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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Formation of black carbon rich `sombric' horizons in the subsoil - A case study from subtropical Brazil

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Chiapini, Mariane [1] ; Schellekens, Judith [1] ; Calegari, Marcia Regina [2] ; de Almeida, Jaime Antonio [3] ; Buurman, Peter [4] ; de Camargo, Plinio Barbosa [5] ; Vidal-Torrado, Pablo [1]
Total Authors: 7
[1] Univ Sao Paulo, Escola Super Agr Luis de Queiroz ESALQ, Dept Ciencia Solo, Av Padua Dias 11, Piracicaba, SP - Brazil
[2] Univ Estadual Oeste Parana UNIOESTE, Dept Geog, Campus Marechal Candido Rondon, Rua Pernambuco 177, BR-85970000 Marechal Candido Rodondo, Parana - Brazil
[3] UDESC, Dept Solos, Ctr Ciencias Agrovet, Av Luis de Camoes 2090, BR-88520000 Loges, SC - Brazil
[4] Wageningen Univ, Earth Syst Sci Grp, POB 47, NL-6700 AA Wageningen - Netherlands
[5] Univ Sao Paulo, Ctr Isotop Energy Agr, Piracicaba - Brazil
Total Affiliations: 5
Document type: Journal article
Source: Geoderma; v. 314, p. 232-244, MAR 15 2018.
Web of Science Citations: 3

The formation of sombric horizons (dark horizons in the subsoil) is still not understood. In order to improve our understanding of the formation of sombric horizons we studied these soils in southern Brazil from various perspectives. The lateral configuration and grain size distribution excluded the possibility that the sombric horizon is a paleosol covered by an eolian deposit or colluvium. Micromorphology showed intense biological activity, indicating strong bioturbation. The absence of clay and OM coatings indicates that the sombric horizon in the study area was not formed by illuviation. Considering changes with depth, phytoliths and delta C-13 isotopes clearly showed that the OM from the sombric horizon had a larger contribution from grasses, while a larger contribution from black carbon (BC) was evidenced by the molecular composition. A larger contribution from grasses and BC both correspond to drier climatic conditions. However, similar depth trends for delta C-13 and PAHs were found in the reference profile (without sombric horizon), in agreement with climatic change but not explaining the different morphology. The molecular composition and C/N ratio showed that the profiles differed in degree of decomposition, with the OM in the soils that contained a sombric horizon being more decomposed than that in the reference profile. The sombric horizon is thus a remnant of an earlier phase of soil formation under a drier climate, which is made visible by differences in decomposition of OM related to subsequent more humid conditions. Stronger decomposition in the profiles with a sombric horizon may be related to better drainage, explaining their occurrence in the highest positions within the landscape and suggesting a topographic control. (AU)

FAPESP's process: 15/03577-2 - Pedogenesis and molecular characterization of sombric horizons in soils in Tijucas do Sul region - PR
Grantee:Mariane Chiapini
Support type: Scholarships in Brazil - Master
FAPESP's process: 13/03953-9 - Organic matter dynamics in tropical peatlands (Diamantina, Brasil) - development of molecular proxies to reconstruct environmental changes
Grantee:Judith Schellekens
Support type: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 14/23969-0 - Soil organic matter dynamics and its relation to the environment: molecular chemistry (pyrolysis-GC/MS) to understand soil formation in tropical soils
Grantee:Pablo Vidal Torrado
Support type: Regular Research Grants