RAPID: Priority effects, functional differentiation, and negative density dependence as drivers of post-hurricane seedling dynamics

University Of Maryland, College Park, College Park MD

Investigators

Abstract

Natural disturbances to forested ecosystems have severe impacts on their composition and functioning. These impacts can ultimately influence the quality of the services that these ecosystems provide to humans (e.g. water quality). Therefore, measuring the rate of forest recovery from disturbance and whether this recovery is predictable are of fundamental importance. The research focuses on the immediate response of the El Yunque National Forest in Puerto Rico to Hurricane Maria. El Yunque is the only tropical rain forest in the United States National Forest System and roughly 20% of the population of island relies on El Yunque for water. The research has two primary objectives. The first is to measure the rate and predictability of tree seedling establishment in the year following Maria. The second is to measure how soil fungal pathogens influence seeding establishment following Maria. The research provides a unique opportunity to experimentally investigate how a vital ecosystem responds to a major disturbance. Two graduate students and one undergraduate student, all from underrepresented groups in science, will be supported by this project. Additionally, the PI will offer an R programming short course at the University of Puerto Rico. Community structure and dynamics are controlled by random and deterministic processes. Determining the relative importance of these processes is of general importance, but particularly important when attempting to predict the response of communities to natural disturbance. This research will first test the hypothesis that community dynamics are functionally deterministic following natural disturbances, but the identity of the species that establish is less predictable. Specifically, the successful establishment of one guild over another is predictable, but which species from that guild will be the representative in the community is less predictable. Next, the research tests the hypothesis that within species negative interactions will be exacerbated post-disturbance due to large numbers of individuals recruiting in the seedling layer. To examine the nature of these negative interactions, the research will consider the phenotypic similarity of individuals and the presence and identities of fungal species in the soil. The research objectives will be met by performing a series of replicated field experiments in El Yunque National Forest, on plots that were established and surveyed in the summer of 2017, before Hurricane Maria. The experiments will be replicated across low elevations in the El Yunque National Forest that vary in their gamma diversity, allowing the research to determine whether gamma diversity influences community predictability.