Soil macrofauna in a Cerrado/Caatinga ecotone under different crops in Southwestern Piauí State, Brazil

portuguesObjetivou-se caracterizar a macrofauna edafica sob diferentes cultivos comparando-os a vegetacao nativa de ecotono Cerrado/Caatinga no Sudoeste do Piaui. As areas estudadas foram: area sob cultivo de ata (Annona squamosa L.); capim andropogon com tres anos de cultivo; capim andropogon com seis anos de cultivo; milho irrigado sob pivo; capim napier e vegetacao nativa. Em cada area foram avaliadas as camadas de 0-0,1, 0,1-0,2 e 0,2-0,3m, inclusive a serapilheira de superficie, segundo recomendacoes do Tropical Soil Biology and Fertility Program (TSBF). A macrofauna edafica nos diferentes sistemas de uso do solo foi identificada ate o nivel de familias e a densidade media de cada taxon foi calculada para cada tipo de manejo do solo e camada. A estrutura da macrofauna edafica foi alterada negativamente nos diferentes cultivos quando comparadas com a vegetacao nativa de cerrado/caatinga, variando quanto a sua ocorrencia nas diversas camadas de solo. Houve correlacao entre os grupos funcionais com a distribuicao granulometrica e umidade do solo. O cultivo de capim napier favoreceu maior abundância da macrofauna edafica, porem com predominância das familias pertencente as ordens Isoptera e Hymenoptera. O milho irrigado sob pivo apresenta numero de familias da macrofauna edafica mais semelhante a vegetacao nativa e maior diversidade de familias em relacao aos demais cultivos estudados, reduzindo o impacto do uso antropico sobre a biodiversidade da macrofauna edafica. Palavras-chave: bioindicadores; capim napier; cultivo irrigado; invertebrados do solo; qualidade do solo EnglishThe aim of this study was to characterize the soil macrofauna under different crop systems and compare them to the macrofauna under the native vegetation of a Cerrado/Caatinga ecotone in southwestern Piaui State, Brazil. The areas studied included areas under sweetsop cultivation (Annona squamosa L.), andropogon grass with three years of use, andropogon grass with six years of use, pivot-irrigated corn, Napier grass, and native vegetation. In each area, soil layers of 0-0.1, 0.1-0.2, and 0.2-0.3m, including the surface litter, were evaluated following the Tropical Soil Biology and Fertility Program (TSBF) recommendations. The soil macrofauna from the different land-use systems were identified to the family level, and the mean density of each taxon was calculated for each soil-management type and layer. The structure of the soil macrofauna was negatively altered under the different crops in comparison to the native Cerrado/Caatinga vegetation, with macrofaunal occurrence varying in the different soil layers. A correlation existed between the functional groups and the soil grain-size distribution and moisture. Napier grass cultivation favored greater soil macrofaunal abundance, with a predominance of families belonging to the orders Isoptera and Hymenoptera. Number of soil macrofaunal families under pivot-irrigated corn was more like the number observed with the native vegetation, and corn also had greater family diversity compared to the other crops studied. Therefore, pivot-irrigated corn can reduce the impact of anthropogenic land use on the diversity of soil macrofauna. Key words: bioindicators; Napier grass; irrigated crop; soil invertebrates; soil quality