ABSTRACT
Soil organic carbon (SOC) affects plant available nutrients and water holding capacity of soils in natural and managed ecosystems and its dynamics influence the environment quality. Several studies have been conducted to evaluate the extent and rate of decrease of SOC and nitrogen contents of the surface layer caused by the conversion of native ecosystems, such as forests to crop and pasture systems. The chapter aims to study SOC dynamics under different land use systems in the acid soil of the Colombian savannas. More specifically, field experiments were conducted to evaluate the relative distribution of SOC in different aggregate size fractions in relation to natural ecosytems and improved pastures. The results show a decrease in total SOC with cultivation. Land management altered the pattern of residue input and affected SOC in both cultivated and grazed land. Cultivation induced a lower equilibrium level of SOC, partly because reduced biomass input and removal of biomass.
