Soil Organic Carbon Storage in Urban Green Space and Its Influencing Factors: A Case Study of the 0–20 cm Soil Layer in Guangzhou City

Urban soils can contribute to organic carbon sequestration. The socioeconomic drivers of soil organic carbon (SOC) in urban areas may differ between regions due to the different land tenure and its derived green space management regimes. Currently, few studies focus on regions where public ownership of land was implemented. We examined the SOC storage and driving factors of urban green spaces in Guangzhou, China at 0–20 cm depth by variance and regression analysis. Our results showed that the total SOC storage did not vary significantly among green space types, with an average value of 2.59 ± 1.31 kg/m2. SOC increased with plot age (2–87 years) by 0.025 kg/m2/year (p = 0.026) and plot size (63–2058 m2) by 0.001 kg/m2/m2 (p = 0.026). Disturbance intensity was negatively correlated to SOC storage. Green space maintenance practices could promote SOC sequestration, but this benefit may be offset by high-intensity disturbances such as trampling, litter and debris removal and fragmentation of green spaces. To increase urban residential SOC storage, except for remediation of compacted soils, it is essential to promote house owners’ initiative in green space management and conservation by improving the current residential green space management regimes.