How do species interactions drive community re-assembly of banksia woodlands?

Degraded land is a major issue globally and impacts human societies on every inhabited continent. To counter the negative effects of land degradation and return ecosystems to reference ecological states, active restoration is often required. However, many restoration efforts suffer from low success in the re-assembly of reference states. As such, there is a need for improvements on current restoration practices. Ecological theory suggests that early plant colonisers could help later arrivals in re-assembly. This theory has the potential to inform restoration efforts. The major goal of my research is to build on current theoretical understanding of plant-plant interactions while at the same time improving restoration practice for banksia woodlands. My study system offers a great test of my ideas because it is highly biodiverse. A greater understanding of plant-plant interactions in space, and interactions between diverse functional groups, will inform the types of species to include in seed mixes and could potentially improve likelihoods of restoration success in other woody ecosystems around the world. Specifically, I used observational and manipulative experiments to test spatial arrangements of plant species and build on theories of plant-plant interactions in early and mid-successional stages of restoration. I tracked re-assembly of banksia woodland after sand mining on the Swan Coastal Plain. I utilized spatial point pattern analysis in two studies to analyse spatial associations of perennial plant species and infer interactions from spatial arrangement. Utilizing knowledge gained from the first two studies, I manipulated the spatial arrangement of seeds to test differences in seedling survival. Finally, I tested different densities of a fire-ephemeral species that could impact survival of seedlings in restoration. Results of my studies demonstrate that plant-plant interactions play a critical role in the survival of some species and spatial arrangement effects restoration outcomes. I found some species have a greater tendency to demonstrate positive interactions, but the strength of positive and negative interactions changes through time and by species. Similarly, density dependent mortality was strong for some species but not others. The spatial arrangement of species was also important to seedling survival. Four of six species had greater survival in concentrated seeding-bare space configurations than completely random dispersed plantings, which are representative of current restoration practices. Few studies of positive plant-plant interactions exist for Australia and my studies demonstrate that both positive and negative interactions drive re-assembly patterns in restoration. A greater understanding of plant-plant interactions in space, and interactions between diverse functional groups, will inform the types of species to include in seed mixes and seeding spatial arrangements. Utilizing spatially-informed restoration practices could improve likelihoods of restoration success in other woody ecosystems around the world