The soil carbon cycle is commonly characterized by photosynthetic inputs of carbon by plants balanced by heterotrophic respiration of accumulated soil humic substances. The role of leaching in decomposition, transport, stabilization and loss of soil organic matter is rarely represented in conceptual or numerical models of belowground carbon cycling. This is despite the fact that leaching is known to be a dominant mechanism of transport and loss of numerous mineral and nutritive elements in humid forest soils. This study seeks to quantify (a) the fluxes and storage of dissolved organic carbon (DOC) in the soil and (b) the seasonal changes in the rate of carbon export to streams from two contrasting coastal California ecosystems. Water fluxes entering, moving through the soil, exiting at the channel head and in the stream networks will be monitored, while solution samples will be analyzed for carbon concentration, composition and age. We will couple this information on DOC fluxes to detailed analyses of the spatial distribution of soil carbon, its relative recalcitrance, age and turnover.
