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Fire ecology is concerned with the processes linking the natural incidence of fire in an ecosystem and the ecological effects of this fire. Many ecosystems, particularly prairie, savanna, chaparral and coniferous forests, have evolved with fire as a necessary contributor to habitat vitality and renewal. Many plant species in naturally fire-affected environments require fire to germinate, establish, or to reproduce. Wildfire suppression not only eliminates these species, but also the animals that depend upon them. Finally, fire suppression can lead to the build-up of flammable debris and the creation of less frequent but much larger and more destructive wildfires. Campaigns in the United States have historically molded public opinion to believe that wildfires 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 This view is based on the outdated belief that ecosystems progress toward an equilibrium and that any disturbance, such as fire, disrupts the harmony of nature.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 of many natural habitats, and that the organisms within these communities have adapted to withstand, and even to exploit, natural wildfire. More generally, fire is now regarded as a 'natural disturbance', similar to flooding, wind-storms, and landslides, that has driven the evolution of species and controls the characteristics of ecosystems.〔Keddy 2007, Chapter 6〕 The map below right shows how each ecosystem type in the United States has a characteristic frequency of fire, ranging from once every 10 years to once every 500 years. Natural disturbances can be described by key factors such as frequency, intensity and area.〔Keddy 2007, Chapter 6〕 The map also shows intensity, since some fires are understory fires (light burns that affect mostly understory plants) while others are stand replacement fires (intense fires that tend to kill the adult trees as well.) 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 components== A fire regime describes the characteristics of fire and how it interacts with 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.〔Bond and Keeley 2005〕 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.〔Byram, 1959〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fire ecology」の詳細全文を読む スポンサード リンク
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