Regeneration growth of the invasive clonal forb Rorippa austriaca (Brassicaceae) in relation to fertilization and interspecific competition

摘要

A special type of clonal growth, spread by lateral roots, is hypothesized to be a favourable trait of invasive, opportunistic plant species of disturbed habitats. We tested this hypothesis for the invasive forb Rorippa austriaca (Brassicaceae). Regeneration from root fragments, subsequent vegetative spread and allocation patterns in relation to varied nutrient supply and intensity and pattern of interspecific competition were analyzed in container experiments. Regeneration success from root fragments was 100% and clonal spread was rapid but vegetative performance was strongly reduced under unfertilized conditions and, particularly, when interspecific competition was present. While the ratio of above- to belowground bio-mass did not differ considerably between treatments, R. austriaca allocated a high amount of resources to belowground growth resulting in low aboveground but high belowground biomass at harvest time relative to the matrix vegetation. Differences in shoot number or biomass between simulated gaps and densely vegetated quadrants in the containers were (relatively) weak. Reproductive effort was less reduced under low resource levels, and the clones did not set seed at all, irrespective of the treatment. Our results show that clonal growth by lateral roots and plasticity in clonal growth patterns in R. austriaca promote both exploitation of gaps and nutrient-rich microsites and resistance to competitors. Such plasticity, combined with its ability to regenerate from widely-dispersed root fragments, contribute to the ability of the species to invade and persist within disturbed and spatially heterogeneous habitats. [References: 45]