02718naa a2200289 a 450000100080000000500110000800800410001902400540006010000160011424501860013026000090031652018230032565000150214865000180216365000190218165300270220065300260222770000160225370000190226970000170228870000170230570000170232270000140233970000140235370000160236777300450238321406812022-03-09       2022    bl uuuu     u00u1 u    #d7 ahttps://doi.org/10.1016/j.catena.2022.1061852DOI1 aRAMALHO, B.  aCarbon and nitrogen storage and stability by mineral-organic association in physical fractions of anthropogenic dark earth and of reference soils in Amazonia.h[electronic resource]  c2022  aThe anthropogenic dark earths (ADEs) are being assumed in recent years as a model representing the result of sustainable soil management practices carried out by Pre-Columbian peoples. However, little is known about the role of mineral-organic associations in organic matter storage in those soils compared to the emphasis generally given to the role of pyrogenic structures. We quantified the changes of carbon and nitrogen and their distribution in physical fractions of ADEs in relation to the reference (adjacent) soil. Four ADEs sites having the different soil textural classes of sandy clay loam, sandy clay, clayey, and very clayey were selected in the Amazon region of Brazil. Soil samples were collected from the 0?10 cm layer and a subset of the sample was separated into large aggregates (&gt500 micrômetro) and small aggregates (&lt500 micrômetro). The ADEs stored on average 45% more total organic carbon (TOC) and 44% more total nitrogen (TN) than the reference soils. Of the incremental TOC and TN in ADE relative to the reference soil, the silt size fraction stored on average 92% of this TOC and 37% of this TN and had C:N ratios as high as 25, which may indicate the presence of pyrogenic material. The clay fraction stored a substantial share of 27-46% of the incremental TOC and 27-66% of the incremental TN. The C:N ratio in the clay size fraction of ADEs, on average 10.5, was lower or not different than in the clay fraction of reference soil (average of 11.1), indicating that the organic matter in the clay fraction even of ADEs was predominantly of microbial origin, and not pyrogenic. We therefore conclude that the clay fraction proved to be an important location to the accumulation and stabilization of TOC and TN in these Anthrosols, possibly by mineral-organic association mechanisms.  aAnthrosols  aClay fraction  aOrganic matter  aPhysical fractionation  aProtection mechanisms1 aDIECKOW, J.1 aMELO, V. de F.1 aBROWN, G. G.1 aSIMON, P. L.1 aIBARR, M. A.1 aCUNHA, L.1 aKILLE, P.1 aTPI NETWORK  tCatenagv. 213, 106185, June 2022. 10 p.