Fire (environmental factor)
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Fire is an abiotic environmental factor which , as a disruption, triggers succession processes .
meaning
Fires in nature are often seen as an ecological catastrophe . However, this only applies to natural landscapes that have already been changed by humans. Artificially created forest monocultures are often unstable against factors such as pest infestation or fire. In natural ecosystems , many living things have adapted to regularly recurring fires in the course of evolution .
If you see through people on purpose - such as B. large-scale slash and burn or unintentionally triggered forest fires, fires in nature are usually caused by lightning strikes or spontaneous combustion . Long periods of drought are a prerequisite for natural fires. Ecosystems in which fire is a typical environmental factor are tundra and taiga , savannah and steppe , the hard deciduous forests in the Mediterranean area , the pine forests of Florida or the eucalyptus forests of Australia .
Types of natural fires
- Canopy Fires:
- These often destroy the entire vegetation and almost all animal creatures that cannot escape from them in time. Often, starting from pioneering societies , the entire succession must first be run through again until the original community has almost been restored.
- Such fires rejuvenate populations and prevent the extinction of organisms that occur in unstable successional societies.
- Wildfire:
- These have a selective effect on living beings. Some living beings are limited by the fires, others are encouraged.
- Wildfires promote the remineralization of organic residues (wood contains 0.2% to 0.8% minerals, especially potassium )
- Nitrogen-fixing legumes e.g. B. thrive particularly well after a fire.
Adaptations of organisms to fire
Larger, immobile plants in particular have developed adaptations to regular fires.
- The Australian grass trees have not only developed adaptations to survive fires, they even need them to grow, as they limit the less fire-resistant competition and promote the remineralization of nutrients.
- The cork oaks are largely protected against fire with their particularly good insulating bark and can regenerate the lost leaves and young branches from the intact cambium .
- Species of the genus Banksia keep their seeds on the mother plant for life. Only when this has been destroyed by fire and the seeds have been exposed to sufficiently high heat can they germinate.
- The southeast of the US -based Southern pine Pinus palustris is more resistant to fire than any other growing tree species there. Their terminal buds are protected by fire-resistant long needles. Without the fires, the pines would be displaced by the non-fire-resistant plants that then increasingly grow.
- Numerous cypress trees only release their seeds from the tightly closed cones when the parent plant is killed by fire. The seedlings then have ideal growing conditions.
- For most animals, the effects of fires are indirect as they can mostly escape them through mobility. The jewel beetle is an exception , as it uses special infrared sensors to target particularly warm wood to lay eggs after a fire.
Climate changes
Fires also change the ecosystem from a climatic point of view:
- The microclimate changes by destroying the vegetation (increase in solar radiation and light absorption on the ground, stronger air movement on the ground, reduction in water retention capacity).
- The local or regional climate is influenced by clouds of smoke from large fires (reduction of solar radiation). The water cycle can also change, e.g. B. in flooding in downstream areas due to a lack of water retention capacity.
- Global climate changes: The accumulation of large fires releases large quantities of carbon dioxide and fine dust and thus contributes to the warming of the atmosphere .
Use of fire in nature conservation
The knowledge about the environmental factor fire has led to the fact that in nature protection fires are set and controlled in a targeted manner in order to preserve the natural vegetation. In England , for example, heather bogs are burned to increase the population of the red grouse , as they feed on the buds of the heather, which grows back after fires . The Freiburg fire ecologist Johann Georg Goldammer practices and promotes this method of environmental care worldwide, often against the resistance of nature conservationists and firefighters. Controlled fires that do not reach the top of the forest are of great benefit to the renewal of the flora. They bring new light and fertilizer to the lower areas of the forest and ensure that dead wood is regularly removed . Small animals often survive this procedure well because they move into adjacent areas. Forests that have not been exposed to fire for a long time, on the other hand, form too much dead wood and dry out to such an extent that the harmful forest fire risk is very high. This completely new knowledge in nature conservation requires a rethinking of the notion of undisturbed forest peace, which was widespread in the 19th century, especially in Germany (see German Forest , Romanticism ): The work of Sir Dietrich Brandis (1824–1907) is still effective in administration and science. to. He worked long in the British colonial administration preaching "Fire is the enemy of the forest."
literature
Web links
- Max Planck Institute for Chemistry: Fire Ecology Working Group
- Interview with Prof. Goldammer (2009)
- Interview with Prof. Goldammer (2019)