Resistance of Soil Organic Matter in “Humic A Horizons” of the Mountainous Region in the State of Rio De Janeiro

Abstract

Soils with high organic carbon content, such as those with "humic A horizon", occur in different regions of Brazil. This study aimed to determine the quantitative and qualitative characteristics of organic matter regarding the humic A horizon under different land uses in Bom Jardim, in Rio de Janeiro State, Brazil. Samples from forest, pasture, Eucalyptus plantation, coffee cultivation, olericulture, and also passion fruit soils were sampled and analyzed. In October 2011, undisturbed samples from humic A horizons, were collected for soil density analysis. In addition, disturbed samples were collected for the determination of organic carbon (C org) content, total carbon, humic substance fractions contents and natural abundance of 13 Carbon (δ 13 C). Low C org contents were observed in areas under olericulture, pasture and passion fruit cultivation. The fulvic acid fraction was higher than other fractions, regardless of land use. The small variability in δ 13 C indicated maintenance of original C org and suggest high resistance of Soil Organic Matter in humic A horizons.

Organic fermentative‐humic soil subhorizon (Ofh) as a ‘natural sponge’ of selected trace elements: Does this feature make it a potential geoindicator of temperate soil quality?

“…The characteristic enrichment of the A horizon in Pb (Figures 3 and 5) may result from three major aspects: (i) interactions between humic substances (HS) and clay minerals, which increase Pb adsorption, but do not affect, for example, Cd adsorption (Xiong et al, 2015), (ii) resistance of SOM of humic horizons (Fontana et al, 2020) and (iii) long‐term exposure to Pb depositions (Dube et al, 2001; Gałka & Łabaz, 2014; Impellitteri et al, 2002; Obrist et al, 2011). The presence of clay mineral‐HS system promotes Pb adsorption, although the role of metal carrier in this system is played by the mineral fraction (Ostergen et al, 2000; Xiong et al, 2013, 2015).…”

Charred plant fragment–aluminium complexes in buried humic horizons of a cumulative volcanic soil profile: Formation, accumulation and potential role

“…Al, Fe, fine mineral phases and humic substances are important factors in the accumulation of SOM (Colombo et al, 2014;Fontana et al, 2020;Hanke & Dick, 2017;Wiesmeier et al, 2019). Whether Al, Fe or clay content is more important for SOM sorption is likely a product of their presence, absence and relative proportions in a given soil.…”