Interactions between Rainfall, Nutrient Cycles and Decomposition in Lowland Tropical Rainforests

热带雨林与大气交换的二氧化碳和水比任何其他陆地生物群都多，因此在气候调节中发挥着重要作用。热带生物群中较潮湿的部分在树木生物量和土壤中储存了大量碳，但这些储量--特别是土壤碳--可能对预测的降雨量变化很敏感。因此，该项目将控制到达哥斯达黎加潮湿雨林土壤的降雨量，并测试这些变化如何改变树叶凋落物和土壤碳分解，以及从土壤表面向大气释放的二氧化碳数量。此外，它还将测试氮和磷的有效性，这两种关键营养物质在整个热带生物群中也存在很大差异，它们如何影响对降雨操纵的反应。作为一个整体，这些实验将展示潮湿热带森林的降雨变化可能如何影响与地球气候直接相关的生态系统过程，重点是土壤碳储存。这里产生的数据将提高对这个巨大的土壤碳库如何应对气候变化的理解，从而提高对它如何减缓或加剧持续的气候变化的理解。最后，该项目将为美国和哥斯达黎加的年轻科学家提供培训和教育，并将为科罗拉多州的学童制定一个推广计划。

Tropical rain forests exchange more carbon dioxide and water with the atmosphere than any other terrestrial biome, and thus play a major role in climate regulation. Wetter portions of the tropical biome store large amounts of carbon in tree biomass and soils, but those reserves - especially soil carbon - may be sensitive to predicted changes in rainfall. Thus, this project will manipulate the amount of rainfall that reaches soils in a wet Costa Rican rainforest, and test how such changes alter leaf litter and soil carbon decomposition, and the amount of CO2 that is released from the soil surface to the atmosphere. In addition, it will test how nitrogen and phosphorus availability, key nutrients that also vary greatly across the tropical biome, affect the responses to rainfall manipulation. Taken as a whole, the experiments will demonstrate how changes in rainfall in wet tropical forests may affect ecosystem processes that have direct relevance to earth's climate, with a focus on soil carbon storage. The data produced here will improve understanding of how this large soil carbon reservoir may respond to a changing climate, and thus how it might moderate or augment continued climate change. Finally, the project will provide training and education to young scientists in the U.S. and Costa Rica, and will develop an outreach program for Colorado school children.