Amazon plinthosols: carbon stocks and physical properties under different land uses

Abstract

The population growth and the climate changes impose challenges to society, especially regarding food supply and the maintenance of desirable soil conditions. Besides, it is necessary to reduce greenhouse gas emissions. Hence, there is a necessity of studies addressing the understanding of soil conditions under different land uses, as soils can become carbon pools or sources depending on management practices. This study was conducted in soil profiles of Amazon Plinthosols under different land uses: undisturbed forests, cattle ranching pastures, and mixed crops. Soil density and carbon fraction were assessed at four depths (0-5, 5-10, 10-20, and 20-40 cm), while particle size and mineralogy were examined at 0-20 and 20-40 cm. Soils under undisturbed forests presented lower densities and higher carbon fractions when compared to other land uses. These soils also presented the highest carbon stock; however, the Tukey test indicated no significant differences. Soil densities were lower in forest environments. Cattle ranching pastures presented higher carbon stocks when compared to mixed crops (at age 10 years). Our results indicated that proper soil management practices are needed to maintain the soil productive capacity after converting forested areas for other uses. Plinthosols, due to its textural and mineralogical characteristics, presented high amounts of quartz, demonstrating how sensitive these environments are to changes in the landscape due to deforestation and how unstable the maintenance of carbon stocks is because of such conditions. This study provides useful information to the understanding of the carbon stock in Amazon Plinthosols. It may be helpful to improve the Brazilian Inventory of Anthropogenic Emissions and Removals of Greenhouse Gases and to understand the impacts of land-use change.