PARENT SESSION
Poster Session #15: Vegetation Analysis.
Tuesday, August 7, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Multivariate analysis of floodplain oak savanna community composition.

Tushenski, Nicole¹, Meisel, Jennifer¹, Weiher, Evan¹, ¹

ABSTRACT- Floodplain oak savanna communities are a threatened vegetation type (e.g., Quercus macrocarpa - Andropogon gerardii communities are listed as G1) but little is known about their understory vegetation. With help of the DNR, we located several areas of floodplain oak savanna along the Chippewa River in western Wisconsin. The chosen sites vary from 10% to 80% tree canopy cover (Quercus macropcarpa and Q. ellipsoidalis). 168 quadrats (0.25 m²) from 10 sites sampled a range of fire frequencies, soil qualities, tree canopies, elevations, and distances from the river. We used indirect gradient analysis with both DCA and NMDS of understory vegetation. The results from DCA showed stronger correlations with environmental factors than NMDS, but the overall patterns were consistent. Disturbance by fire, soil moisture, light availability, tree canopy, and soil quality were all significantly correlated with ordination scores. In a nutshell, Andropogon gerardii dominated a core community type, and the communities graded into (1) Schizachyrium - Koeleria sand barrens (if very sandy) (2) Sorghastrum - Solidago mesic prairie (if low soil P) (3) Solidago / Carex / Spartina / Cornus savanna complex (if richer soil & frequently burned), and (4) Solidago gigantea / Carex / Teucrium savanna (if richer soil & greater canopy). The next step is to use Structural Equation Modeling to untangle the multiple dependencies among the variables.

KEY WORDS: gradient, fire, floodplain, savanna