Rising CO2 Boosts Southern Africa C4 Grass Output 28% Over 3 Decades
Updated
Updated · Nature.com · Aug 19
Rising CO2 Boosts Southern Africa C4 Grass Output 28% Over 3 Decades
3 articles · Updated · Nature.com · Aug 19
Summary
A 32-year record from 533 plots in South Africa’s Kruger National Park found annual C4 grass production rose 28%, or 75.1 g per square meter, as atmospheric CO2 increased by 65 ppm.
A meta-analysis of 70 CO2-enrichment experiments showed the boost was strongest under dry conditions, where higher CO2 reduced stomatal water loss and improved plant water status while lifting photosynthesis.
Rainfall patterns did not trend in a way that explained the biomass gains, and warming should have suppressed growth; rising herbivory and limited evidence for nitrogen deposition also failed to account for the increase.
The increase was larger on nutrient-rich basalt soils than sandy granite soils, and shifts toward taller, more productive grasses explained only part of the rise.
Model simulations suggest CO2 fertilization of C4 grasses will continue through 2100, though heat and aridity will dampen gains and the effects on fire, woody encroachment and long-term carbon storage remain uncertain.