Fall acclimation and spring deacclimation of root cold tolerance for two perennial asters1

Abstract

Snow is an important temperature insulator for overwintering plants, and as the depth and duration of snowpack decreases with warmer weather and the frequency of extreme climate events increases, belowground tissues may be exposed to colder temperatures. Determining the cold tolerance of overwintering plant tissues for native species could help predict species persistence following winter climate change, yet most plant cold tolerance studies are about agricultural crop species, woody plants, or aboveground tissues. Also, plants can acclimate and deacclimate to winter so measuring cold tolerance across seasons provides a more accurate assessment of a species susceptibility to winter climate change. Here, we measure root cold tolerance of two native perennial grassland forbs (Solidago rigida and Silphium integrifolium) in a restored prairie across time to examine cold acclimation and deacclimation to seasonal temperature changes. Average root cold tolerance varied between the two species. Over time, the roots of S. rigida predictably gained cold tolerance as fall progressed and lost cold tolerance in spring. However, roots of S. integrifolium had variable cold tolerance across both seasons. The differences in cold tolerance development between grassland forb species may be a contributing factor explaining species persistence under continued winter climate change. Further research on the cold tolerance of native plant species and belowground tissues is needed to predict the response of temperate plant species and communities to winter climate change.