Warming and water deficit impact the nutritional performance of a C4 and C3 tropical grass

• Autor(a) principal: Viciedo, Dilier Olivera [UNESP]
• Data de Publicação: 2019
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/183182
• topic: Tropical pasture; Nutrients uptake; Combined stresses; Climate change; Stoichiometric homeostasis

Global warming is predicted to increase the intensity and duration of extreme weather events, such as droughts, heat waves, and floods, especially in tropical regions. Climate change affect growth of forage species. However, information regarding the effects of global climate change on the nutritional performance of tropical pastures is lacking, especially under field conditions. We, thus, conducted two field experiment with Panicum maximum and Stylosanthes capitata 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 nutrients accumulation, nutrient use efficiency (NUE), the stoichiometric patterns of C:N:P and leaf biomass production. Both experiments was conducted using a randomized complete block design in a factorial arrangement. Our findings revealed in plants of P. maximum (C4- grass) that the N and P leaf concentration greatly decreased under water-stressed, 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 results also showed that homeostatic instability under rainfed conditions resulted in decreased leaf biomass production, and it was concluded that warming is only beneficial for plant growth under well-irrigated conditions. Meanwhile, drought decreased NUE of K, Ca, and B and the leaves dry biomass, while root growth was stimulated. However, under combined warming and irrigation increased the leaves dry biomass, root dry biomass, root length density, root surface area and the NUE of N, P, K, Ca, Mg, Cu, Mn, and Zn. On the other hand, in the second experiment with plants of S. capitata (C3-pasture), our results showed that drought conditions decreased phosphorous (P) concentrations and increased N:P ratio in different plant organs. We found that aboveground biomass production declined significantly under drought and high temperature conditions (wSaT and wSeT); we observed a decrease in nitrogen (N) content, a decrease in leaf/inflorescence and leaf/stem ratios, and an increase in C:N ratio in vegetative organs. However, under warm and well-irrigated conditions, the leaf biomass increased approximately 33%. We have concluded that warm and well-watered conditions without restrictions in soil nutrient availability can enhance plant production, presumably due to a higher level of stoichiometric homeostasis.