黄土高原不同土地利用类型有机碳和黑碳的储量及意义

Implication and storage of soil organic carbon and black carbon in different land use types in the topsoil of Loess Plateau

以黄土高原为研究对象,研究三种不同利用方式的表层土壤样品(0—20 cm),分析其有机碳(soil organic carbon,简称SOC)和黑碳(black carbon,简称BC)的含量、分布特征及其储量变化及意义。研究表明,黄土高原不同利用方式土壤有机碳和黑碳含量的平均值分别为:玉米地8.01 g?kg^(-1)和1.01 g?kg^(-1),林地6.80 g?kg^(-1)和0.59 g?kg^(-1),未利用地5.01 g?kg^(-1)和0.43 g?kg^(-1),有机碳和黑碳的含量均为玉米地最高,未利用地最低;耕地和自然土壤表土有机碳储量分别为0.796 Pg和0.710 Pg,表土黑碳储量分别为0.0858 Pg和0.0730 Pg,耕地相对于自然土壤有机碳和黑碳的储量分别增大12.1%和17.5%;说明黄土高原耕地是一个碳汇,起着固定碳的作用;采用推荐的管理实践活动和合理的土地利用方式,能够增加土壤碳储量,提高土壤质量和农作物产量,抵消部分二氧化碳的排放。

Background, aim, and scope Changes in soil carbon storage have far-reaching effects on global climate change, which are mainly concentrated on the transition of landuse. The impact of different types of landuse on soil carbon storage has been investigated by reserchers around the world in regional and national scales. As a country with a long cultivation history, to study the effect of land use on soil carbon storage in China is very important and meaningful. In order to gain a further understanding of the influence made by different ways of land use on organic carbon （OC） and black carbon （BC） in the Loess Plateau, soil samples are collected in this study based on different landuse patterns in the Loess Plateau in Shaanxi, Shanxi region. Via chemical analysis in the lab, the impact and significance of organic carbon and black carbon and its change in carbon stocks can be studied and understood. Materials and Methods The samples are collected by the method called shove lacquisition which requires using a stainless steels hovel to collect the top soil sample in depth from 0--20 cm in the Loess Plateau. The litter on surface of the ground has been removed before sampling. Samples are dried under a natural ventilation indoor, and the grits with the diameter more than 2 mm are removed as well as roots and debris. We used portable GPS for sampling sites locating, including 17 samples of corn land, 14 samples of forest land and 20 samples of unused land. Results （1） The results show that average SOC and BC concentration are 8.01 g.kg 1 and 1.01 g.kg-1, 6.80 g.kg-1 and 0.59 g.kg-1, 5.01 g.kg 1 and 0.43 g.kg 1 for corn, forest and unused land, respectively. The maximum and the minimum concentration appeared in corn and unused land. The SOC and BC storage under cultivated land in Loess Plateau are 0.815 Pg and 0.088 Pg, compare with the SOC and BC storage of 0.727 Pg and 0.0748 Pg under present-day soil in Loess Plateau. （2） Human activities have an impact on the quantity and distribution of soil organic carbon and black carbon. From the statistical analysis, there is a significant difference （p〈 0.05） of the black carbon from the soil between the corn land and forest land, as well as between the corn land and unused land. However, there was no significant difference of black carbon between the forest land and unused land （p〉 0.05）. Those results can be explained by the strong influence made by the different land use patterns and human management activities. （3） In unused land, the determining factor of black carbon and soil organic carbon （SOC） equation was extremely significant （p〈 0.0001）. It indecated that black carbon is closely related to secondary organic carbon. So there may be a special binding formation mechanism. However, the correlation coefficient between BC and SOC of the forest land and corn land did not reach that significant level and it is 0.51 and 0.32, respectively which also much smaller than that in unused land. In the Loess Plateau area, most corn straw was removed by combustuion right after the harvest. Biomass burning lead to massive remains of combustion residue on site （Skjemstad et al, 2002）. Meanwhile, the chronic process of black carbon degradation causes the black carbon accumulation in the corn land. This is indicating that the quantity of black carbon is not only related to soil organic matter, but also to human activities. Discussion （1） Changes in organic carbon and black carbon quantity are indicated in following order： maize land〉forest land〉unused land, land〉uncultivated land. （2）Affected by human activities, the quantities of both organic carbon and black carbon in the Loess Plateau are higher than that of natural soil. However, the density of the organic carbon in arable land is still lower than that of the national average. Conclusions Affected by human activities, the storage of organic carbon and black carbon has been increased in the cultivated land of the Loess Plateau. The increased soil organic carbon and soil carbon storage in Loess Plateau are able to improve the soil quality in general and maintaining sustainable use of land. The increasing of the black carbon storage indicates both land use and human activities can convert the carbon dioxide in the atmospheric into a stable black carbon stocks, therefore to reduce the atmospheric concentration of carbon dioxide. Recommendations and perspectives A rational use of land and improving agricultural management play a key role in environmental sustainability. It not only has a great effect on the carbon cycle and global climate change, but also buys us some time to find new energy sources.