An exploratory study of the immediate and medium-term effects of bench terrace construction on the ground-dwelling arthropod communities in eucalypt plantations

Forest terracing operations imply a massive mobilization of topsoil. Nonetheless, its impacts on soil properties, functions and ecosystem services have been poorly quantified so far. Therefore, this study aimed to explore how bulldozer bench terracing may impact the abundance and diversity of ground-dwelling arthropod communities of eucalypt plantations. To this end, three neighbouring sites were selected of which one had not been terraced a –(NT), one had been terraced recently (two months earlier; -RT) and one had been terraced more than a decade (14 years ago; OT). The exploratory nature of this study involved furthermore a single sampling occasion (during spring), and taxonomic identification till the level of order and, in the case of the most frequent orders, (sub-)family. The arthropod communities of the RT site and the NT site did not reveal significant differences in terms of either total abundance or order richness, suggesting that immediate effects of terracing on these aspects of biodiversity may be limited. Nonetheless, notable differences did exist between these two sites for two out of the three prevailing orders. Araneae occurred with a markedly lower abundance as well as family richness at the RT site than at the NT site, while the opposite was true for the Coleoptera, at least in terms of family richness. The communities of the RT site and the OT site also did not evidence substantial differences in abundance or order richness, indicating that terracing effects on these aspects may not increase with time-since-terracing. In fact, the opposite was suggested, since none of the three prevailing orders revealed significant differences in abundance or richness between the two sites. In spite of the reduced effects observed here of massive soil mobilization by bulldozer terracing, further research is plainly justified not only because of the exploratory nature of this study but also the widespread bench terracing in the study region. The present results suggested that such further research should focus on the impacts during the first decade.