Factors influencing ecosystem respiration in different cultivated grassland ecosystems in Guiyang

Urban grassland areas are expanding as urbanization accelerates, and their role in the regional carbon cycle is becoming increasingly important. The carbon emissions of urban grassland ecosystems hold significance for the construction of urban green spaces and low-carbon cities. We used the LI-8100 soil gas flux system to determine the ecosystem respiration (ER) and related hydrothermal factors of five common urban grassland ecosystems in Guiyang City from April to October 2018. We found that the ER showed obvious seasonal changes, with average emissions ranked as follows: Trifolium repens > Lolium perenne > Cynodon dactylon > Ophiopogon japonicus > Ophiopogon bodinieri. ER was positively correlated (P < 0.05) with soil temperature at 5 cm and air temperature, but negatively correlated ( P < 0.05) with soil water content. The Q₁₀ values of air temperature and soil temperature were 1.22～2.06 and 1.15～1.85, respectively. The cumulative emissions of Trifolium repens and Lolium perenne were significantly higher than those of Cynodon dactylon, Ophiopogon japonicus, and Ophiopogon bodinieri (P < 0.05). Cumulative ER emissions were significantly positively correlated ( P < 0.05) with total soil nitrogen, aboveground biomass, soil microbial carbon, and soil urease. Our study shows that there are significant differences in CO ₂ emissions between different types of grasslands and that these are affected by multiple factors, such as hydrothermal conditions and soil nutrients, indicating that grass type should be taken into consideration in planning for low-carbon urban development.