The effects of climate change on the competitive ability of Impatiens glandulifera relative to a native plant community

Impatiens glandulifera is one of the most widespread invasive plant species in the UK. This thesis explores how invasive plants such as I. glandulifera utilise ‘plant-soil feedbacks’ to alter the biotic and abiotic components of soil in order to facilitate invasions, and how this phenomenon responds to climate change. Native plants commonly co-occurring with I. glandlifera, alongside the invader itself, were grown in two experiments simulating different effects of climate change. The first investigated the effects of water availability, with I. glandulifera and a native community grown in a range of watering treatments simulating different water availability scenarios under climate change. The second experiment explored the temperature effects of climate change, and consisted of two phases. In the first, exclusive communities of I. glandulifera or native plants were grown in two growth chambers simulating present-day and warmer future temperatures. In the second, I. glandulifera and a native community were grown in those same pots in the chambers, allowing the effects of invader plant-soil feedbacks to be observed. Plant physical parameters were recorded in both studies, with results confirming that 1) I. glandulifera consistently shows a greater competitive ability than native species, even under watering treatments that negatively affect its growth, and 2) that I. glandulifera exhibits a positive plant-soil feedback effect, and that this effect can complement the warming effects of climate change to negatively affect a native community. Finally, soil extracts from the temperature experiment had their DNA extracted and sequenced for metabarcoding of the soil bacterial and fungal communities, further investigating the drivers of invasive species plant-soil feedbacks. This analysis exhibited potential effects of I. glandulifera soil conditioning on microbial communities, as well as microbial responses to increased temperature under climate change. The findings of these three studies have important implications for future efforts to manage invasive species.