ÁCIDOS HÚMICOS DE SOLOS EM DIFERENTES FORMAÇÕES FLORESTAIS NA FLORESTA NACIONAL DE IRATI, PR

Abstract

This study aimed to identify the contribution of plantations of Araucaria angustifolia and Pinus elliottii with 50 years in the characteristics of humic acids of soils formed under Mixed Montane Ombrophyllous Forest in FLONA/PR. Forty subsamples were collected from soil that comprised a composite sample for each of the three forest types: Forest Montana (FOM), Plantation of Araucaria angustifolia and Pinus elliottii. Humic acids were extracted according to the methodology of Isolation of Humic Substances of Agricultural Chemistry Laboratory, University of Napoli, Italy, by Alessandro Piccolo. For the characterization of humic acids extracted from soil samples using three spectroscopic methods: Ultraviolet Visible Spectroscopy of Diffuse Reflectance (DRUV-Vis) Spectroscopy Fourier Transform Infrared (FTIR) Spectroscopy and Electron Paramagnetic Resonance (EPR). AH training Planting Pinus elliottii (PIN) at a depth of 0-20 cm, showed a higher value for E4/E6 ratio calculated from the spectra of DRUV-Vis and lower ratio of the intensities of the bands in 1720 and 1620 cm -1 in FTIR spectra, thus indicating lower molecular weight and lower condensation of aromatic carbons. In the analysis of EPR spectra of sample FOM at 0-20 cm depth showed signal for domains diluted Fe3+, g = 4.3, with greater intensity, suggesting the formation of humic acid has a higher iron content in areas thinned. For the formation of PIN (Pinus elliottii) spin density of the sample, unlike the other two formations, remained practically constant in the same way that carbon deep in the soil. Regarding the potential to sequester carbon in forest soils may indicate that a forest of Pinus elliottii 50 years has the potential to sequester carbon, because the formation of organic matter undergoing a slow decomposition process. So that soil humic acid remains longer in the process of humification and the carbon structures of humic acid likewise spend more time sequestered in soil. Although the plantations of Araucaria and Natural Forest present process of decomposition of organic matter more rapidly, the structures formed are more aromatic and condensed, making HA more resistant to other processes of microbial decomposition and its carbon. Thus it is necessary to study the management systems of forest soils for conservation of soil and humic substances to guarantee the permanence of carbon sequestered in soil and humic substances.