Fire ecology - AbsoluteAstronomy.com

Fire ecology is concerned with the processes linking the natural incidence of fire

Fire

Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

in an ecosystem

Ecosystem

An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

and the ecological

Ecology

Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

effects of this fire. Many ecosystems, such as the North American prairie

Prairie

Prairies are considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and grasses, herbs, and shrubs, rather than trees, as the dominant vegetation type...

and chaparral

Chaparral

Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...

ecosystems, and the South African savanna

Savanna

A savanna, or savannah, is a grassland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to support an unbroken herbaceous layer consisting primarily of C4 grasses.Some...

, have evolved with fire as a natural and necessary contributor to habitat

Habitat

* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

vitality and renewal. Many plant species in naturally fire-affected environments require fire to germinate. Fire suppression can lead to the build-up of inflammable debris and the creation of less frequent but much larger and destructive wildfires.

Campaigns in the United States have historically molded public opinion to believe that wildfire

Wildfire

A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...

s are always harmful to nature. This view is based on the outdated belief that ecosystems progress toward an equilibrium and that any disturbance, such as fire, disrupts the harmony of nature. More recent ecological research has shown, however, that fire is an integral component in the function and biodiversity

Biodiversity

Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

of many natural habitats, and that the organisms within these communities have adapted to withstand, and even to exploit, natural wildfire.

Fire suppression, in combination with other human-caused environmental changes, has resulted in unforeseen consequences for natural ecosystems. Some uncharacteristically large wildfires in the United States have been caused as a consequence of years of fire suppression and the continuing expansion of people into fire-adapted ecosystems. Land managers are faced with tough questions regarding where to restore a natural fire regime

Fire regime

A fire regime is the pattern, frequency and intensity of the bushfires and wildfires that prevails in an area. It is an integral part of fire ecology, and renewal for certain types of ecosystems. If fires are too frequent, plants may be killed before they have matured, or before they have set...

Fire Components

A fire regime describes the pattern that fire follows in a particular ecosystem. Its "severity" is a term that ecologists use to refer to the impact that a fire has on an ecosystem. Ecologists can define this in many ways, but one way is through an estimate of plant mortality. Fire can burn at three levels. Ground fires will burn through soil that is rich in organic matter. Surface fires will burn through dead plant material that is lying on the ground. Crown fires will burn in the tops of shrubs and trees. Ecosystems may experience predominantly one of these fire regimes, or a mix of all three.

Fires will often break out during a dry season, but in some areas wildfires may also commonly occur during a time of year when lightning is prevalent. The frequency over a span of years at which fire will occur at a particular location is a measure of how common wildfires are in a given ecosystem. It is either defined as the average interval between fires at a given site, or the average interval between fires in an equivalent specified area.

Defined as the energy released per unit length of fireline (kW m^-1), wildfire intensity can be estimated either as the product of the linear spread rate (m s^-1), the low heat of combustion (kJ kg^-1) and the combusted fuel mass per unit area, or it can be estimated from the flame length.

Abiotic responses

Fire has important effects on the abiotic (non-living) components of an ecosystem, particularly the soil. Fire can affect the soil by direct contact with it and by its effects on the plant community associated with it. By removing overhead vegetation, fire can lead to increased solar radiation on the soil surface by day, resulting in greater warming, and to greater cooling through the loss of radiative heat at night. Fewer leaves left to intercept rain will allow more moisture to reach the soil surface. In addition, plant transpiration

Transpiration

Transpiration is a process similar to evaporation. It is a part of the water cycle, and it is the loss of water vapor from parts of plants , especially in leaves but also in stems, flowers and roots. Leaf surfaces are dotted with openings which are collectively called stomata, and in most plants...

(the process by which water travels through plants and evaporates through pores in the leaves) will be reduced following a fire, allowing the soil to retain more moisture. Exposure to sunlight, wind and evaporation, however, will work in the other way, to dry the soil. The fire may have created an impermeable crust at the soil surface, if organic matter on the ground was heated by the fire into a waxy residue, and if this has happened, it may lead to increased soil erosion through surface run-off.

Fire may cause nutrient

Nutrient

A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

loss through a variety of mechanisms, including oxidation, volatilization, and increased erosion and leaching by water. Temperatures must be very high, however, to cause a significant loss of nutrients, which are often replaced by organic matter left behind in the fire. Charcoal

Charcoal

Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

is able to counteract some nutrient and water loss because of its absorptive properties.

Overall, soils become more basic

Base (chemistry)

For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

(higher pH) following fires because of acid

Acid

An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

combustion. By driving novel chemical reactions at high temperatures, fire can even alter the texture and structure of soils by affecting the clay content and the soil's porosity.

Plants

Plants have evolved many adaptation

Adaptation

An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s to cope with fire. In chaparral

Chaparral

Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...

communities in Southern California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, for example, some plants have leaves coated in flammable oils that encourage an intense fire. This heat causes their fire-activated seeds to germinate and the young plants can then capitalize on the lack of competition

Competition (biology)

Competition is an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. Limited supply of at least one resource used by both is required. Competition both within and between species is an important topic in ecology, especially community ecology...

in a burnt landscape. Other plants have smoke-activated seeds, or fire-activated buds. The serotinous

Serotiny

Serotiny is an ecological adaptation exhibited by some seed plants, in which seed release occurs in response to an environmental trigger, rather than spontaneously at seed maturation. The most common and best studied trigger is fire, and the term serotiny is often used to refer to this specific case...

cones of the Lodgepole pine

Lodgepole Pine

Lodgepole Pine, Pinus contorta, also known as Shore Pine, is a common tree in western North America. Like all pines, it is evergreen.-Subspecies:...

(Pinus contorta) are sealed with a resin that a fire melts away, releasing the seeds. Many plant species, including the shade-intolerant giant sequoia (Sequoiadendron giganteum), require fire to make gaps in the vegetation canopy that will let in light, allowing their seedlings to compete with the more shade-tolerant seedlings of other species, and so establish themselves. Because their stationary nature precludes any fire avoidance, plant species may only be fire-intolerant, fire-tolerant or fire-resistant.

Fire intolerance

Fire-intolerant plant species tend to be highly flammable and are destroyed completely by fire. Some of these plants and their seeds may simply fade from the community after a fire and not return, others have adapted to ensure that their offspring survives into the next generation. “Obligate seeders” are plants with large, fire-activated seed banks that germinate, grow, and mature rapidly following a fire, in order to reproduce and renew the seed bank before the next fire.

Fire tolerance

Fire-tolerant species are able to withstand a degree of burning and continue growing despite damage from fire. These plants are sometimes referred to as “resprouter

Resprouter

Resprouters are plant species that are able to survive fire by the activation of dormant vegetative buds to produce regrowth.Plants may resprout by means of lignotubers at the base or epicormic buds on the trunk or major branches....

s.” Ecologists have shown that some species of resprouters store extra energy in their roots to aid recovery and re-growth following a fire. For example, after an Australian bushfire

Bushfires in Australia

Bushfires in Australia are frequently occurring events during the hotter months of the year due to Australia's mostly hot, dry climate. Large areas of land are ravaged every year by bushfires, which also cause property damage and loss of life....

, the Mountain Grey Gum tree (Eucalyptus cypellocarpa) starts producing a mass of shoots of leaves from the base of the tree all the way up the trunk towards the top, making it look like a black stick completely covered with young, green leaves.

Fire resistance

Fire-resistant plants suffer little damage during a characteristic fire regime. These include large trees whose flammable parts are high above surface fires. Mature Ponderosa Pine

Ponderosa Pine

Pinus ponderosa, commonly known as the Ponderosa Pine, Bull Pine, Blackjack Pine, or Western Yellow Pine, is a widespread and variable pine native to western North America. It was first described by David Douglas in 1826, from eastern Washington near present-day Spokane...

(Pinus ponderosa) is an example of a tree species that suffers virtually no crown damage under a naturally mild fire regime, because it sheds its lower, vulnerable branches as it matures.

Animals, birds and microbes

Like plants, animals display a range of abilities to cope with fire, but they differ from plants in that they must avoid the actual fire to survive. Although birds are vulnerable when nesting, they are generally able to escape a fire; indeed they often profit from being able to take prey fleeing from a fire and to recolonize burned areas quickly afterwards. Mammals are often capable of fleeing a fire, or seeking cover if they can burrow. Amphibians and reptiles may avoid flames by burrowing into the ground or using the burrows of other animals. Amphibians in particular are able to take refuge in water or very wet mud. Some arthropods also take shelter during a fire, although the heat and smoke may actually attract some of them, to their peril. Microbial organisms in the soil vary in their heat tolerance but are more likely to be able to survive a fire the deeper they are in the soil. A low fire intensity, a quick passing of the flames and a dry soil will also help. An increase in available nutrients after the fire has passed may result in larger microbial communities than before the fire.

Long term impacts

Fire behavior is different in every ecosystem and the organisms in those ecosystems have adapted accordingly. One sweeping generality is that in all ecosystems, fire creates a mosaic of different habitat

Habitat (ecology)

A habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...

patches, with areas ranging from those having just been burned to those that have been untouched by fire for many years. This is a form of ecological succession

Ecological succession

Ecological succession, is the phenomenon or process by which a community progressively transforms itself until a stable community is formed. It is a fundamental concept in ecology, and refers to more or less predictable and orderly changes in the composition or structure of an ecological community...

in which a freshly burned site will progress through continuous and directional phases of colonization following the destruction caused by the fire. Ecologists usually characterize succession through the changes in vegetation that successively arise. After a fire, the first species to re-colonize will be those whose seeds are already present in the ground, or those whose seeds are able to travel into the burned area quickly. These are generally fast-growing herbaceous

Herbaceous

A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...

plants that need lots of light and are poor competitors in crowded areas. As time passes, more slowly growing, shade-tolerant, and competitive, woody species will crowd out the herbaceous plants. These woody plants may be shrubs or trees.

Different species of plants, animals, and microbes specialize in exploiting different stages in this process of succession, and by creating these different types of patches, fire allows a greater number of species to exist within a landscape. Soil characteristics will be a factor in determining the specific nature of a fire-adapted ecosystem, as will climate and topography.

Forests

Mild to moderate fires burn in the forest

Forest

A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...

understory

Understory

Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...

, removing small trees and herbaceous groundcover

Groundcover

Groundcover refers to any plant that grows over an area of ground, used to provide protection from erosion and drought, and to improve its aesthetic appearance .- Ecosystem :...

. Only high-intensity fires will burn into the crowns of the tallest trees. Crown fires may require support from ground fuels to maintain the fire in the forest canopy (passive crown fires), or the fire may burn in the canopy independently of any ground fuel support (an active crown fire). Fires used in the management of woodlands will typically aim for low to moderate intensity, whereas wildfires can evolve into crown fires. When a forest burns frequently and thus has less plant litter build-up, below-ground soil temperatures rise only slightly and will not be lethal to roots that lie deep in the soil. Although other characteristics of a forest will influence the impact of fire upon it, factors such as climate

Climate

Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...

and topography

Topography

Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...

play an important role in determining fire severity and fire extent. Fires spread most widely during drought years, are most severe on upper slopes and are influenced by the type of vegetation that is growing.

Forests in British Columbia

In Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, forests cover about 10% of the land area and yet harbor 70% of the country’s bird and terrestrial mammal species. Natural fire regimes are important in maintaining a diverse assemblage of vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

species in up to twelve different forest types in British Columbia

British Columbia

British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...

. Different species have adapted to exploit the different stages of succession, regrowth and habitat change that occurs following an episode of burning, such as downed trees and debris. The characteristics of the initial fire, such as its size and intensity, cause the habitat to evolve differentially afterwards and influence how vertebrate species are able to use the burned areas.

Shrublands

Shrub

A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...

fires typically concentrate in the canopy and spread continuously if the shrubs are close enough together. Shrubland

Shrubland

Shrubland, scrubland, scrub or brush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity...

s are typically dry and are prone to accumulations of highly volatile fuels, especially on hillsides. Fires will follow the path of least moisture and the greatest amount of dead fuel material. Surface and below-ground soil temperatures during a burn are generally higher than those of forest fires because the centers of combustion lie closer to the ground, although this can vary greatly. Common plants in shrubland or chaparral include manzanita

Manzanita

Manzanita is a common name for many species of the genus Arctostaphylos. They are evergreen shrubs or small trees present in the chaparral biome of western North America, where they occur from southern British Columbia, Washington to California, Arizona and New Mexico in the United States, and...

, chamise

Adenostoma fasciculatum

Adenostoma fasciculatum is a flowering plant native to California and northern Baja California. This shrub is one of the most widespread plants of the chaparral biome.-Description:...

and Coyote Brush.

California shrublands

California shrubland, commonly known as chaparral

Chaparral

Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...

, is a widespread plant community of low growing species, typically on arid sloping areas of the California Coast Ranges or western foothills of the Sierra Nevada. There are a number of common shrubs and tree shrub forms in this association, including salal

Salal

Gaultheria shallon is a leathery-leaved shrub in the heather family , native to western North America. In English it is known as salal, shallon, or in Britain simply Gaultheria.-Ecology:...

, toyon

Toyon

Heteromeles arbutifolia , and commonly known as Toyon, is a common perennial shrub native to California down to Baja California....

, coffeeberry

Rhamnus californica

Rhamnus californica , is called coffeeberry because its berries contain seeds which look like coffee beans—it is also called California buckthorn...

and Western poison oak. Regeneration following a fire is usually a major factor in the association of these species.

South African Fynbos shrublands

Fynbos

Fynbos is the natural shrubland or heathland vegetation occurring in a small belt of the Western Cape of South Africa, mainly in winter rainfall coastal and mountainous areas with a Mediterranean climate...

shrublands occur in a small belt across South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

. The plant species in this ecosystem are highly diverse, yet the majority of these species are obligate seeders, that is, a fire will cause germination of the seeds and the plants will begin a new life-cycle because of it. These plants may have evolved into obligate seeders as a response to fire and nutrient-poor soils. Because fire is common in this ecosystem and the soil has limited nutrients, it is most efficient for plants to produce many seeds and then die in the next fire. Investing a lot of energy in roots to survive the next fire when those roots will be able to extract little extra benefit from the nutrient-poor soil would be less efficient. It is possible that the rapid generation time that these obligate seeders display has led to more rapid evolution

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

and speciation

Speciation

Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...

in this ecosystem, resulting in its highly diverse plant community.

Grasslands

Grasslands burn more readily than forest and shrub ecosystems, with the fire moving through the stems and leaves of herbaceous plants and only lightly heating the underlying soil, even in cases of high intensity. In most grassland ecosystems, fire is the primary mode of decomposition

Decomposition

Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...

, making it crucial in the recycling of nutrients

Nutrient cycle

A nutrient cycle is the movement and exchange of organic and inorganic matter back into the production of living matter. The process is regulated by food web pathways that decompose matter into mineral nutrients. Nutrient cycles occur within ecosystems...

South African savanna

In the savanna

Savanna

of South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

, recently burned areas have new growth that provides palatable and nutritious forage compared to older, tougher grasses. This new forage attracts large herbivores from areas of unburned and grazed grassland that has been kept short by constant grazing. On these unburned "lawns", only those plant species adapted to heavy grazing are able to persist; but the distraction provided by the newly burned areas allows grazing-intolerant grasses to grow back into the lawns that have been temporarily abandoned, so allowing these species to persist within that ecosystem.

Fire suppression

Fire serves many important functions within fire-adapted ecosystems. Fire plays an important role in nutrient cycling, diversity maintenance and habitat structure. The suppression of fire can lead to unforeseen changes in ecosystems that often adversely affect the plants, animals and humans that depend upon that habitat. Wildfires that deviate from a historical fire regime because of fire suppression are called “uncharacteristic fires.”

Chaparral communities

In 2003, southern California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

witnessed powerful chaparral

Chaparral

Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...

wildfires. Hundreds of homes and hundreds of thousands of acres of land went up in flames. Extreme fire weather (low humidity, low fuel moisture and high winds) and the accumulation of dead plant material from 8 years of drought, contributed to a catastrophic outcome. Although some have maintained that fire suppression contributed to an unnatural buildup of fuel loads, a detailed analysis of historical fire data has showed that this may not have been the case. Fire suppression activities had failed to exclude fire from the southern California chaparral. Research showing differences in fire size and frequency between southern California and Baja has been used to imply that the larger fires north of the border are the result of fire suppression, but this opinion has been challenged by numerous investigators and is no longer supported by the majority of fire ecologists.

One consequence of the fires in 2003 has been the increased density of invasive

Invasive species

"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

and non-native

Introduced species

An introduced species — or neozoon, alien, exotic, non-indigenous, or non-native species, or simply an introduction, is a species living outside its indigenous or native distributional range, and has arrived in an ecosystem or plant community by human activity, either deliberate or accidental...

plant species that have quickly colonized burned areas, especially those that had already been burned in the previous 15 years. Because shrubs in these communities are adapted to a particular historical fire regime, altered fire regimes may change the selective pressures on plants and favor invasive and non-native species that are better able to exploit the novel post-fire conditions.

Fish impacts

The Boise National Forest

Boise National Forest

The Boise National Forest is a US national forest located north and east of the city of Boise, Idaho. It is about 2,612,000 acres in size, ranging in elevation from 2,600 to 9,800 feet . The mountainous landscape developed through uplifting, faulting, and stream cutting...

is a US national forest located north and east of the city of Boise, Idaho

Boise, Idaho

Boise is the capital and most populous city of the U.S. state of Idaho, as well as the county seat of Ada County. Located on the Boise River, it anchors the Boise City-Nampa metropolitan area and is the largest city between Salt Lake City, Utah and Portland, Oregon.As of the 2010 Census Bureau,...

. Following several uncharacteristically large wildfires, an immediately negative impact on fish populations was observed, posing particular danger to small and isolated fish populations. In the long term, however, fire appears to rejuvenate fish habitats by causing hydraulic changes that increase flooding and lead to silt

Silt

Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...

removal and the deposition of a favorable habitat substrate. This leads to larger post-fire populations of the fish that are able to recolonize these improved areas. But although fire generally appears favorable for fish populations in these ecosystems, the more intense effects of uncharacteristic wildfires, in combination with the fragmentation of populations by human barriers to dispersal such as weirs and dams, will pose a threat to fish populations.

Ponderosa pine forests

Prior to European settlement, a typical Ponderosa pine forest in the southwest United States was mostly savanna

Savanna

, a grassland ecosystem with scattered stands of trees, resulting in less than 25–30% of the ground shaded by an interlocking crown cover of Ponderosa Pine

Ponderosa Pine

trees. Fires occurred at intervals of perhaps less than ten years or so in any one place, with average burns covering 3000 acres (12.1 km²). These forests historically suffered mild to moderate fires that generally did not reach the crown and left most of the trees alive.

Ponderosa pine

Ponderosa Pine

forests now face severe damage under harsher fire regimes brought on by fire suppression and aggravated by natural drought cycles. Fires in these forests now result in crown fires that cause extensive tree-mortality. Fire suppression may also lead to increased defoliation of the trees by herbivorous insects, whose populations might otherwise be controlled by more regular outbreaks of wildfire.

An important factor in the increased intensity and destructive power of wildfire in the Ponderosa pine forests is the impact of cattle grazing on public land. Prior to the arrival of railroads in the American West in the 1880s and 1890s, cattle and sheep grazing had a relatively low impact in this sort of terrain because livestock could not be transported to markets on the east and west coasts. Before the railroads, the average Ponderosa Pine stand density was 40–60 trees per acre (100–150 per hectare), based on evidence from the analysis of old photographs. Historically, throughout the west of the United States, Ponderosa pine forests experienced low-temperature, rapidly moving surface fires every ten years or so, which burned the grasses and herbaceous vegetation on the savanna floor, along with seedling pines, maintaining a low stand density and an open canopy. The introduction of cattle grazing, however, significantly reduced the fuel load on the ground, which effectively halted this natural wildfire regime. Over the next century, photographic evidence reveals that the stand density of the Ponderosa Pine increased from 40–60 to 600–800 stems per acre (from 100–150 to 1500–2000 per hectare). These trees are crowded together with a closed canopy, competing for both water and light. The lower branches are dead and bare.

As a result of this, the present-day fire regime is predominantly characterized by intense, devastating crown fires which volatilize nutrients, create tremendous erosion problems and pose an increased risk to firefighters and communities alike. US Forest Service Ranger Bill Armstrong of Los Alamos, New Mexico

Los Alamos, New Mexico

Los Alamos is a townsite and census-designated place in Los Alamos County, New Mexico, United States, built upon four mesas of the Pajarito Plateau and the adjoining White Rock Canyon. The population of the CDP was 12,019 at the 2010 Census. The townsite or "the hill" is one part of town while...

, prior to the 2000 Cerro Grande Fire

Cerro Grande Fire

The Cerro Grande Fire was a disastrous forest fire in New Mexico, United States of America that occurred in May 2000. The fire started as a controlled burn, and became uncontrolled owing to high winds and drought conditions. Over 400 families in the town of Los Alamos, New Mexico lost their homes...

, thinned an area of Pajarito Plateau

Pajarito Plateau

The Pajarito Plateau is a volcanic plateau in north central New Mexico, United States. The plateau, part of the Jemez Mountains, is bounded on the west by the Valles Caldera and on the east by the White Rock Canyon of the Rio Grande...

to 40 stems per acre. The Cerro Grande Fire burned all the forest around the thinned area, but only burned ground cover within the experimental area. Similar effects of thinning back tree density to that seen before the coming of the railroad show similar results.

Fire as a management tool

Restoration ecology

-Definition:Restoration ecology is the scientific study and practice of renewing and restoring degraded, damaged, or destroyed ecosystems and habitats in the environment by active human intervention and action, within a short time frame...

is the name given to an attempt to reverse or mitigate some of the changes that humans have caused to an ecosystem. Controlled burn

Controlled burn

Controlled or prescribed burning, also known as hazard reduction burning or Swailing is a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement. Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for...

ing is one tool that is currently receiving considerable attention as a means of restoration and management. Applying fire to an ecosystem may create habitats for species that have been negatively impacted by fire suppression, or fire may be used as a way of controlling invasive species without resorting to herbicides or pesticides. But what should managers aim to restore their ecosystems to? Does “natural” mean pre-human? Pre-European? Native American use of fire

Native American use of fire

In addition to simple cooking, Pre-Columbian Native Americans used fire in many and significant ways, ranging from protecting an area from fire to landscape-altering clearing of prairie.-Human-shaped landscape:...

, not natural fires, historically maintained the diversity of the savannas of North America

Pre-Columbian savannas of North America

Pre-Columbian savannas once existed across North America. These were created and maintained in a fire ecology by Native Americans until the 16th century death of most natives. Surviving natives continued using fire to clear savanna until European colonists began colonizing the eastern seaboard...

. When, how, and where managers should use fire as a management tool is a subject of debate.

The Florida everglades

The Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

Everglades

The Everglades are subtropical wetlands in the southern portion of the U.S. state of Florida, comprising the southern half of a large watershed. The system begins near Orlando with the Kissimmee River, which discharges into the vast but shallow Lake Okeechobee...

is one example of an ecosystem with a historical regime of frequent fires. Currently, the everglades are undergoing long-term and large-scale restoration. A problem that ecologists and managers have is how frequently to prescribe burns. There is a strong relationship between climate and fire in Florida and it may be that climate holds the key to this question. The El Niño Southern Oscillation increases the frequency of lighting strikes, opening up a window for fire before there is too much precipitation. It is possible, however, that human-induced climate change may result in a perpetual El Niño that never allows conditions to become dry enough for fire in the future.

The Great Plains shortgrass prairie

A combination of heavy livestock grazing and fire-suppression has drastically altered the structure, composition, and diversity of the shortgrass prairie ecosystem on the Great Plains

Great Plains

The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...

, allowing woody species to dominate many areas and promoting fire-intolerant invasive species. In semi-arid ecosystems where the decomposition of woody material is slow, fire is crucial for returning nutrients to the soil and allowing the grasslands to maintain their high productivity.

Although fire can occur during the growing or the dormant seasons, managed fire during the dormant season is most effective at increasing the grass and forb

Forb

A forb is a herbaceous flowering plant that is not a graminoid . The term is used in biology and in vegetation ecology, especially in relation to grasslands and understory.-Etymology:...

cover, biodiversity

Biodiversity

and plant nutrient uptake in shortgrass prairie. Managers must also take into account, however, how invasive and non-native species respond to fire if they want to restore the integrity of a native ecosystem. For example, fire can only control the invasive spotted knapweed (Centaurea maculosa) on the Michigan prairie grasslands in the summer, because this is the time in the knapweed’s life cycle that is most important to its reproductive growth.

Mixed conifer forests in the Sierra Nevada

Mixed conifer forests in the United States Sierra Nevada used to have fire return intervals that ranged from 5 years up to 300 years, depending on the local climate. Lower elevations had more frequent fire return intervals, whilst higher and wetter elevations saw much longer intervals between fires. Native Americans tended to set fires during fall and winter, and land at a higher elevation was generally occupied by Native Americans only during the summer.

In areas that formerly had frequent fire return intervals, fire suppression has modified the previous fire regime, resulting in the heavy accumulation of forest fuels such as downed coarse woody debris

Coarse woody debris

Coarse woody debris is a term used in English-speaking countries for fallen dead trees and the remains of large branches on the ground in forests. Some prefer the term coarse woody habitat . A dead standing tree is known as a snag and provides many of the same functions as coarse woody debris...

and ladder fuels composed of shade tolerant species such as white fir (Abies concolor). Forests whose burning is to be managed, usually have their ground fuels and forest structure modified beforehand, so that wildland fire burning can be more as it used to be. Treatments are done either by hand crews, with mechanical equipment or through a combination of the two. Hand thinning has the advantage of being very "light on the land" but has the disadvantages of high cost and can be ineffective when the ladder fuels are above 14 inches (355.6 mm) in diameter measured at breast height. While mechanical treatment methods can remove valuable small diameter logs and biomass, they cannot easily treat steep slopes and they can compact soils if great care is not taken. Both hand thinning and mechanical treatments can leave in place the fuel that is important for creating wildlife habitats, such as large fallen trees and snags.

The material removed from the woodland by both hand thinning and mechanical treatments must be properly disposed of before managed or natural wildland fires can be reintroduced into the stand. In the case of hand thinning, piles are usually created and burned. Mechanical treatments can remove the slash and then burn or crush it. Regardless of the method used, once the forest has been treated, fire can be reintroduced.

United States

Fire policy

Policy

A policy is typically described as a principle or rule to guide decisions and achieve rational outcome. The term is not normally used to denote what is actually done, this is normally referred to as either procedure or protocol...

in the United States involves the federal government, individual state governments, tribal governments, interest groups, and the general public. The new federal outlook on fire policy parallels advances in ecology and is moving towards the view that many ecosystems depend on disturbance for their diversity and for the proper maintenance of their natural processes. Although human safety is still the number one priority in fire management, new US government objectives include a long-term view of ecosystems. The newest policy allows managers to gauge the relative values of private property and resources in particular situations and to set their priorities accordingly.

Techniques such as sophisticated risk assessment

Risk assessment

Risk assessment is a step in a risk management procedure. Risk assessment is the determination of quantitative or qualitative value of risk related to a concrete situation and a recognized threat...

strategies, that integrate the latest in ecological research with the social and economic consequences of a particular outcome, are one way to make the most informed fire policy decisions based on the interests of many stakeholders. The US government now recognizes that the longer fuel accumulates in fire-suppressed areas, the greater will be the damage when an unexpected fire burns out of control. One of the primary goals in fire management is to improve public education in order to suppress the “Smokey Bear

Smokey Bear

Smokey Bear is a mascot of the United States Forest Service created to educate the public about the dangers of forest fires. An advertising campaign featuring Smokey was created in 1944 with the slogan, "Smokey Says – Care Will Prevent 9 out of 10 Forest Fires". Smokey Bear's later slogan,...

” fire-suppression mentality and introduce the public to the benefits of regular natural fires.

Fire reintroduction will need to be mindful of regulations set by the Clean Air Act

Clean Air Act

A Clean Air Act is one of a number of pieces of legislation relating to the reduction of airborne contaminants, smog and air pollution in general. The use by governments to enforce clean air standards has contributed to an improvement in human health and longer life spans...

and the Environmental Protection Agency concerning wildfire emissions, limited fire professionals, potential property damage from escaped fire and complaints about smoke and destruction of scenic views.

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Fire Components

Abiotic responses

Plants

Fire intolerance

Fire tolerance

Fire resistance

Animals, birds and microbes

Long term impacts

Forests

Forests in British Columbia

Shrublands

California shrublands

South African Fynbos shrublands

Grasslands

South African savanna

Fire suppression

Chaparral communities

Fish impacts

Ponderosa pine forests

Fire as a management tool

The Florida everglades

The Great Plains shortgrass prairie

Mixed conifer forests in the Sierra Nevada

United States

See also

External links