|CLINE, NATHAN - Brigham Young University
|ROUNDY, BRUCE - Brigham Young University
|CHRISTENSEN, WILLIAM - Brigham Young University
Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2017
Publication Date: 12/11/2017
Citation: Cline, N., Roundy, B., Hardegree, S.P., Christensen, W. 2017. Using germination prediction to inform seeding potential: II. comparison of germination predictions for cheatgrass and potential revegetation species in the Great Basin, USA. Journal of Arid Environments. 150:82-91. https://doi.org/10.1016/j.jaridenv.2017.11.019.
Interpretive Summary: Cheatgrass threatens millions of acres of rangeland in the Intermountain western US by preemptively utilizing available soil resources and altering the fire cycle. Germination-prediction models could potentially be used in conjunction with field information to evaluate plant materials for their suitability and adaptation to local site conditions. In this study, we used wet-thermal-time models to predict potential field-germination response of cheatgrass and several perennial restoration species. We found that most plant materials could be expected to germinate in both the spring and fall, with little difference attributed to specific sites, years and tree-removal treatments, although prescribed-burning greatly increased potential germination rate. These treatments, however, do influence relative timing of germination within a given season, and the timing of subsequent root growth and the probability for seedling establishment. The prediction of germination timing may be a very useful tool for characterization of site potential, and evaluation of effects of seedbed modification and seed treatments designed to improve seedling survival.
Technical Abstract: Germination models predict germination timing under seedbed water potential and temperature conditions. Using a wet thermal time model for germination prediction, we estimated progress toward germination (PTG) of 31 seedlots (10 species) as a function of hourly seedbed temperature (> 0 °C) when soils were above a water potential of -1.5 MPa. Seasonally-summed progress toward germination with a value >1 indicates that germination will occur for that season. We used near surface (1-3 cm) soil water potential and temperature measurements collected at 24 sites in the Great Basin to determine effects of site, season, and year on PTG. On tree encroached sites, we also determined effects of tree infilling phase at time of tree removal, removal method, and microsite on estimated PTG. Soils were wet and warm enough in early spring, late spring, and fall for PTG > 1 indicating potential germination for most seedlots and species on most sites and years. Prescribed burning increased PTG as much as three times more than either tree cutting or mechanical shredding. Germination prediction could help to screen for plant materials adapted to specific sites or assess effects of seed additives or treatments that time germination to maximize seedling survival.