State of the art of studies on earthworm populations in the state of Paraná

In this review, we included all the studies performed in the state of Paraná, Brazil, which had data on earthworms. We reviewed the literature for all publications (journal articles, dissertations, theses, conference proceedings, book chapters) carried out in the state of Paraná, Brazil, which had data on earthworms. The period evaluated ranged from 1986 (earliest date in the state) to 2020. Searches were performed in online databases including Sicence Direct, Scielo, CAPES and the digital collection of dissertations and theses from Brazilian Universities (BDTD). 

Overall 51 publications had earthworm data, including abundance, biomass, species, richness or just presence/absence. Data were extracted from these publications and compiled into an excel file. The dataset contains information gathered from 62 of the 399 municipalities in Paraná, and includes separation in ten geopolitical regions (IBGE 2010), as well as topographic regions and climate (Köppen, 1931). The ten geopolitical mesoregions are: West (WE), Northwest (NW), Center West (CW), Center North (CN), North Pioneer (NP), Center East (CE), Metropolitan (MT), Center South (CS), Southeast (SE) and Southwest (SW). The three topographic regions include the First, Second and Third Plateaus, and the Coastal Lowland. 

Earthworm data are presented as total abundance (number of individual m^-2), fresh biomass (in g m^-2) and species richness (total number). We also provide information on each species encountered, its ecological category, and whether it is native or exotic to the state of Paraná. For earthworm species, ecological category information follows the classification of Bouché (1977), including the intermediate categories: e.g., anecic, epigeic, endogeic, polyhumic endogeic, mesohumic endogeic, epi-endogeic, endo-epigeic. For each species, full names (when available), and species author(s) and year of the description are provided.

Geographic location is provided when possible, with latitude, longitude and altitude, soil types according to the Sistema Brasileiro de Classificação de Solos - SiBCS (Santos et al. 2018). Sampling date and season are also provided, when available.

When known, the sampling method(s) used were given. These included quantitative methods involving handsorting, such as 1) the standard Tropical Soil Biology and Fertility (TSBF) Programme method (Anderson & Ingram 1993), in which soils are handsorted from monoliths 25x25 cm square to depths ranging from 10 to 40 cm (identified as TSBF in the spreadsheets); or 2) other monolith dimensions like 20x20, 40x40 and 50x50 cm (identified as Handsorting in the spreadsheets). Qualitative sampling (e.g. Bartz et al. 2014) included: 1) collecting in various niches like deeper soil layers, litter, under rocks, in and under rotting logs, next to water bodies like streams, lakes and swamps; 2) chemical extraction using a diluted formalin solution (usually over an area 50x50 cm), following recommendations of ISO 23611-1 (2017), and pouring of the solution either on the soil surface, or at the bottom of the pit; 3) electrical extraction using a modifed apparatus (Azevedo et al. 2010), based on the Octet-Method (Thielemann 1986).

The determination of LUS was based on Nadolny et al. (2020), which characterized Native Vegetation, Forest Plantation (including forest with Pinus sp. and Eucalyptus sp.), Pasture, Integrated Systems (e.g., agropastoral, silvopastoral or agrosilvopastoral systems) and agricultural areas (Conventional Tillage, No-Tillage and Minimum Tillage). In addition to these, Perennial Crops, Grass Lawns and Agroforestry Systems were included.

The soil chemical and physical analysis data were included in the dataset when performed in the same places as the earthworm sampling. Chemical data included: pH, H+Al, K, Ca, Mg, P, C, sum of Bases, CEC, Base saturation, N, Na. Physical data included: sand, clay and silt proportions, texture, porosity, density and resistance to penetration.

All data are provided in excel format and include 5 tabs: Readme, Legend, Earthworms + environment, Species distribution and References. The Readme tab provides information on the associated publication in the Revista Brasileira de Ciência do Solo authored by Dudas et al. (see https://doi.org/10.36783/18069657rbcs20220159). The Legend tab provides a description of the variables used in the other (data) tabs. Earthworms + environment has information on the sampling methods used, the earthworm abundance, biomass and richness found at the different sampling sites in Paraná, and the data on soil and environmental variables. The Species distribution tab provides information on the species found, places of origin, ecological category, sampling method used and LUS. The References tab provides detailed bibliographic information on the sources of the data used to build the tables and the dataset.

Overall, in the state of Paraná, 90 species of earthworms were found in 51 counties of the state, of which 66 were native and 24 were exotic. A large number of species (46) are likely new and still must be formally described. Higher species richness was found in native vegetation, which also had a higher proportion of native species (75%). The other LUS with more native species were: Forest Plantation (FP) and No-Tillage (NT), while Conventional Tillage (CT) sites had only 17% native species. Earthworm abundance and biomass were highest in less disturbed LUS such as agroforestry systems, native vegetation, forestry plantation,
grass lawns, and permanent crops, compared to the highest disturbance LUS including soil preparation (MT and CT), where the lowest abundance and biomass were found. However, as only 16% of the 399 counties in Paraná have been sampled so far, much further research is needed in order to adequately assess the relationships between earthworms and land use.