The experiment


The Gigante Litter Manipulation Experiment was established on Gigante Peninsula, in the Barro Colorade Nature Monument, Panama, between 2000 and 2003. There are 15 plots measuring 45-m x 45-m each; the plots were trenched to 50-cm depth to limit transfer of water and nutrients among plots. All trees with a diameter at breast height (DBH) > 10 cm were tagged, measured, identified and mapped for the first time between 2000 and 2001. Starting in 2003, we have removed the litter from five 'litter removal' plots (L-) and added it to five 'litter addition' (L+) plots every 4-8 weeks, leaving 5 plots as controls.

The experiment has run continuously ever since, with only a short break in the regular application of treatments during the Covid-19 pandemic!



  • Tree growth is measured at least every two years (since 2000)
  • Litterfall has been collected monthly since February 2002 (except for 6 months during the Covid-19 pandemic). 
  • Soil, litter, and live leaf concentrations have been measured periodically since 2003
  • Soil respiration (CO2 efflux) was measured up to monthly from 2003-2009 and from 2016-2017


Over the years, we have also conducted studies of:

  • Methane and nitrous oxide fluxes from soils and tree stems
  • Fine root biomass and production
  • Soil microbial and mycorrhizal communities
  • Soil extracellualr enzymes
  • Seedling growth and photosynthesis
  • Arthropods in soil, litter and deadwood

See the full list of publications arising from the experiment below

If you are interested in working with any of our datasets or you would like to conduct studies within the experimental plots, please contact emma.sayer(at)


Peer-reviewed papers

  1. Sayer EJ, Baxendale C, Birkett AJ, Bréchet LM, Castro B, Kerdraon-Byrne D, Lopez-Sangil L, Rodtassana C (2021)†Altered litter inputs modify carbon and nitrogen storage in soil organic matter in a lowland tropical forest.Biogeochemistry, 156:115-130.
  2. Sayer EJ, Rodtassana C, Sheldrake M, Bréchet LM, Ashford O, Lopez-Sangil L, Kerdraon-Byrne D, Castro B, Turner BL, Wright SJ, Tanner EVJ (2020)† Revisiting nutrient cycling by litterfall – insights from 15 years of litter manipulation in old-growth lowland tropical forest. Advances in Ecological Research, 62:173-223.
  3. Sayer EJ, Lopez-Sangil L, Crawford JA, Brechet LM, Birkett AJ, Baxendale C, Garnett M, Weiss L, Schmidt MWI (2019)† Tropical forest soil carbon stocks do not increase despite 15 years of doubled litter inputs. Nature Scientific Reports, 9:18030.
  4. Welch B, Gauci V, Sayer EJ (2019)† Tree stem bases are sources of CH4 and N2O in a tropical forest on upland soil during the dry to wet season transition. Global Change Biology, 25:361-372.
  5. Rodtassana, C., & Tanner, E. V. J. (2018). Litter removal in a tropical rain forest reduces fine root biomass and production but litter addition has few effects. Ecology99, 735-742.
  6. Sheldrake M, Rosenstock MP, Mangan S, Revillini D, Sayer EJ, Olsson PA, Wallander H, Tanner EVJ, Wright SJ, Turner BL (2018)† Responses of arbuscular mycorrhizal fungi to long-term inorganic and organic nutrient addition in a lowland tropical forest. ISME Journal, 12:2433–2445.
  7. Gora EM, Sayer EJ, Turner BL, Tanner EVJ (2018) Decomposition of coarse woody debris in a long‐term litter manipulation experiment: A focus on nutrient availability. Functional Ecology, 32:1128-1138.
  8. Cusack, D. F., Halterman, S. M., Tanner, E. V., Wright, S. J., Hockaday, W., Dietterich, L. H., & Turner, B. L. (2018). Decadal-scale litter manipulation alters the biochemical and physical character of tropical forest soil carbon. Soil Biology and Biochemistry124, 199-209.
  9. Sheldrake M, Rosenstock N, Revillini D, Olsson PA, Mangan S, Sayer EJ, Turner BL, Tanner EVJ (2017)† Arbuscular mycorrhizal fungal community composition is altered by long-term litter removal but not litter addition in a lowland tropical forest. New Phytologist, 214:455-467.
  10. Tanner, E. V. J., Sheldrake, M. W., & Turner, B. L. (2016). Changes in soil carbon and nutrients following 6 years of litter removal and addition in a tropical semi-evergreen rain forest. Biogeosciences13, 6183-6190.
  11. Gross, A., Turner, B. L., Wright, S. J., Tanner, E. V., Reichstein, M., Weiner, T., & Angert, A. (2015). Oxygen isotope ratios of plant available phosphate in lowland tropical forest soils. Soil Biology and Biochemistry88, 354-361.
  12. Schreeg, L. A., Mack, M. C., & Turner, B. L. (2013). Leaf litter inputs decrease phosphate sorption in a strongly weathered tropical soil over two time scales. Biogeochemistry113, 507-524.
  13. Vincent, A. G., & Tanner, E. V. (2013). Major litterfall manipulation affects seedling growth and nutrient status in one of two species in a lowland forest in Panama. Journal of Tropical Ecology29, 449-454.
  14. Ashford OS, Foster WA, Turner BL, Sayer EJ, Sutcliffe L, Tanner, EVJ (2013)† Litter manipulation and the soil arthropod community in a lowland tropical rainforest. Soil Biology & Biochemistry, 62:5-12.
  15. Sayer EJ, Tanner EVT, Wright SJ, Yavitt JB, Harms KE, Powers JS, Kaspari M, Garcia MN, Turner BL. (2012) Variable responses of lowland tropical forest nutrient status to fertilization and litter manipulation. Ecosystems, 15:387-400.
  16. Sayer EJ, Heard MS, Grant HK, Marthews TR, Tanner EVJ (2011) Soil carbon release enhanced by increased tropical forest litterfall. Nature Climate Change, 1:304-307.
  17. Vincent, A. G., Turner, B. L., & Tanner, E. V. (2010). Soil organic phosphorus dynamics following perturbation of litter cycling in a tropical moist forest. European Journal of Soil Science61, 48-57.
  18. Sayer EJ & Tanner EVT (2010) Experimental investigation of the importance of litterfall in lowland semi-evergreen tropical forest nutrient cycling. Journal of Ecology, 98:1052-1062.
  19. Sayer EJ & Tanner EVJ (2010) A new approach to trenching experiments for measuring root-rhizosphere respiration in a lowland tropical forest. Soil Biology & Biochemistry, 42:347-352.
  20. Sayer EJ, Sutcliffe L, Ross R, Tanner EVJ (2010)† Arthropod abundance and diversity in the forest floor of a lowland tropical forest: the role of habitat space vs. nutrient concentrations. Biotropica, 42:194-200.
  21. Sayer EJ, Powers JS, Tanner EVJ (2007) Increased litterfall in tropical forests boosts the transfer of soil CO2 to the atmosphere. PLoS One, 2:e1299.
  22. Sayer EJ, Tanner EVJ, Cheesman AW (2006)† Increased litterfall changes fine root distribution in a moist tropical forest. Plant & Soil, 281:5-13.
  23. Sayer EJ, Tanner EVJ, Lacey AL (2006)† Litter quantity affects early-stage decomposition and meso-arthropod abundance in a moist tropical forest. Forest Ecology & Management, 229:285-293.


Book chapters

  1. Tanner EVJ, Rodtassana C, Bréchet LM, Vincent AG, Leitman SF, Wright SJ and Sayer EJ (in press) The Gigante Litter Manipulation Experiment. In: The First 100 Years of Research on Barro Colorado: Plant and Ecosystem Science (HC Muller-Landau and SJ Wright, Eds.), Smithsonian Contributions to Botany Series, Smithsonian Institution Scholarly Press.
  2. Sayer EJ & Banin LF (2016) Tree nutrient status and nutrient cycling in tropical forest – lessons from fertilization experiments. In: Tropical Tree Physiology pp. 275-297 (eds. G Goldstein and LS Santiago), Springer.