Abstract
To identify soil factors affecting regional difference in aboveground productivity (AGP), soil and plant samples were collected from three typical steppe grasslands of Inner Mongolia exhibiting different productivity levels, and subjected to different grazing conditions. The sampling sites were located in grasslands used for grazing at Keshiketeng Banner (site 1; S1), Xilinhot city (S2), and Siziwang Banner (S3). Three grazing conditions (high grazing intensity: HG; low grazing intensity: LG; no grazing: NG) were categorized in each site. In early May, three fences (2 m × 2 m) for protecting land from grazing were built each in the HG and LG sites. Soil and plant samples were collected from three quadrate areas (1 × 1 m each) in each of the three sampling sites. Concentrations of total nitrogen (TN), total phosphorus (TP), nitrate nitrogen (NO3--N), and P2O5 in the soil and plant samples were measured.Significant effects of grazing on AGP, plant species diversity, and plant coverage rates were observed only when S2 was subjected to HG. This may have contributed to degradation of vegetation in HG of S2 with a highest grazing intensity. On the one hand, the correlations between AGP and TN or TP in the 0-5 cm depth soil were significant (r=0.820 and 0.543, respectively, P<0.05). Notably, TP levels in soil and plant were lower than those in the 1960s. Thus, soil TP may be a factor limiting AGP. However, soil NO3--N and P2O5 levels did not correlate with AGP, and thus may not contribute to productivity differences among sampling sites.
