Since 1972, twelve scientists representing several research disciplines have collaborated in integrated studies to determine the chronic effects of photochemical oxidant air pollutants on a western mixed conifer forest ecosystem. An enormous amount of data has been collected, describing present and past natural conditions of twelve subsystems comprising the conifer forest ecosystems of the San Bernardino Mountains of Southern California. A computer data bank is being developed to allow efficient storage and retrieval of these numerous data sets. The systems simulation modeling process has begun early in 1975. The basic unit for modeling purposes was defined as the forest stand, which may be comprised of from 10 to 200 trees with equivalent land areas of from 100 to 25,000 sq m. Time resolution varies according to the subsystem in question and may be hourly, daily, biweekly, monthly, seasonal, annual, or multi-annual. The subsystems receiving attention at the stand level are defined as: tree population dynamics, oxidant flux canopy response, stand-tree growth, stand moisture dynamics and microclimate, stand mortality responses related to bark beetles and root disease, tree seedling establishment, cone and seed production, litter production, litter decomposition, and small mammal population dynamics.

"EPA 600-3-77-104." "September 1977." Cover title. Study conducted by the Statewide Air Pollution Research Center, University of California, Riverside and the University of California, Berkeley. Prepared for the U.S. Environmental Protection Agency, Office of Research and Development, Corvallis Environmental Research Laboratory, Corvallis, Or., under contract numbers 68-03-0273 and 68-03-2442. Includes bibliographical references (pages 251-263).

General description of ecosystem properties -- Definition of the conifer forest ecosystem as a group of coupled ecological models -- Tree population dynamics subsystem -- Oxidant flux-canopy response subsystem -- Stand-tree growth subsystem -- Stand moisture dynamics and microclimate subsystems -- Western Pine Bark Beetle population dynamics- stand mortality response subsystem -- Root pathogen dynamics and stand mortality subsystem -- Tree seedling establishment subsystem -- Cone and seed production subsystem -- Small mammal population dynamics subsystem.