Short-term warming and water stress affect Panicum maximum Jacq. stoichiometric homeostasis and biomass production.

Climate changes affect the growth of forage species. However, information regarding the effects of global climate change on the stoichiometry of tropical pastures is lacking, especially under field conditions. Such information is crucial to understand how temperature conditions and water availability states are likely to affect the stoichiometric homeostasis and biomass production of Panicum maximum, an important C4 tropical forage species, under future climate change scenarios. Thus, we, conducted a field experiment using a temperature free-air controlled enhancement system and evaluated the effects of two temperature conditions, ambient temperature and moderate warming (2 °C above ambient canopy temperature), and two levels of water availability, irrigated and non-irrigated, on the stoichiometric patterns of C:N:P and leaf biomass production. The experiment was conducted using a randomized complete block design in a factorial arrangement with four replications over 3 weeks. Our findings revealed that the N and P leaf concentration greatly decreased in water-stressed plants, which increased the C:N and C:P ratios, while warming increased the N:P ratio. Leaf biomass production was impaired by up to 16% under water stress and ambient temperature conditions, but the biomass production was improved by 20% under warming and irrigated conditions. Our findings showed that homeostatic instability under rainfed conditions resulted in decreased leaf biomass production. Therefore, we concluded that warming is only beneficial for plant growth (i.e., a high homeostatic capacity was maintained) under well-irrigated conditions.