Skogen, Krissa A. , Holsinger, Kent E. , Cardon, Zoe G. .
Does atmospheric nitrogen deposition contribute to the decline of a native nitrogen-fixing species, Desmodium cuspidatum?
Nitrogen (N) deposition is one of three anthropogenic factors most likely to cause biodiversity changes in the future. Increased N deposition may have an especially large impact on temperate forests, which are highly N limited and occur in regions with the highest levels of atmospheric N deposition. Legumes growing in temperate forests may be especially sensitive. N2-fixing plants, including legumes, often have a competitive advantage in areas of N limitation, but they may be outcompeted by other species when N deposition increases. The influence of N fertilization on agricultural species and on community-level properties has been extensively documented, but only recently have plant conservationists begun to consider the possible role of N deposition in species declines. This project investigates whether N deposition in the northeastern United States has contributed to the loss of a N2-fixing species, Desmodium cuspidatum (Fabaceae). Desmodium cuspidatum disappeared from suitable habitat in New England in the last 30-40 years. A greenhouse experiment tested whether D. cuspidatum competition with Solidago sp. is influenced by levels of applied N. To control for density effects, plants were grown alone, with another D. cuspidatum, or with Solidago sp. Five N treatments – no N, three simulated N deposition rates, and half-strength Hoagland’s solution - were applied weekly for 10 weeks. Measures of plant size were collected weekly. At harvest, aboveground and belowground biomass, number of nodules and delta 15N stable isotope ratios were measured. Delta 15N signatures identify the source of N used by each plant. The relationship between applied N, nodulation, and delta 15N and the implications of these results for D. cuspidatum population dynamics will be discussed.
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1 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
2 - University of Connecticut, Ecology & Evolutionary Biology, Ecology and Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lake Ontario/Hilton
Date: Monday, July 9th, 2007
Time: 11:00 AM