediately; instead, it may be delayed several years
following a fire.
Other factors such as soil texture also influence the erosion
potential of a site.
Erosion
For example, in general, coarse-textured soils are considered
more erodible than fine textured soils.
Overall, a variety of factors including slope steepness,
aspect, soil texture, vegetation recovery time, the
amount of residual litter and duff and climatic factors
such as the timing, intensity, and amount of
precipitation, all interact with one another to determine
a sites susceptibility to erosion. When compared to
unburned sites, the overall extent of erosion will vary
considerably from excessive, to little, if any change.
The agent responsible for erosion is also dependant on
local climatic and topographic parameters. Past
studies have found post-fire erosion to be facilitated by
wind, water, and/or gravity. This includes all of the
following types of erosion: raindrop splash, sheet and
rill erosion, soil creep, and mass wasting.
NUTRIENT PROPERTIES
Numerous exchangeable cations including P, Mg,
K, Ca, and Mg typically increase following a fire.
This results in an abrupt release of elements,
which in the absence of fire, would only have
become gradually available through the slow
decay of plant litter.
These cations are generally released during
various combustion stages with the total
amount released being dependant on fire
severity, intensity and fuel type.
Overall, in most cases, a fire increases the
amount of nutrients available, and as a result
nutrient cycling is increased.
NUTRIENT PROPERTIES
Nitrogen may be reintroduced back into an ecosystem
via symbiotic and non-symbiotic fixation. Fixation,
which is commonly more active following fires, can in
some ecosystems actually restore lost nitrogen.
This process is generally facilitated by both
heterotrophic bacteria as well as symbiotic fixation
taking place within nodulated plant roots. Nodulated
plant roots occur in numerous plants species including
various legumes.
Depending on the site, bacterial fixation in decomposing
wood may also provide an important post-fire nitrogen
source. The process is enhanced by the ash and the
blackened soil surface which acts as a black body
(absorbs energy and warms quickly).
NUTRIENT PROPERTIES
While various nutrients can become more available during
and after a fire, others may be volatilized and thus lost
during a fire.
Volatilization, which is temperature dependant, most
commonly affects nitrogen and to a lesser extent,
sulphur, phosphorus and carbon.
Even though volatilization removes nutrients from a
system, it can also convert them to a more available
form.
For example, nitrogen is often converted to the more
available form ammonium, during the volatilization
process.
Thus, even though the total amount of nitrogen on a site
decreases, the amount of available nitrogen to plants
may actually increase or decrease, depending on the
site.
Nutrients
Some nutrients may also be lost by other means
including convection, runoff, or leaching.
This loss while generally insignificant for prescribed
burns, may, depending on fire severity, be significant
during or after intense wildfires.
When compared to fire severity, fire frequency appears
to play a minor role in nutrient loss.
For example, several light to moderately severe
controlled burns may have less impact on the soil than
a single severe wildfire resulting from large fuel
accumulation.
This is not always the case however. For example, on
some nitrogen deficient sites, such as semi-arid
rangelands, nitrogen may actually be lost by frequent
fires.
SOIL TEMPERATURE
Following vegetation removal, an increase in soil
temperature is often experienced.
Numerous factors contribute to this increase including,
the removal of vegetative cover, consumption of fuels,
thinning or removal of the litter and/or duff layer, the
enhanced “black body” thermal characteristics of the
charred material on the soil surface.
The removal of vegetation is significant since plant
residue (stubble), litter and duff cover, all moderate
soil temperatures by intercepting direct sunlight and
moderating the loss of soil heat by radiation.
Higher surface temperatures often enhance seed
germination and plant growth.
SOIL TEMPERATURE
All of these effects, combined with increased
nutrient availability, are hypothesized as being
the reason why plant growth is often stimulated
following a fire.
In fact, increased soil temperatures may actually
be more important than increased nutrient
availability.
Reduced shade combined with increased soil
temperatures, may however, impact nutrient
cycling by allowing the soil surface to dry, thus
decreasing soil microbial activity.
SOIL MOISTURE
Fires can either reduce or increase soil moisture.
Reductions in soil moisture occur when increased
soil temperatures decrease water viscosity, thus
allowing more water to percolate through the
soil profile. In addition, reduced shade,
combined with increased soil temperatures,
also results in higher evaporation rates, which
in turn, restricts the movement of water into the
soil profile.
Late season fire-induced effects may also reduce soil
moisture.
SOIL MOISTURE
For example, if increased plant productivity occurs (due
to increased soil temperatures and nutrient availability)
higher transpiration rates will result, further lowering
soil moisture levels. Other factors, such as decreased
infiltration rates, resulting from hydrophobicity
(discussed above) can also further reduce soil
moisture levels.
While the above factors may reduce soil moisture, other
fire effects can actually increase soil moisture levels.
For example, early in the year, before vegetation gets
firmly established, a site will be subjected to
decreased plant interception and transpiration.
SOIL MOISTURE
This allows a greater amount of water to enter the
soil profile than what would have occurred
during pre-burn conditions.
Overall, the impact of fire on soil moisture is
important, since it facilitates both seed
germination and plant development.
For example, most bunchgrasses require
sufficient soil moisture to enable a seedling to
reach the three-leaf or greater stage of growth
and thus allow it to survive an extended
dormant period.
SOIL BIOTA
Following fire, soil biota (living soil organisms) is
commonly affected to varying degrees.
In general, it appears that soil will often protect
subsurface soil biota (including insect pupae) from fire.
This level of protection is dependant upon the depth of
the organism in relation to the depth of heat
penetration.
In general, hot fires typically have a more significant and
longer-lasting impact on soil biota than low intensity
fires which tend to have little or no effect on soil biota.
Overall, it appears that changes in soil biota are typically
minor, and thus have little impact on the ecosystem as
a whole. The exact impact of fire on soil biota
however, is complex, and for the most part still poorly
understood.
Fire Effects on Grasses
Fire is a dynamic process that affects grass in a variety
of different ways.
When determining the effects of fire on individual
species and ecosystems, it is important to understand
the condition of the plant community and individual
species existing before a fire occurs.
That is, the impact of fire on an individual plant species
or communities may increase if the community has
been subjected to other disturbances such as drought,
disease, insect infestations, overgrazing, or a
combination of these factors.
The response of individual grasses to fire varies significantly
between, and within, species and is dependant on the
parameter being measured.
Fire Effects on Grasses
Moreover, this response is influenced by a variety of fire
parameters including intensity, severity (e.g.,, amount
of organic matter consumed), residence time, soil
heating, season of burn, and time since last fire, all of
which can vary significantly among fires and within a
fire.
These variations can and will cause differences in the
response of individual species and the community as
a whole.
In addition, numerous physical and climatic factors (e.g.
fuel condition, weather, slope, and aspect) as well as
biological factors (plant morphology and physiology)
will influence post-fire effects on plant communities.
Fire Effects on Grasses
This includes direct effects such as the ability of
individual species to resist the heat of a fire
(depending on age and seasonality) and the
mechanisms by which they recover after fire.
Finally, in addition to fire parameters and individual
species response, numerous external factors such as
post-fire weather, post-fire animal use, and plant
competition can also determine how the grassland and
individual species will respond to fire.
Common effects include grass mortality, increased
flowering and seed production, increased and
decreased productivity, increased forage quality,
reduced/increased vigour and abundance of dominant
species when compared to long-term unburned
communities.
FIRE EFFECTS ON INDIVIDUAL GRASSES
Seasonality generally has the greatest influence in
determining the effect of fire, with fires occurring
during a metabolically active period tending to be the
most damaging.
If a plant is actively metabolizing (e.g. growing)
consumption of the entire aboveground portion of the
plant, will stress the plant or even cause plant
mortality.
However, grasses are more likely to die if growing
points, including meristems and buds, are subjected to
lethal temperatures or increased residence time.
Whether or not lethal temperatures occur is dependant
on growth form, fuel loading, adjacent plant species as
well as foliar and fuel moisture levels.
FIRE EFFECTS ON INDIVIDUAL GRASSES
The importance of growing point location in determining
fire impacts on grass tillers is primarily related to the
susceptibility of growing points to fire as well as the
cycling of plant energy reserves.
The location of these growing points is critical since
aboveground herbaceous material rarely survives fire.
Exactly where these growing points are, and when they
are elevated, is species specific and dependant on
plant maturity and plant-growth characteristics.
For example, even though species may occur within the same
community, some may be actively growing with their
growing points elevated above the soil surface, whereas
others may have these points buried in the soil, thus
increasing their tolerance of fire.
FIRE EFFECTS ON INDIVIDUAL GRASSES
In general, if stem elongation has occurred (actively
growing annuals and perennials) the greater the
chance these growing points will be exposed to lethal
temperatures, and thus be damaged or killed.
The individual is also vulnerable since most of its
carbohydrate reserves have already been used to
produce foliage or seeds. This compromises it’s ability
to sprout from dormant buds.
If the growing points are at or below the soil surface, an
individual grass tiller generally has a greater chance of
tolerating a fire.
This tolerance is attributed to the fact that the upper 2.5
cm of soil typically only experiences a very brief
increase in temperature.
Seed Production
Due to their ability to reproduce vegetatively, the
impact of fire on flowering and fruit set in
rhizomatous grasses is typically insignificant.
Seed vulnerability, is typically dependant on seed
position as well as the amount of moisture they
contain.
In general, the higher seeds are aboveground the more
likely they are to be damaged. Furthermore, if a burn
occurs prior to seed shed the impact of the fire on
the individual tiller, as well as the seeds, is typically
greater than what would have occurred if the seeds
had dropped.
Seed Production
The increase in vulnerability to the individual tiller
is greater due to low levels of carbohydrate
reserves whereas seed impact is greater, due
to the higher amount of lethal heat experienced
aboveground. In general, when compared to
sites that were not burned the number of grass
flowering stems typically increase following a
fire.
Seed Production
Overall, the effect of fire on seed production
appears to be highly variable and dependant on
species whereas seedling establishment is
generally dependant on source of viable seed,
adequate seed coverage, suitable germination
temperatures, competition, and the availability
of adequate soil moisture to facilitate seeding
development.
If soil moisture is lacking, a seedlings ability to
survive fall and winter droughts will likely be
compromised.
Fire Effects on Trees and Shrubs
The response of trees and shrubs to fire varies
significantly between and within species, and is
dependant on the parameter being measured.
Moreover, this response is influenced by a variety
of fire parameters including intensity, severity
(e.g., amount of organic matter consumed),
residence time, soil heating, season of burn,
and time since last fire, all of which can vary
significantly among fires and within a fire.
These variations will cause differences in how
individuals and the community as a whole respond.
Fire Effects on Trees and Shrubs
In addition, numerous physical and climatic factors (e.g.,
fuel condition, weather, slope, and aspect) as well as
biological factors (plant morphology and physiology)
also influence post-fire effects on plant communities.
This includes direct effects such as the ability of
individual species to resist the heat of a fire
(depending on age and seasonality) and the
mechanisms by which they recover after fire.
In addition to fire parameters and individual species
response, numerous external factors such as post-fire
weather, post-fire animal use, and plant competition,
can also determine how the grassland and individual
species will respond to a fire. Common effects include
plant mortality, increased flowering, seed production
and numerous communal affects.
INDIVIDUAL PLANT TISSUE
Numerous studies have attempted to define the
temperature required to kill vascular plant
tissue. A temperature of 60oC has been
considered as a reasonable approximation of a
lethal temperature required to kill shoot tissues
of land plants, while others reported
temperatures as low as 45oC resulted in tissue
death.
Other, more recent publications, described 50 to 55oC
as being the temperature that typically results in
tissue death.
INDIVIDUAL PLANT TISSUE
In general, the likelihood of plant tissue being
killed is dependant on the amount of heat it
receives, which is described as being the
combination of the temperature reached and
the duration of exposure.
Overall, it appears that individual plant mortality
can occur at high temperatures after a short
period as well as low temperatures over longer
periods with individual plant sensitivity varying
depending on season.
For example, growing points are often considered
more sensitive to heat when they are actively
growing and their moisture content is high.
FIRE EFFECTS ON INDIVIDUAL SHRUBS
Seasonality (e.g., moisture content), site characteristics
(e.g., fuel loading), geographic and climatic factors all
play an integral role in determining fire intensity and
severity and, when combined with plant morphology,
all influence the impact of fire on shrubs.
Whether or not this impact is negative or positive is
species dependant, with many species experiencing
both positive and negative effects depending on fire
severity.
Seasonality affects fire severity by influencing the
moisture content in the target plant and in the fuels
surrounding the plant. In general, as moisture content
of bark, leaves and twigs increases, so does the
amount of heat required to raise them to ignition
temperature.
FIRE EFFECTS ON INDIVIDUAL SHRUBS
Moisture content typically varies throughout the growing
season with highest levels being reached during active
leaf formation and shoot elongation, declining to a
lower level for the remainder of the growing season
and then declining further following dormancy.
Although it often takes a greater amount of heat to ignite
a fire in the winter and early summer, this is generally
when shrubs have utilized the majority of their energy
reserves (to facilitate new growth) and thus are most
vulnerable to fire. Thus, if a fire occurs during this
time, there may be inadequate energy reserves to
promote new growth.
FIRE EFFECTS ON INDIVIDUAL SHRUBS
If fire occurs during or immediately following dormancy however,
shrubs are typically more tolerant due to their ability to spend
the majority of the growing season accumulating energy
reserves (via photosynthesis), and thus if not severely
damaged are more likely to sprout during the following spring.
Various other morphological characteristics also determine a
shrubs vulnerability to fire including crown size and shape,
height, branch density, ratio of live to dead crown material,
crown base location with respect to surface fuels, and total
crown size.
Other morphological characteristics including bud and branch size
also influence the impact of fire on a shrub.
In general, small buds and branches, due to their small mass and
high surface area to volume ratios, are more susceptible to
lethal heating than large buds.
FIRE EFFECTS ON INDIVIDUAL SHRUBS
How a fire impacts a shrubs stem (cambium tissue) is generally
dependant on the protective quality of bark, which is
determined by its thickness, composition, cracks, and moisture
content, all of which influence the bark's ability to absorb and
transmit heat.
Bark thickness is generally species specific and dependant on
various factors including shrub diameter and age, distance
aboveground, site characteristics, and shrub health and vigour.
As with trees, bark thickness varies with age with younger shrubs,
because of their thin bark, being more vulnerable to fire than
older plants.
Since most shrubs have relatively thin bark, any charring will
typically result in shrub death. Depending on severity, fire can
also cause root mortality, that is, as fire severity increases so
does root mortality.
FIRE EFFECTS ON INDIVIDUAL SHRUBS
Typically, root damage will accompany stem damage and thus
cause cumulative impacts on a shrub. Root damage or mortality
can also occur however, when there is little or no apparent
crown damage and can be significant enough to cause shrub
mortality. In general, shrub survival is typically determined by
flame length, fire severity including flaming residence time, and
stem char height with most shrubs typically only surviving fires
of low severity or fires that fail to result in significant crown, root
damage or cambium damage.
Overall, fire typically affects shrubs by opening stands and
rejuvenating sprouting shrubs whereas weaker sprouting
species typically take years to recover. Non-sprouting species,
which reproduce solely by seed, can be effectively removed
from a system if their growing points are either consumed or
exposed to lethal temperatures.
FIRE EFFECTS ON INDIVIDUAL TREES
Individual tree and shrub mortality typically occurs when
several plant parts are damaged. For example, crown
damage combined with a significant amount of
cambium and/or root damage is more likely to result in
death than if only one of these components was
damaged.
During intense/severe fires, tree and shrub mortality may
be instantaneous. Under less severe situations, death
may not occur or be delayed several years.
Where death is delayed several years, it is often caused
by secondary disturbances, such as infections by
insects and pathogens that are able to enter the tree
or shrub either due to decreased resistance or thru the
provision of entry points (wound sites).
FIRE EFFECTS ON INDIVIDUAL TREES
Fire effects on individual trees is dependant on tree age
as well as numerous adaptations including
germination, rapid growth and development, fire
resistant bark and foliage, adventitious or latent
growing points and serotinous cones, all of which have
the ability to influence post-fire plant community
dynamics.
In general, as a tree increases in age, so does its
resistance to fire as plant tolerance is generally
correlated to increased crown size, stem diameter,
and bark thickness as well as an increase in the height
from the base to the live crown.
The age at which a tree develops these attributes is
dependant on tree species as well as site conditions.
FIRE EFFECTS ON INDIVIDUAL TREES
For example, trees subjected to poor conditions often
take longer to develop fire resistance characteristics
than those growing under ideal conditions.
Germination adaptations can include hard-coated seeds
that lie dormant until a fire passes and the seed is
scarified, while rapid growth and development
adaptations can include adventitious or latent axillary
buds that allow a plant species to complete its life
cycle quickly and disperse seed in the event of two
closely spaced fires.
In general, fire-resistant foliage and bark have the
greatest influence in determining plant survival.
Combinations of these characteristics determine how
a tree responds to a fire.
FIRE EFFECTS ON INDIVIDUAL TREES
For example, how fire impacts a tree’s crown is
influenced by seasonality, tree morphology and foliage
characteristics.
Seasonality, particularly moisture content, plays an
integral role in determining fire severity and intensity.
In general, as moisture content of leaves and twigs
increase, so does the amount of heat required to raise
them to ignition temperature.
Tree moisture content varies throughout the growing
season with highest levels being reached during active
leaf formation and shoot elongation, declining further
to a lower level for the remainder of the growing
season, and then declining again following dormancy.
FIRE EFFECTS ON INDIVIDUAL TREES
Various other morphological characteristics also
determine a tree’s vulnerability to fire including crown
size and shape, tree height, branch density, ratio of
live to dead crown material, crown base location with
respect to surface fuels, and total crown size. or
example, the aerial portions of small stature species
are usually killed whereas larger trees, especially
those that self-prune their dead lower branches are
often unharmed as they typically do not facilitate
crown fires.
Overall, in situations where trees are not completely
scorched, tree morphology combined with seasonality
generally influences fire effects on the aboveground
portions of a tree.
FIRE EFFECTS ON INDIVIDUAL TREES
When describing stem effects, bark thickness typically
has the greatest influence on how a fire impacts a tree
stem.
Bark thickness is generally species specific, and
dependant on various factors including tree diameter
and age as well as distance above the ground, site
characteristics, and tree health and vigour.
The amount of influence that bark thickness has on stem
fire effects can be understood from the following
example.
When charring occurs on the stem of a thick-barked
tree, it does not necessarily mean that the cambium is
extensively damaged, in fact, it often only corresponds
to a fire scar.
FIRE EFFECTS ON INDIVIDUAL TREES
Fire scars are typically caused by an uneven distribution
of heat that often occurs on the upslope and/or lee
side of a tree.
However, when the stems of thin-barked trees, are
charred it generally corresponds to tree death.
Typically, the survival of thin-barked trees is related to
flame length, flaming residence time, and stem char
height with most of these trees only surviving patchy
fires which fail to damage the cambium throughout its
circumference.
As stated above, thicker barked trees, can often sustain
a substantial amount of bark char before cambium
damage occurs.
FIRE EFFECTS ON INDIVIDUAL TREES
Moreover, older, thick-barked trees are often only damaged or
killed when the cambium is subjected to complete girdling
or when the trees are subjected to subsequent fires.
This generally only happens when these trees are
subjected to long duration burns such as those that
occur during the burnout of logs, deep litter, and duff
(smouldering ground fires).
Most stands however, due to their low fuel loads, often
cannot sustain a fire of this magnitude and thus
cannot facilitate the complete girdling of a tree.
Overall, thick bark increases tolerance to most ground
fires, even those that burn into the bark. The deeper
the fire burns however, the more likely complete
girdling is to occur.
Thus, thick-barked trees are more likely to succumb to
fire from crown damage than stem damage.
POST-FIRE SPROUTING
In general, the physiological processes controlling
post-fire sprouting is similar for all plants
including trees, shrubs, and grasses.
The ability of an individual plant to sprout
following a fire is dependant on the location of
its dormant buds, the subsurface distribution of
reproductive structures, and the depths below
the surface from which new shoots can
develop.
POST-FIRE SPROUTING
These morphological characteristics, combined
with fire severity, typically determine the
number of growing points (reproductive buds or
bud primordia) that are able to survive a fire.
That is, the relationship between the depths of
reproduction organs, combined with the depth
of lethal temperature penetration, will determine
a plant’s ability to survive and sprout following a
fire.
POST-FIRE SPROUTING
For example, high-severity burns were described as
having the potential to retard or reduce suckering,
especially when the shallow roots were exposed to
lethal heating.
In general, many common shrubs and trees are able to
sprout from surviving plant parts following a fire.
Re-sprouting typically occurs when their buds are
protected by bark, dense leaf bases, or soil. Whether
or not lethal temperatures occur is dependant on
numerous factors including growth form, fuel loading,
adjacent vegetation and fuel and foliar moisture levels.
Fuel loading, as well as heat from adjacent vegetation
(grasses, shrubs, and trees), can dry and preheat
trees to ignition temperature.
POST-FIRE SPROUTING
This can increase tree mortality, especially when
compared to similar sites, burned under similar
conditions, with lighter fuels loads and/or sites with
fewer trees and shrubs.
If however, plants are actively growing, or if a site is
relatively moist, foliar and fuel moisture levels may
prevent fire from entering a stand of plants.
Other indirect impacts can also influence survival and
sprouting following a fire.
For example, increased erosion may result in
pedestalling around individual plants thus exposing
previously protected plant parts to either predation or
increasing the possibility of drought stress on these
plants, both of which can reduce vigour, limit
sprouting, or even cause death.
POST-FIRE SPROUTING
In addition, long-term fire intervals generally increase
fuel accumulation and fire severity whereas short-term
fire intervals can influence community composition by
decreasing seeding establishment. Changes in fire
return intervals may impact individual species or
communities that are adapted to specific returnintervals.
Factors such as tree age can also determine sprouting
ability.
For example, decreased amounts of post-fire sprouting
observed in older aspen stands was hypothesized as being
attributed to the deterioration of the roots to a point that
prohibited re-sprouting.
POST-FIRE SPROUTING
Also, depending on species, younger plants that have
developed from seed may not be able to sprout until
they have reached a certain age.
Exactly when re-sprouting occurs is dependant on
seasonality and fire severity.
If fire occurs early in the growing season and soil
moisture is or becomes available, plants may sprout
soon after a fire. If the fire occurs after dormancy
occurs, sprouting will not occur until the following
spring.
Depending on season, increases in soil temperature and
nutrient availability associated with fires may also enhance
sprouting.
POST-FIRE SPROUTING
Whether sprouting actually occurs however, is
determined by the availability of nutrients and
carbohydrates in the regenerating structures or
adjacent roots.
If sufficient amounts of energy are not available to
support new growth, until it is able to become
photosynthetically self-sufficient, sprouting will
generally not occur.
Overall, fire tolerant species, as well as species
that are able to re-sprout or develop quickly
from seed, tend to become important
components of the post-fire community.
Fire Effects on Livestock and Wildlife
Fire also affects livestock and wildlife, the effects
include immediate effects (direct) and long-term
effects (secondary).
These effects will vary depending on fire type,
timing, size, severity, and intensity and while
direct effects can be significant, secondary
effects generally have the greatest amount of
impact on livestock and wildlife. In general, fire
effects on livestock and wildlife are either:
Fire Effects on Livestock and Wildlife
• Immediate: Immediate impacts include direct
injury or mortality to plants and animals,
animals fleeing (insects, small mammals, and
birds) or seeking refuge.
• Secondary: Secondary impacts include an
alteration of forage productivity, availability and
quality, and animal performance as well as
creating, destroying, enhancing, or degrading
various habitat attributes such as cover, shelter,
structure, and natal/breeding.
Fire Effects on Livestock and Wildlife
IMMEDIATE EFFECTS
Animals: Most livestock and wildlife are directly
impacted by a fire and respond relatively predictably to
its passage.
The degree of impact is dependant on numerous factors
including mobility as well as fire uniformity, severity,
size and duration.
Even though relatively few livestock and wildlife are
directly killed or injured by fire, it can and does
happen.
In general, an ambient temperature of over 63 oC is
needed to result in animal mortality. While most fires
have the potential to injure and kill animals it is
generally season of burn and fire intensity and severity
that determines whether or not this occurs.
Fire Effects on Livestock and Wildlife
Season of burn can be an important variable in
determining mortality. For example, a fire that
occurs when animals are nesting or have young
with limited mobility (especially small mammals)
may cause significant mortality.
This effect would be dependant on nesting
characteristics, with those species who
construct surface-level nests (e.g. harvest mice)
being more vulnerable to fire than deepernesting species. Generally, when compared to
other species smaller mammals, such as mice,
due to their limited mobility, are more vulnerable
to fire.
Fire Effects on Livestock and Wildlife
Livestock and larger mammals, due to their size,
must escape a fire by seeking refuge, either in
an unburned patch within a fire or outside the
extent of the fire. They are more likely to be
caught in a fire when the fire is actively
crowning, its fronts are wide, and it is fast
moving with thick ground smoke present.
When subjected to fire, some studies have
observed that small animals appear to panic
more readily than large, highly mobile animals.
In fact, larger mammals are often described as
moving calmly around the fire perimeter.
Fire Effects on Livestock and Wildlife
Plants: Fire also impacts forage availability by
directly consuming plant material.
Thus, when considering the effect of fire on all
forms of livestock and wildlife, it is important to
consider the lag in forage availability.
For example, if a fire occurs during late summer
or fall, forage availability in the burned areas
will often be non-existent or decreased
significantly until at least the following growing
season.
Fire Effects on Livestock and Wildlife
SECONDARY EFFECTS
Forage Productivity- Increased productivity tends to be
short-lived and generally results from a variety of
factors including, fire-induced vegetative reproduction
and regeneration, fire-enhanced seedling germination
and establishment, improvements in soil nutrient
regime, and increases in soil temperature. There are
numerous benefits associated with increased
productivity. These include increased forage
productivity (due to canopy removal and nutrient
increases) which can benefit mammals by increasing
habitat availability.
Trees and Shrubs- The growth of many shrubs and trees is
often facilitated by fire.
Fire Effects on Livestock and Wildlife
Forage Availability- Besides considering the
direct effect that fire has on forage availability
(see above), fire can also have secondary
impacts on forage availability. For example, if a
fire occurs early in the growing season, forage
will not only be available in the same year as
the fire, it may also hold its quality longer into
the late summer In general, fire will increase
forage availability by:
Fire Effects on Livestock and Wildlife
• Removing obstacles to grazing- this includes
the removal of dead plant material such as
plant residue (stubble) and litter as well as
fallen trees and shrubs, all of which may allow
animal access to food resources that may have
been unavailable prior to the fire. On a
landscape level, this effect may include the
removal of natural range barriers.
• Increasing forage availability- this includes
reducing the size of shrubs and/or trees so that
they are more accessible to the reach of
grazing mammals.
Fire Effects on Livestock and Wildlife
Animal Performance
Studies often contradict one another and
practices such as prescribed burning do not
always correlate to increased wildlife.
Prescribed burning in fact may actually
deteriorate wildlife ranges by reducing total
nutrient availability, especially in grasslands
with low cation exchange capacities (i.e.,
reduced ability to hold nutrients).
Fire Effects on Livestock and Wildlife
In order for any changes in habitat parameters to
be beneficial to the large mammal in question,
the improved parameter must have first been
somewhat lacking in the pre-fire habitat.
That is, if the mammal in question is not limited by
forage production, forage quality, or forage
availability, and if other limiting factors remain
unaltered, fire will not theoretically improve
mammal performance or increase mammal
populations.
Fire Effects on Livestock and Wildlife
OTHER ANIMALS
Predators and Omnivores - The response of
carnivores to fire is primarily dependant on
herbivore response.
That is, if prey populations increase, so will the
population of carnivores.
Other predators, have been known to be
negatively impacted by fires, as fires are
typically detrimental to their prey and overall
habitat.
High severity fires that result in fauna mortality will
benefit carnivores and scavengers.
Fire Effects on Livestock and Wildlife
BIRDS
In general, fire effects on birds are typically secondary in
nature.
Direct effects are typically dependant on season, fire
uniformity, and severity.
Due to their mobility, mortality of adult birds is usually
considered minor. If the fire occurs during nesting
however, nestling and fledgling mortality will occur.
In addition to seasonality, severity also determines
whether or not nests are damaged.
While ground-nesters are vulnerable to most understory
fires, canopy nesters can also be injured by
moderately to severe surface and crown fires. In
general, fire impacts on birds can be summarized as
follows:
Fire Effects on Livestock and Wildlife
• Fire-intolerant species decrease in abundance
after fire and as a result are present only in
areas characterized by very low fire frequencies
and severities. These species are closely
associated with closed canopy forests and
generally prefer dense nesting and foraging
cover. This includes ground-nesting birds that
become fire-intolerant when fire eliminates
insect resources, destroys existing nests, and
removes the protective cover necessary for
constructing new ones.
Fire Effects on Livestock and Wildlife
•
• Fire-impervious bird species are unaffected by
fire, that is, they neither increase nor decrease
after fire. These species often have niches that
include both shade-intolerant and shadetolerant plant communities. Due to these
generalist and opportunistic qualities, these
species often show the highest flexibility in
response to fire. Examples include crows,
ravens, robins and many waterfowl.
Fire Effects on Livestock and Wildlife
• Fire-adapted bird species increase in
abundance following a fire, due to their
preference for fire-opened habitat. Many
songbirds, raptors, woodpeckers and
secondary cavity nesters fall into this category.
For example, following a burn, pre-fire infected
and decaying trees, often provide nesting and
perching sites, initially for woodpeckers and
then for secondary cavity nesters. Once these
snags fall, alternative nesting sites are provided
as other fire-killed trees decay.
Fire Effects on Livestock and Wildlife
• Fire-dependent bird species only occur in early
succession areas such as those influenced by
fire.
REPTILES AND AMPHIBIANS
Very little research has measured the effect of fire on
reptiles and amphibians.
As with other wildlife, the influence of fire on reptiles
and amphibians appears to be predominately
secondary.
Fire Effects on Livestock and Wildlife
That is, the influence of fire on habitat attributes, such
as plant species composition and structure, appear to
be the primary factor in determining immigration
and emigration.
For example, species that prefer open sites may benefit
and increase following fire whereas species that
prefer or tolerate dense vegetation often decrease.
HABITATS
Effects of Fire- can have direct or indirect effects on soils, soil
moisture balance, vegetation and animals.
Effects of fire on soils
a) Changes rates of soil organic formation and accumulation.
b) Influences number of soil organisms.
c) Changes rates of permeability.
d) Influences soil compaction through subsequent sheet
runoff.
Effects of fire on soil moisture
(a) Changes rates of transpiration and evaporation
(b) Changes rates of permeability
(c) Changes stream and river structure through destruction of
vegetation on river banks.
HABITATS
Effects of fire on vegetation
(a) Affects plant physiology
(b) Affects plant organic matter, structure and shape
(c) Affects plant quality in terms of nutrient
availability and content.
Effects of fire on animals
(a) Changes the shape and amount of plant cover.
(b) Changes plant palatability and availability.
(c) Indirectly alters water availability.
(d) Causes death and injuries especially to small
animals.