Document: JOS-3-38-18

Plant invasions are reduced by abundance of native perennial bunchgrass.

FARGIONE, J.* and D.TILMAN

University of Minnesota, St. Paul, MN, USA ¹

Abstract:
An experimental gradient of the native perennial bunchgrass Schizachyrium scoparium was created via seed addition to a newly abandoned agricultural field using a regression design. Natural invasions were allowed to proceed for six years. The experimental gradient of S. scoparium abundance decreased plant species richness from 10 species per 0.5 m² to 3 species per .5 m². At the peak of its growing season, S. scoparium reduced available soil nitrogen in the top 10 cm of soil from 0.461 mg/kg to 0.118 mg/kg, a reduction of almost 75%. This is consistent with resource competition as a mechanism influencing invasion success. Invader species included species that were only able to invade at low seeded densities of S. scoparium; these species may coexist via a competition-colonization trade-off. Other invader species were cold season species that were able to invade across seed densities; these species may coexist via phenological complementarity. In addition, the effect of S. scoparium on available soil nitrogen was stronger at the depth of 0-10 cm than it was at 10-20 cm, suggesting the possibility of resource partitioning along this vertical gradient.

Keywords: Invasions, Competition, Coexistence

This abstract is being presented at: 11:15 AM in session:
Oral Session #72: Plant Competition.