DECOMPOSITION AND MASS OF WOODY DETRITUS IN THE DRY TROPICAL FORESTS OF THE NORTHEASTERN YUCATAN PENINSULA, MEXICO

The decomposition rates and mass of fine ( < 10-cm-diameter) and coarse ( > 10-cm-diameter) woody detritus were measured in the dry tropical forests of the northeastern Yucatan Peninsula. The smallest mass of woody detritus was found in undisturbed stands: fine fractions averaged 4.7 Mg ha(-1) and coarse fractions ranged between 13 and 38 Mg ha(-1). The largest mass of fine woody detritus (32.2 Mg ha(-1)) was found in a hurricane-disturbed forest; whereas, the largest mass of coarse woody detritus (99.5 Mg ha(-1)) was found in stands disturbed by catastrophic fires. A decomposition time-series study installed in 1989 indicated that decomposition rates varied greatly among species and diameters of branch segments. Over a 4-year period, the decomposition rate constant for fine woody detritus ranged from 0.151 to 1.019 year(-1) and that for coarse woody detritus ranged from 0.008 to 0.615 year(-1). The half-life of woody detritus increased 33-fold (among pieces ranging from 1 to 30 cm in diameter) for the most decay-resistant species (Manilkara zapota) but was relatively constant for the least decay-resistant species (Bursera simaruba). The wide range in decomposition rates observed in these forests indicates that the poor substrate quality of some species may override climatic (e.g., warm temperatures) and biotic (e.g., termites) factors favorable to rapid decomposition, leading to a substantial accumulation of woody detritus.