Pattern of Tropical Forest Succession Subsequent to Hurricane Damage

1988年，飓风琼严重破坏了尼加拉瓜东海岸大片热带雨林。该提案旨在继续对受损地区飓风后森林演替进行为期12年的研究。自飓风以来，森林发生了重大变化，现在正进入一个关键的变薄（死亡）阶段。在这个节骨眼上，有必要确定个别树木是否因其物种特性而随机死亡。这个问题与热带雨林物种多样性维持的最新理论有关，并代表了对理解这种森林中种间树木竞争如何与冠层生长相关的潜在重要贡献。间伐林冠层的死亡事件随机发生是中性理论的一个重要方面。该理论的一部分假设，首先，在变薄的树冠层中招募和生长是随机的，其次，随后从变薄的树冠层中死亡也是随机的（就物种身份而言）。根据一些分析，即使是对这一关键假设的微小偏差也可能产生严重的后果。数据将通过对9个永久地块的所有树木和大型树苗进行年度监测来收集。知识价值。本研究将有助于厘清基于演替状态的生态物种群落的定义。“以生态位为基础”的模型，替代中性模型，认为随着森林变薄的进行，一些物种将更有可能在森林变薄过程开始时死亡，而另一些物种将在该过程结束时死亡。最近的理论强调了可能的殖民-竞争权衡，在这种权衡中，物种被置于一个连续体上，在贫穷的竞争者/好的殖民者和良好的竞争者/贫穷的殖民者之间。大多数中立性理论的支持者认为，中立性只适用于树种行会（先锋、原始森林物种和中间物种），而不适用于这些行会，因为只有少数行会，所以某种形式的中立性很可能成为主导力量。另一方面，基于生态位理论的支持者认为，先驱者和非先驱者的模糊划分只是最初的粗略划分，更精细的划分不仅是可能的，而且还可以解释物种共存的大部分原因。虽然理论已经发展到对这些演替生态位进行更完整的划分，但迄今为止，这些观点所依据的数据并不完全令人满意。更广泛的影响。大约100名尼加拉瓜、4名哥斯达黎加和30名北美（主要来自密歇根大学、胡德学院和圭尔夫大学）的研究生和本科生参与了该项目的数据收集。除了项目的直接实地工作外，鼓励所有学生开发与一般主题相关的个人项目。在实地活动之前，参与的学生将获得为期一周的强化课堂和实验室课程，内容包括生物多样性、森林自然史、基础生态理论和实地研究方法，由PI、联合PI和参与合作者（包括密歇根大学的研究生）通过尼加拉瓜加勒比海岸自治区大学（URACCAN）教授。部分由于这个研究项目及其教学价值，URACCAN建立了他们的自然资源、环境和可持续发展研究所（IRENMADES），该研究所现在赞助这些年度实地课程，其中包括继续进行这项研究的两个地点。1996年，该小组因其在该国自然资源方面的最佳研究项目而获得尼加拉瓜森佩维伦斯奖。以当地语文制作了各种实地指南和有插图的通俗小册子，供环境教育使用。

Hurricane Joan severely damaged an extensive area of tropical rain forest on the easternseaboard of Nicaragua in 1988. This proposal seeks to continue a twelve-year study on post hurricane forest succession in the damaged area. Since the hurricane the forest has undergone significant changes and is now entering a critical as thinning (mortality) stage. At this juncture it is essential to determine whether individual trees die at random with respect to their species identity. This question is relevant to recent theories of the maintenance of species diversity in tropical rain forests and represents a potentially important contribution to the understanding of how interspecific tree competition is related to canopy growth in such a forest. It is a crucial aspect of Neutrality Theory that mortality events in the thinning canopy happen randomly within guilds of tree species. Part of the theory supposes first, that recruitment and growth into the thinning canopy is at random and second, that subsequent mortality from the thinning canopy is also random (with respect to species identity). According to some analyses, even small deviations from this critical assumption may have dramatic consequences. Data will be collected by yearly monitoring of all trees and large saplings in nine permanent plots. Intellectual merit. This research project will help to clarify the definitions of ecological species guilds based on successional status. "Niche-based" models, alternative to the neutrality models, suggest that as thinning proceeds, some species will be more likely to die at the beginning of the thinning process and others will do so at the end of that process. Recent theory emphasizes the probable colonization-competition tradeoff, in which species are placed on a continuum between poor competitors/good colonizers and good competitors/poor colonizers. Most proponents of neutrality theory would argue that it is within tree species guilds (pioneers, primary forest species and intermediates), not among such guilds, that neutrality applies, and since there are only a few guilds, some form of neutrality is likely to be a dominant force. Alternatively, proponents of niche-based theory would argue that the faint division into pioneers and non-pioneers is only an initial rough cut and that finer divisions are not only possible, but also explain much of species coexistence. While theory has been developed to treat a more complete division of these successional niches, thus far the data on which these ideas are based are not quite fully satisfying.Broader impacts. Approximately 100 Nicaraguan, four Costa Rican, and 30 North American (mainly from the University of Michigan, Hood College, and University of Guelph) graduate and undergraduate students have participated in data gathering for this project. In addition to the direct field work on the project, all students are encouraged to develop their own individual projects related to the general subject matter. Prior to field campaigns, participating students are provided with an intensive one-week classroom and lab course in biodiversity, forest natural history, basic ecological theory, and field research methods, taught by PI, co-PI and participating collaborators (including graduate students at Michigan) through the University of the Autonomous Regions of the Nicaraguan Caribbean Coast (URACCAN). Partly as a result of this research project and its teaching value, URACCAN developed their Institute of Natural Resources, Environment and Sustainable Development (IRENMADES)which now sponsors these yearly field course, and which includes the two sites at which this research continues. In 1996 the group received the Nicaraguan Sempervirens Award for the best research project on natural resources in the country. Various field guides and illustrated popular pamphlets have been produced in local languages for use in environmental education.