Fire In The Forest Of Insects

Fire In The Forest Of Insects

24 August 2006

published by http://www.innovations-report.de


Forest fires often take place, but they are studied to a little extent. K.B. Gongalsky, specialist of the Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, spent several years to investigate the life of arthropoda inhabiting soil in burnt down sites. As it has turned out, forest fires destroy the majority of ground animals, however, the burnt down area does not remain empty for a long time: it is taken up by aboriginals remaining intact and those that are hunting about the forest in search of fresh fire-sites.

Forest fire kills all arthropoda inhabiting the forest litter and several upper centimeters of the soil. Only those arthropoda that ran away, flew away or buried themselves deep can survive (some of not very mobile Collembola, ticks and beetle larvae are protected from overheating by strong coverings). Some aboriginals manage to save themselves on unburnt sites miraculously remaining intact. After the fire, when the soil gets cold the unhurt insects crawl out of their refuges and look around the site of fire. It is difficult to recognize. The fire modifies physical and chemical properties of the soil, impacts the presence of nutrients in it and finally it completely destroys flora and forest litter. The site of fire turns into a flat surface without shelters, where forest litter inhabitants cannot exist. Even having survived the fire, they leave. Only those that inhabit relatively deep soil layers – larvae and Collembola – remain.

However, the fire-site desolation is seeming, as it is attractive for many living creatures. Within several hours, pyrophilic species (that need burnt forests for existence) fly together to the fire-site. Such are, for example, pyrophilic ground beetles or Phaenops cyanea, which develop exclusively on burnt wood. Researchers never determined where these insects hide themselves when there is no fire. Probably they are dispersed in the forest and gather in noticeable quantities only at sites of fire (these insects can feel smoke at the distance of 20 and more kilometers). At the fresh fire-site, pyrophilic ground beetles can make up to 80 percent of the arthropoda quantity, but they are soon forced out by other species, such as flies and leafhoppers. They are attracted by abundance of food (burnt wood and forest litter, and fungi and microbes growing upon them) as well as absence of predators. It is the lack of predators that allows them to colonize the fire-site quickly.

The scene of conflagration is gradually overgrown by mosses and other vegetation, and then phytophagans appear on it (i.e., plant-eaters): thrips (Thripidae), leafhoppers and plant-louses. The new site swarms with them, as even two years after the fire there are still no predators there. Predators are absent because the forest litter necessary for them has not been formed and the required grass has not grown up yet. Although, the game is in abundance at the site of fire, but predators have no place to live and hide themselves, so they are unable to hunt. According to K.B. Gongalsky, the initial biodiversity of the ground fauna is not restored even within 4 to 5 years after the fire.

For the former life (with flora, phytophagans and predators in place) to be in full swing again at the fire-site, the forest litter is to be restored. The restoration time depends not on the fire-site square, but on the fire intensity, that is, it depends on how much the flora has been burnt down, if wisps of grass remain intact at the site of fire, to what depth the soil got warmed up. The rate of biodiversity restoration also depends on fire-site surroundings: if there is an untouched forest around, forest insects wander into the site of fire, and inhabitants of open places arrive from motorways and fields. In other words, to restore the ground animal communities after the fire it is first of all necessary that the ecosystems should be restored.


 

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