Jayne Belnap Sasha C. Reed Timothy M. Wertin 2016 <p>1. Drylands represent our planet's largest terrestrial biome and, due to their extensive area, maintain large stocks of carbon (C). Accordingly, understanding how dryland C cycling will respond to climate change is imperative for accurately forecasting global C cycling and future climate. However, it remains difficult to predict how increased temperature will affect dryland C cycling, as substantial uncertainties surround the potential responses of the two main C fluxes: plant photosynthesis and soil CO₂ efflux. In addition to a need for an improved understanding of climate effects on individual dryland C fluxes, there is also notable uncertainty regarding how climate change may influence the relationship between these fluxes.</p><p>2. To address this important knowledge gap, we measured a growing season's <i>in situ</i>photosynthesis, plant biomass accumulation, and soil CO₂ efflux of mature <i>Achnatherum hymenoides</i> (a common and ecologically important C₃ bunchgrass growing throughout western North America) exposed to ambient or elevated temperature (+2°C above ambient, warmed via infrared lamps) for three years.</p><p>3. The 2°C increase in temperature caused a significant reduction in photosynthesis, plant growth, and soil CO₂ efflux. Of important note, photosynthesis and soil respiration appeared tightly coupled and the relationship between these fluxes was not altered by the elevated temperature treatment, suggesting C fixation's strong control of both above-ground and below-ground dryland C cycling. Leaf water use efficiency was substantially increased in the elevated temperature treatment compared to the control treatment.</p><p>4. Taken together, our results suggest notable declines in photosynthesis with relatively subtle warming, reveal strong coupling between above- and below-ground C fluxes in this dryland, and highlight temperature's strong effect on fundamental components of dryland C and water cycles.</p> application/pdf 10.1111/1365-2435.12708 en Wiley Experimental warming in a dryland community reduced plant photosynthesis and soil CO₂ efflux although the relationship between the fluxes remained unchanged article