Vulnerability of organic matter in the soil to temperature increase

• Grant number: 05/59585-1
• Support Opportunities: Regular Research Grants
• Start date: April 01, 2006
• End date: September 30, 2008
• Field of knowledge: Biological Sciences - Ecology - Ecosystems Ecology
• Principal Investigator: Carlos Clemente Cerri
• Grantee: Carlos Clemente Cerri
• Host Institution: Centro de Energia Nuclear na Agricultura (CENA). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

During the process of decomposition of organic matter in the soil (OMS) greenhouse effect gases are formed which are released into the atmosphere, contributing to global warming. It is believed that this global warming may affect retroactively the rate of decomposition of the OMS potentiating the release of carbon (C) from the soil and the mineralization of nitrogen (N). The OMS is compartmentalized in fractions with different sensitivities to temperature. Earlier research has suggested that the oldest fraction of AC is more recalcitrant and less sensitive to temperature. In addition to this, some mechanisms of physical, chemical and biochemical protection may act to reduce the sensitivity of the OMS to the increase in temperature. Possible modifications in the structure of the microbiological community, caused by the increase in temperature, may interfere in the process of decomposition of the OMS by means of alterations in its protection mechanisms. And the conversion of the original (forest) vegetation into pasture promotes modification in the ground, enabling an indication of what is the origin and quantity of C released in the form of CO2. With the objective of evaluating the dynamic of the decomposition of the OMS wewill carry out incubations (for 660 days) of clay and sandy soils, under forest and pasture, at three temperatures: 25°, 35° and 45°C. We will evaluate the relationship between the texture x OMS, the origin of the C released, the sensitivity of the labile-C x recalcitrant-C and how the possible alterations to the protection mechanisms of the OMS may contribute to the release of CO2 into the atmosphere and in the rate of mineralization of N. (AU)