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Plant-Growth-Stress Model (PGSM) is a physiologically based process model that integrates the effects of ozone, acid deposition, elevated carbon dioxide, temperature, drought, and nutrient deficiency. The model uses an hourly time step for photosynthesis and a daily time step for all other plant and soil processes. It can be set up to run for as many years as needed. The model was applied to simulate the growth pattern of ponderosa pine seedlings under the experimental conditions of ozone and drought stresses. The simulated diameter and biomass of canopy, roots, and stem were comparable to the measured. Major effect of drought stress was root mortality; however, its sublethal effect on stomata opening caused significant reductions of photosynthesis, canopy, roots, and stem. Ozone stress increased litterfall and decreased canopy. Trees compensated by growing more new needles. The canopy photosynthesis was not reduced to the extent of an across-the-board decrease of roots and stem. Ozone and drought stresses had an antagonistic effect, in which the biomass reductions due to the combined stresses were less than the sum of reductions from individual stresses. However, the observed data indicate a protective effect, not simulated by the model. For. Sci. 40(2): 267-288.
Systech Engineering, Inc., 3744 Mt. Diablo Blvd., Suite 101, Lafayette, CA 94549
Publication date: May 1, 1994
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Forest Science is a peer-reviewed journal publishing fundamental and applied research that explores all aspects of natural and social sciences as they apply to the function and management of the forested ecosystems of the world. Topics include silviculture, forest management, biometrics, economics, entomology & pathology, fire & fuels management, forest ecology, genetics & tree improvement, geospatial technologies, harvesting & utilization, landscape ecology, operations research, forest policy, physiology, recreation, social sciences, soils & hydrology, and wildlife management.