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

人类已经极大地改变了全球的氮循环。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正日益引起一系列环境和公共卫生问题。因此，了解生态系统如何获得、储存和损失氮，以及随着氮循环的变化真正成为全球范围的变化，在日益多样化的生态系统中这样做变得至关重要。该项目旨在了解热带雨林的氮平衡，部分原因是目前和预计未来氮循环的变化在世界热带地区最为明显。该项目探讨了为什么最潮湿的热带森林，如哥斯达黎加南部的一个田野为典型，似乎表现出与热带生物群落的干燥部分截然不同的氮循环。将使用各种各样的技术——从流域氮平衡到同位素测量，再到试验性施肥地块——来探索氮是如何在这个生态系统中循环的，以及什么形式的氮主导了对周围环境的损失。碳和磷循环的关键方面将与氮的重点同步测量，因为在该地点的先前工作表明，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向沿海海洋输出营养物质的热点地区，也是热带森林保护的关键地区。该项目将揭示这类森林在生态系统规模上是如何运作的，从而有助于预测它们如何不仅对不断变化的氮循环作出反应，而且对气候和土地利用的变化作出反应。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，该项目将支持私家侦探署与一名专业记者之间的新合作，目的是向更广泛的受众宣传热带森林的重要性。

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.