PARENT SESSION
Poster Session #57: Invasive Species Ecology: Grasslands.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC
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Effects of dominance and diversity on invasibility of a C4-dominated grassland.
Smith, Melinda*,1, Wilcox, Julia1, Kelly, Theresa1, Knapp, Alan1, 1 Division of Biology, Manhattan, Kansas
ABSTRACT- Although there is evidence for species diversity positively influencing invasibility of ecosystems, diversity and invasion can covary with extrinsic factors, such as disturbance or community productivity. We examined how native plant diversity and dominance influence invasion by adding seeds of an invasive legume, Melilotus officinalis, to grassland plots (Konza Prairie, Kansas) over a two-yr period (2000-1). The grassland plots either varied 1) naturally in species richness and dominance (cover of C4 grasses) due to differences in disturbance and productivity, or 2) experimentally in native richness and dominance as a result of permanent removal of rare and uncommon species or reductions in abundance of dominant grasses. This allowed us to examine the importance of community characteristics vs. extrinsic factors in influencing invasibility in this grassland. Invasibility was quantified as the establishment, survival and growth of Melilotus seedlings in each plot. Establishment and survivorship of Melilotus seedlings was not influenced (P>0.05) by natural patterns of diversity or by a 3-fold decline in richness in the experimental plots. In contrast, dominance by C4 grasses strongly influenced establishment, survivorship and growth of the Melilotus seedlings. For example, establishment was positively related (r2=0.24, P<0.001) and survivorship was negatively related to density of C4 grasses (r2=0.16, P<0.001). These results suggest that extrinsic factors that enhance dominance by C4 grasses and indirectly reduce native diversity likely play a key role in influencing invasibility of this grassland ecosystem.
KEY WORDS: grassland, invasibility, invasion, seedling establishment