DOI: 10.5061/dryad.3tx95x6cc
title: A “Dirty” Footprint: Soil macrofauna biodiversity and fertility in Amazonian Dark Earths and adjacent soils

description: Amazonian rainforests once thought to hold an innate pristine wilderness,
 are increasingly known to have been densely inhabited by populations
 showing a diverse and complex cultural background prior to European
 arrival. To what extent these societies impacted their landscape is
 unclear. Amazonian Dark Earths (ADEs) are fertile soils found throughout
 the Amazon Basin, created by pre-Columbian societies as a result of more
 sedentary habits. Much is known of the chemistry of these soils, yet their
 zoology has been neglected. Hence, we characterised soil macroinvertebrate
 communities and activity in these soils at nine archaeological sites and
 adjacent reference soils in three Amazonian regions, totaling eighteen
 sampling sites. Furthermore, we characterized various soil chemical and
 physical properties associated with soil fertility. The current dataset
 contains data on soil macroinvertebrate biodiversity (26 taxa), with a
 special focus on termites, earthworms and ants. It also contains data on
 soil macromorphology, bulk density and porosity, soil carbon,
 nitrogen, macro and micronutrients, magnetic susceptibility
 and apparent electrical conductivity. The results show similar
 overall macrofauna morphospecies richness in ADE and adjacent
 soils, but distinct communities in each soil type. They also show
 higher soil fauna activity in ADEs when compared to adjacent
 reference soils, associated with greater earthworm populations.
 Finally, they also confirm the well-known high soil fertility in ADEs
 compared with adjacent soils. Land use was an important determinant of
 both macrofauna biodiversity and soil fertility. These findings support
 the idea that humans have built and sustained a contrasting high fertility
 ecosystem that persisted until our days, altering biodiversity
 distribution patterns in Amazonia.
description: Soils
 were sampled in Brazilian Amazonia in the municipalities of Iranduba-AM,
 Belterra-PA and Porto Velho-RO. In each region, paired sites with
 anthropogenic dark earths (ADE) and nearby reference (REF)
 non-anthropogenic soils were sampled under three different land-use
 systems: native secondary vegetation (<i>dense ombrophilous
 forest</i>) classified as old secondary forest when &gt;20 years
 old, or young regeneration forest when &lt;20 years old, and
 agricultural systems (maize in Iranduba, soybean in Belterra, and
 introduced pasture in Porto Velho). At each site,
 soil and litter macrofauna were collected using the Tropical Soil Biology
 and Fertility (TSBF) method (Anderson and Ingram, 1993) at five sampling
 points (soil monoliths 25x25 cm up to 30 cm depth) within a 1 ha plot,
 four at the corners and one on the center of a 60 x 60 m square, resulting
 in an “X” shaped sampling design. Each soil monolith was divided into
 surface litter and three 10 cm-thick soil layers (0-10, 10-20, 20-30 cm).
 Macroinvertebrates (animals with &gt;2 mm body width) were manually
 hand-sorted and fixed in 92% ethanol. Earthworms, ants and termites were
 identified to species or genus level and other macroinvertebrates were
 sorted into morphospecies with higher taxonomic level assignations.
 Density (number of individuals) and biomass of the soil macrofauna
 surveyed using the TSBF method were extrapolated per square
 meter. For the
 earthworms, ants and termites (ecosystem engineers) additional samples
 were performed, especially in forest sites to better estimate species
 richness of these taxa. Earthworms were collected at four additional
 cardinal points of the grid at all sites, and hand-sorted from holes of
 similar dimensions as the TSBF monoliths. Termites were sampled in the
 forest sites only forests (except one of the REF young forests at Porto
 Velho), in five 20 m<sup>2</sup> (2 x 10 m) plots (close to
 the five main soil monoliths) by manually digging the soil and looking for
 termitaria in the soil, as well as in the litter and on trees using a
 modification of the transect method (Jones and Eggleton, 2000). Ants were
 sampled in 10 pitfall traps (300 ml plastic cups) set up as two 5-trap
 transects on the sides of each 1 ha plot, as well as in two traps to the
 side of each TSBF monolith (distant ~5 m) only in the forest systems of
 Iranduba and Belterra (not Porto Velho). Each cup was filled to a third of
 its volume with water, salt and detergent solution. Termites and ants were
 preserved in 80% ethanol and earthworms in 96% ethanol and the alcohol
 changed after cleaning the samples within 24 h. All the animals
 (earthworms, ants, termites) were identified to species level or
 morphospecies level (with genus assignations) by co-authors SWJ/MLCB
 (earthworms), AA (termites) and ACF/RMF (ants). Soil samples
 for chemical and particle size analysis were collected from each TSBF
 monolith after the soil fauna hand-sorting. Around 2 to 3 kg soil from
 each depth (0-10, 10-20, 20-30 cm) and the following soil properties were
 evaluated according to standard methodologies (Teixeira et al., 2017): pH
 (CaCl<sub>2</sub>); Ca<sup>2+</sup>,
 Mg<sup>2+</sup>, Al<sup>3+</sup> (KCl 1 mol
 L<sup>-1</sup>); K<sup>+</sup>, P, Fe, Zn, Mn, Cu
 and Ni (Mehlich-1); Pseudo-total contents of trace elements (Ba, Cd, Co,
 Cu, Ni, Pb, Se and ZN) were determined by acid digestion
 (HNO<sub>3</sub> + HCl); Fe (sulfuric extract); total nitrogen
 (TN) and carbon (TC) using an element analyzer (CNHS). Base saturation and
 cation exchange capacity (CEC) were calculated using standard formulae
 (Teixeira et al., 2017) and particle size fractions (% sand, silt, clay)
 were obtained following standard methodologies (Teixeira et al.,
 2017). Soil magnetic susceptibility (MS) and apparent electrical
 conductivity (EC<sub>a</sub>) (Siemens per meter – S
 m<sup>-1</sup>) were obtained using a KT-10 S/C magnetic
 susceptibility/conductivity meter (Terraplus) with 10 Hz of operating
 frequency.             Soil macromorphology
 samples were taken close to the TSBF monolith (~2 m) using a 10 x 10 x 10
 cm metal frame. The collected material was separated into different
 fractions including: living invertebrates, litter, roots, pebbles, pottery
 sherds, charcoal (biochar), non-aggregated/loose soil (NA), physical
 aggregates (PA), root-associated aggregates (RA), and fauna-produced
 aggregates (FA) using the methodology proposed by Velasquez et al. (2007).
 Soil bulk density and total porosity were determined using undisturbed
 core samples (0.05 m diameter, 0.05 m depth) collected at ~2 m from the
 TSBF samples following the method proposed by Teixeira et al.
 (2017). All data is
 provided in excel format, and includes 11 tabs in the data file: Metadata,
 Coordinates, Soil chem, BD+POR, Macromorph, Macro_den, Macro_bio,
 Morpho_TSBF, Add_worm, Add_ants, Add_termites. The Legend tab provides a
 detailed explanation for each variable included in each table, including
 the units used for each. The Metadata tab describes the main types/classes
 of variables included in each table. Soil chem, BD+POR and Macromorph
 tables contain the data about chemical and physical soil variables. The
 Macro_den and Macro_bio contain the data about density and biomass on all
 the soil invertebrate taxa found, respectively. The Morphosp_TSBF,
 Add_worm, Add_ants and Add_termites tables contain the invertebrate
 species/morphospecies occurrence in TBSF and extra samples for earthworms,
 ants and termites, respectively.
description: <b>References used in
 methods section</b> Anderson, J.M., Ingram, J.S.I., 1993. Tropical Soil Biology and Fertility: A handbook of methods, 2 edition. ed. Oxford University Press, Oxford. Jones, D.T., Eggleton, P., 2000. Sampling termite assemblages in tropical forests: testing a rapid biodiversity assessment protocol. Journal of Animal Ecology 37, 191–203. Teixeira, P.C., Donagemma, G.K., Fontana, A., Teixeira, W.G., 2017. Manual de métodos de análise de solo, 3<sup>o</sup>. ed. Embrapa, Brasília. Velasquez, E., Pelosi, C., Brunet, D., Grimaldi, M., Martins, M., Rendeiro, A.C., Barrios, E., Lavelle, P., 2007. This ped is my ped: Visual separation and near infrared spectra allow determination of the origins of soil macroaggregates. Pedobiologia 51, 75–87. doi:10.1016/j.pedobi.2007.01.002