Global Tree Conservation

Earth Forest Fertilization Experiment (EFFEX): Understanding Nutrient Limitation in Tropical Forests

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Contemporary human activities worldwide are altering the resources required by plants (e.g., carbon dioxide, precipitation, and nutrients) at an alarming rate. Understanding how ecosystems are responding to these resource alterations is important for predicting feedbacks between the atmosphere and the biosphere, which have large impacts on global climate and thus human society.

EFFEX is the longest-running nutrient addition experiment in the wet lowland tropics, located at EARTH University Forest Reserve in the Caribbean lowlands of Costa Rica. Since 2007, the project partners have been adding nitrogen (N) and phosphorus (P) fertilizer to 30 x 30m plots and observing how this increased nutrient availability influences different forest processes, such as net primary productivity (NPP), decomposition of organic matter, and emissions of greenhouse gases from the forest soil. More than 20 undergraduate students and researchers have been involved in the experiment so far and the project aims to continue as long as feasibly possible.

Additional Resources


EARTH University 

Funding Sources

  • University of Florida
  • National Science Foundation
  • Universidad de Costa Rica
  • The Morton Arboretum
  • Smithsonian Tropical Research Institute



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