Plant diurnal cycle drives the variation in soil respiration in a C4-dominated tropical managed grassland exposed to high CO2 and warming

• Published in: Plant and soil 2020-11, Vol.456 (1-2), p.391-404
• Main Authors: Dias de Oliveira, Eduardo Augusto, Manchon, Fernanda Tomita, Ricketts, Michael P., Bianconi, Matheus, Martinez, Carlos Alberto, Gonzalez-Meler, Miquel A.
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; Ecology; Life Sciences; Plant Physiology; Plant Sciences; Regular Article; Soil Science & Conservation
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-020-04718-7

Aims To identify factors driving soil respiration (R soil ) in a tropical C 4 -dominated perennial managed grassland ecosystem exposed to elevated carbon (C) dioxide concentration ([CO 2 ]) and temperature. Methods The perennial grass Panicum maximum was grown at 600 μmol CO 2 mol −1 and + 2 °C above ambient temperatures for one full growing cycle (from grazing to regrowth for about ~30–45 days) using a free-air CO 2 and infrared warming system. Plant growth and CO 2 fluxes were measured during the growing cycle. Results Both high [CO 2 ] and warming increased canopy photosynthesis but warming alone increased biomass by 53% and R soil by 26%. There was a strong diel effect on R soil , which was 16% greater at noon than at 18:00 h. R soil had low sensitivity to soil temperature (Q 10  ~ 1) regardless of the CO 2 treatment. Conclusions In this tropical managed pasture, diel variation in photosynthesis strongly affected R soil , suggesting that R soil may be more limited by substrate availability than abiotic factors such as temperature. Predicted changes in climate for the region will likely affect the C dynamics of C 4 -dominated tropical pastures. Although, the short-term experiment may limit the extrapolations of our findings, the highly controlled settings of the experiment highlighted the role of canopy photosynthesis on R soil respiration in tropical C 4 -pastures.