Abstract
We assessed the abundance patterns of three theridiid species: Hetschkia gracilis (Keyserling 1886); Phycosoma altum (Keyserling 1886); and Thwaitesia affinis O.P.-Cambridge, 1882 in four habitats: Araucaria Forest (native forest) and plantations of A. angustifolia, Pinus spp., and Eucalyptus spp. in Floresta Nacional de Sao Francisco de Paula Reserve, southern Brazil. The plantation stands in the study system are managed by the selective cutting of adult trees, allowing longer rotation intervals. We collected spiders in 2003 and 2004 by beating the vegetation inside three replicates of each forest type. We performed a permanova to test whether there were differences on species abundances between habitats. We tested the influence of the stand sizes, distance between stands, and vegetation cover composition on each spider species abundance. Stands with higher vegetation cover of bushes and vines presented higher abundances of Hetschkia gracilis and Thwaitesia affinis . Phycosoma altum abundance did not respond to any explanatory variables. Results highlighted the importance of alternative management of plantation stands to enhance and maintain the understory vegetation diversity, which in turn support the spider populations. Key words: Araucaria Forest, Habitat structure, Pinus plantation, Eucalyptus plantation, Forest management.
Highlights
Forest ecosystems worldwide were transformed by human activities
The subtropical humid forest of the upland landscape of southern Brazil is dominated by Araucaria angustifolia (Bertol.) Kuntze (Araucariaceae) and is part of the Atlantic Forest biome
Araucaria Forest forms the matrix, i.e., the dominant patch type in the region and plantations of two exotic commercial woody species are embedded in the Araucaria Forest: Pinus spp. and Eucalyptus spp., as well as plantations of Araucaria angustifolia (Figure 1)
Summary
Forest ecosystems worldwide were transformed by human activities. In temperate and subtropical regions, large areas are still suffering heavy exploitation. The subtropical humid forest of the upland landscape of southern Brazil is dominated by Araucaria angustifolia (Bertol.) Kuntze (Araucariaceae) and is part of the Atlantic Forest biome (lato sensu). From the beginning of European colonization of the region in the 1850’s, the Araucaria Forest suffered heavy timber exploitation, as well as habitat loss due to agricultural expansion, in particular cattle grazing. These practices caused the degradation of about 86% of the natural landscape. In the 1960’s, large scale reforestation began, mainly with Eucalyptus (Myrtaceae), Pinus (Pinaceae), and Acacia (Mimosaceae) species (IBDF, 1983) This practice persists until today, creating a heterogeneous landscape mosaic. Spider assemblages can show different patterns of distribution and occurrence, suggesting differential response to structural changes imposed by human activities (Cattin et al, 2003)
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