PARENT SESSION
Poster Session #26: Soil Ecology I.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Ecotones and gradients as determinants of Darlingtonia fen community structure: The roles of fire and soil and water nitrogen (NH₄ and NO₃).

Tolman, Deborah^*,1, ¹ Portland State University, Portland, OR

ABSTRACT- The Darlingtonia fens of southern Oregon and northern California, found only in serpentine soil ecosystems, are distinct communities that frequently undergo dramatic changes in size and shape. These changes occur in response to a wide array of environmental factors. This study analyzes the effects of a soil and water nitrogen (NH₄ and NO₃) gradient and the periodic disturbance of fire on the structure of fen communities in southern Oregon using canonical coorespondence analysis (CCA). As part of a more comprehensive analysis of succession in these communities, CCA is used to examine the role of soil and water nitrogen in the maintenance of community boundaries. Transects were established at three study sites with different fire histories. Each transect, oriented perpendicular to community boundaries and to the main environmental gradient, contained at least twelve soil and twelve vegetation sample plots, and was replicated six times at each site. Results of the analysis indicate that the availability of both NH₄ and NO₃ significantly and independently determine the distribution of individual plant species in these systems.

KEY WORDS: ecotones, gradients, Darlingtonia, nitrogen