Comparison of soil invertebrate communities in organic and conventional production systems in Southern Brazil

Invertebrates play important functional roles in soils, affecting several essential ecosystem services. However, their populations are sensitive to disturbance, and are therefore often used as bioindicators of soil quality. Conservation agriculture covers extensive areas in Brazil, and organic production techniques have been rapidly spreading, but little is known regarding their impacts on belowground invertebrate communities. Thus, the present study evaluated the effects of different land-use and management systems on macro- and mesofauna communities in rural areas near Quitandinha, Southern Brazil. Samples were taken in a native forest (NF), organic (OH) and conventional horticulture farms (CH) and a conventional reduced tillage field (RT). Soil macrofauna and earthworms were collected by hand sorting, using the Tropical Soil Biology and Fertility (TSBF) method, and mesofauna were collected using a modified Berlese funnel apparatus. Enchytraeids were sampled using the standard ISO 23611-3 method. Six earthworm species were found, in the genera Glossoscolex and Amynthas as well as Ocnerodrilidae juveniles and an unidentified species. Four genera of enchytraeids were found, two of them cosmopolitan (Fridericia, Enchytraeus) and two native (Guaranidrilus, Hemienchytraeus). Soil tillage practices (in CH and OH) were associated with lower earthworm populations, while ants, spiders, ecosystem engineers and enchytraeids were more associated with organic fertilization and no pesticide use. Conventional systems (RT and CH) had lower macrofauna, enchytraeid and ant populations than NF and OH, and CH had the lowest richness of both macro- and mesofauna, as well as the lowest abundance of earthworms, spiders, fly larvae and “other” macro and mesofauna. Reduced tillage had higher earthworm and mite populations, while NF had the highest macrofauna and earthworm taxonomic richness and termite abundance. Reducing tillage in OH and CH may improve conditions for soil fauna, but further work is still needed to determine the best suite of management practices that promote soil fauna and their contributions to soil function and ecosystem services in these systems.