Pioneer plants depend upon canopy disturbance for recruitment, and years with high disturbance rates generate pulses of recruitment that might result in highly skewed stage or age distributions that persist for many years. We investigated this potential in five common species of pioneers at Monteverde, Costa Rica with demographic models based on 26 years of forest disturbance data and 16 years of plant demography data.   

Results/Conclusions

Two species (Phytolacca rivinoides and Bocconia frutescens) are short-lived as adults but have persistent soil seed banks, while two others (Cecropia polyphlebia and Urera elata) are relatively long-lived and have transient seed banks. Guettarda poasana is long-lived as an adult and has persistent seeds. Annual canopy disturbance rates varied from <0.5% to 8.7%, and averaged 1.7% from 1983 to 2009. Recruitment of pioneer seedlings of all five species was up to 300% greater than the long-term average following heavy disturbance years, but for most species these large cohorts were not projected to persist into reproductive stage classes due to high mortality in rapidly-regenerating gaps. Short-lived pioneers may be exceptions to this pattern, since they mature before most gaps regenerate. Survival of seeds in the soil is a key feature of the life history of all five species (> 99.9% of each population consists of dormant seeds), yet elasticity analyses showed that seed survival is the most important stage transition for only three of the five species. We will discuss contrasting results of stochastic and deterministic population models for species with these different demographic features.