Effects of land-use system on the soil macrofauna in western Brazilian Amazonia
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Agroforestry systems are presented as a valuable alternative to pastures to sustain crop production in forested areas. In order to evaluate their effect on soil macroinvertebrate communities, sampling was conducted during the rainy season at four localities located in the Rondônia and Acre states of Brazil. Four land-use systems were selected (fallow, annual crop, agroforestry systems and pasture), and compared to nearby disturbed forests. We used the sampling method recommended by the Tropical Soil Biology and Fertility Programme. Soil macrofauna responded more readily than soil parameters to different cultivation practices. Co-inertia analysis, however, showed a relationship between soil parameters and soil macrofauna. Comparison of communities showed a significant impact of land-use practices. All systems had quite abundant invertebrate communities with relatively low densities in the forest (884 ind. m–2) and in pastures (841 ind. m–2), and higher densities in fallow, agroforestry system and annual crop (1,737–1,761 ind. m–2). Earthworms were dominant in pastures (155 ind. m–2 and 56.2 g m–2 on average), whereas termites thrived better in annual crops and fallows (with respective densities of 1,287 and 816 and biomasses of 2.32 and 1.38 g m–2). Macrofauna communities in agroforestry systems were rather similar to the forest, in spite of higher densities of social insects. The termite:earthworm ratios were very low in pastures (0.2), had similar values in the forest (7.9) and the agroforestry system (8.8), which is much lower than in fallows (20.4) and annual crops (21.4) This study showed that all land-use practices were able to sustain sizeable macrofaunal communities with agroforestry communities rather similar to the those of a disturbed forest.
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