Physical protection of soil organic carbon through aggregates in different land use systems in the semi-arid region of Brazil

摘要

The objectives of this work were to quantify the soil organic carbon (SOC) stock and to evaluate the distribution of soil aggregates and their respective SOC and labile carbon (LC) present inside the aggregates in different perennial land use systems in the semi-arid region of Brazil. Soil samples were collected in four land use systems: two forage palm cultivation systems of different ages, a mango orchard, and natural forest. A higher amount of SOC stored in the 0-60 cm layer was observed in the mango orchard, increasing the soil carbon stock by 16.4% in relation to the natural forest. Palm cultivations presented larger amounts of macroaggregates from the 10-20 cm layer until 60 cm depth, while the mango orchard and natural forest presented a similar pattern in all fraction size classes. SOC averages of non-occluded particulate organic matter (POM) and aggregate occluded organic matter (AOM) in the macroaggregates of the 0-10 cm layer were higher in the mango orchard and natural forest compared to palm cultivations; however, the LC of AOM was higher in palm crops. Soil microaggregates were little influenced by land use systems, however this class represented an average of 24% of SOC stock.