Consequences of the Physical Management of an Invasive Alien Plant for Riparian Plant Species Richness and Diversity

Abstract

Management methods to control or eradicate invasive alien species should be guided by research into their efficacy in relation to the target species as well as their wider effects on the community. Impatiens glandulifera Royle (Balsaminaceae) is an invasive alien species, which has spread rapidly across Europe and North America, particularly colonizing riverbanks, wet woodlands, and wastelands. The effectiveness of two mechanical control measures and their impacts on community plant species richness and diversity within the riparian zone of the urban river Brent, London, England, was assessed. Over 2 years, an experiment was performed across three sites that exhibited contrasting levels of invasion of I. glandulifera: high, moderate and low. The experiment involved three treatments on replicated plots at all three sites: pruning at 6‐week intervals, weeding at 6‐week intervals, and a control. The effects of these control measures were most clearly seen at the site with the highest level of invasion and, to a smaller extent, at the moderately invaded site. Weeding was more successful in controlling the species than pruning, and the greatest impact of these treatments on community plant species richness and diversity was only apparent after 2 years of the experiment. Although seedlings of 10 other alien species were found, there was no evidence that their presence on the plots was detrimental to native species during the experimental period. Three common native species each approached 10% cover on the weeded plots at the heavily invaded site by the end of the experiment: Poa annua, Rumex obtusifolius, and Urtica dioica. These assessments provide guidance for implementing mechanical control of I. glandulifera in riparian zones. Copyright © 2012 John Wiley & Sons, Ltd.

Species- and developmental stage-specific effects of allelopathy and competition of invasive Impatiens glandulifera on co-occurring plants

“…glandulifera was in a comparable order of magnitude as the competitive effect of the natives on their conspecifics (intraspecific competition). In contrast to the afore-mentioned field studies [ 16 , 17 ] found a rather negative impact of I . glandulifera on riparian vegetation.…”

“…This moderate ranking was justified with the mixed results from field studies on the impact of I . glandulifera on native plant communities [ 11 , 16 – 19 ]. Thus, a deeper understanding of the interaction between I .…”

Micro-habitat and season dependent impact of the invasive Impatiens glandulifera on native vegetation

“…The habitat depending impact of I. glandulifera indicates that the impact gets stronger with increasing cover of I. glandulifera. This is also indicated by Cockel et al (2014). In our study the wet-dark micro-habitat with the lowest cover of I. glandulifera, was the least affected.…”

“…German and European Union nature conservation authorities emphasize the impact on diversity and threat to other species (European Union 2014, Nehring et al 2015). Taking this study and all available ones into account, the impact of I. glandulifera on plant species diversity can be rated to be relatively low (Hejda and Pyšek 2006, Hejda et al 2009, Diekmann et al 2016, Čuda et al 2017 even if some studies showed stronger effects (Hulme and Bremner 2006, Cockel et al 2014, Kiełtyk and Delimat 2019. Indeed, we found a negative impact on the dominant natives, U. dioica and F. ulmaria, but they are in general very common and widespread in Central Europe and thus not expected to be threatened (Schreiber 1958, Weber 1995.…”

“…However, field studies showed ambiguous results. In riparian habitats Cockel et al (2014) and Hulme and Bremner (2006) found a strong negative impact of I. glandulifera on the native vegetation, while others found a weak impact in riparian habitats (Hejda and Pyšek 2006, Hejda et al 2009, Diekmann et al 2016 and in forests (Čuda et al 2017). Sometimes the weak effect of I. glandulifera is thought to be due to high fluctuations in its population size (Kasperek 2004, Diekmann et al 2016.…”