Remote Sensing and Geographical Information System techniques are used to explore the spatial-temporal dynamic change of pedodiversity pattern under the impact of the quickly growing urbanization process in the past 20 years in the Yangtze delta, China. The results document the rapid expansion of urbanization in Nanjing used as a case study area, as well as the soil types occupied by the urbanization process. The urban area of Nanjing has increased 43544 ha, 2 times more than in 1984. The urban area expanded at an annual rate of 6.9 %. Thirty of the total 32 soil types (soil families) within the city were more or less utilized by the urbanization process among which Loamy typic-Fe-leachic-stagnic anthrosol ranked the highest (12007 ha). The loss of surface land to urban use in Nanjing area has ranged from 4.8% in 1984 to 11.8% in 2003. Growing urbanization may threaten food security, soil diversity and sustainability. Clay loamy fimic-ferri-udic argosol and Loamy car-mottlic-fimic-orthic anthrosol may be in danger of disappearing under urban/suburban structures because they have been decreased by 41.4% and 62.4 % respectively only in the past 20 years. The regional pedodiversity pattern and dynamic change at three times (1984, 1995, and 2003) have been quantitatively analyzed by the method of multi-source information integration and muti-phase successive comparison. Combined with the soil map of the city, the pedodiversity indices including diversity (HP), evenness (Jsw) and richness (R2) borrowed from biological studies are calculated before the spatial-temporal dynamic change of pedodiversity pattern in Nanjing area is presented. Finally, gray correlative analysis model was used to explore the impact of urbanization on pedodiversity. Results show that the expansion of different level administration units has various impact on pedodiversity with village, the most significant impact, sharing 60%, town about 26%, city 7%, and county seat 7%, of the total study area. Statistical analysis in this study indicates that urbanization as a significant driving force results in an obvious impact on pedodiversity dynamic change in the studied area. This work was supported by NSFC 40171044, 40541003 and CAS KZCX3-SW-427.

Keywords: Yangtze delta, Nanjing, urbanization, impact, pedodiversity measures