| Sumario: | The contribution of the introduced species Amynthas gracilis (Kinberg, 1867) and
Octolasion cyaneum (Savigny, 1826) to the physical stability of the soil was evaluated in
a mesocosm experiment. Pore formation and stable aggregates were measured; as well
as changes in bulk density, porosity, and soil moisture. Mesocosm pots were organized
into three treatments: 1- soil + Amynthas gracilis, 2- soil + Octolasion cyaneum and 3- soil
(control containers). The experiment ran for 13 weeks and it was conducted in controlled
conditions in a greenhouse. At the end of the experiment both treatments with earthworms
had higher number of pores and stable aggregates at the two considered depths
(0 - 5 cm and 5 - 10 cm). The presence of both earthworm species favors the formation
of a significantly higher proportion of stable aggregates larger than 5 mm (60%), when
compared to the control without worms. These structures helped maintaining bulk
density and porosity and improved water circulation. The results show that when
compared to the control, both treatments had a lower loss of pore space, lower bulk
density, and higher soil moisture, all attributable to earthworm presence. It is concluded
that, despite both being introduced species, in intensive agricultural systems, A. gracilis
and O. cyaneum can contribute to the maintenance of soil physical stability thus helping
to preserve the sustainability of agro-ecosystems, even if native species became rare or
locally extinct.
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