I am a plant functional ecologist interested in the ecological and evolutionary significance of diverse physiological and morphological traits of plants, especially those of tropical woody species. In particular, I am interested in trait-mediated trade-offs in ecological strategies, such as growth-survival trade-offs. In species-rich tropical forests, some species can grow fast but exhibit low survival rates, while other species survive well in the shaded understory where they grow slowly. In various comparative studies, I compare biomass allocation patterns, physical defense, photosynthetic rates, stored energy reserves and other stress-tolerance mechanisms and examine their correlation with demographic traits of the species in the field and under standardized conditions in green houses and common gardens. The results of my comparative studies have shown that functional traits affect demographic characteristics of plant species and their interaction with bitotic and abiotic environmental factors, and thus important for community assembly processes in tropical forests. These results support a view that plant communities consist of opportunistic species that rapidly colonize and reproduce in ephemeral resource-rich environments as well as persistent species that can withstand low resource availability through tolerance of various biotic and abiotic stresses.
The majority of my research projects on community-wide comparison of plant functional traits have been conducted in Neotropical forests in Panama and Bolivia. Most of my work in Florida, in contrast, has aimed to elucidate the functional basis for the competitiveness of several exotic invasive plant species. In addition, I am increasingly interested in application of plant functional ecology to evaluate the impacts of global changes on ecosystem carbon balance and community dynamics in coupled human-natural systems in the tropical forest biome. In all these research areas, my work has shown that ecological significance of physiological and morphological traits of plants require consideration of their ecological interactions with not only abiotic environmental factors such as light and soil nutrients and other plants, but also biotic factors, i.e., animals and microbes that may act as consumers, pathogens, or mutualists.
Westbrook, J. W., Kitajima, K., Burleigh, J. G., Kress, J. W., Erickson, D., Wright, S. J. 2011. What makes a leaf tough? Patterns of correlated evolution between leaf toughness and demographic rates among 197 shade-tolerant woody species in a Neotropical forest. American Naturalist 177: 800-811
Kitajima, K and Poorer, L. 2010. Tissue-level leaf toughness, but not lamina thickness, predicts sapling leaf lifespan and shade tolerance of tropical tree species. New Phytologist 168: 708-721
Kitajima, K. and Poorter, L. 2008. Functional basis for resource niche partitioning by tropical trees. In: Schnitzer, S. A. and Carson, W. P. (eds.) Tropical Forest Community Ecology, Blackwell Science, Pp. 160-181.
Kitajima, K. and Myers, J. A. 2008. Seedling ecophysiology: strategies towards achievement of positive carbon balance. In: M. A. Leck, V. T. Parker, and R. L. Simpson. Seedling Ecology and Evolution. Cambridge University Press. Pp. 172-188.
Alvarez-Clare, S. and Kitajima, K. 2007. Physical defense traits enhance seedling survival of neotropical tree species. Functional Ecology 21: 1044-1054.
Myers, J. A. and Kitajima, K. 2007. Carbohydrate storage enhances seedling shade and stress tolerance in a neotropical forest. Journal of Ecology 95: 383-395.
Poorter, L. and Kitajima, K. 2007. Carbohydrate storage and light requirements of tropical moist and dry forest species. Ecology 88: 1000-1011
Kitajima, K., Fox, A. M., Satoh, T. and Nagamatsu, D. 2006. Cultivar selection prior to introduction may increase invasiveness: evidence from Ardisia crenata. Biological Invasions 8:1471-1482.
Graham, E. A., Mulkey, S. S., Wright, S. J., Kitajima, K. and Phillips, N. G. 2003. Cloud cover limits productivity in a tropical rain forest tree during La Nina. Proceeding of the National Academy of Science 100: 572-576.
Kitajima, K., Mulkey, S. S., Samaniego, M., and Wright, S. J. 2002. Decline of photosynthetic capacity with leaf age and position in two tropical pioneer tree species. American Journal of Botany 89: 1925-1932.
Kitajima, K. 2002. Do shade-tolerant tropical tree seedlings depend longer on seed reserves? Functional growth analysis of three Bignoniaceae species. Functional Ecology 16: 433-444.
Kitajima, K., Mulkey, S. S. and Wright, S. J. 1997. Seasonal leaf phenotypes in the canopy of a tropical dry forest: photosynthetic characteristics and associated traits. Oecologia 109: 490-498.
Kitajima, K. 1994. Relative importance of photosynthetic and allocation traits as correlates of seedling shade tolerance of 15 tropical tree species. Oecologia 98: 419-428.