Spatial and temporal variations of soil organic carbon and total nitrogen pools in the coastal reclamation area, eastern China

The spatial and temporal variation of soil organic carbon (SOC) and soil total nitrogen (STN) in a coastal reclamation area in eastern China were studied based on the ordinary kriging method. The 0–20 cm soil organic carbon pool (SOCP) and soil total nitrogen pool (STNP) ranged from 4.38 to 15.92 Mg/ha and from 0.24 to 2.37 Mg/ha, respectively, during the observed period. The results show there was a low level of spatial variation in both SOC and STN, which is to some extent the result of the same farmland management practiced in this region. The seasonal variation of SOC was attributed to plant growth and crop residue returning back to soil, while the spatial variation was mainly resulted from the fertilization practice. The average 0–20 cm SOCP and STNP were 10.38 ± 2.50 and 1.27 ± 0.38 Mg/ha, respectively, in the study region, both of which were much lower than in other ecosystems. Further analysis indicated that SOC was positively correlated with STN. This work revealed that the reclamation area from the tidal flat should be a potential sink for SOC and STN.