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的大片热带雨林。这项提议寻求继续一项为期12年的关于受灾地区飓风后森林演替的研究。自飓风以来，森林发生了重大变化，现在正进入关键的疏伐(死亡)阶段。在这一关头，至关重要的是要确定个别树木是否因其物种特性而随机死亡。这个问题与最近关于维持热带雨林物种多样性的理论有关，并可能对理解树种间竞争如何与热带雨林树冠生长有关的问题做出重要贡献。稀疏树冠中的死亡事件在树种协会内随机发生，这是中立理论的一个重要方面。该理论的一部分假设，第一，进入稀疏树冠的补充和生长是随机的，第二，稀疏树冠的后续死亡也是随机的(就物种身份而言)。根据一些分析，即使是与这一关键假设的微小偏离也可能产生戏剧性的后果。数据将通过对9个永久地块的所有树木和大树苗的年度监测来收集。智力上的优点。这项研究将有助于澄清基于演替地位的生态物种协会的定义。替代中性模型的“生态位”模型表明，随着间伐的进行，一些物种将更有可能在间伐过程开始时死亡，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，物种被置于糟糕的竞争者/优秀的殖民者和优秀的竞争者/糟糕的殖民者之间的连续体。大多数中立理论的支持者会争辩说，中立是在树种公会(拓荒者、主要森林物种和中间人)中适用的，而不是在这些公会中适用的，而且由于只有几个公会，某种形式的中立很可能是主导力量。或者，生态位理论的支持者会争辩说，对先锋和非先锋的模糊划分只是一种初步的粗略划分，更精细的划分不仅是可能的，而且还解释了许多物种共存的原因。虽然已经开发了理论来处理这些继承利基的更完整的划分，但到目前为止，这些想法所基于的数据并不完全令人满意。约有100名尼加拉瓜人、4名哥斯达黎加人和30名北美人(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。除了项目上的直接实地作业外，所有学生都被鼓励发展他们自己的与一般主题相关的项目。在实地活动之前，参加活动的学生将通过尼加拉瓜加勒比海沿岸自治区大学(URACCAN)接受为期一周的关于生物多样性、森林自然历史、基本生态学理论和实地研究方法的强化课堂和实验室课程，由PI、共同PI和参与活动的合作者(包括密歇根的研究生)授课。部分由于这一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，其中包括这项研究继续进行的两个地点。1996年，该小组因该国关于自然资源的最佳研究项目而获得尼加拉瓜森佩维伦斯奖。以当地语言编写了各种实地指南和图文并茂的小册子，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.