Collaborative Research: Long-Term Dynamics of Caribbean Maritime Forest Ecosystems in the Context of Major Disturbance Events: The Role of Hurricanes and Fires

lisa M. Kennedy， Kam-biu liu弗吉尼亚理工大学，路易斯安那州立大学关于飓风对生态影响的文献很多，但几乎所有的研究都集中在相对短期（年）的变化上。这些研究中出现的一个持久的问题是，飓风是否会长期（几十年到几个世纪）改变森林的组成。此外，对于美国东南部的亚热带海洋森林来说，飓风后火灾危险的增加已经被假设，但这种关系是否适用于热带森林仍然是一个问号。最近的进展允许在沉积物剖面中识别飓风登陆的代理记录，这为解决这些问题提供了机会。该项目将通过对多米尼加共和国沿海湖泊沉积物记录的古生态学分析，研究飓风对热带森林的长期（几十年到几百年）影响，以及飓风与火灾之间可能存在的联系。研究人员将分析沉积物中包含的地质、地球化学和生物代用物，并使用放射性碳定年法来确定飓风登陆的记录，并检查这些登陆如何影响植被组成以及在长时间尺度上与火灾相互作用。本研究的一个关键目标是通过研究飓风冲积沉积物上下紧密间隔的样本中的花粉粒和微观木炭，记录飓风后植被变化是否长期持续，以及飓风袭击后热带生态系统的火灾危险是否增加（即飓风-火灾相互作用的假设）。在飓风登陆频率相对较高的多米尼加共和国的多个研究地点，将可以比较飓风对热带干燥和潮湿森林生态系统中植被和火灾的影响。湖泊沉积物中现代花粉雨和历史飓风袭击特征的研究将为沉积代用资料解释古环境变化和事件提供依据。与中高纬度地区相比，人们对热带地区的气候和植被动态知之甚少。该项目将生成多米尼加共和国古飓风活动的代理记录，多米尼加共和国位于加勒比海地区，对评估千年时间尺度上影响飓风活动的机制具有战略意义。这项研究的结果将阐明气候和环境历史的其他方面，可能包括前哥伦布时期的人类活动，并将有助于更广泛地了解加勒比地区的环境变化，那里的长期历史记录仍然很少。这项研究将提供一个长期的观点，并产生第一个基于代理的飓风回归期和多米尼加共和国登陆概率的估计，这可能对决策者在灾害规划和管理方面有用。该项目将为研究生和本科生提供参与国际研究的机会，包括实地研究和实验室研究。

NATIONAL SCIENCE FOUNDATIONABSTRACTBCS-0964138, BCS-0964043Lisa M. Kennedy, Kam-biu LiuVirginia Tech, Louisiana State UniversityThe body of literature on the ecological impacts of hurricanes is large, but nearly all the studies have focused on relatively short-term (years) changes. A persistent question arising from many of these studies is whether hurricanes change forest composition over the long term (decades to centuries). In addition, increased post-hurricane fire hazards have been hypothesized for the subtropical maritime forests of the southeastern U.S., but whether this relationship holds for tropical forests is still a question mark. Recent advances allowing identification of proxy records of hurricane landfalls in sediment profiles provide an opportunity to address such questions. This project will examine the long-term (decades to centuries) impacts of hurricanes on tropical forests and the possible link between hurricanes and fire through paleoecological analyses of sediment records from coastal lakes in the Dominican Republic. The investigators will analyze geological, geochemical, and biological proxies contained in the sediments, and use radiocarbon dating, to identify records of hurricane landfalls and to examine how these landfalls influence vegetation composition and interact with fire over long time scales. A key objective of this research is to document whether post-hurricane vegetation changes persist over the long term and whether fire hazards increase in tropical ecosystems after hurricane strikes (i.e., the hypothesis of hurricane-fire interactions) through the study of pollen grains and microscopic charcoal in closely spaced samples above and below hurricane overwash deposits. Multiple study sites in the Dominican Republic, where there are relatively high frequencies of hurricane landfalls, will allow comparisons between hurricane effects on vegetation and fire in tropical dry and moist forest ecosystems. The study of modern pollen rain and the signatures of historical hurricane strikes in lake sediments will provide a basis for interpreting paleoenvironmental changes and events from sedimentary proxy data.Climate and vegetation dynamics are poorly understood in tropical areas in comparison to mid- and high-latitude areas. This project will produce proxy records of paleohurricane activity from the Dominican Republic, a location in the Caribbean region strategic for evaluating mechanisms affecting hurricane activity on millennial timescales. The results of this study will shed light on other aspects of climate and environmental history, including possibly pre-Columbian human activities, and will help to provide a broader understanding of environmental change in the Caribbean, where long-term history is still poorly documented. This research will provide a long-term perspective and generate the first proxy-based estimates of hurricane return periods and landfall probabilities for the Dominican Republic, which may be useful to decision makers in terms of disaster planning and management. This project will provide opportunities for graduate and undergraduate students to participate in international research with field and laboratory components.