Retenção de carbono em latossolo sob efeito de restauração de matas ciliares

Abstract

Riparian Forest have been threatened due to the occupation process and the advance of the agricultural frontier. The soils under these ecosystems can store carbon, aiding in limiting global warming, which results, among other things, in emissions of carbon dioxide by the inadequate use of the soil. We aimed at quantifying the content and stock of carbon accumulated in areas with clayey Latosol under different ages of reforestations and under sugarcane, pasture, soybean, maize and sorghum cultivations, in addition to associating carbon with soil attributes and correlating the reforestations with the vegetation’s phytosociological parameters. The soil samples were collected in July and August of 2013 from the layers of 0-5, 5-10, 10-20, 20-40 cm, in 10 areas with different history: MTN: native wood; REF20: 20-year reforestation; REF19: 19-year reforestation; REF 16: 16-year reforestation; REF13: 13-year reforestation; REF12: 12-year reforestation; REF7: 7-year reforestation; CAN: conventional sugarcane cultivation; SMS: soybean-maize-sorghum tillage; PAS: pasture. The contents of C were analyzed by dry combustion on the model Vario TOC Cube equipment. The results indicated that there was significant difference on the contents of carbon on the different vegetative topping, with the highest values being observed on the soil’s surface layer. The mean stratification rate ranged from 1.84 for REF20 and 1.18 for REF7, showing higher C rates on the surface than on the subsoil for the wood and reforested areas of over 16 years. Regarding the carbon stock, the area reforested over 16 year is that which most stores C (158 mg ha-1); the area with annual cultures stores around half of the C stored on the 16-year reforestation, considering the 0-40 cm layer. For the evaluated soil attributes, the results indicate that there was a significant difference in the soil density of the different areas, and the density is correlated with the content of C up to the soil depth of 10 cm. There was no relation between the carbon stocks and the average fertility index of the soils and the time of reforestation implantation, however, the direct association between the C stock with species richness and the plant diversity index in the reforested areas was verified. Considering the C retention factor (CRF) equal to 1 for the native wood, the soybean, maize, sorghum and pasture cultivations markedly reduced C storage in the soil, which, in these areas, was around half of that measured in the wood area.