HR: 11:15h
AN: NB22F-04    [Abstracts]
TI: Effects of Urbanization on Allochthonous Inputs to Small Puget Sound Lowland Streams
AU: * Roberts, M L
EM: mindyr@u.washington.edu
AF: University of Washington, Center for Water and Watershed Studies Box 352700, Seattle, WA 98195-2700 United States
AB: Urbanization produces fundamental changes to abiotic and biotic functions in streams, with shifts affecting everything from flow regimes to benthic communities. However, development patterns are manifested in changes to riparian vegetation communities as well, and these changes alter the sources and fate of organic matter in streams. This ongoing study in the Puget Sound Lowlands evaluates the influences of urbanization on allochthonous inputs to small streams. The study area includes 16 litterfall sites with riparian vegetation composition spanning the disturbance spectrum. Vegetation types include minimally altered conifer and mixed forests (western hemlock, big leaf maple, red alder), deciduous (red alder), landscape trees associated with residential development, and minimal forest cover with prevalent invasive species. While conifer/mixed and red alder forests produce similar peak litterfall rates, as much as 10 g m^-2d^-1, red alder litter contains more nitrogen, resulting in higher nitrogen loads to streams. Short-term laboratory leaching studies indicate that red alder leaves lose 25% of their mass within 24 hours, as compared with 1% for conifer materials. Highly disturbed areas with little or no riparian vegetation produce low allochthonous inputs (peak 0.1 g m^-2d^-1); grass clippings, for example, do not compensate for the loss of tree cover.
DE: 1803 Anthropogenic effects
DE: 1851 Plant ecology
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly