Testing watershed size and slope, soil C:N and carbon storage as indicators of riverine dissolved organic carbon concentration and export

Several predictors of riverine dissolved organic carbon export have been presented over the last decade. The relationship between dissolved organic carbon export and a) watershed size and slope, b) mean watershed carbon storage and c) mean biome soil C:N ratio have all had measurable success as predictors of riverine DOC export. We tested each of these major predictors within a cool temperate conifer biome in Nova Scotia and New Brunswick, Canada. Soil cores were taken from thirteen watersheds, and the organic and mineral soil horizons were analyzed for carbon and nitrogen. The number of soil cores taken from each watershed depended on the size of the watershed. We retrieved 12 cores from the smallest and 35 from the largest watersheds. Bulk density was calculated for each soil sample so that watershed carbon storage could be derived. Watershed area, forest cover, slope and altitude were also logged for each soil sample point. Watershed size ranged from 6.3 x 10³ ha to 1.25 x 10⁵ ha. Altitude from 88 to 1458 ft. Individual soil C:N ratios ranged from 16.5 to 48.9 in organic soil horizons and from 6.1 to 29.8 in mineral soil horizons. Dissolved organic carbon export for each of the watersheds was calculated and range between 29.9 and 123.5 kg DOC ha^-1 yr^-1. Ten watersheds were used to derive empirical relationships between DOC export and each of aforementioned major predictors of DOC export. The remaining three watersheds, not included in empirical modeling were used for testing each model.