Acrisols, Ferralsols, Leptosols and Planosols were sampled in layers down to I m under dense caatinga, open caatinga, pasture and agriculture. Agricultural Leptosols and Planosols had the lowest C and N concentrations among the land uses, although in some cases differences were not statistically significant. On average, conversion of dense caatinga to agriculture reduced C stocks from 63 to 47 Mg ha(-1). Acrisols had the highest concentrations of C and N. and Planosols had the lowest concentrations and stocks. Conversion to pasture did not reduce stocks, but open caatinga also had lower C stocks (50 Mg ha(-1)) than dense caatinga. Nitrogen stocks did not differ among land uses, implying that losses are greater for C than for N. Despite the fact that the western portion of Pernambuco state covers 3% of the Brazilian semi-arid area, it stocks about 020 Pg of C (and 0.019 Pg of N), which represents 2% of the total estimated soil C stock in the semiarid region (8.9 Pg). Therefore, the stock per hectare in the west portion of Pernambuco is about one-third smaller than the stock per hectare in the whole Brazilian semiarid region, probably a consequence of the lower average C concentration in the 20 an superficial layer, a higher proportion of agricultural fields and shallower depths of some soil classes in western Pernambuco than in the whole semiarid region. (C) 2019 Elsevier B.V. All rights reserved.