Document: WIL-3-99-136

Interactive effects of resources and herbivory on tree growth: Experimental tests using a native and an invasive exotic species.

ROGERS, W.E.* and E.SIEMANN

Rice University, Houston, TX 77005 USA ¹

Abstract:
The alien tree, Chinese tallow, Sapium sebiferum, is a major invader which threatens the biotic integrity of a variety of ecosystems throughout the southeastern United States. We conducted a pot experiment examining the interactive effects of three levels of light, three levels of nitrogen, and three levels of simulated herbivory on the growth of Chinese tallow and Hackberry, Celtis laevigata, a native tree species. As we predicted, Chinese tallow and Hackberry tree seedlings were able to thrive under a variety of light and nitrogen conditions, but Chinese tallow stem diameter and plant mass were significantly larger than Hackberry in all of the resource combinations. Our prediction that Chinese tallow would lack tolerance of leaf defoliation, despite being resistant to herbivory in the United States, was not supported. Like Hackberry, which is regularly damaged by folivorous herbivores, Chinese tallow showed significant tolerance and compensatory regrowth following leaf defoliation. Combined these findings suggest that Chinese tallow is an "herbivore tolerant" plant that is currently reaping the benefits of a "herbivore resistant" plant without the associated costs. Greater morphological and physiological plasticity coupled with a current release from top-down herbivore regulation likely account for the marked success of Chinese tallow as an invasive tree.

Keywords: Sapium sebiferum

This abstract is being presented at: 9:45 AM in session:
Oral Session #60: Forest Restoration.