Abstract
Amazonian rainforests, once thought to be pristine wilderness, are increasingly known to have been widely inhabited, modified, and managed prior to European arrival, by human populations with diverse cultural backgrounds. Amazonian Dark Earths (ADEs) are fertile soils found throughout the Amazon Basin, created by pre‐Columbian societies with sedentary habits. Much is known about the chemistry of these soils, yet their zoology has been neglected. Hence, we characterized soil fertility, macroinvertebrate communities, and their activity at nine archeological sites in three Amazonian regions in ADEs and adjacent reference soils under native forest (young and old) and agricultural systems. We found 673 morphospecies and, despite similar richness in ADEs (385 spp.) and reference soils (399 spp.), we identified a tenacious pre‐Columbian footprint, with 49% of morphospecies found exclusively in ADEs. Termite and total macroinvertebrate abundance were higher in reference soils, while soil fertility and macroinvertebrate activity were higher in the ADEs, and associated with larger earthworm quantities and biomass. We show that ADE habitats have a unique pool of species, but that modern land use of ADEs decreases their populations, diversity, and contributions to soil functioning. These findings support the idea that humans created and sustained high‐fertility ecosystems that persist today, altering biodiversity patterns in Amazonia.
Highlights
The Amazon basin still contains the largest continuous and relatively well-preserved tract of tropical forest on the planet
Termite and total macroinvertebrate abundance were higher in reference soils, while soil fertility and macroinvertebrate activity were higher in the Amazonian Dark Earths (ADEs), and associated with larger earthworm quantities and biomass
Our study found over 670 macroinvertebrate morphospecies in the 18 sites from three Amazonian regions, including at least 70 new species of ecosystem engineers
Summary
The Amazon basin still contains the largest continuous and relatively well-preserved tract of tropical forest on the planet. Soil animal communities have been little studied in megadiverse regions such as the Amazonian rainforest (Barros et al, 2006; Franco et al, 2018; Marichal et al, 2014), and these habitats may be home to thousands of described and still undescribed species (Brown et al, 2006), smaller invertebrates such as nematodes and mites (Franklin & Morais, 2006; Huang & Cares, 2006) and macroinvertebrates (Mathieu, 2004) These invertebrates may be susceptible to land-use changes such as deforestation (Decaëns et al, 2018; Franco et al, 2018; Mathieu et al, 2005) and can be used as bioindicators of both soil quality and of environmental disturbance (Gerlach et al, 2013; Lawton et al, 1998; Rousseau et al, 2013; Velásquez & Lavelle, 2019). We predicted that (1) soil biodiversity and soil enrichment in anthropic soils would reflect a unique habitat (explained by a pre-Columbian footprint) and that (2) animal species richness, biomass, and activity, as well as nutrient contents in these soils, would be determined by present-day land use
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