Maintaining landscape connectivity for spider assemblages in temperate grasslands: The role of firebreaks in Eucalyptus dunnii plantations

The Río de la Plata Grasslands have experienced significant land use and land cover changes as a result of agricultural and silvicultural conversion, which have heavily impacted natural environments. In Uruguay, large-scale afforestation has fragmented dominant grassland landscapes. Spiders, as generalist predators sensitive to environmental changes, serve as useful indicators for biodiversity studies in these fragmented environments. This study aims to understand the role of firebreaks within Eucalyptus plantations in Uruguay, hypothesizing that firebreaks might act as connectors for grassland spider populations due to their higher environmental similarity with natural grasslands. Spider assemblages were studied in a grassland-dominated landscape with commercial Eucalyptus dunnii plantations. Local environmental variables were measured, and spiders were collected with two methods —pitfall traps and G-vac (garden vacuum)— across three types of environments: grasslands, firebreaks and tree plantations. Species richness and abundance were significantly higher in grasslands compared to Eucalyptus plantations, but there were no significant differences between grasslands and firebreaks. At family level and among guilds, spider species composition in grasslands was more similar to that of the firebreaks than to that of the tree plantations. Similarity in the species composition was significantly explained by the types of environments (grasslands vs. firebreaks, grasslands vs. Eucalyptus plantations) rather than by the distance between sampling units. Overall, these findings provide new insights into the role of firebreaks in Eucalyptus plantations, suggesting that firebreaks, having environmental characteristics similar to grasslands, could serve as habitats and corridors for numerous spider species, facilitating their establishment, reproduction, and movement within the afforestation landscape.