Precise estimation of soil organic carbon stocks in the northeast Tibetan Plateau.

There is a need for accurate estimate of soil organic carbon (SOC) stocks for understanding the role of alpine soils in the global carbon cycle. We tested a method for mapping digitally the continuous distribution of the SOC stock in three dimensions in the northeast of the Tibetan Plateau. The approach integrated the spatial distribution of the mattic epipedon which is a special surface horizon widespread and rich in organic matter in Tibetan grasslands. Prediction models resulted in high prediction accuracy. An average SOC stock in the mattic epipedon was estimated to be 4.99 kg m(-2) in a mean depth of 14 cm. The amounts of SOC in the mattic epipedon, the upper 30 cm and 50 cm accounted for about 21%, 80% and 89%, respectively, of the total SOC stock in the upper 1 m depth. Compared with previous estimates, our approach resulted in more reliable predictions. The mattic epipedon was proven to be an important factor for modelling the realistic distribution of the SOC stock in Tibetan grasslands. Vegetation-related covariates have the most important influence on the distribution of the mattic epipedon and the SOC stock in the alpine grassland soils of northeast Tibetan Plateau.

[Estimation of soil organic carbon density and storage in Zhejiang Province of East China by using 1:50000 soil database].

As an important component of the carbon pool of terrestrial ecosystem, soil carbon pool plays a key role in the studies of greenhouse effect and global change. By using a 1:50000 soil database, the organic carbon density in the 0-100 cm layer of 277 soil species in Zhejiang Province was estimated, and the soil organic carbon (SOC) density and storage in the whole Province as well as the spatial distribution of the SOC density and storage in the main soil types of the Province were analyzed. In the whole Province, the SOC density ranged from 5 kg.m-2 to 10 kg.m-2. Among the main soil types in the Province, humic mountain yellow soil had the highest SOC density (52.80 kg.m-2), whereas fluvio-sand ridge soil had the lowest one (1.82 kg.m-2). Red soil and paddy soil had the largest SOC storages, with the sum accounting for 63.8% of the total SOC storage in the Province. The total area of the soils in the Province was 100784.19 km2, the estimated SOC storage was 875. 42 x 10(6) t, and the estimated SOC density was averagely 8.69 kg.m-2. The analysis with the superposition digital elevation model showed that the SOC density presented an obvious variation trend with the changes of elevation, slope gradient, and aspect.