Out to Dry

Scientists expect that rising carbon dioxide levels in the atmosphere will boost the growth of many plants. But a decade-long study has revealed that high CO2 levels have little long-term effect on plants in the desert.

Plants need carbon dioxide to perform photosynthesis and grow. Previous studies have suggested that high CO2 conditions often increase plant growth in forests, grasslands, and croplands, but little work had been done in deserts.

To fill the gap, researchers set up an experiment in the Mojave Desert, Nevada in 1997. For 10 years, the team maintained nine plots of shrubs, grasses, and other plants. Some plots had normal CO2 levels, while others had unusually high CO2 levels. In 2007, the researchers harvested and analyzed the plants.

When the team compared the plants grown in normal and high CO2 conditions, they didn’t see much of a difference in mass or canopy cover. The high-CO2 plants may have not shown any net improvement in growth because the area suffered a four-year-long drought, which cancelled out extra growth during wetter periods. In other words, desert plants can’t take advantage of the added CO2 unless they also have enough water. Roberta Kwok | 27 February 2013

Source: Newingham, B.A. et al. 2013. No cumulative effect of ten years of elevated [CO2] on perennial plant biomass components in the Mojave Desert. Global Change Biology doi: 10.1111/gcb.12177.

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