Yearly vegetative growth in Midwestern prairie plants is dominated by below ground bud bank recruitment as opposed to the germination of new individuals. Reliance on the buds over seed germination means researching the stress tolerances of the bud bank is a critical step in understanding prairie response to climate change. Winters in temperate regions are changing quickly, with increased frequency of freeze-thaw cycles and a loss of continuous snow cover. The literature surrounding bud bank stress tolerances focuses almost exclusively on response to drought and fire/grazing, with little focus paid to the effect of cold. Therefore, our main research goal was to determine the effects of winter climate change on prairie plant bud bank survival and growth. Rhizomes from two dominating prairie grasses, Andgerpogon gerardi and Bromus inermis, were collected in June 2019. Samples were collected from four different management scenarios: spring burn, fall burn, mowing, and no management. Bud cold tolerance was measured by removing buds from rhizomes and placing them in a cold bath with a programmed cooling rate. A thermal camera recorded the temperature of the buds to determine the temperature of ice nucleation.
Results/Conclusions
Average cold tolerance varied significantly between the two grass species, as average cold tolerance of A. gerardi ranged from -7.8 ℃ to -17.0 ℃ and average cold tolerance of B. inermis ranged from -11.0℃ to -16.7℃. To date, measurements have indicated soils in the area currently reach as low as -15℃, with the potential to get colder as a result of climate change. Cold tolerance did not vary significantly between species across land treatment. The emergence of B. inermis early in the growing season is one possible explanation for the greater cold tolerance of this species. By sending up shoots as soon as the soil thaws, B. inermis is risking exposure to a late in the season freeze event. Buds with greater cold tolerance will better equip this species with the ability to withstand such events. Because A. gerardi is a warm season grass, it usually does not come under threat by the late spring freezes. Understanding the cold tolerance of prairie plant bud banks is crucial in order to determine best management practices and interpret how the composition of prairies may shift with climate change. The higher cold tolerance of B. inermis indicates its potential to withstand climate change and become an even greater invasive problem.