Drought in a warmer, CO-rich climate restricts grassland water use and soil water mixing.

Soil water sustains terrestrial life, yet its fate is uncertain under a changing climate. We conducted a deuterium labeling experiment to determine whether elevated atmospheric carbon dioxide (CO), warming, and drought impact soil water storage and transport in a temperate grassland. Elevated CO created a wetter rootzone compared with ambient conditions, whereas warming decreased soil moisture.

Individual Versus Combined Effects of Warming, Elevated CO and Drought on Grassland Water Uptake and Fine Root Traits.

Increasing warming, atmospheric CO and drought are expected to change the water dynamics of terrestrial ecosystems. Yet, limited knowledge exists about how the interactive effects of these factors will affect grassland water uptake, and whether adaptations in fine root production and traits will alter water uptake capacity. In a managed C grassland, we tested the individual and combined effects of warming (+3°C), elevated CO (eCO; +300 ppm) and drought on root water uptake (RWU) as well as on fine root production, trait adaptation, and fine root-to-shoot production ratios, and their relationships with RWU capacity.