Abstract: Wetland conversion to cropland was a typical land use change in the middle and lower reaches of Yangtze River. As the largest freshwater lake of China, there were 1466.9 km² reclaimed croplands in Poyang Lake region. To clarify the dynamics of soil organic carbon (SOC) and total nitrogen (TN) contents in the reclaimed croplands in Poyang Lake region, we collected soil samples from paddy fields that were reclaimed during six different periods in typical reclamation area. Subsequently, SOC and TN were measured. Our results showed that SOC content ranged from 13.7 to 28.5 g·kg^-1 for 0-10 cm soil layer, 7.1 to 15.3 g·kg^-1 for 10-30 cm soil layer, and 5.1 to 10.4 g·kg^-1 for 30-50 cm soil layer, respectively. TN contents in the corresponding soil layers varied from 1.2 to 3.6, 0.9 to 2.0 and 0.7 to 1.3 g·kg^-1, respectively. SOC contents were significantly positively correlated with TN contents (P<0.01). Soil layers, reclamation periods and their interactions had significant impacts on SOC and TN contents. SOC and TN contents decreased with soil depth. Moreover, SOC and TN contents in top soils showed a significantly increasing trend with increasing reclamation duration. The soil C/N ratios were maintained relatively stable.

Key words: soil organic matter, spatial interpolation, regression Kriging, geographically weighted regression Kriging.