三江平原沼泽湿地全新世火演化及其与植被和气候关系研究

The knowledge of fires evolution in the wetlands is critical for the improvement of the theory concerning the fires ecology. While up to now little is known about this knowledge, which should be attributed to the fact that most traditional studies usually employ only one-core records with qualitative analysis. In this study, we will construct the quantitative relationships among pollen, vegetation and climate of the typical plant communities in the modern wetlands across the Sanjiang Plain. After that, six sediment cores will be collected from the different typical peatlands, and they will be treated with dating as well as charcoal, pollen and plant residuals analysis. With the assistance of modern relationships among pollen, vegetation and climate, the quantitative reconstruction of the Holocene vegetation and climate can be achieved. These multiple-cores and multiple-proxies data will provide great potential to reveal a more detailed fire evolution history and its relations to Holocene vegetation and climate changes. This research will combine the studies on the modern process and those on the past process of the wetlands and employ multiple peat-core results to provide a more detailed Holocene evolution process of the fires in the wetlands. And what is more important, this study will provided more reliable data and knowledge for the development of the theory on the long-time evolution of fires in the wetlands.

充分了解湿地火长期演化规律及其驱动机制是完善火生态学理论的基本前提。然而，以往相关研究多利用单一地层钻孔资料和定性分析方法推断区域火及环境信息，其结果的不确定性是导致对火演化规律认识难以深入的重要原因。鉴于此，选择环境变化响应敏感地区利用多钻孔数据结合定量重建方法开展工作是突破研究现状的有效途径。本项目以三江平原沼泽湿地为研究对象，在建立现代典型植物群落孢粉-植被-气候转换函数关系基础上，利用不同区域环境条件下6个泥炭柱芯的高分辨率炭屑、孢粉、植物残体等资料和详细年代学数据，开展全新世火、植被和气候定量重建和综合对比研究，探讨三江平原全新世火时空演化规律及其与植被和气候间的耦合关系。本研究基于“古今结合”的研究思路，利用多钻孔和多指标数据并借助定量分析方法，旨在提升研究结果的可靠性和区域代表性，从而为完善沼泽湿地火长期演化理论提供更为科学可靠的基础数据和理论依据。

为揭示全新世以来三江平原沼泽湿地火灾演化过程及其与环境因子关系，本项目本项目以三江平原天然沼泽湿地为研究对象，选择128个典型沼泽湿地植物群落进行植物样方调查、现代气候条件特征分析并采集表层沉积物进行孢粉、粒度、有机质、磁化率、碳酸盐等环境指标分析，揭示了不同植被群落下表层沉积物中各环境代用指标特征及与周围植被组成和现代气候条件间的定量转换函数关系。在此基础上，选取发育典型、受人类活动干扰相对较小洪河、黑瞎子岛、申家店等天然泥炭地，在其典型植物群落下采集泥炭柱芯，并对各泥炭柱芯进行了详细的年代学研究以及以1cm为分辨率的炭屑、孢粉、粒度、有机质、磁化率和植物残体分析。在现代表层沉积物环境指标与采样点水位、植被和气候定量关系参照下，结合地层古环境代用指标记录定量重建了不同沼泽湿地古水文、古火灾、古植被与古气候演化历史。综合对比分析各泥炭沉积柱芯多环境代用指标数据，揭示了三江平原不同沼泽湿地古洪水、古火、古植被和古气候的长期演化过程，探讨了全新世古火灾与古洪水演化规律及其与植被和气候变化间的耦合关系。研究结果表明，三江平原沼泽湿地火灾高发阶段很好得对应了区域相对温暖干燥的气候条件和乔木植物相对茂盛的植被条件，表明火灾演化与区域气候和植被条件联系紧密。湿地火灾状况和土壤中碳累积之间存在显著正相关性，表明湿地火灾对沼泽湿地全新世土壤碳汇功能的发挥起到了积极影响。上述研究成果无论对完善湿地火生态因子的长期演化理论，还是对未来全球变化条件下制定科学的沼泽湿地火管理策略，都具有重要理论和现实指导意义。