Holocene Hydroclimate and Carbon Cycle Dynamics in the Central Congo Basin

热带陆地生态系统生产力很高，是全球碳循环的重要组成部分。刚果盆地是地球上第二大河流流域，其中部有广阔的沼泽林，被称为“刚果小中心”。与这些沼泽森林相关的泥炭积累代表着一个具有全球重要性的主要地下碳库。最近对这些泥炭地的描述和绘图需要进一步的研究努力，以了解这些敏感生态系统的历史，以便更好地预测它们在未来气候和土地利用变化方面的脆弱性。甲骨文项目将专注于刚果小中心泥炭地的环境演变。泥炭地的碳储存依赖于永久的高地下水位，而在热带地区，这是由高降雨频率维持的。据预测，干旱频率/降雨季节性的增加将降低/停止碳储存。这些泥炭地基本上不受人类活动的影响，被认为非常容易受到碳氢化合物勘探、伐木、排水、农业和其他形式的干扰，这些干扰可能会对它们产生重大影响：在砍伐森林和更干燥的气候条件的共同影响下，它们的干扰可能会导致大量二氧化碳排放到大气中。甲骨文公司提议重建刚果中部沼泽泥炭地的历史，以(I)更好地了解热带全新世碳循环的一个关键区域，(Ii)提供全新世期间区域泥炭积累/损失的详细记录，以及(Iii)解决这些生态系统变化的驱动因素(自然和人为)。为了解决这些问题，我们计划收集和分析刚果共和国的泥炭岩芯，方法是将经典的碳积累测定与新的分子和同位素技术相结合，例如来自陆地高等植物的脂肪生物标记物的dd、d13C和d14C，以及从细菌膜和孢粉中分析泥炭衍生的支链甘油二烷基甘油四醚膜脂，以评估生态系统变化。这些分析将伴随着对文物的考古调查和年代测定。这种多学科的方法将可以重建泥炭增减、水文气候、植被覆盖、温度、pH和人类活动的历史。甲骨文的结果将有助于更好地预测Cuvette Centrale刚果生态系统面临气候变化和人类活动的脆弱性。它们将对古生态学家和古气候学家，包括气候建模人员，更好地了解中非生态系统的全新世气候和生态演变具有极高的价值。需要揭示过去气候变化以及潜在的人类活动对湿地植被结构和组成的影响，以及碳循环，以改进保护战略。

Tropical terrestrial ecosystems are highly productive and constitute a critical component of the global carbon cycle. The Congo Basin, the second largest river basin on Earth, accommodates extensive swamp forests in its central part, known as the “Cuvette Centrale Congolaise”. Peat accumulation associated with these swamp forests represents a major below-ground carbon reservoir of global importance. The recent description and mapping of these peatlands calls for further research efforts to understand the history of these sensitive ecosystems to better predict their vulnerability with respect to future climate and land-use changes. The project ORACLE will focus on the environmental evolution of the peatlands in the Cuvette Centrale Congolaise. Carbon storage in peatlands depends on a permanently high water table, which in the tropics is maintained by high rainfall frequency. An increase in drought frequency/rainfall seasonality has been predicted to lower/stop carbon storage. Still largely unaffected by human activities, these peatlands are considered highly susceptible to hydrocarbon exploration, logging, drainage, agriculture, and other forms of disturbance that could significantly affect them: their disturbance, under the combined effects of deforestation and drier climatic conditions, could result in massive CO2 emissions into the atmosphere. ORACLE proposes to reconstruct the history of the peatlands of the Cuvette Centrale Congolaise to (i) better understand a key region of the Holocene carbon cycle in the tropics, (ii) provide a detailed record of regional peat accumulation/loss during the Holocene, and (iii) resolve the drivers (natural and anthropogenic) of changes in these ecosystems. To address these issues, we plan to collect and analyze peat cores in the Republic of Congo by combining classical carbon-accumulation determinations with novel molecular and isotopic techniques, such as dD, d13C, and D14C of lipid biomarkers derived from terrestrial higher plants together with analysis of peat-derived branched glycerol dialkyl glycerol tetraether membrane lipids from bacterial membranes and palynology to assess ecosystem changes. These analyses will be flanked by an archaeological survey and dating of artefacts. This pluri-disciplinary approach will allow reconstructing the history of peat accretion/loss, hydroclimate, vegetation cover, temperature, pH, and human activity. The results from ORACLE will help to better predict the vulnerability of the Cuvette Centrale Congolaise ecosystems facing climate change and human activity. They will be highly valuable for paleo-ecologists and paleo-climatologists, including climate modellers, to better understand the Holocene climatic and ecological evolution of Central African ecosystems. Unravelling the effects of past climate changes and, potentially, human activities on the structure and composition of wetland vegetation and carbon cycling are needed to improve conservation strategies.