Using germination prediction to inform seeding potential: I. Temperature range validation of germination prediction models for the Great Basin, USA

Abstract

Wet thermal germination regression models predict when subpopulations of seeds will germinate based on the summation of thermal time when seedbed soil water potential > −1.5 MPa. Germination rates fit models well at temperatures greater than 5 °C and less than 25 °C, but may not fit as well outside of that range. To better determine accuracy of these models, we quantified and compared seasonal wet degree days (WDD – a measure of thermal time) of sagebrush (Artemisia L.) -steppe seedbeds at five temperature ranges for up to 9 yr across 24 sites. Estimated thermal effects of three piñon and juniper (Pinus spp. and Juniperus spp.) tree removal treatments and three woodland infilling phases at time of tree reduction were also compared. We found that seedbeds sum a majority of WDD between 5 °C and 25 °C. Exceptions amounted to a relatively small percentage (12–20%) of total WDD in a season. Tree infilling or removal added WDD at 0 to <5 °C and 25 to <30 °C on a few sites, but germination models should still be accurate enough to predict germination for many sagebrush steppe sites and also predict the effects of vegetation manipulations on germination potential.