Banca de DEFESA: YAN VIDAL DE FIGUEIREDO GOMES DINIZ

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : YAN VIDAL DE FIGUEIREDO GOMES DINIZ
DATE: 25/05/2022
TIME: 14:00
LOCAL: videoconferência
TITLE:

Effect of prescribed burning on chemical attributes and organic matter fractions of soils from an area of high-altitude grasslands, in the Itatiaia National Park, RJ.

KEY WORDS:

Forest fires. Atlantic Forest. Humic substances.

PAGES: 60
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

Forest fires can negatively affect ecosystems, depending on the frequency and intensity of fire, and studies are needed to understand the role played by fire in a given ecosystem and its impact on the soil. The hypothesis of this study is that prescribed burning, that is, the use of fire under controlled conditions, will have a limited impact on the chemical attributes and organic matter fractions of soils in the high-altitude fields environment in the Itatiaia National Park (PNI). The general objective of the study is to evaluate short- and medium-term effects of prescribed burning on soil chemical attributes and soil organic matter (SOM) fractions in the high-altitude grassland ecosystem. The prescribed burning has been evaluated in the PNI as a practice to reduce the amount of plant biomass on the surface and, in this way, to prevent the potential risk of severe forest fires, in the ecosystem of high-altitude fields and in Histosols, soils of greater vulnerability. It was conducted in 2019, in an experimental area of about 6 hectares in the upper part of the PNI. Soil samples were collected at three depths, 0-10, 10-20 and 20-40 cm, in 8 composite sampling points (3 samples for each point), in five different time periods: before the event, at 10, 30, 90 and 240 days after burning (DAB). As a physical attribute, the soil bulk density was analyzed; for the chemical attributes the following were evaluated: pH in water, sorption complex (Ca⁺², Mg⁺², Al⁺³, K⁺, Na⁺, H + Al), P (Mehlich -1), and the sum of bases (SB) and base saturation (V%) were calculated. Total carbon and nitrogen contents were quantified and carbon (estC) and nitrogen (estN) stocks were calculated. Regarding SOM and its fractions, total organic carbon (TOC); the humic fractions, which are humin (HUM), humic acids (HA) and fulvic acids (FA); and labile soil carbon (CL) were analyzed. For HA spectroscopic analysis, soil samples obtained before burning and at 10 and 240 DAB were used, being evaluated by means of FTIR and 13C NMR CP/MAS combined with chemometric analysis with principal component analysis. Management with prescribed burning modified the chemical characteristics of the soil and SOM fractions at all times after the event, with greater expression in the most superficial layer, where there is greater sensitivity to the effects of fire. Changes in the HA structures were observed at 10 DAB, but there was similarity in the average spectra from before burning and at 240 DAB, indicating the recovery and the importance of spectroscopic analysis via FTIR-ATR and ¹³C NMR via CP/MAS, to characterize the organic compounds in the HA. The prescribed burning management, after 240 days, indicated the structural recovery of HA, with little variation in the TOC content. In addition to an increase in P, Mg⁺², Na⁺ and SOM fractions, such as fulvic acid, humic acid and labile carbon. Although it is necessary to evaluate for a longer period of time and in other sites, in the area of high-altitude fields in the PNI, the results of the study, in the period of 240 days, indicate that the practice of prescribed burning can be recommended as a way of preventing large fires, without major negative effect on Histosols.

BANKING MEMBERS:
Externo à Instituição - ADEMIR FONTANA - EMBRAPA
Presidente - 387335 - LUCIA HELENA CUNHA DOS ANJOS
Interno - 1060711 - MARCOS GERVASIO PEREIRA