Observing the tripartite interaction between three invasive plant species, alongside the ecological restoration of biodiversity in habitats invaded by Japanese knotweed

Reynoutria japonica (Japanese knotweed) is an invasive species that negatively impacts local biodiversity and ecosystems globally. Control methods are inefficient and laborious, and long-term restoration data is sparse. One of the characteristics that contributes to the invasiveness of a plant is allelopathy, which has been recorded in Solidago canadensis (Canadian goldenrod). Allelochemicals can reduce the fitness of native species, outlined by the native weapons hypothesis, and therefore may negatively impact other invasive species, such as R. japonica. To test this, a pot trial was set up, which firstly aimed to determine whether S. canadensis negatively affected the health of R. japonica aboveground growth. The two species were grown together with and without isolation treatments. The weekly growth rates and chlorophyll fluorescence were measured and compared to single species controls. Secondly, the pot trial aimed to assess the interactions between R. japonica, S. canadensis, and Impatiens glandulifera and growth rate and chlorophyll fluorescence were measured weekly. S. canadensis had higher mean chlorophyll fluorescence in its pairwise and tripartite treatments than the R. japonica and I. glandulifera (p =0.0016 and p < 0.0111, respectively). I. glandulifera had the highest mean growth rate in the tripartite treatment (p = 0.0001). S. canadensis had higher chlorophyll fluorescence than R. japonica when grown together or separately.To understand the long-term effects of using native plant functional traits in habitat restoration, I continued the data collection of Hocking, 2021, to measure the restorative success of various specific seed mixes sown on land previously dominated by R. japonica and treated with glyphosate. Plants was selected due to functional traits which aided land restoration and prevented secondary invasions. Community and seedbank analyses of plots with the tailored restorative seed mixes were carried out to assess the subsequent species diversity and richness. High and low functional diversity seed mixes provided the highest species diversity and richness within treatments