Аннотация:Past studies of forest structure have suggested that both plant and animal communities may be organized into several distinct vertical strata, the number of strata increasing with decreasing latitude. Hypotheses are proposed to explain the development of such strata. It is suggested that stratification may (1) optimize light utilization, (2) increase CO2 concentrations within the forest canopy, (3) increase pollination and dispersal rates, (4) reduce predation on flowers, fruit, and leaves, and (5) increase structural integrity of the forest. Causal explanations for stratification are also proposed.