Dr. Susan E. Meyer
Modelling Seed Dormancy Loss and Germination Phenology in Grasses
Dr. Phil Allen, Brigham Young University, Provo UT
Dr. Bruce Roundy, Brigham Young University, Provo UT
We obtained funding from the CSREES Rangelands Special Grants Program in 1992 to begin our efforts to model seed dormancy loss and germination phenology in the field. We chose two species, the annual weed cheatgrass (Bromus tectorum ) and the early seral native bunchgrass squirreltail (Elymus elymoides, aka Sitanion hystrix) as our model organisms. We combined three elements in order to develop our models: 1) detailed laboratory studies quantifying dormancy loss and germination as a function of temperature and water potential, 2) instrumented cheatgrass-dominated field sites at Whiterocks, in Skull Valley UT, and at Point of the Mountain, just north of Provo UT, where data loggers provided hourly records of temperature and water potential in the seed zone, and 3) seed retrieval studies at the instrumented sites, with weekly verification of the status of seeds in the field. These three sets of data, combined with a theoretical framework, enabled us to test alternative models for dormancy loss and germination regulation under field conditions. We later added a number of annual grass species from the Negev Desert of Israel to our study, through cooperative funding from the International Arid Lands Consortium. We continue to obtain useful generalizations from these model-building efforts and also to refine our approach to predicting the fate of seeds in the real world.