PATTERNS IN TROPICAL LEAF-LITTER AND IMPLICATIONS FOR ANGIOSPERM PALEOBOTANY

One hectare of undisturbed Amazonian forest, containing about 175 spec ies of trees larger than 10 cm diameter at breast height, was studied to determine the relationship between high-richness forest and the aut ochthonous litter produced by the forest. Litter samples contained up to 52 species, of which one-third represented epiphytes, vines, and li anas. These modem leaf litter studies from southeast Amazonian Peru in dicate that reconstructions of ancient high-diversity forests are poss ible using autochthonous leaf litter deposits. In comparison to temper ate litter samples, however, more sampling must be done to recreate fa irly simple descriptors of ancient communities such as species richnes s and heterogeneity. Samples must be large, relatively closely spaced, and maintained as distinct collecting localities to retrieve the maxi mum amount of data from rich, angiosperm-dominated localities. There a re many advantages justifying more intensive collections. For example, biomass contribution of major life-form categories in the source fore st is reflected in leaf litter accumulating under tropical forest cano pies. Tropical forests, because of their extreme heterogeneity, also c an provide the opportunity to reconstruct individual species character istics from litter signatures. The relative rarity of most species cre ates distinct leaf shadows from which the canopy breadth and volume of many individuals can be estimated. The principles derived from modem tropical litter studies can be applied to existing fossil collections; however, their power lies with those collections originating from aut ochthonous assemblages, for which spatial control during collecting ha s been maintained, and time averaging has been kept to a minimum. Thes e reflections of community structure available from the leaf litter pr ovide a means for paleobiologists to contribute significantly to the s tudy of community evolution and stability.