大兴安岭中段森林土壤的黑碳含量及其在不同粒级中的分布

土壤黑碳由于具有生物化学惰性被视为土壤稳定碳库的主要成分.本文量化了大兴安岭中段森林土壤黑碳,分析了黑碳在各粒级内的分布,并探讨了黑碳的稳定机制及其在土壤碳库中的重要性.结果表明: 土壤黑碳表聚现象明显,表层黑碳占总剖面(64 cm)的68.7%,随着土层加深黑碳含量显著降低,但黑碳占有机碳的比例却呈现上升趋势.气候条件影响大兴安岭地区土壤黑碳的分布,相对寒冷和湿润的气候条件提高了土壤固持黑碳的潜力;土壤黑碳在各粒级内所占比例表现为黏粒>粉粒>细砂>粗砂,尽管黏粒中黑碳含量最高,并随土层深度增加而升高,但黏粒中黑碳占有机碳的比例却无明显变化,黑碳/有机碳的升高主要源于细砂与粉粒中黑碳的增加;黑碳的生物化学惰性是表层黑碳的主要稳定机制,而深层的黑碳除了其自身抗性外,黏粒矿物的化学保护发挥着重要作用;黑碳不仅作为稳定碳库的主要成分,在颗粒有机碳组分中仍占相当大的比例,因此黑碳的存在提高了土壤稳定性碳储量与碳汇能力.

Black carbon content and distribution in different particle size fractions of forest soils in the middle part of Great Xing’an Mountains,China.

Soil black carbon (BC) is considered to be the main component of passive C pool because of its inherent biochemical recalcitrance. In this paper, soil BC in the middle part of Great Xing’an Mountains was quantified, the distribution of BC in different particle size fractions was analyzed, and BC stabilization mechanism and its important role in soil C pool were discussed. The results showed that BC expressed obvious accumulation in surface soil, accounting for about 68.7% in the whole horizon (64 cm), and then decreased with the increasing soil depth, however, BC/OC showed an opposite pattern. Climate conditions redistributed BC in study area, and the soil under cooler and moister conditions would sequester more BC. BC proportion in different particle size fractions was in the order of clay>silt>fine sand>coarse sand. Although BC content in clay was the highest and was enhanced with increasing soil depth, BC/OC in clay did not show a marked change. Thus, the rise of BC/OC was attributed to the preservation of BC particles in the fine sand and silt fractions. Biochemical recalcitrance was the main stabilization mechanism for surface BC, and with the increasing soil depth, the chemical protection from clay mineral gradually played a predominant role. BC not only was the essential component of soil stable carbon pool, but also took up a sizable proportion in particulate organic carbon pool. Therefore, the storage of soil stable carbon and the potential of soil carbon sequestration would be enhanced owing to the existence of BC.