Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/1998
Publication Date: N/A
Interpretive Summary: Millions of acres of public and private rangeland in the intermountain west have been converted to undesirable weedy species following wildfire disturbance. Revegetation success is difficult to predict on these lands because they experience such a high level of variability in temperature and moisture availability for plant establishment. Development of tools for predicting establishment success under field-variable environmental conditions would help us develop new management strategies for revegetating disturbed rangelands. In this study, we tested models for predicting seed germination under field-variable temperature regimes. We determined that laboratory measurements at constant temperature could be used to predict germination response under complex field-temperature conditions that vary in daily and seasonal temperature pattern. This makes it possible to determine how different species and seedlots might behave in different years and under alternative seedbed management treatments.
Technical Abstract: Germination of non-dormant seeds under variable-temperature conditions can be predicted from constant-temperature germination data if it is assumed that instantaneous germination rate is independent of thermal history. Very few thermal-response models of this type have been validated under field-variable temperature conditions. The purpose of this experiment was to evaluate germination response of thickspike wheatgrass [Elymus lanceolatus (Scribn. and J.G. Smith) Gould], bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) L¿ve], Sandberg bluegrass (Poa sandbergii Vasey.) and bottlebrush squirreltail [Elymus elymoides (Raf.) Swezey] under both constant and field-variable temperature regimes in the laboratory. Seeds were germinated at 7 constant temperatures between 5 and 35øC, and under 18 variable-temperature regimes simulating 6 planting dates at three field sites. Constant-temperature germination rates were used to estimate cumulative germination response under variable temperature conditions. Predictions of germination-time were accurate to within a fraction of one day up to a cumulative germination percentage of 70% for thickspike wheatgrass, 60% for bluebunch wheatgrass, 55% for Sandberg bluegrass and 70% for bottlebrush squirreltail.