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

地理学和空间科学基金会摘要BCS-0964138、BCS-0964043关于飓风对生态影响的文献数量很多，但几乎所有的研究都集中在相对短期（几年）的变化上。这些研究中的一个持续存在的问题是，飓风是否会长期（数十年至数百年）改变森林的组成。此外，美国东南部的亚热带海洋森林在飓风后可能会增加火灾危险，但这种关系是否适用于热带森林仍然是一个问号。最近取得的进展使人们能够在沉积物剖面中确定飓风登陆的替代记录，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进行古生态分析，研究飓风对热带森林的长期（数十年至数百年）影响以及飓风与火灾之间的可能联系。研究人员将分析沉积物中所含的地质，地球化学和生物代理，并使用放射性碳测年，以确定飓风登陆的记录，并研究这些登陆如何影响植被组成并在长时间内与火灾相互作用。这项研究的一个关键目标是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），通过研究飓风过冲沉积物上方和下方密集样本中的花粉粒和微观木炭。多米尼加共和国境内飓风登陆频率较高，在那里进行的多个研究地点可比较飓风对热带干旱和潮湿森林生态系统植被和火灾的影响。现代花粉雨的研究和历史上飓风袭击湖泊沉积物的签名将提供一个基础，从沉积代用数据解释古环境变化和事件。气候和植被动态在热带地区相比，中高纬度地区知之甚少。该项目将制作多米尼加共和国古飓风活动的代用记录，多米尼加共和国是加勒比区域的一个地点，对于评价千年时间尺度上影响飓风活动的机制具有战略意义。这项研究的结果将有助于了解气候和环境历史的其他方面，可能包括哥伦布发现美洲大陆之前的人类活动，并将有助于更广泛地了解加勒比地区的环境变化，那里的长期历史仍然缺乏文献记载。这项研究将提供一个长期的视角，并产生第一个基于代理的多米尼加共和国飓风重现期和登陆概率估计数，这可能有助于决策者进行灾害规划和管理。该项目将为研究生和本科生提供参与国际研究的机会，包括实地和实验室部分。

NATIONAL SCIENCE FOUNDATION GEOGRAPHY AND SPATIAL SCIENCES PROGRAM ABSTRACT BCS-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.