How Tropical Trees Overcome Nutrient Limitations

In order to grow, thrive, and trap carbon dioxide, forests need nutrients. Our lab is working to understand how deficiencies in nutrients such as nitrogen and phosphorus impact forest growth and carbon sequestration. We’re also exploring the other side of the coin: What tools and strategies do trees have to overcome nutrient limitations?

Our past research indicates that plants can employ a variety of techniques to acquire and use nutrients in nutrient-limited environments. For example, symbiotic nitrogen fixation can allow trees to thrive in nitrogen-poor soils. Other strategies to get around nutrient deficiencies include utilizing mycorrhizal fungi, adjusting phosphatase enzyme activity levels on roots, or changing how resources are allocated throughout the plant, such as investing in roots instead of shoots.

Understanding the tradeoffs and limits of these strategies will be essential to predicting the impacts of nutrient constraints on the global carbon sink.

Our group aims to resolve the degree to which trees use different combinations of strategies, and explore which strategies are most important for alleviating nutrient limitation in tropical forests. To address these questions and others, we are using a landscape-scale fertilization experiment in Panama, where we have been tracking tree dynamics in 76 0.16 ha plots treated with nitrogen, phosphorus, nitrogen plus phosphorus, or an unfertilized control for up to 26 years. We will combine new measurements of productivity and tree nutrient acquisition and use strategies with new analytical tools and simple ecosystem models.

Resolving the role of nutrient strategies in tropical forests will provide guidance for which tree species are best to use for reforestation. In addition to informing best practices for policymakers and practitioners seeking to use tropical reforestation as a natural climate solution, this work promises to improve climate change models by providing a more realistic picture of how trees can use strategies to buffer changing nutrient demands, and how much carbon tropical forests can be expected to absorb in the future.