PARENT SESSION
Poster Session #14: Plant Competition.
Tuesday, August 7, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
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Contrasting effects of neighboring vegetation on Ulmus rubra seedlings in successional grassland.
Ross, Adam1, Foster, Bryan1, Loving, Galen1, 1
ABSTRACT- In the absence of fire, woody plants readily invade grassland in eastern Kansas. However, rates of grassland conversion to woody plant dominance may be strongly influenced by resident herbaceous vegetation and resource availability. Using a plant-removal experiment, we examined effects of plant neighbors and water availability on growth and survivorship of elm (Ulmus rubra) seedlings in unburned successional grassland in eastern Kansas. Spring 2000, we located and marked 100 first-year elm seedlings that established naturally within the grassland site. We randomly assigned seedlings to a 2x2 factorial arrangement of treatments: two levels of plant neighbors (neighbors present; neighbors removed) and water availability (water added; water not added). To establish the removal treatments, all vegetation within a 20x20 cm area surrounding each of 50 target seedlings was removed. Seedlings receiving water were irrigated regularly throughout the growing season. Plant neighbors facilitated seedling survival in the un-watered treatments. That facilitation was mediated by neighbor amelioration of water stress was suggested by a lack of facilitation of survival in the water addition treatments. In contrast to what was observed for survival, neighbors suppressed growth of the surviving seedlings, both in the un-watered and watered treatments. The results indicate that grassland vegetation can have contrasting effects on the performance of invading tree seedlings depending upon the measure of performance considered and the level of drought stress in the habitat.
KEY WORDS: competition, facilitation, grassland, plant-removal experiment