Seasonal Variation and Processing of Vascular Plant Organic Matter in Tropical Montane Catchments as Reflected by Riverine DOC Compositions

热带系统面临着发展中国家土地利用变化以及即将到来的气候变化的未知影响所带来的越来越大的压力。河流溶解有机碳(DOC)的浓度和组成在与土地利用变化和气候变化相关的时间尺度上是陆地过程的综合指标。由于地处偏远，基础设施有限，大多数热带河流的研究具有挑战性，该项目将利用现有的基础设施和波多黎各卢基洛临界区天文台(CZO)正在进行的研究。具体地说，研究人员将在一年的时间里测量高等植物的生物标志物木质素衍生酚的组成和浓度，这些样本来自两条河流，这两条河流排水的集水区有相似的植被，但岩性和侵蚀率不同，目的是表征DOC组成和浓度的季节性、事件驱动和集水区差异。结果将与来自温带农业流域的类似数据集进行比较和对比，以调查分配效应、低流量和高流量时的水文流动路径的影响，以及使用木质素的碳标准化产量作为DOC来源的端元。该项目将有助于在这些河流内建立碳循环基线测量，因此，社会影响将是提高了解敏感热带系统即将发生的气候和土地利用变化的能力。此外，这是对流域内基本过程的调查，可能适用于几乎任何DOC关于河流的研究，因此结果将对未来的研究产生广泛影响。该项目的成果将在科学会议上发表，并发表在同行评议的期刊上。Hernes教授本科生和研究生课程，涵盖全球碳循环、气候变化和河流生物地球化学的各个方面，从该项目收集的数据将用于演示易受国家因素变化影响的重要过程。将积极的研究融入到课程课程中，提高了教师和学生的积极性，经常导致本科生实习。这样的本科生将参加对样本的实验室分析，并有机会在校园内的本科生研究论坛上展示结果。将在研究网站上公布研究结果，并将数据提供给与卢基洛CZO有关的适当国家和国际数据库，以供广泛使用。

Tropical systems face increasing pressure from land-use change in developing countries as well as unknown effects of imminent climate change. The concentration and composition of riverine dissolved organic carbon (DOC) serves as an integrator of terrestrial processes on timescales relevant to land-use change and climate change. Whereas most tropical rivers are challenging to study due to their remote locations and limited infrastructure, this project will take advantage of existing infrastructure and ongoing studies in the Luquillo Critical Zone Observatory (CZO) in Puerto Rico. Specifically, the investigator will measure the composition and concentration of biomarkers for higher plants, lignin-derived phenols, on weekly samples over the course of one year from two rivers that drain catchments of similar vegetation but contrasting lithologies and erosion rates with the goal of characterizing seasonal, event-driven, and catchment differences in DOC composition and concentration. Results will be compare and contrasted with a similar dataset from a temperate agricultural watershed to investigate partitioning effects, the effects of hydrologic flowpaths during low and high discharge, and the use of carbon-normalized yields of lignin as an endmember for DOC sources. This project will help to establish carbon cycling baseline measurements within these rivers, hence the societal impact will be an increased ability to understand impending climate and land-use changes in sensitive tropical systems. In addition, this is an investigation of fundamental processes within watersheds that are likely to be generalizable to nearly any DOC studies on rivers, hence results will have broad impact toward future studies. Results from this project will be presented at scientific meetings and published in peer-reviewed journals. The PI, Hernes, teaches undergraduate and graduate classes that cover various aspects of the global carbon cycle, climate change, and river biogeochemistry, and data collected from this project will be used to demonstrate important processes that are susceptible to changing state factors. Incorporation of active research into course curriculums increases the enthusiasm of both the instructor and the students, frequently leading to undergraduate internships. One such undergraduate from a group under-represented in science will participate in the laboratory analyses of samples and will have the opportunity to present results at undergraduate research forums on campus. Results will be posted on research websites and data contributed to appropriate national and international data bases associated with the Luquillo CZO for widespread use.