Fire and ants

Paulo Pereira
Mykolas Romeris University, Vilnius, Lithuania

Ants are amazing creatures, not only for the recognized work capacity, but also due their great resilience to disturbance. They are considered ecosystem engineers and have an important impact on soil physical (e.g moisture, porosity), chemical (organic matter accumulation and redistribution and CO2 emissions) and biological properties. Ants build a complex network of tunnels and galleries in soil subsurface transporting sediments, with important impacts on soil erosion, and nutrients. These changes have implications on favourable conditions for plant germination.

Ants activity is an indirect indicator of ecosystem restoration and important to soil biodiversity and ecosystem function. Fire, if reach high temperatures can induce important disturbances in soil properties. However, ants are very resilient to fire impact, since they can hide in the subsoil, and be protected from the high temperatures produced by fire in soil surface. Soil it is a bad energy conductor (especially in dry conditions) and protects ants from high temperatures. After the fire, ants are one of the first soil inhabitants to colonize the surface, in low and high severity fires (Figure 1 and 2).

Figure 1. Ant nest a) one month and one year after a low severity prescribed fire in Dzukija National Park, Lithuania.

A fire more than a constrain or ecological problem, can be an opportunity to ecosystem restoration. Many questions are addressed concerning the high capacity of ants (re)colonization. Fire has a mineralization effect that depends on the temperature reached, time of exposition and burned specie. This fire mineralized organic matter, known as ash, is very rich in available nutrients, that immediately after the fire increase soil nutrients and as consequence biological activity. In addition physical ash properties might have also an important role in soil biological activity, including ants. Black ash colour reduces the albedo and increases soil temperature until ash removal, by infiltration and erosion. This situation is considered an advantage for biological activity. Such conditions can be one of the explanations for ants rapid (re)colonization. Ants activity have important impacts on ash and soil sediments and nutrients (re)distribution. In the present still, little is known about the post-fire impact of ants in soil characteristics, and further research is needed to improve or knowledge about this topic. This will help us to understand ant relation with fire.

Figure 2. Ant nest two days after a high severity wildfire in Portugal.

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