2006 BES Annual Meeting Presentation and Poster Abstracts
Altered Hydrology & Vegetation: Effects on the Transport and Breakdown of Organic Matter in Urban Streams
Co-Authors: K. T. Belt, C. Swan, R. V. Pouyat, S. Kaushal, P. M. Groffman, I. Turcsanyi, W. P. Stack, G. T. Fisher
Abstract: A better understanding of how urbanization and trees interact to alter organic matter (OM) transport and cycling processes is needed to assess retention in catchments and streams. The influx of particulate and dissolved organic matter (POM/DOC) to natural headwater streams normally originates within or near riparian areas, and is important to aquatic food webs. Urban catchments, however, have large drainage densities (storm drains) that facilitate transport, creating an OM “gutter subsidy” to streams that likely dwarfs riparian input. In 8 Baltimore streams, DOC water concentrations and areal flux rates were dependent on flow rates, and were higher in urban catchments than in forested and agricultural reference sites, suggesting that urban infrastructure alters export rates. In-stream leaf breakdown rates in a suburban and a forested stream were measured using leaf litter from riparian American Sycamore (Platanus occidentalis) and its hybrid cross, London Planetree (Platanus acerifolia.) Breakdown rates in the suburban stream were generally faster than in the forested stream, and were faster for suburban/urban landscape litter than for riparian litter. Moreover, these rates were much faster than literature values for Platanaceae in forested streams, especially the urban litter. Urban landscapes not only seem to deliver more POM/DOC mass to streams, but have litter that breaks down quickly. High nutrient concentrations, faster litter breakdown rates, and substantially higher upland fluxes of organic matter in urban streams suggest that carbon exports downstream are substantial, with implications for heterotrophy, high dissolved oxygen demands and pollutant fate and transport.