Reducing invasion by targeting vulnerable life stages: effects of fire on survivorship of Lespedeza cuneata

Abstract

There is growing interest in whether invasive species may be controlled by targeting key life stages or by tailoring different management strategies to the specific characteristics of particular life stages. In this study, I test whether fire targeted at seed or seedling stages of sericea can increase mortality and potentially limit the spread of this invader. Two field experiments were performed manipulating the timing of fire and a laboratory experiment was conducted that quantified germination rates. The field experiments revealed that seedling survivorship varied with timing of burns and plant age, but these variables only accounted for a small amount of the variability in survivorship (R2 = 0.09, P = 0.032), suggesting that sericea seedlings quickly reach a size from which they can resprout. At the seed stage, fire greatly enhanced cumulative germination in the field burns. In contrast, the lab experiment showed that fire inflicted extremely high mortality on sericea seeds, suggesting that, in the field, seeds gain protection from fire as they mix with soil and that fire may increase germination due to enhanced resource availability. Taken together, my results illustrate that, although targeting vulnerable life stages is a sound strategy for invasive species control, careful preliminary studies may be needed to unravel complex interactions between biotic and abiotic variables before effective solutions can be devised.