Measurements of concentration of Mg, K, Ca, Na, dissolved organic carbon (DOC) and total N were made on the soluble fraction of leaves decomposing on the floodplain of a prairie stream. Differences in the concentrations of these nutrients were dependent on the species of leaf material and location on the floodplain. Leaves placed in the grassland reach of the stream had lower concentrations of soluble nutrients than leaves placed in the gallery forest. Correlations between concentration of leachable nutrients and cumulative precipitation or DOC were both positive and negative. Species differed in rank order of the nutrient concentration in leachates of their leaves. Bluestem and sycamore leaf leachate concentrations were low, whereas hackberry, elm and bur oak leaf leachate concentrations were relatively high. INTRODUCTION The import of dissolved organic carbon into streams depends on season and weather conditions. Autumn leaf fall provides direct import of leaves to the stream and soluble fractions are leached. McDowell and Fisher (1976) suggested that leaf fall into streams in eastern deciduous forests significantly increases the dissolved organic load. Accumulations of leaf litter in and along the channels of intermittent streams may be a significant source of the concentrated soluble carbon observed during the ascending limb of hydrographs (Gurtz et al., 1982). Imports of soluble nutrients into streams from the floodplain during rainstorms or snowmelt probably contribute higher concentrations for longer durations (McArthur et al., 1985a). Changes in leaf litter nutrient concentrations associated with forested watersheds have been observed during decomposition (Cronan, 1980; Fogel and Cromack, 1977; Gosz et al., 1973; Lang and Forman, 1978; Likens et al., 1967; Witkamp, 1966). Other researchers (Buldgen, 1982; Buldgen and Remacle, 1981; Howard and Howard, 1980; Witkamp and Frank, 1970) followed nutrient changes in decomposing forest litter in response to experimentally introduced environmental changes (e.g, temperature, rainfall). Leachates from these sources are known to be a source of nutrient input to soil water. While soil water may eventually find its way into streams, the nutrients associated with soil water are used by soil microbes and plants or are retained in the soil. Even so, Wallis (1981) showed that stream microbial communities effectively remove significant amounts of dissolved organic carbon from soil water after it reaches the stream. However, during periods of extensive rainfall, or snowmelt, leachate from leaf litter would be directly imported to the stream. This import of dissolved nutrients (organic and inorganic) would not be subjected to soil microbial processing and might be of different quality. Microbial response to substrates is related to the quality of the material. We know that such variability occurs, but we are less certain about which qualities of the substrate drive microbial responses, or by what mechanism the variations are controlled. The observations that we report here document some sources of such variability (watershed vegetation, decomposition, floodplain condition, precipitation patterns). Since the nutrient composition of leaf material changes as it decomposes, we desired