The zonation of riparian vegetation on the Konza Prairie Natural Area of Kansas (tallgrass prairie ecosystem) provided a situation where the influences on uptake rates of the different DOC qualities could be measured in the field. Leachates from grasses disappeared rapidly from stream water in in situ chambers at upstream sites in grassland reaches and at downstream sites in forested reaches. The reverse observation, uptake of leachates from trees, revealed that DOC disappeared rapidly from chambers placed in the forested reaches but bacteria in the grassland reaches did not utilize tree leachate as rapidly. The pattern varies seasonally. The interpretation of these observations was aided by aseptic laboratory culture on the different substrate types and by measurements in poisoned chambers to evaluate abiotic uptake