Response of grassland greenhouse gas emissions to different human disturbances – A global Meta-analysis

Human disturbances have increased greenhouse gas (GHG) emissions from grassland, worsening global warming. However, the response of grassland GHG (CO₂, N₂O, and CH₄) to human disturbances across various climatic zones requires further elucidation, as does the intricate relationship between GHG emissions and temperature and precipitation. A Meta-analysis of the effects of human disturbances on GHG in grassland over the past 40 years revealed that grazing, fertilization, mowing, and burning significantly influenced the total emissions of N₂O, CH₄, CO₂, and GHG from grassland. However, the light and moderate grazing exerted no substantial impact on CO₂ emission flux. In frigid zone grassland, the N₂O emission flux was most significantly affected by grazing, the CH₄ emission flux affected by fertilization was higher than grazing, and the CO₂ emission flux was more sensitive to heavy grazing than severe fertilization. In temperate grassland and savanna, GHG emission flux was most sensitive to fertilization, with CO₂ emission flux in savanna being particularly responsive to burning. The effect of increased temperature and precipitation on CO_2e in fertilized grassland was approximately double that of grazed grassland and quadruple that of mowed grassland. This study emphasizes the increased effect of human disturbances on GHG emissions in the grassland, especially with the most significant impact of fertilization disturbances on GHG emissions in most grassland areas. Lowering the level of fertilization during grassland management could serve as a crucial step in mitigating GHG emissions from grassland. In summary, rigorous control of disturbance intensity represented an effective strategy for mitigating greenhouse gas emissions, albeit potentially impacting grassland productivity. Future endeavors should focus on determining the optimal disturbance intensity to strike a balance amidst these complex effects.