VELASCO-MOLINA, M.; ALMEIDA, J.A.; VIDAL-TORRADO, P.    MACIAS, F.. Chemical fractionation of carbon on Acrisols with sombric horizon from South Brazil. []. , 33, 1, pp.277-286. ISSN 0871-018X.

Sombrics horizons (subsurface, dark and with a high content of C) have a genesis poorly understood and can be conceived as a potential sink of C in subtropical envi­ronments. The maximum accumulation of C bound to Fe and Al extracted by pyrophos­phate and oxalate solution was observed in sombric horizons of two Acrisols of Santa Catarina State (S-Brazil), but this is not in­dicative of podzolisation, andosolisation or solodisation processes or accumulation of C due hydromorphy conditions. Most of its C was found at intermediate wet oxidisable fraction (oxidisable with K₂Cr₂O₇, cold, but not by KMnO₄). Recalcitrant C (non­oxidisable and difficult oxidisable) was an important pool (20-45%), but variable into profile. Changes on land use with different input of necromass and vegetations fire ef­fects seem to be involved in its formation.

: Brazil; C fractions; C recalci­trant; oxidisable organic matter; sombric ho­rizon.

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