Abstract
Bioturbation involves the incorporation of residues from the surface soil into the subsoil; however, common small soil ‘bioengineers’, such as earthworms or termites, are unlikely to transport human artifacts to deeper soil horizons. However, such artifacts occur in the deeper soil horizons within Amazonian Anthrosols (Terra Preta). Here we test the assumption that such tasks could be carried out by fly larvae, which could thus play a crucial role in waste decomposition and associated soil mixing under tropical conditions. We performed two greenhouse experiments with sandy substrate covered with layers of organic waste, ceramic fragments, and black soldier fly larvae (BSFL) (Hermetia illucens (L.) (Dipt.: Stratiomyidae)). We used in-situ images to assess the rate of bioturbation by BSFL, and then designed our main study to observe waste dissipation (reduction of organic carbon and phosphorus contents from waste model trials with and without charcoal) as related to larval-induced changes in soil properties. We found that the bioturbation of macroinvertebrates like BSFL was able to bury even large (> 5 cm) ceramic fragments within hours, which coincided with high soil growth rates (0.5 cm h-1). The sandy soil was subsequently heavily enriched with organic matter and phosphorus originating from organic waste. We conclude that BSFL, and possibly other fly species, are important, previously overlooked soil ‘bioengineers’, which may even contribute to the burial of artifacts in Anthrosols and other terrestrial waste dumps.
Highlights
Anthrosols are soils that have been transformed, influenced, or created by human activities [1]
The control without larvae showed no hints of decay, no buried ceramics, or evident bioturbation, as shown in Fig 1 and S2 Fig. We conclude that black soldier fly larvae (BSFL) can displace even large, broken ceramic sherds and consume organic waste mixed with charcoal, as shown in the follow-up video
BSFL bioturbation includes the burying of ceramic sherds and represents a new paradigm that could explain how potsherds were transported into deeper layers in Amazonian Anthrosols profiles
Summary
Anthrosols are soils that have been transformed, influenced, or created by human activities [1] These soils are found in different places around the world [2,3,4]. Special attention has been paid to Amazonian Anthrosols in the past decades [5], which occur in and around ancient tropical settlements [6]. These soils that presumably formed in pre-Columbian middens are known as Archaeological Black Earths (ABE), Amazonian Dark Earths (ADE), or Terra Preta (Black soils in Portuguese), because they generally have a darker coloration, higher fertility than surrounding soils, and show the presence of potsherds and charcoal in different.
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