Collaborative Research: Controls Over Nitrogen Loss from Very Wet Tropical Forests

人类已经极大地改变了全球氮循环。这些变化给社会带来了明显的好处，但现在许多生态系统中存在的过量氮越来越多地引起了一连串的环境和公共卫生问题。因此，随着氮循环的变化成为真正的全球性变化，了解生态系统如何获得、储存和损失氮，并在越来越多样化的生态系统中做到这一点，变得至关重要。这个项目试图了解热带雨林的氮平衡，部分原因是目前和预测的氮循环变化在世界热带地区最为明显。该项目探索了为什么热带森林中最潮湿的部分，如哥斯达黎加南部的一个野外地点，似乎表现出与热带生物群中较干燥的部分截然不同的氮循环。将使用各种技术--从分水岭氮平衡到同位素测量，再到化肥试验田--来探索氮在这个生态系统中是如何循环的，以及什么形式的氮主导着对周围环境的损失。碳和磷循环的关键方面将与对氮的关注一起进行测量，因为该站点之前的工作表明，这两种元素可能在决定氮损失的大小和形式方面发挥重要作用。最潮湿的热带森林仍然是世界上研究较少的生态系统之一，但它们似乎是碳储存和营养物质出口到沿海海洋的热点，以及热带森林保护的关键区域。该项目将阐明这种森林如何在生态系统规模上发挥作用，从而有助于预测它们不仅可以对不断变化的氮循环做出反应，而且还可以对气候和土地利用的变化做出反应。该项目还将为许多初级科学家提供支持，包括一名早期助理教授和几名本科生和研究生。最后，该项目将支持P.I.和一名专业记者之间的新合作，旨在向更广泛的受众传播热带雨林的重要性。

Humans have changed the global nitrogen cycle to an extraordinary degree. Such changes have brought clear benefits to society, but increasingly, the excess of nitrogen now present in many ecosystems is causing a litany of environmental and public health concerns. Thus, it has become critical to understand how ecosystems gain, store and lose nitrogen, and to do so in an increasingly varied range of ecosystems as changes in the nitrogen cycle become truly global in scope. This project seeks to understand the nitrogen balance of a tropical rainforest, in part because current and predicted future changes to the nitrogen cycle are most pronounced in the tropical portions of the world. The project explores why the wettest of tropical forests, as typified by a field site in southern Costa Rica, seem to exhibit a much different nitrogen cycle than do the drier portions of the tropical biome. A variety of techniques will be used - ranging from watershed nitrogen balance, to isotopic measurements, to experimental fertilizer plots - to explore how nitrogen is cycled within this ecosystem, and what forms of nitrogen dominate losses to the surrounding environment. Key aspects of the carbon and phosphorus cycles will be measured in tandem with a focus on nitrogen, because prior work in this site suggests that both elements may play important roles in determining the size and forms of nitrogen loss.The wettest of tropical forests remain one of the more poorly studied ecosystems of the world, and yet they appear to be hotspots for carbon storage and for nutrient export to coastal oceans, as well as key regions for tropical forest conservation. This project will shed light on how such forests work on an ecosystem scale, thereby aiding the ability to predict how they may respond not only to a changing nitrogen cycle, but also to changes in climate and land use. The project will also provide support for numerous junior scientists, including an early stage assistant professor and several undergraduate and graduate students. Finally, the project will support a new collaboration between the P.I. and a professional journalist that is aimed at communicating the importance of tropical forests to a broader audience.