Effect of bench terracing on ground dwelling arthropods

Eucalypt trees are the most planted tree in the world, and in Portugal these plantations occupy 26% of the forested area. The area of Eucalypt monoculture is growing since the 50’s due to the importance of this tree for the pulp and paste industry. With short rotation cycles, it is important to facilitate the cut and transport of the logged trees. In this sense, many forested areas in mountainous regions are being terraced with bulldozers.

Terracing is a well know soil conservation practice, reducing runoff peak flows, increasing water infiltration and subsequent low soil erosion rates. Nevertheless, the impacts of terracing for eucalypt plantations are still unknown, especially in terms of biodiversity of soil fauna. Hence, to address this research gap, the present study aimed to assess the impacts of terracing on the ground dwelling arthropods in eucalypt plantations.

This study took place in a mountain slope with old eucalypt trees that were logged (May 2019) and then terraced (July) as ground preparation to receive a new eucalypt plantation. The community of ground dwelling arthropods were accessed using pitfall traps.  The arthropods were collected before the terracing process, in Spring 2019, and then seasonally after terracing until the Spring of 2020Total abundance and richness at order level, as well as, abundance, richness, Shannon-Wiener diversity and Pielou’s Evenness indexes, at Family level of Coleoptera, Araneae and Hymenoptera, were used to depict differences between pre- and post-terracing. The results showed that although terracing did not reduce the total abundance or richness, it changed the community structure. In particular, it was observed an increase in opportunist and generalist families after terracing such as Staphylinidae and Myrmicinae. The spider community also changed, with more hunter families captured after the terrace construction. In overall, the results of our study reveal that although the total abundance and richness of arthropods was not altered by the construction of terraces, their structure was modified.