Contrasting Effects of Allelochemicals from Two Invasive Plants on the Performance of a Nonmycorrhizal Plant

Abstract

In addition to resource competition, allelopathy is believed to contribute to the invasiveness and impact of several plant invaders of North America. In this study, we examined whether aqueous leaf extracts of Alliaria petiolata and Lonicera maackii, two invaders of deciduous forests in North America, affected growth and reproduction of a target nonmycorrhizal plant and whether effects varied across a soil fertility gradient. While nutrient addition substantially improved the performance of Arabidopsis thaliana grown in field soils in pots in a growth room, addition of A. petiolata extracts to these soils had no significant independent or interactive effects on growth or reproduction. In contrast, addition of L. maackii extracts both directly reduced growth and reproduction of A. thaliana and greatly constrained increases in growth and reproduction of A. thaliana in response to increasing nutrient availability. Use of a nonmycorrhizal target plant revealed that effects of L. maackii were independent of allelopathic effects on mycorrhizae, an effect attributed to A. petiolata in other studies.

Experimental Light Treatments Affect Invasion Success and the Impact of Microstegium vimineum on the Resident Community

“…There were strong allelopathic effects of L. maackii leaf extracts on germination, growth, resource allocation pattern, and mycorrhizal inoculation. Other studies have found allelopathic effects of Lonicera maackii on germination (Dorning and Cipollini 2006;Cipollini, Titus, and Wagner 2012;Cipollini and Flint 2013) and growth (Cipollini, Stevenson, and Cipollini 2008). McEwan et al (2010) similarly found stronger allelopathic effects of extracts of L. maackii compared to extracts of native species and also found that the effects varied with target species.…”

The Sign and Strength of Plant-Soil Feedback for the Invasive Shrub, Lonicera maackii, Varies in Different Soils

“…Plants in introduced habitats may also profit from "enhanced mutualisms"; beneficial microbial allies or mutualists that they have not encountered in their native regions [13,14]. Plants can also affect the presence of nutrient cycling microbes which in turn can create positive feedback mediated by effects on nutrient cycling [3,[15][16][17][18]. The tendency for plant soil feedbacks to be positive in introduced habitats (versus negative in native habitats) may be partly responsible for nonnative plants becoming invasive in introduced areas [4,19,20].…”

“…Phenolic compounds, as a group, are known to play a role in plant-soil interactions through allelopathic effects on plants and soil microbes, as well as through effects on soil pH and mineral availability [4,18,[21][22][23]. A species in its introduced range may use such biochemical weapons to inhibit neighbors directly or disturb other ecosystem properties giving the invader some advantage.…”

“…These same weapons may be ineffective against neighbors in its native range, which are adapted to cope with such allelochemicals [22][23][24][25][26][27][28]. Phenolic-containing extracts of the invasive shrub, Lonicera maackii, for example, can inhibit seed germination, delay plant development, and inhibit plant responses to enhanced nutrient availability [18,[24][25][26].…”

“…Maxim (Amur honeysuckle: Caprifoliaceae), hereafter referred to as Lonicera, is a nonnative invasive deciduous shrub found throughout much of the midwestern and Eastern United States. This shrub negatively affects individual plants and plant communities through such mechanisms as competition for light and soil resources and allelopathy [17,18,26,[28][29][30]. The potential role of plant-soil feedbacks in its invasive success has never been examined.…”