Rising CO2 Boosts Growth of African C4 Savanna Grasses Under Dry Conditions
A synthesis of experiments, three decades of field data from Kruger National Park, and model simulations shows that higher atmospheric CO₂ enhances above-ground production of wild C4 grasses, especially when water is limited.
Researchers combined a meta-analysis of 70 CO₂-addition experiments, a 32-year record of grass biomass from 533 plots in Kruger National Park, and climate-vegetation modelling to assess how rising atmospheric CO₂ affects C4 savanna grasses. Experiments show that elevated CO₂ reduces stomatal conductance under water stress, leading to higher photosynthetic rates and greater shoot biomass. In the Kruger dataset, grass production increased consistently over three decades, with larger relative gains in drier, clay-rich soils, despite no systematic change in rainfall and a warming trend that slightly suppresses growth.
Model runs using the Community Land Model reproduce the observed patterns and project continued increases in C4 grass productivity into 2100, though higher temperatures will offset some of the CO₂ fertilization effect. The study demonstrates that CO₂ directly fertilizes wild C4 grasses by improving water use, with implications for savanna carbon dynamics, fire regimes, and vegetation shifts.
Why it matters
Understanding CO₂ impacts on savanna grasses helps predict future carbon storage, fire risk, and ecosystem changes in a warming world.
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