Facilitation competition and parasitic facilitation amongst invasive and native liana seedlings and a native tree seedling
French K; Robinson S; Smith L; Watts E
Lianas are prevalent in gaps and edges of forests where they compete intensely with trees reducing growth and recruitment. Invasive lianas have the potential to be particularly harmful as the competitive advantage of the liana life history may be coupled with the more competitive qualities of invasiveness. However in early stages of growth of lianas and native tree seedlings facilitatory interactions or competitive interactions associated with soil nutrients may be more prevalent. We investigated interactions at the early stages of growth between native and invasive lianas with a common rainforest tree of temperate Australian rainforests under different light conditions. Invasive lianas as a group were not more competitive than native lianas in reducing growth of a native rainforest seedling. At this stage in the life cycle most lianas were as competitive as a conspecific seedling. However one invasive liana Anredera cordifolia was particularly competitive and reduced biomass of tree seedlings. Light had little effect on growth of lianas nor on the impact of competition however specific leaf area differed between low and medium light conditions. Moderate light did improve growth in the rainforest tree seedling. When lianas were grown with a rainforest tree three liana species overyielded while one species was unaffected by growing with the tree seedling. Overyielding suggests a strong positive interaction with the neighbouring plant mediated through below-ground processes. We discuss the potential for these interactions to be facilitative parasitic or competitive. We therefore show that interactions early in the life of rainforest species can be complex mixtures of interactions which are likely to influence the ability of lianas to dominate rainforests.