Balancing trade-offs: Enhanced carbon assimilation and productivity with reduced nutritional value in a well-watered C pasture under a warmer CO-enriched atmosphere.

The concentration of atmospheric CO and temperature are pivotal components of ecosystem productivity, carbon balance, and food security. In this study, we investigated the impacts of a warmer climate (+2 °C above ambient temperature) and an atmosphere enriched with CO (600 ppm) on gas exchange, antioxidant enzymatic system, growth, nutritive value, and digestibility of a well-watered, managed pasture of Megathyrsus maximus, a tropical C forage grass, under field conditions. Elevated [CO] (eC) improved photosynthesis and reduced stomatal conductance, resulting in increased water use efficiency and plant C content.

Warming offsets the benefits of elevated CO in water relations while amplifies elevated CO-induced reduction in forage nutritional value in the C grass .

Tropical grasslands are very important to global carbon and water cycles. C plants have increased heat tolerance and a CO concentrating mechanism that often reduces responses to elevated concentrations of CO ([CO]). Despite the importance of tropical grasslands, there is a scarcity of studies that elucidate how managed tropical grasslands will be affected by elevated [CO] and warming.