Allen, Phil S. , Meyer, Susan E. .
Predicting field germination phenology of two facultatively fall-emerging grass species using a hydrothermal time model.
IN semiarid habitats, the process of seed germination is regulated primarily by seed zone temperature and water potential. Hydrothermal time modeling provides a way of integrating the effects of these two variables on seed germination under fluctuating conditions. This makes it possible to use models developed in the laboratory to predict field germination phenology. To validate such field models, it is necessary to place seeds in the field and measure subsequent fluctuations in seed zone conditions. This is relatively easy for temperature, but difficult for water potential, requiring the testing of several alternative approaches. We placed seeds of two species (Bromus tectorum and Elymus elymoides) in the field at salt desert and sagebrush steppe study sites and monitored seed bed conditions and germination phenology during three successive years. We compared two types of predictive models: classical hydrothermal time models and thermal time models using a water potential threshold (below which germination directed-physiology is defined as not occurring). Model predictions were most accurate when germination flushes occurred in response to major precipitation events following long dry periods. In order to refine the predictive ability of these models, we need a better understanding of the effects of intermittent wetting and drying, especially of partially after-ripened seeds.[c.e.:srb]
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1 - Department of Plant and Animal Sciences, Brigham Young University, Provo, Utah, 84602, USA
2 - USDA Forest Service, Rocky Mountain Research Station, Shrub Sciences Laboratory, 735 N 500 E, Provo, Utah, 84606, USA
field germination model.
Presentation Type: Oral Paper:Papers for Topics
Date: Tuesday, August 1st, 2006
Time: 10:15 AM