Soil carbon storage affected by urban land use change in Shanghai, China

Background/Question/Methods

    The rapid urbanization has yielded cities of unprecedented size and form that considerably modify major biogeochemical cycles, especially the carbon cycle. Understanding the relationship between urban sprawl and the carbon cycle is of great importance to ensure sustainable urban planning and management. Soil is the largest terrestrial carbon pool. However, how urban land use change affects soil carbon storage is largely unclear. In this study, the major objective was to quantify the spatial pattern of soil organic carbon (SOC) density in Shanghai City, China, which has undergone rapid urban expansion and intense land-use change since the 1980s. We established 4 sampling transects radiating from the Shanghai urban core to the edge of the city. Soil sampling was conducted at 120 sites along the 4 transects, covering 7 different land-use types (business area, residential area, educational area, park green space, arterial road, industrial zone and agricultural area).Soils were sampled at 0-15cm, 15-30cm and 30-50cm depths at each site between Oct. 2013 and April 2014.

Results/Conclusions

  The city-wide mean SOC density between 0—50 cm depth was 8.10±2.43 kg m^-2, with significant spatial difference among the four transects in the order as: South > East > West > North. There was no significant relationship between SOC density (mg cm^-3) and the sampling plot’s distance from the urban core. However, the SOC density at suburb and agricultural area was slightly lower than that at urbanized area. Among the 7 land use types, there was obvious difference in SOC density, with highest SOC density occurring in business area (averagely 8.74±2.33 kg m^-2), followed by green park, educational area and agricultural area with close SOC value (around 8.48 kg m^-2). The residential soil showed the lowest SOC density among all land use types (6.81±2.49 kg m^-2). The SOC density at park green space and commercial area increased significantly with their built-up time, i.e. elder parks have higher SOC storage. Urban soil characteristic were affected by a variety of natural factors and human disturbances. Our results indicate that soil forming history is a potential driving factor for soil carbon storage in Shanghai city.