Mechanisms underlying the impacts of exotic plant invasions

Abstract

Although the impacts of exotic plant invasions on community structure and ecosystem processes are well appreciated, the pathways or mechanisms that underlie these impacts are poorly understood. Better exploration of these processes is essential to understanding why exotic plants impact only certain systems, and why only some invaders have large impacts. Here, we review over 150 studies to evaluate the mechanisms underlying the impacts of exotic plant invasions on plant and animal community structure, nutrient cycling, hydrology and fire regimes. We find that, while numerous studies have examined the impacts of invasions on plant diversity and composition, less than 5% test whether these effects arise through competition, allelopathy, alteration of ecosystem variables or other processes. Nonetheless, competition was often hypothesized, and nearly all studies competing native and alien plants against each other found strong competitive effects of exotic species. In contrast to studies of the impacts on plant community structure and higher trophic levels, research examining impacts on nitrogen cycling, hydrology and fire regimes is generally highly mechanistic, often motivated by specific invader traits. We encourage future studies that link impacts on community structure to ecosystem processes, and relate the controls over invasibility to the controls over impact.

Ecological Impacts of Genetically Modified Crops: Ten Years of Field Research and Commercial Cultivation

“…Invasions have been recognized in a growing number of environments as being serious threats to the preservation of what we choose (by our choice of time scale) to be regarded as native fauna and flora [118][119][120]. Although the great majority of accidental introductions undoubtedly failed to become established, a substantial number became established, and some of these became serious pests [121].…”

“…They are only of minor importance globally with regard to invasive weed problems especially compared to other plant groups [129]. Globally, the feral plants that cause much of the economic damage are imported horticultural plants [118][119][120]. Unlike annual crops, these horticultural plants are mostly perennials that have extensive sexual and asexual reproduction.…”

How to Achieve Effectiveness in Problem-Oriented Landscape Research: The Example of Research on Biotic Invasions

“…It also became evident that the presence of invasive species can have a strong influence on the functioning of the invaded ecosystem (Levine et al, 2003;Vitousek, 1990), and in particular that in some cases invasive species change habitat conditions in a way that facilitate further invasions (Simberloff, 2006).…”

“…Drake et al, 1989;Vitousek et al, 1987). However, only recently have frameworks for a more systematic research on impacts been suggested (Levine et al, 2003;Parker et al, 1999;Vitousek, 1990). Invasive species have been shown to substantially change ecosystem processes such as nutrient cycling, fire and other disturbances regimes, or hydrology (Levine et al, 2003;Mack et al, 2000).…”

Studying the patterns of alien and native floras of some habitats in Srinagar city, Kashmir, India

“…A recent crosscontinental comparison revealed that invasive plants significantly reduce native plant diversity in non-native habitats but not at home (Shah et al 2014). The invasive species can do so through many mechanisms (Levine et al, 2003), and the role of urbanisation-driven changes in ecological settings to influence such mechanisms is yet poorly understood.…”