River nutrient uptake and transport across extremes in channel form and drainage characteristics.

摘要

The overarching goal of this dissertation is to understand how ecosystem form and landscape setting dictate aquatic biogeochemical functioning and elemental transport through rivers. An emphasis is placed on understanding how wetland ecosystems influence river nutrient deliveries. Following an overview (chapter 1), I address the above goal by examining: aquatic nutrient retention in a comparative study of stream and flow-through wetland ecosystems of northern Wisconsin (chapter 2); net fluxes of inorganic and organic solutes through a mature (>100 year old) reservoir-wetland in agricultural southern Wisconsin, which was subjected to a dam removal manipulation (chapter 3); the central tendency and variability of long-term river mass export from contrasting catchments throughout the state, which spanned large gradients of terrestrial and aquatic composition (chapter 4). A synthesis of the dissertation, with particular attention to the spatial and temporal scales of study, is contained in chapter 5. Results emphasize that differences in the biogeochemical functioning of lotic vs. lentic ecosystems are linked to differences in both placement and strength of hydrologic connections.