Litterfall as a key source of nutrients for trees in tropical forests: Insights from 15 years of experimental litter manipulation

Emma J. Sayer, Lancaster Environment Centre, Lancaster University, Lancaster, United Kingdom; Smithsonian Tropical Research Institute, Panama, Panama, S. Joseph Wright, Smithsonian Tropical Research Institute, Panama and E.V.J. Tanner, Department of Plant Sciences, University of Cambridge, Cambridge, United Kingdom

Background/Question/Methods:
Tropical forest productivity and diversity are being affected by climate changes and human disturbance, creating feedbacks to ecosystem carbon and nutrient cycling that are largely mediated by plant litter inputs. Efficient nutrient cycling via litterfall can explain the high productivity of tropical forests on infertile soils, and leaf litter also makes a major contribution to soil organic matter storage. Changes in both the quality and quantity of litter inputs can thus modify ecosystem carbon and nutrient dynamics, which in turn affects tree growth, ecosystem carbon storage, and greenhouse gas exchange with the atmosphere.
To investigate the importance of tropical forest nutrient cycling via litterfall, we established a large-scale litter manipulation experiment in lowland tropical forest in Panama, Central America. Continuous monthly litter removal and litter addition treatments have been applied to large-scale forest plots since 2003, allowing us to assess the effects of long-term changes in litter inputs on tree growth and soil nutrient availability.
Results/Conclusions:
During the 17 years of the experiment, we have gained numerous insights into the importance of leaf litter for nutrient cycling and ecosystem carbon storage. I will present the most recent results from this unique experiment to demonstrate how the long-term litter treatments have advanced our understanding of ecosystem processes in tropical forests, and highlight intriguing lines of enquiry to assess the potential impacts of global change on tropical forest ecosystem function.