Introduction

The 1992 PACLIM meeting featured the Long-Term Ecological Research (LTER) program, sponsored by the National Science Foundation. Ranging from hot to cold and wet to dry climatic regimes, these 18 sites are attempting to understand the web of relationships in different locations as communities evolve over time scales of years to decades to centuries. During this time they are subject to external forcings, including those that vary smoothly and somewhat predictably, like the seasons, upon which are superimposed random "shocks" of various magnitudes.