ABSTRACT Paraná State has approximately 74 % of its territory destined for agricultural activities. Several agricultural management practices modify soil quality and biodiversity, including earthworm populations that can contribute to soil health. This study aimed to review the studies carried out in the state of Paraná, Brazil, focusing on earthworm populations (abundance, biomass, richness, proportion of native and exotic species) in different land-use systems. In total, 51 publications were compiled, including peer-reviewed papers, book chapters, dissertations and theses. We used studies that analyzed chemical and physical soil properties (n = 14) to perform a principal component analysis to explore the relationships between these properties and earthworm populations. In total, 90 earthworm species are known from Paraná, of which more than half (n = 46) may be new species that still must be formally described. Of the total, 24 are exotic and 66 are native species, though only 62 (16 %) of the 399 counties have earthworm records. Of the land-use categories sampled, the lowest abundance and biomass were recorded in annual crops under conventional tillage, and the highest populations were found in agroforestry systems. Higher earthworm abundance and species richness were related to higher chemical fertility (soil P and base contents), while biomass was related to higher silt and sand contents.

Resumo: As minhocas são frequentemente relacionadas a solos férteis e, também, bastante usadas como indicadores da qualidade ambiental. No entanto, para otimizar seu uso como bioindicadores, as populações de minhocas devem ser avaliadas juntamente com as variáveis ambientais e antropogênicas que regulam as suas comunidades. Esta revisão buscou identificar os atributos relacionados à amostragem de minhocas, físicos e químicos dos solos, e ambientais e antropogênicos avaliados em 124 estudos publicados que quantificaram a abundância de minhocas (>7.300 amostras) em 765 locais com diferentes tipos de clima, solos, uso da terra e sistemas de manejo no Brasil. Os atributos químicos e físicos do solo (exceto pH) foram menos relatados (≤50% dos estudos) do que outras variáveis ambientais, como data de coleta, altitude, temperatura, precipitação, tipo de solo e de clima, e uso do solo (>50% dos estudos). As minhocas foram raramente identificadas (24%) e poucos estudos (31%) mediram sua biomassa, embora a maioria tenha fornecido informações adequadas sobre o protocolo de amostragem. Com base na sua importância para a regulação das populações de minhocas, propõe-se um conjunto de variáveis que devem ser avaliadas no estudo de comunidades de minhocas e outros grupos da macrofauna do solo. Isso deve ajudar a guiar futuros estudos sobre minhocas no Brasil e em outros países, otimizar a coleta e a replicabilidade de dados, permitir comparações entre diferentes estudos e promover o uso de minhocas como bioindicadores da qualidade do solo.

Abstract: Earthworms are often related to fertile soils and are also frequently used as environmental quality indicators. However, to optimize their use as bioindicators, earthworm populations must be evaluated together with the environmental and anthropogenic variables regulating their communities. This review sought to identify the earthworm-sampling, soil chemical and physical, and environmental and anthropogenic attributes evaluated in 124 published studies that quantified earthworm abundance (>7,300 samples) in 765 sites with different types of climate, soils, land use, and management systems in Brazil. Soil chemical and physical attributes (except pH) were less reported (≤50% of studies) than other environmental variables such as sampling date, altitude, temperature, precipitation, climate and soil type, and land use (>50% of studies). Earthworms were rarely identified (24%) and few studies (31%) measured their biomass, although most provided adequate information on sampling protocol. Based on their importance in regulating earthworm populations, a set of variables is proposed to be evaluated when studying earthworm communities and other macrofauna groups. This should help guide future studies on earthworms in Brazil and other countries, optimize data collection and replicability, allow comparisons between different studies, and promote the use of earthworms as soil quality bioindicators.