Abstract: Characteristics of soil carbon, nitrogen and phosphorus stoichiometry at regional scale is key factors to understand spatial pattern, and reveal responses of terrestrial ecosystem to global change and human activities. In this study, we measured organic C, total N, total P concentrations and C:N, N:P, C:P in topsoil of typical desertified regions of northern China, and statistically analyzed their spatial pattern. The result showed that the average organic C, total N, total P concentrations and C:N, C:P, N:P are 12.2 g·kg^-1, 1.2 g·kg^-1, 0.8 g·kg^-1, 10.1, 15.7 and 1.63, respectively. The concentrations of organic C, total N, C:P, and N:P in topsoil of typical desertified regions of northern China remained a relatively low level in contrast with the results nationwide, but the concentration of total P was relatively higher. Compared with grassland, the concentration of surface layer soil organic C, total N and total P in cropland were significantly higher. However, soil C:N and N:P showed no significant difference between grassland and cropland. We found that topsoil organic C, total N, total P, and their ratios of typical desertified regions of northern China were significantly coupled. But the coupling relationships revealed significant differences between grassland and cropland. With latitude increasing, the soil organic C, total N, total P stoichiometric value of grassland and cropland were also increasing in desertified regions of Northern China. Except total P and N:P, other indices were significantly linearly correlated. Meanwhile, soil organic C, total N, total P stoichiometric value were firstly decreased and then increased with longitude increasing in typical desertified regions of Northern China. Regression analysis revealed that these indices exhibited polynomial distribution with longitude.

Key words: desertified regions, soil, ecological stoichiometry, grassland, cropland