Effects of pine silviculture on the ant assemblages (Hymenoptera: Formicidae) of the Patagonian steppe

In NW Patagonia, forestry with rapid growing species is an expanding practice, especially in the semi-arid steppe. To provide data for managing forests for biodiversity, we studied the impact of forestry on the native ant assemblages. We sampled ants using pitfall traps in a wide geographical area, including steppe sites and pine plantations, both dense (forest cover 87% in average) and sparse (forest cover 52% in average) designs. We measured and analyzed ant abundance, species richness and species composition as response variables. Through our results, we show that ants are highly sensitive to pine tree forests. Ant abundance within plantations is lower and species composition significantly impoverished. However, the more open plantations sustained ant assemblages which resemble those of the native steppe samples. This is probably because the open forests allow for native under-story vegetation to grow as in the natural steppe sites. We suggest that tree presence in an otherwise shrub and grass dominated area is responsible for the changes in the ant assemblages. We also note that the presence of native vegetation cover predicts ant assemblage composition in these arid zones. From an applied point of view, our findings suggest that a more open plantation design will be accompanied by higher ant abundances and species richness, which in turn may bring about consequences for sustainable forest management in the area. (c) 2005 Elsevier B.V. All rights reserved.