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

自然干扰对森林生态系统的组成和功能产生严重影响。这些影响最终会影响这些生态系统为人类提供服务的质量（例如水质）。因此，测量森林从干扰中恢复的速度以及这种恢复是否可预测是至关重要的。这项研究的重点是波多黎各的埃尔云克国家森林对飓风玛丽亚的即时反应。El Yunque是美国国家森林系统中唯一的热带雨林，岛上大约20%的人口依赖El Yunque的水。这项研究有两个主要目标。首先是测量玛丽亚后一年树苗建立的速率和可预测性。二是测量Maria后土壤真菌病原菌对种子建立的影响。这项研究提供了一个独特的机会来实验研究一个重要的生态系统如何对一个主要的干扰作出反应。本项目将资助两名研究生和一名本科生，他们都来自科学界代表性不足的群体。此外，PI将在波多黎各大学提供R编程短期课程。群落结构和动态受随机和确定性过程控制。确定这些过程的相对重要性具有普遍意义，但在试图预测群落对自然干扰的反应时尤为重要。这项研究将首先测试这样一个假设，即在自然干扰之后，群落动态在功能上是确定的，但建立的物种的身份是不可预测的。具体来说，一个行会的成功建立是可以预测的，但该行会中的哪个物种将成为社区的代表却很难预测。接下来，研究验证了物种内部由于大量个体在幼苗层聚集而导致干扰后的负相互作用加剧的假设。为了检查这些负面相互作用的性质，研究将考虑个体的表型相似性和土壤中真菌物种的存在和身份。研究目标将通过在El Yunque国家森林进行一系列重复的现场实验来实现，这些实验是在2017年夏天玛丽亚飓风之前建立和调查的。这些实验将在伽马多样性不同的El Yunque国家森林的低海拔地区重复进行，从而使研究能够确定伽马多样性是否影响群落的可预测性。

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.