Winter belowground: Changing winters and the perennating organs of herbaceous plants

Abstract

Abstract The physical avoidance of overwinter damage is important for determining the success of herbaceous perennial plants in climates with cold winters. Exposure to damaging frost can be affected by contemporary climatic change, which can include an increase in winter air temperatures, changes in precipitation and changes in the timing and severity of warm and cold events. In this review, we consider the specific adaptations of herbaceous plants to avoid harsh winter conditions via perennating organs, what is known about their responses to warming winters, and what future directions the research of overwintering in herbs should explore. Herbaceous plants have adapted to harsh winter conditions in part by investing carbohydrates into belowground organs of perennation instead of aboveground biomass. The location of renewal buds and stored carbohydrates belowground increases their protection against freezing temperatures, and they can be further protected via insulation from plant litter or snow cover. Climate change can affect overwintering organs by altering snow cover depth and duration, thus increasing or decreasing the exposure of plants to frost, and may initiate an earlier or a later onset of growth in the spring. Winter warming can increase productivity in some species, but directly or indirectly decrease it in others and may lead to a loss of specialized plants, for example, in snowbed communities. Plants with shallow structures and taproots may be particularly vulnerable to increased soil frost penetration resulting from reduced snow cover. Measures of organ biomass and storage carbohydrate content can be used to assess how winter conditions affect allocation, storage, and the potential for growth in the spring. When destructive measures cannot be taken, the use of trait measures, such as perennating organ type, or its traits, such as depth and size of bud bank, can add further strength to the assessment of responses across multiple species. To fully understand the effects of changing winter conditions on perennial herbaceous plants, researchers must better account for plant overwintering strategies, their drivers, costs, and benefits. A free Plain Language Summary can be found within the Supporting Information of this article.