Options for Soil Organic Matter Fractionation in Tropical Soils

Soil organic matter (SOM) plays an important role in maintaining the productivity of tropical soils. An estimated 70% of the terrestrial C stocks that participate in the atmospheric C cycle are stored in soil organic matter. Since SOM exists in a wide diversity of forms with considerable variability in decomposition rates, fractions of SOM that reflect management effects deserve particular attention because they predict trends in soil productivity. Fractions that are more sensitiveto management and land-use changes than total C can serve as early indicators of potential decline in soil organic matter, soil productivity and net emissions of CO2. Several fractions of SOM have been identified and characterized with varying sensitivities to changes in management and land-use. In this review, we examine the contemporary knowledge on the more common SOM fractions in tropical ecosystems.