Gas diffusivity and production of CO2 in deep soils of the eastern Amazon

Abstract

The rate of gaseous diffusion in soils affects the exchange of gases between the soil and the atmosphere, thereby affecting rates of soil respiration and other soil microbial processes. In a study of sources of CO2 in deep soils of forests and pastures of the eastern Amazon, we estimated gaseous diffusivity from bulk density and volumetric water content using published equations that assume the soil to be either an aggregated or nonaggregated medium. About 70-80% of the measured CO2 flux from the soil surface was produced in the top 1 m of soil (including litter in the forest). The 20-30% produced below 1 m results from root respiration and microbial decay of root inputs at depth, indicating that deep soil processes are a non-trivial component of carbon cycling in these deep-rooting ecosystems. -from Authors