Isotopic composition and carbon dioxide fluxes in an area of Cerrado (State Park of Vassununga, SP)

Author(s)

Jádson Dezincourt Dias

• Document type: Doctoral Thesis
• Press: Piracicaba. , ilustrações.
• Institution: Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB)
• Defense date: 2010-01-08

Examining board members

Plinio Barbosa de Camargo; Antonio Natal Gonçalves; Sergio Tadeu Meirelles; Jean Pierre Henry Balbaud Ometto; Edgard Siza Tribuzy

• Advisor: Plinio Barbosa de Camargo
• Field of knowledge: Biological Sciences - Ecology
• Indexed in: Banco de Dados Bibliográficos da USP-DEDALUS; Biblioteca Digital de Teses e Dissertações - USP
• Location: Universidade de São Paulo. Biblioteca do Centro de Energia Nuclear na Agricultura; (043) 11121; D541c

Abstract

The presente study was carreid out in area o Cerrado strictu senso located at the State Park of Vassununga, closed to the Santa Rita do Passa Quatro city, São Paulo State, Brazil. The aim was of the present work was to measure de CO2 fluxes released through respiration processes of the vegetation and soil (heterotrophic and autotrophic) to check the relative importance of each of these ecosystems components on the respiration of overall ecosystem using the isotopic approach. The Keeling plot line was used to determine the isotopic values of carbon dioxide respired by the ecosystem and its components (litter, dead wood, roots, leaves and branches). The results show that isotopic values of the carbon dioxide were significantly affected by seasonality, being more enriched in 13C during the wet period. The correlations among \'delta\'13C-CO2 values respired by the ecosystem components and the environmental factors such as humidity and temperature indicated a significant relation with the gas exchanges. The \'delta\'13C-CO2 values respired by the entire ecosystem were less enriched in 13C when there was high level of water in the soil. This \'delta\'13C-CO2 value was 25,26%o . Partitioning the ecosystem respiration below and above ground, the data show that 75% of the total respiration has its origin of belowground (roots + microorganisms). Partioning the autotrophic and heterotrophic respiration, 54% of the total respiration has its origin on the vegetation. Therefore, for these results, the plant water availability followed by precipitation were the most important factors that contributed to the variability of \'delta\'13C of organic carbon, \'delta\'13C-CO2 respired carbon and fixed by the ecosystem. The results found in the study are relevant to a better comprehension of the carbon cycle within the Cerrado biome, as well as, open an opportunity to utilize the isotopic approach to define \'delta\'13C-CO2 patterns respired by the entire ecological system, utilizing these results as indicators of gas exchange alterations in the global change scenario (AU)

• FAPESP's process: 06/56863-3 - Isotopic composition in the fluxes of CO2 in the cerrado area (Vassununga State Park)
• Grantee: Jadson Dezincourt Dias
• Support Opportunities: Scholarships in Brazil - Doctorate