Diurnal and seasonal variations on soil CO2 fluxes in tropical silvopastoral systems

Abstract

AbstractThis study aimed to quantify the dynamics of soil CO2 fluxes in two silvopastoral systems based on Leucaena leucocephala, one associated with Panicum maximum (L + P) and another with Cynodon plectostachyus (L + C). We measured CO2 fluxes fortnightly during the dry and rainy seasons in the morning and the afternoon, with an infrared gas analyzer. Simultaneously, we measured soil temperature, soil moisture, ambient temperature, and relative humidity. Soil CO2 fluxes ranged from 6.0 ± 0.14 to 6.1 ± 0.12 µmol CO2/m2/s but no statistical differences were observed between systems. Soil CO2 flux in the L + P was 12.5% higher in the rainy season compared with the dry season but the season did not affect the fluxes in L + C. Regarding the diurnal variation, CO2 fluxes were 17.6%–34.8% higher in the morning compared with afternoon measurements. Soil moisture and temperature were higher in L + C, but the ambient temperature and relative humidity showed no statistical differences between systems. In both systems, soil temperature was greater in the afternoon, while the soil moisture and relative humidity were greater in the morning. The diurnal variation of soil CO2 fluxes in silvopastoral systems correlated positively with soil temperature and ambient temperature, but negatively with relative humidity. We concluded that soil CO2 fluxes did not vary between silvopastoral systems but respond differently to the seasons. The results have important implications on the establishment and management of Leucaena‐based silvopastoral systems for the mitigation of soil CO2 fluxes from extensive livestock production lands.