Ecological implications of allelopathic interferences with reference to Phragmites australis

The effects of plant invasions on ecosystem structure and function are well studied but the pathways and mechanisms that underlie these effects remain poorly understood. In depth investigation of invasion mechanisms is vital to understanding why invasive plants impact only certain systems, and why only some invaders have disproportionately large impacts on the invaded community. There are many mechanisms such as lack of natural enemies or control mechanisms, the individual characteristics of the invader and invaded communities, direct and indirect resource competition, evolution or hybridisation, altered ecosystems processes, and allelopathy that may explain the invasion processes of plant species. Among these possible influences on invasion, allelopathy has received increased attention and study with the rise in understanding of its implications and potential disproportionate influence. However, identifying allelopathy and consequent phytotoxic effects as an important mechanism of plant invasion is a difficult task due to the potential for an individual plant to have many component chemicals with multiple modes of action, interactive effects, and synergistic interactions. For allelopathy to be implicated as a mechanism that facilitates invasion, multiple aspects of the plant species allelopathic properties must be examined. This research investigated allelopathy as a mechanism of the invasion process in Phragmites australis by a series of ecologically realistic experiments in the laboratory, greenhouse and field