Abstract:
Soil organic carbon (SOC) is the largest carbon pool in terrestrial ecosystems, whilst the most important process causing carbon loss from soils is soil respiration (Rs). Both SOC and Rs directly link to the atmospheric carbon dioxide absorption. Despite a great deal of research, there currently remains uncertainty whether urban park soils have potential to sequester carbon or release more carbon to the air. Twenty-nine soil samples were collected at a 15-cm depth across the CU Centenary Park. Soil physical and chemical properties were measured to explain SOC stocks and Rs rates. Annually, average SOC stocks and Rs rates were 2.29±1.73 kg C m⁻² and 3.44±2.05 kg C m⁻² y⁻¹, respectively. Values of SOC stocks and Rs rates significantly varied across lawn grass, bush/weeds, and soils surrounded by trees. Two principal components, derived by principal component analysis (PCA), occupied 67.7% of the total explained variance. The first principal component was dominated by organic matter, SOC, clay particles, and soil temperature, explaining 48.7% of the total variance. The second component was loaded by soil bulk density, Rs, and soil moisture, accounting for 19.0% of the total variance. Overall, the carbon exchange process highlighted a major mechanism of carbon emissions from the soil systems. This study recommended growing bushes or weeding plants to increase more SOC storage. Controlling factors described by PCA should also be taken into consideration in order to increase SOC stock and reduce CO₂ in the urban atmosphere.
