Giesemann Anette
Institute of Agroecology, Federal Agricultural Research Centre, Bundesallee 50, 38116 Braunschweig, Germany.
Rapid Commun Mass Spectrom. 2005;19(11):1373-80. doi: 10.1002/rcm.1909.
FACE (Free Air Carbon dioxide Enrichment) has been used since 1999 to evaluate the effects of future atmospheric CO(2) concentrations on an arable crop agroecosystem. The experiment conducted at the Institute of Agroecology at the Federal Research Centre in Braunschweig consists of a typical local crop rotation of winter barley, a cover crop, sugar beet and winter wheat. The atmospheric CO2 concentration of ambient air is about 375 ppm with a delta13C value of -7 to -9 per thousand, and 550 ppm (delta13C value = -20.2 per thousand) during daylight hours in the rings fumigated with additional CO2. Thus, the surplus C can be traced in the agricultural system. Over the course of the first experimental period (3-year crop rotation period), the C-isotopic composition and the C concentration in soil were monitored monthly. Plant samples were analysed according to the relevant developmental stages of the crop under cultivation. A 13C depletion was observed in plant parts, as well as in soil samples from the FACE rings under CO2 enrichment, indicating that labelled C has reached both respective ecosystem compartments. Albeit farming management practice (especially ploughing) leads to a mixing of 'old' and 'new' C compounds throughout all soil horizons down to the end of the ploughing layer and resulted in a heterogeneous distribution of newly formed C compounds in the soil, isotope analysis of soil C reflected where the surplus C went.
自1999年以来，自由空气二氧化碳浓度增高（FACE）技术已被用于评估未来大气二氧化碳浓度对可耕地作物农业生态系统的影响。在不伦瑞克联邦研究中心农业生态研究所进行的试验，采用了典型的当地作物轮作模式，包括冬大麦、覆盖作物、甜菜和冬小麦。环境空气中的大气二氧化碳浓度约为375 ppm，δ13C值为千分之-7至-9，而在额外二氧化碳熏蒸的试验圈内，白天期间的浓度为550 ppm（δ13C值=-20.2‰）。因此，可以在农业系统中追踪多余的碳。在第一个试验期（3年轮作期）内，每月监测土壤中的碳同位素组成和碳浓度。根据所种植作物的相关发育阶段对植物样本进行分析。在二氧化碳浓度增加的FACE试验圈的植物部分以及土壤样本中均观察到13C贫化，这表明标记的碳已进入各自的生态系统组分。尽管耕作管理措施（特别是犁耕）会导致“旧”碳化合物和“新”碳化合物在整个土壤层直至犁底层底部混合，并导致新形成的碳化合物在土壤中分布不均，但土壤碳的同位素分析反映了多余的碳的去向。
