The Role of the Canopy Subsystem in Tropical Forest NutrientCycles: Mechanisms and Models

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Dr. Nadkarni will investigate the functional role of the canopy- dwelling epiphyte community in nutrient cycling in a primary tropical montane cloud forest. She hypothesizes that epiphytic matter functions as a "keystone component" by contributing to atmospheric nutrient recruitment and within-system nutrient retention. Nadkarni combines several research approaches including: 1) a process-oriented experimental approach in the lab and field to test specific hypotheses on how epiphytes increase nutrient recruitment and nutrient retention within the canopy and, 2) a plot approach to quantify nutrient pools and fluxes, including an estimation of ecosystem-level ephiphyte biomass, litterfall, throughfall, and certain gaseous fluxes. This information will be integrated into a nutrient cycling model that will be tested and validated with measurements of nutrient pools and fluxes in an adjacent secondary forest which has virtually no epiphytes. This work will relate canopy processes to other aspects of ecosystem ecology in tropical forests and will contribute to the growing body of knowledge of the poorly known tropical tree canopy. More generally, this can be viewed as a case study for any complex ecosystem that contains "keystone ecosystem elements", certain components that may have greater functional importance than their biomass or appearance suggests. Dr. Nadkarni is an outstanding researcher in the area of tropical epiphytic communities. The Marie Selby Botanical Gardens provides exemplary support for Dr. Nadkarni in this critical area of research.