Invasive plant species impact both ecosystems and economies worldwide, often by displacing native biota. Many plant species exude/emit compounds into the surrounding environment with minor consequences in their native habitat due to a long coevolutionary history. However, upon introduction to ecosystems naïve to these compounds, unpredictable interactions can manifest. The majority of the putative allelochemicals studied have been root exudates, despite the large number of plant species that emit volatile organic compounds. We quantified the concentrations and ecological consequences of volatile monoterpenes from the North American invasive perennial Artemisiavulgaris. Ambient monoterpene-mixing ratios inside an A.vulgaris canopy were 0.02–4.15 ppbv in May and 0.01–0.05 ppbv in August, but were negligible (below instrument detection limit of 0.01 ppbv) 10 m away. Foliar disturbance increased total monoterpene concentration to a maximum of 27 ppbv. However, this level remains 1,000-fold lower than that shown to be phytotoxic to sensitive species in laboratory assays. In contrast, soil monoterpene concentrations were >74-fold higher inside [≤35 ± 11 ng g−1 (SDW)] and 19-fold higher at the edge [9 ± 3 ng g−1 (SDW)], compared to outside the A.vulgaris stand [0.48 ± 0.05 ng g−1 (SDW)]. A common native competitor species, Solidagocanadensis, grown in pots and resident soil in situ yielded up to 50% less aboveground biomass inside as compared to outside the A.vulgaris stand. Activated carbon had no effect on greenhouse-grown S.canadensis performance when grown with A.vulgaris, suggesting root-derived exudates are not responsible for field observations. Results from this study suggest that A.vulgaris-derived monoterpenes have little direct activity in their volatile gaseous state, but are concentrated in the soil matrix within and bordering the A.vulgaris stand, thereby reducing interspecific performance and potentially fostering the subsequent local invasion of this species.
Abrahim D, Braguini WL, Kelmer-Bracht AM et al (2000) Effects of four monoterpenes on germination, primary root growth, and mitochondrial respiration of maize. J Chem Ecol 26:611–624. doi:10.1023/A:1005467903297CrossRefGoogle Scholar
Barney JN, Whitlow TH, DiTommaso A (2008) Evolution of an invasive phenotype: shift to belowground dominance and enhanced competitive ability in the introduced range. Plant Ecol . doi:10.1007/s11258-008-9481-3Google Scholar
Kovacevic N, Pavlovic M, Menkovic N et al (2002) Composition of the essential oil from roots and rhizomes of Valerianapancicii Halácsy & Bald. Flavour Fragr J 17:355–357. doi:10.1002/ffj.1100CrossRefGoogle Scholar
Siemens TJ, Blossey B (2007) An evaluation of mechanisms preventing growth and survival of two native species in invasive Bohemian knotweed (Fallopia × bohemica, Polygonaceae). Am J Bot 94:776–783. doi:10.3732/ajb.94.5.776CrossRefGoogle Scholar
Yun KW, Kil B-S, Han DM (1993) Phytotoxic and antimicrobial activity of volatile constituents of Artemisiaprinceps var. orientalis. J Chem Ecol 19:2757–2766. doi:10.1007/BF00980705CrossRefGoogle Scholar