Journal of Conference Abstracts

A Comparison of Nitrogen Storage in Terrestrial and Wetland Vegetation: Implications for Watershed N-Cycling

Joseph M. Bischoff¹ (jmbisc01@homer.louisville.edu),
Paul Bukaveckas¹ (pabuka01@ulkyvm.louisville.edu) & Myron Mitchell² (mitchell@mailbox.syr.edu)

¹ University of Louisville, Dept. of Biology, Louisville, Kentucky 40292, U.S.A.

² SUNY-ESF, Faculty of Environmental and Forest Biology, Syracuse, New York 13210, U.S.A.

Wetlands, until recently, have not been considered an important factor in controlling catchment-scale (watershed-level) nitrogen cycling. Two important sinks for nitrogen in wetlands are plant assimilation and denitrification. The objectives of this study were to compare the storage of nitrogen in wetland and terrestrial vegetation in a subcatchment of the Arbutus Lake watershed (Adirondack Park, NY). The Arbutus Lake watershed is 134.75 ha and is approximately 4 % wetlands. Vegetation data were collected from a representative wetland (peatland) ecotone and compared to terrestrial vegetation data collected as part of the Integrated Forest Study (IFS). IFS data were collected from plots on the Huntington Wildlife Forest in close proximity to the Arbutus Lake watershed. Monthly vegetation samples were collected using square meter plots for herbaceous vegetation and litter traps for foliar inputs. Tree and Alder biomass was estimated using diameter at breast height allometric equations. Total nitrogen content in plant tissues and peat was measured using a Perkin Elmer CHN analyser. The vegetational compartment included N storage in tree and herbaceous biomass, as well as the organic horizon of the soil (terrestrial) or upper 1.4 m of peat (wetland). Herbaceous production in the wetland was dominated by Sphagnum spp. ( 60 % of herbaceous production) followed by a variety of grasses, Rubus hispidus, Dennstaedtia punctilobula, Osmunda cinnamomea, and Phegopteris connectilis. Woody production was dominated by Alnus incana followed by Picea spp. Total organic nitrogen stored in terrestrial vegetation excluding the soil compartment was 392 kg ha^-1; whereas, storage in the wetland vegetational compartment (excluding soil) was 251 kg/ha. Terrestrial soil (organic layer) and root storage was 1,217 kg ha^-1 whereas wetland soil and root storage was 29,725 kg ha^-1. Total nitrogen in terrestrial vegetation and soil was 208,124 kg; total nitrogen in wetland vegetation and peat was 161,570 kg. Although the wetland represented only 4 % of the watershed, it accounted for 44 % of the stored nitrogen.

Riparian Zone Hydrology as the Control of DOC in Runoff from a Forested Catchment in Northern Sweden

Kevin Bishop (Kevin.Bishop@sek.slu.se) & S. Köhler (Stephan.Kohler@sek.slu.se)

Department of Forest Ecology, University of Forestry, 90183 Umeå, Sweden.

Dissolved organic carbon (DOC) is of decisive importance for the quality of many surface waters in boreal zones. The ability to understand how climate change, land use and other anthropogenic factors affect DOC requires an understanding of what controls DOC concentrations in runoff. This paper uses observations of soil solution, hydraulic potential, and soil moisture from three soil profiles along a hillslope transect adjacent to a stream to test the hypothesis that changes in flow pathways on the order of 5 to 15 vertical centimeters (and the soil water intersected by these flow pathways) explain large fluctuations in runoff DOC. During the snow free period, the amount and character of DOC at most observation points in the hillslope remained stable, despite large fluctuations in runoff DOC. During one episode, DOC in runoff increased from 9 mg L^-1 to 24 mg L^-1, at the same time as more superficial flow paths with higher DOC concentrations became active.

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