PARENT SESSION
Oral Session # 87: Riparian Ecology II: Landuse, Diversity, Structure, and Function.
Presiding: M Stevens
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 205.

Stream ecosystem structure and function at multiple scales: Effects of land use and impervious surface.

Nelson, Karen^*,1, Palmer, Margaret¹, Hassett, Brooke¹, ¹ University of Maryland, College Park, MD, karen-nelson@erols.com

ABSTRACT- An important issue in both theoretical and applied ecology is understanding the scale at which landscape processes affect ecological response. In this talk we examine the impacts of land use change on stream ecosystem structure (concentrations of nitrate, ammonia, and phosphate) and function (uptake velocity of ammonia and phosphate). We identify 3 possible scales of impact - whole watershed, riparian corridor, and in-stream features - and determine their relative importance. Our dataset includes measurements of nutrient concentrations (4 seasons per site) and uptake (1 measurement per site), as well as extensive in-stream habitat and GIS-based land use information, at 71 sites arranged hierarchically within 4 watersheds in Maryland, USA. We found that concentrations responded most to land use, less so to riparian status, and least to in-stream features, suggesting that nutrient loading rather than uptake is the dominant factor determining concentrations. In addition we found that impervious surface and residential/commercial land use were associated with lowered nutrient concentrations, probably due to decreased agricultural nutrient inputs and/or availability of metals to which nutrients may adsorb. Uptake velocities had lower association with land use, and higher associations with in-stream features, particularly the presence of fine sediment.

Key words: land use change, nutrient spiralling, impervious surface, scale