PS 26-67 - Cold tolerance of prairie plant species during germination

Background/Question/Methods

In many regions, including the Midwestern USA, the climate is changing faster during winter than during any other season. A loss of snow and increased temperature variability can expose overwintering organisms to cold temperatures and greater temperature fluctuations. Knowing how species may respond to these changes during critical developmental times, like seed germination, helps us understand possible ecological implications of winter climate change. To address this concern, we measured seed dormancy and cold tolerance of temperate grassland species in the field and lab. In the field, we deployed seeds within a snow manipulation experiment at three locations across a latitudinal gradient of temperature and snow accumulation. We measured germination biweekly from seeds subjected to ambient and reduced snow cover until spring to examine how varying winter conditions influence seed dormancy and germination success. This was paired with germination trials in the lab testing the cold tolerance of an additional 18 species.

Results/Conclusions

Across locations for the field experiment, there was an increase in germination success through early winter, followed by a decrease in germination success through spring. There was little to no effect of the snow removal on germination success, and when accounting for effects of seasonal timing and snow removal treatment, there was remaining unexplained variability in germination success. From lab trials, cold tolerance varied among species, with seed mortality ranging from < 10% to 100% following freeze events. Seed cold tolerance was not associated with specific dormancy requirements (e.g. cold stratification times) or seed size. Future tests which include additional species and ecological traits to will help us search for possible phylogenetic signals and indicate predictive traits for cold tolerance. Given that winter climate change is projected to continue, the variation in seed cold tolerance through time and among species may contribute to altered community composition in temperate grasslands.