Factors influencing decomposition of leaves for five plant species at El Verde

We evaluated the influences of leaf quality, climate and microsite on the decomposition of leaves of five tropical tree species. Single-species litterbags were used to determine weight loss during the first three months of decomposition in the Luquillo Experimental Forest, Puerto Rico. Significant differences were found in decomposition rates among leaf species (Inga fagifolia < I. vera < Manilkara bidentata < C-roton poecilanthus << Sapium laurocerasus), but only S. laurocerasus differed significantly from the other species. Lignin had a suggestive negative correlation with leaf decomposition while carbon content and the lignin:N ratio were significantly correlated with mass loss. Content of N, P, Ca, and polyphenol were not significantly correlated with mass loss, but several of the litter quality variables were correlated with each other. Leaf species decomposed faster under canopies of their source trees than in a common plot where the source species were absent. Decomposition in two species in the Euphorbiaceae, S. laurocerasus and C. poecilanthus, was significantly affected by microsite. Leaching losses during the first three weeks were greater under source trees than in the common plot, and may have been associated with differences in canopy structure and throughfall. Differences in detrital communities, however, could have contributed to the differences in decomposition between microsites. Leaves of all species decomposed significantly faster in the wet than in the dry period (P = 0.001) despite little climatic variation in this subtropical wet forest type. This suggests that decomposition of tropical leaf litter might be sensitive to microclimatic changes on the forest floor resulting from either global climate change, or from natural or anthropogenic disturbances that open the canopy. Support for this work was provided by grants BSR-8811902, DEB-9411973, DEB-9705814 , DEB-0080538, DEB-0218039 , DEB-0620910 , DEB-1239764, DEB-1546686, and DEB-1831952 from the National Science Foundation to the University of Puerto Rico as part of the Luquillo Long-Term Ecological Research Program. Additional support provided by the University of Puerto Rico and the International Institute of Tropical Forestry, USDA Forest Service.