Small mammal abundance in Mediterranean Eucalyptus plantations: how shrub cover can really make a difference

- Shrub cover is the main driver of small mammal abundance changes within plantations.
- Season (autumn) showed a positive influence on abundance.
- Stands homogeneity influences population structure of Crocidura russula.
- Edge distance affects sex-ratio variation in Crocidura russula.

In the last decades production forests have expanded their range worldwide, and in many regions (e.g., southern Europe) Eucalyptus spp. have been the target species used by foresters. However, Eucalyptus characteristics and management intensity of its plantations may impose constraints to local wildlife, often considered highly harmful for wildlife. However, although Portugal and Spain encompass the widest Eucalyptus production forests in Europe, and the Mediterranean area is a biodiversity hotspot, no study has yet tested specifically the impact of this exotic forest inner structure on rodent's populations. Aiming to evaluate whether this negative influence of Eucalyptus stands' on wildlife was associated with any specific structural characteristics of plantations, we tested the effect of plantation's understory structure and homogeneity on small mammal abundance and population structure. Small mammal were live-trapped in autumn and spring in nine sampling sites in Eucalyptus plantations in central west Portugal, one km apart. By using a GLMM approach we detected that the percentage of shrub coverage was the main driver of small mammal abundance, although season (autumn) also showed a positive influence. Only for Crocidura russula we detected an influence of stands homogeneity in population structure, with a sex-ratio variation according to edge distance. Thus, our study clearly indicates that by maintaining an understory layer within exotic Eucalypus plantations, managers may assure that these anthropic environments may still support an abundant small mammal community, thus contributing to the preservation of key ecosystems functions.