Interplay of limiting factors explains context dependence
in invader abundance
Using a grassland experiment, we show that the interplay of limiting
factors can explain context dependence in plant invasions, including why
relationships can oscillate between positive, negative and neutral
depending on circumstances. Evidence suggested that seeds primarily
limited fast invader cover in early and mid successional communities,
resources limited invasion of both groups in late succession, and
invader growth rate primarily limited slow invaders in early and mid
succession (Fig. 5). The key limiting factor in each situation was only
detectable, and a nuanced effect of each treatment only visible, when
temporal trends and effects of the four treatments were collectively
examined. For example, the strength of resource-limitation in late
successional communities only became apparent through time, and the
varied effects of disturbance illustrated changes in the relative
importance of resource limitation with succession. By manipulating
invader seed dose, imposing disturbance that altered resource
availability and examining temporal trends of invaders with different
growth rates, we were able to ascertain the hierarchy of limiting
factors affecting cover abundance of two invader groups in three
successional stages, and explain context dependence of the invasion
relationships observed (Fig. 5).