The role of soil biota during invasion of Impatiens glandulifera Royle and restoration at invaded sites.

Abstract

This thesis focuses on the exotic plant Impatiens glandulifera, which has invaded many habitats in the UK, including north-east England. Soil biota are frequently implicated in influencing plant invasions and here this is investigated by examining the soil-mediated impacts of I. glandulifera on native plant species. Select native plants, along with I. glandulifera, were grown in field-collected soil that had been invaded and not invaded by I. glandulifera. Sterilised versus unsterilised soil was used to test if any differences detected were mediated by soil microbes. Results showed that the growth of the native plant species was not necessarily negatively affected by growing in soils invaded by I. glandulifera. Evidence was also found that I. glandulifera may alter mycorrhizal colonisation of a native plant species in invaded soils. A consistent effect of soil origin was also found, which demonstrates the complexity and context-dependency of plant invasions. Findings from plant-soil interaction studies were then applied to the context of native plant restoration at invaded sites; a management approach often side-lined in invasive plant species control. The utility of two soil treatments were tested for I. glandulifera control, firstly addition of arbuscular mycorrhizal fungi (AMF), which is a significant contributor to plant biodiversity in natural systems; secondly, additions of activated carbon (AC), which is often used to negate the negative soil-mediated impacts of invasive plant species, through adsorption of allelochemicals. No effect of AMF on plant cover was detected and results suggested that AC may actually increase cover of I. glandulifera and thus may not be a suitable restoration tool.