Using integrative biology to explore constraints on evolution.

0169-5347/99/$ – see front matter © 1999 Elsevier Science. All rights reserved. PII: S0169-5347(98)01505-5 5 significant long-term changes in nutrient mineralization, which causes major and often unexpected changes in plant species composition. Combined with Foster and Gross’s observation about the strong effects of litter on plant species establishment, these results imply that litter production and decomposition must be considered if we are to understand the long-term dynamics of plant communities. We are only just beginning to understand how litter-mediated mechanisms might determine species composition and diversity of plant communities. Effects of accumulated litter on the light intensity and spectral composition experienced by seeds and seedlings are certainly important, but there are many other effects that should also be taken into account. For example, we should consider the effects of litter on air humidity and pathogen transfer and the subsequent implications for seedling survival. We also need to know more about how changes in the quantities and chemical composition of the litter produced affect the accumulation of soil organic matter. Changes in the dynamics of soil organic matter could strongly affect nutrient mineralization and soil acidity, which are among the most important factors that determine the diversity in species-rich communities.