Diurnal and Seasonal Variation of Soil CO2 and N2O Fluxes Under Rotational and Continuous Grazing in a Mediterranean Annual Forage System

Mediterranean grasslands can contribute to soil greenhouse gas emissions, but their flux dynamics remain poorly constrained because of strong temporal, seasonal, and management-related variability. This study compared the effects of grazing management, stage-wise variation across seasons, and diurnal variability on soil carbon dioxide (CO2) and nitrous oxide (N2O) fluxes under rotational grazing (RG) and continuous grazing (CG). High-frequency monitoring captured flux patterns across non-grazed and grazed stages in spring ryegrass–clover and summer teff trials. Generalized linear models identified soil temperature as the environmental variable most strongly and consistently associated with CO2 and N2O flux variability (p < 0.001). Segmented regression showed significant CO2 temperature breakpoints (~32–34 °C) under both systems, while N2O showed a sharp threshold (~30 °C) only under CG. Soil CO2 flux was significantly higher under RG than CG throughout the spring trial (p < 0.05). In the summer trial, CG showed higher CO2 and N2O fluxes than RG early on (p < 0.001 for both), with no difference by the end of the trial. N2O did not differ between systems for most of the spring trial. Afternoon fluxes generally exceeded morning fluxes for both gases (p < 0.05). These are stage-specific, context-dependent instantaneous fluxes from a single-site, one-year comparison rather than cumulative seasonal budgets. Overall, the relative effects of rotational and continuous grazing on soil CO2 and N2O fluxes changed across sampling stages, demonstrating that grazing-related soil GHG dynamics in this Mediterranean forage system are primarily context dependent rather than governed by a consistently superior grazing strategy.