Quantily and quality of organic material in the soil in forest-pasture succession in Rondônia

• Grant number: 00/12189-0
• Support Opportunities: Regular Research Grants
• Start date: May 01, 2001
• End date: June 30, 2003
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• 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

The general objective of this research is to study the dynamic of organic matter of the soil (SOM) when typical tropical forest vegetation is replaced with pasture vegetation, from the quantitative and qualitative aspects. Parallel indicators, such as the mineralization of organic carbon (C) in aggregates, intact and after their destruction, and the chemical nature of the vegetal residues deposited will also be investigated. To attain this objective, it is intended to carry out the following specific goals: 1) to quantify the stocks of C and nitrogen (N) and evaluate the relative contribution of C derived from pasture in the different fractions of the SOM, based on the natural abundance of 13C; 2) to determine the alterations in the quality of SOM through the analysis of its different fractions with chemical and spectroscopic techniques; 3) to estimate the rates of deposition and decomposition of litter in the pasture; 4) to evaluate whether there is a difference in the quality of the vegetal residue (litter and roots) in the forest and in the pastures and what is the influence on the quality of the SOM; 5) to evaluate the existence of a possible physical protection mechanism for the organic matter in soil aggregates in the two ecosystems, through the determination of the inter- and intraaggregated “light fraction” and the mineralization of C with the incubation of intact and destroyed aggregates. An essential condition for the carrying out of this study will be the use of a chronosequence consisting of a forest and three pastures of different ages, in the same class of soil representative of the Amazon basin. (AU)