Leaf decomposition in five common species was studied in the Los Tuxtlas tropical rain forest, Veracruz state, Mexico. The species were: Nectandra ambigens (Blake) C. K. Allen, Pseudolmedia oxyphyllaria Donn. Sm, Dussia mexicana (Standl.) Harms, Ficus yoponensis Desvaux and Poulsenia armata (Mig.) Standl. Two experimental studies were done using litter bags, one comparing hat and slope conditions, and the second one in closed canopy and gap conditions. In addition, decomposition was compared between the dry and rainy season. There were significant differences in decomposition rates between species and seasons, but not between zones (flat and gentle slope, and dosed forest and gap conditions). The highest decomposition rates were observed for species with high nutrient contents, and also during the rainy season. The data were hued to three mathematical models derived from the negative simple exponential
the double exponential model for decay was significant. Also, the negative, simple, exponential model which assumes that k is nor constant, turned out to be significant for the experiment in dosed canopy and gap conditions.