ORONO, Maine — Tropical forests can mitigate climate change by absorbing carbon dioxide from the atmosphere. But as carbon dioxide levels continue to rise, some forests may not be able to sequester more of it because their habitats lack sufficient supplies of nutrients. Amanda Olsen, a University of Maine associate professor, says one way plants receive nutrients is through weathering, a process in which bedrock breaks down due to physical, chemical and biological forces and releases nutrients to soils. Determining if weathering releases minerals from bedrock fast enough to support tropical forest productivity, particularly in nutrient-poor areas, is the focus of her latest study in collaboration with Bill McDowell, a professor with the University of New Hampshire. The National Science Foundation awarded more than $311,000 for the project, which will examine chemical weathering in forested areas in southwestern Puerto Rico.