[Differences in soil organic carbon and total nitrogen and their impact factors under different restoration patterns...

Knowledge of the effect of different vegetation restoration measures on soil organic carbon (SOC) and total soil nitrogen (TN) is of importance to better understand carbon and nitrogen cycling in terrestrial ecosystems and deal with the global greenhouse effect. The differences in SOC and TN content in 0-100 cm soil profile between different restoration measures and their impact factors were investigated in the Loess Plateau. The results showed that artificial vegetation restoration led to a significant increase in both SOC and TN content in the 0-100 cm soil profile compared with that of cropland. The highest increase in average SOC content was observed in the artificial woodland(1.43 times that of the cropland), followed by the artificial shrubland (1.36 times) and artificial grassland (1.21 times); whereas the highest increase in average TN content was observed in the artificial woodland (1.30 times that of the cropland), followed by the artificial grassland (1.21 times) and artificial shrubland (1.13 times). Compared with the cropland, there was a significant difference in SOC and TN content and fine root density up to a maximum depth of >100 cm in the artificial woodland and shrubland, but about 60 cm in the artificial grassland. The fine root density, soil C:N ratio and aboveground litter production of artificial woodland, shrubland and grassland were significantly higher than that of cropland, and fine root density was significantly linearly correlated with SOC and TN (P<0.01). The quantity and quality of fine root and litter biomass might be the dominant factors contributing to the observed difference in SOC and TN contents between the different artificial vegetation types in the Loess Plateau.