Abundance and stratification of soil macroarthropods

In arid and semiarid environments, seasonality usually exerts a strong influence on the composition and dynamics of the soil community. The soil macroarthropods were studied in a Caatinga forest located in the Reserva Particular do Patrimônio Natural (RPPN) Fazenda Almas, São José dos Cordeiros, Paraíba, Brazil. Samples were collected during the dry and rainy seasons following the method proposed by the Tropical Soil Biology and Fertility Program (TSBF), with minor modifications. At each station, 15 soil blocks (20 × 20 × 30 cm: 12 L) were extracted and divided into three layers: A (0-10 cm), B (10-20 cm), and C (20-30 cm). In the rainy and dry seasons 1,306 ± 543(se) and 458 ± 212 ind.m–2 macroarthropods were found, respectively, with 35 and 18 respective taxa recorded. The abundance of individuals and taxa were significantly higher in the rainy season. Isoptera (57.8%) was the most abundant taxon, followed by Hymenoptera: Formicidae (17.2%), Coleoptera larvae (7.3%), and Araneae (3.5%). In the rainy season, abundance in layer A (576 ± 138 ind.m–2) was significantly higher than that of layer C (117 ± 64 ind.m–2), but was not different from layer B (613 ± 480 ind.m–2). There was also no difference between the layer B and C abundances. In the dry season, abundance in layer B (232 ± 120 ind.m–2) was not significantly different compared to layer A (182 ± 129 ind.m–2), but was significantly higher than abundance in layer C (44 ± 35 ind.m–2). During the rainy season, layer A (34 taxa) was significantly richer in taxa than layers B (19 taxa) and C (11 taxa). On the other hand, during the dry season the richnes