Nitrogen, an essential plant nutrient, is most readily absorbed by plants in its ammonium and nitrate forms. Because of the very low nitrate levels found in arctic tundra soil, scientists had assumed that plants in this biome do not use nitrate. But a new study co-authored by four Marine Biological Laboratory (MBL) Ecosystems Center scientists challenges this notion. The study has important implications for predicting which arctic plant species will dominate as the climate warms, as well as how much carbon tundra ecosystems can store.