Carbono orgânico e propriedades de solos da Serra da Boa Esperança, MG: efeito da altitude e do cultivo do cafeeiro

Abstract

Soil organic carbon (SOC) is a key property affecting soil quality for agriculture and the environment as a whole. However, in high altitude ecosystems, little is known about how SOC would respond to land use change, which is critical since these areas can be highly susceptible to climate change. This work aimed to assess the changes in the SOC contents and stocks, as well as in chemical and physical soil properties under coffee cultivation, at two different altitudes in the Boa Esperança range, Minas Gerais, Brazil. Thus, two Inceptisols were sampled under native forest and coffee plantations, at altitudes of 940 m and 1260 m, in the pre-established depths of 0-5, 5-10, 10-20 and 20-40 cm. Soil physical, chemical and micromorphological analyzes were carried out, as well as total and particulate carbon, used to calculate SOC stocks. The experimental design was completely randomized, with 4 treatments corresponding to the two land uses at two different altitudes, in 4 soil depths and in 3 replications. The two reference soils under native forest were classified as Dystrudepts, with clayey textural class at the lowest altitude, and clay loam texture at the highest altitude. These soils were highly stony, especially the soil at a higher altitude, which was also shallower and with clay contents in depth, consistent with a lower degree of weathering. At both altitudes, the native soils were dystrophic due to low natural fertility, high acidity and low effective cation exchange capacity. The conversion of native forest to coffee plantation significantly decreased soil acidity at all depths, and increased Ca2 +, Mg2 + and the sum of bases at the two altitudes. At all sampling points, SOC concentrations decrease with increasing soil depth. In addition, most SOC was associated with the clay+silt fractions, indicating a stage of greater humification. SOC stocks, corrected for compaction and stoniness or not, were significantly higher in the soil under coffee plantation at 1260 m than under native forest. Soil micromorphology illustrated textural differences between soils under different altitudes and also the marked presence of particulate and humified SOC in the 0-10 cm layer, especially in soils at 1260 m.