Woody seedling survival responses to conspecific density, soil nutrients, and irradiance vary with seedling age in a wet Costa Rican tropical forest

Background/Question/Methods

In tropical forests, differences among species in seedling survivorship responses to multiple resources and local conspecific density (LCD) could promote coexistence. To examine survivorship effects of soil resource availability, irradiance, and LCD, we fit species- and age-specific models to survivorship and resource data of seedlings of 68 woody species at La Selva Biological Station in Costa Rica. The temporal resolution of this long-term data set (2000-present) is unique, with seedling censuses occurring every 6 weeks for the last 14 years. 

Results/Conclusions

In decreasing order of prevalence, seedling survivorship was related to LCD, soil base cations, irradiance, nitrogen, and phosphorus. Across the community, species’ responses to different factors were infrequently correlated, suggesting species do not occupy a single continuum of sensitivity to multiple mortality agents. Survival responses to all factors varied over the course of the average seedling’s lifetime, indicating that seedling requirements change with age and that effects depend on temporal resolution. These results support that seedling regeneration niches are defined by multiple dimensions, which provide multiple opportunities for resource partitioning together with negative density dependence.