The potential role of allelochemical compounds in altering of interspecific and intraspecific competitive effects in Ailanthus altissima and Robinia pseudoacacia.
Hanna, Alyssa*,1, McGraw, James1, 1 West Virginia University, Morgantown, WV
ABSTRACT- In the U.S. Ailanthus altissima (Tree-of-Heaven) is an aggressive, invasive plant that forms dense monotypic stands, reducing biodiversity in the areas it invades. Currently, researchers hypothesize that A. altissima out competes surrounding native species for resources and may utilize mechanisms such as allelopathy to aid this process. Previous research suggests leaf, root, and bark extracts contain quassinoids, including ailanthones, which prevent or inhibit germination and growth of commonly used bioassay species. Little is known about the effects of such compounds in realistic concentrations in natural soil environments. In this study, a short-term competition experiment was performed with Ailanthus altissima and Robinia pseudoacacia (Black Locust.) We varied both frequency and density in pots, and added activated carbon to half of the pots in each treatment to determine whether the outcome of competition would be altered by the absorption of exudates released by A. altissima into the soil. With soil carbon, the additive effect of A. altissima was to increase R. pseudoacacia biomass, while in the absence of carbon the opposite trend was observed (2-way ANOVA, competitor x soil type interaction, p=0.0528). There was a significant stimulation of A. altissima biomass (p<0.0001) and height (p=0.0004) in soils with activated carbon, indicating possible autotoxicity. Relative crowding coefficients and relative yield totals also varied between soil carbon treatments suggesting possible allelochemical effects. As with other soil carbon studies, in this short-term experiment it appears the competitive outcome may be modified by exudates produced by the invasive.
Key words: invasive plants, allelopathy, Ailanthus altissima
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