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盆地，其中部有大片的沼泽森林，被称为“中央刚果”。与这些沼泽森林相关的泥炭积累代表了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测绘要求进一步的研究努力，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。ORACLE项目将侧重于刚果中部泥炭地的环境演变。泥炭地的碳储量取决于永久的高地下水位，而在热带地区，高降雨频率维持了高地下水位。据预测，干旱频率和降雨季节性的增加会降低或阻止碳储存。这些泥炭地在很大程度上仍未受到人类活动的影响，它们被认为极易受到油气勘探、伐木、排水、农业和其他形式的干扰的影响，这些干扰可能会对它们产生重大影响：在森林砍伐和气候条件干燥的综合影响下，它们的干扰可能会导致大量二氧化碳排放到大气中。ORACLE建议重建刚果中部泥炭地的历史，以便(i)更好地了解全新世热带碳循环的关键区域，（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，我们计划在刚果共和国收集和分析泥炭岩心，将经典的碳积累测定与新型分子和同位素技术相结合，如陆生高等植物脂质生物标志物的dD、d13C和D14C，以及来自细菌膜和孢粉的泥炭衍生的支链甘油二烷基甘油四醚膜脂分析，以评估生态系统的变化。在这些分析的同时，还将进行考古调查和人工制品的年代测定。这种多学科的方法将允许重建泥炭增加/损失，水文气候，植被覆盖，温度，pH值和人类活动的历史。ORACLE的结果将有助于更好地预测刚果中部库维特生态系统面对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，包括气候建模者，更好地了解中非生态系统的全新世气候和生态演化具有很高的价值。为了改善湿地保护策略，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以及碳循环的影响。

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.