Invasive plant species in southwest Sweden: Evaluation methods of removal by empirical study and literature review

Sammanfattning: Invasive alien species (IAS), are one of the five biggest threats to biodiversity worldwide. An instrument for biodiversity protection in Sweden is the establishment and management of nature reserves. The goal of nature reserves is to protect valuable nature and rare species to preserve biodiversity. All over the planet, invasive alien species affect protected areas. Despite an abundance of studies on biological invasions, fairly little is known about which methods have been used to control these invasive plants. In this master thesis, three different studies were conducted to evaluate the most effective methods in removing invasive alien plants from nature reserves using a field experiment, literature review and survey. Two different removal methods were tested in the field to remove the study species Lysichiton americanus. In method 1 the root of the plants was destroyed. In method 2, the whole plant was removed with a spade. The literature review included research on the study species Lupinus polyphyllus & Impatiens glandulifera to find the most effective removal method for each species. The current situation of combating IAS in Sweden were reviewed by sending out a questionnaire to authorities and stakeholders, to understand what the incentives and motivations are for combating invasive alien species. The field experiment resulted in no significant difference between treatment methods. The results from the literature review show that there might not be one single most effective removal method for I. glandulifera and L. polyphyllus. The methods recommended to use are mechanical (cutting, mowing, hand-pulling and hot water). Combating invasive plants was deemed by the survey to be of high importance and that the work with invasive alien plants should be of an even higher priority than it currently is. Improved knowledge of effective removal methods of invasive alien species was needed in most municipalities in Västra Götaland.