土壤生态系统中黑碳研究的几个关键问题

因人类活动的影响，全球大气C02浓度自1750年以来呈现逐步上升的趋势。农业生产活动与气候变化紧密相关，因土地利用方式的改变以及高度集约化的粮食、食物生产等农业活动都有可能增加CO2等温室气体的排放。如何遏制和减少大气中的CO2浓度是当前的热点问题，黑碳这一物质形式有可能为这一问题的缓解或解决提供新途径。生物质黑碳是生物质材料在低氧或无氧状态下经热裂解而形成的一种富含碳元素的有机连续体，其中碳（C）元素的含量高达70％-80％，并且大多以稳定的芳香环形式而存在。人类生存环境中所形成黑碳的80％以上最终都要归于土壤，且由于其较强的抗分解能力而长期滞留于土壤环境中。利用黑碳的这些特性及其碳封存能力，实施积极而有效的土壤管理措施，有可能增加土壤生态系统中的碳储存，从而为人类社会应对全球气候变化提供新的机遇。在文献资料调研的基础上，描述了土壤中黑碳的来源及其增加土壤碳储存、减缓陆地生态系统碳循环的潜力；阐释了量化土壤中黑碳的重要性以及精确测定土壤黑碳含量的关键所在；揭示了黑碳在土壤环境中的稳定性，探讨了外源黑碳与土壤本体有机碳的相互作用关系，并分析了黑碳对土壤温室气体排放的影响及其不确定性。揭示这些问题有助于客观评价黑碳能否作为一个有效的土壤有机碳库，也益于明确黑碳在全球碳循环以及中国农业减排过程中的作用与地位。

Several key issues related to black carbon in soil ecosystems

Carbon dioxide （CO2） is the most important anthropogenic greenhouse gas and its global concentration in the atmosphere has increased since 1750s due to human activities. Agriculture is of relevance to climate change due to emissions in food production and emissions through land use change. The reduction in emissions of CO2 and the sequestration of atmospheric CO2 has become a hot issue and should be strongly pursued. ＂Biochar＂, biomass-derived black carbon （BC）, has emerged as a potential strategy for climate change mitigation. Black carbon is a general term used to describe products derived from incomplete combustion of vegetation and fossil fuels. It is a continuum of carbon （C） forms and has high carbon content. A characteristic of biochar that is common to black carbon in general is that it comprises mainly stable aromatic forms of organic carbon. About 80% of BC produced from different sources ends up in soils and sediments where it resides for hundreds to thousands of years due to its resistance to biological and chemical breakdown. As a result, BC could be an alternative for us to fight against climate change. Active soil managements offers the possibility to increase terrestrial carbon stores in various forms in soils. Based on literature review, this paper described the sources of BC and its potential role to increase C storage in the soils. We emphasized the importance in quantifying BC and the key to determine content of BC in soils. In this paper the stability of BC in the soils was stated, and the interaction between the added BC and native soil organic matter as well as the effect of BC on soil greenhouse gas production was also discussed. The key to estimating BC stocks and its environmental performance in soils and sediments is an understanding of the implication of BC served an effective soil carbon pool, which can be useful for us to draw the conclusion on the role of BC in the global carbon cycle and agricultural carbon-negative process in China.