ABSTRACT Cactus seeds in seasonal dry tropical forests are subject to several stressors, such as salt stress which limits imbibition and therefore germination. Thus, this study aimed to compare germination performance of Cereus jamacaru subsp. jamacaru and Pilosocereus pachycladus subsp. pernambucoensis seeds under salinity conditions. To this end, NaCl and KCl solutions were used in the following osmotic potentials: 0.0 (control),-0.2,-0.4,-0.6,-0.8,-1.0, and-1.2 MPa. Seeds were placed to germinate at 25 °C and 12-hour photoperiod. The number of germinated seeds was counted daily for 21 days after root protrusion. The variables analyzed were: water content, germination, normal seedlings, germination speed index, and average germination time. The experimental design was completely randomized, following a 2 × 7 factorial scheme (species × osmotic potential) for each saline source. Water restriction and ionic effect caused by salts favored seed germination and vigor in both species at-0.2 and-0.4 MPa. However, from-0.8 MPa onwards, germination decreased significantly for both salts. Seeds of C. jamacaru subsp. jamacaru and P. pachycladus subsp. pernambucoensis were tolerant to salt stress since they germinated up to-0.8 MPa (NaCl) and-1.2 MPa (KCl). The latter occurred only for P. pachycladus subsp. pernambucoensis.

ABSTRACT The objective of this study was to evaluate the effect of the conversion of secondary native vegetation (NV) to conventional systems (agriculture and pasture) in soil organic carbon (SOC) and carbon of fractions particulate organic matter (POM) and mineral-associated organic matter (MAOM) in the Brazilian semi-arid region. The study was carried out in the municipalities of Delmiro Gouveia, Inhapi and Pariconha, in Alagoas, Brazil. Soils were collected in the layers of 0-0.1, 0.1-0.2 and 0.2-0.3 m. The treatments analyzed were: agricultural crops with 4, 15 and 30 years and pasture with 10 years. As a reference, the secondary Caatinga was used. The results show that in soils with sandy texture (Neossolos Quartzarênico and Regolítico – Arenosols and Regosols, respectively), there were reductions in SOC levels and carbon in the compartment associated with minerals. The inverse can be observed in the clay-textured Argissolo (Acrisols), with 30 years of cultivation, in which there was an increase in SOC and C in the quantitative fractions of soil organic matter. In addition, despite the sandy texture of the Neossolo Regolítico, POM levels were increased in the pasture system in comparison to native vegetation, but it was not enough to recover the original SOC content of this system.