Abstract
Boundaries between habitats are usually accompanied by transitions in the diversity and structural complexity of insect as- semblages. Edge effects on carabid beetle assemblages across forest-meadow ecotones in Dinaric beech-fir forests were determined in the Gorski Kotar region of western Croatia. Carabid beetles were sampled using pitfall traps set along gradients extending 60 m from the forest edge into its interior and 60 m into the meadow. Embedded forest edges were greater than 100 years old and had a similar composition and structure of vegetation to that in the adjacent forest. A total of 20,526 individuals belonging to 66 carabid beetle spe- cies were recorded. Carabid assemblages in the ecotones were more similar to those in the forest interiors than those in the meadows. The classical edge effect hypothesis was not supported, since the ecotones were less diverse than the meadows, while the carabid as- semblages of the forest interiors were the least diverse. Soil temperature, soil humidity and light intensity did not differ significantly between the ecotones and the forest interior. Therefore, embedded forest edges reduced the microclimate edge effect by providing stable microclimatic conditions for carabid assemblages similar to those in the forest interior. In addition, this enabled forest specialists and generalists to occur right up to the forest edge and maintain stable populations in the ecotone. On the other hand, ecotones acted as filters for certain forest generalist species and true barriers for most open-habitat species. This study confirmed that the structure and ages of the vegetation at edges may play a key role in determining the spatial pattern of carabid beetles across forest-meadow ecotones.
Highlights
Dinaric beech-fir forests are characterized by a natural composition and structure of vegetation and cover approximately 150,000 ha in the Dinaric Mountains in Croatia (Vukelić, 2012)
The multiple comparison post hoc test revealed that mean light intensity was significantly higher in the meadow than the ecotone (p < 0.001) and the forest interior (p < 0.001), with no significant difference in that recorded for the ecotone and the forest interior (p > 0.05)
The present study revealed that (1) carabid beetle assemblages in the ecotone were more similar to those in the forest interior than in the meadow; (2) the life-history traits appeared to be a more appropriate tool for detecting an edge effect than broad estimators such as total species richness and activity density; (3) old forest edges are barriers to the movement of open habitat species, but act as filters for some forest species and (4) the main environmental variables did not differ significantly between forest interior and ecotone, providing stable microclimatic conditions for forest species to move to the forest edge
Summary
Dinaric beech-fir forests are characterized by a natural composition and structure of vegetation and cover approximately 150,000 ha in the Dinaric Mountains in Croatia (Vukelić, 2012) They are managed using uneven-aged silviculture practices, which result in forest stands composed of trees of different ages and sizes growing together in the same area (Boncina, 2011). Rucner, 1994; Vujčić-Karlo, 1999; Štrbenac et al, 2008) These Dinaric beech-fir forests have been subjected to centuries of sporadic anthropogenic activities, which may have contributed to their high conservation value and the development of the contrasting boundaries between forest and open habitats such as fallows or hay meadows (Klepac, 2001). These habitat edges are usually connected with a large forest matrix area and may play a crucial role in the preservation of biological diversity, especially of grassland biota (Mihoci et al, 2006; Topić & Vukelić, 2009)
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