水热波动及氮输入协同作用对东北典型沼泽湿地固碳潜力影响

Impacts and driving mechanisms of warming and water level flucation compling with nitrogen input on carbon sequestration potental by northern wetlands in China are hot spot of climate chang research. Based on literature meta-analysis and information collection, this projects aimes to evaluate carbon sequestration potential of typical wetlands in Northeast China by 137Cs dating technology. A sets of opening-up box (OTC) are built to relize warming, water fluctation and nitrogen iput control, and to operate litter decompostion experiment, to monitor biomass and quality of wetland vegetations (leaves, stems, roots and litters) and enviromental factors, and to analyze microbie commuinites and activities (microbiomass carbon, nitrogen and phosphorus). Results from on simulation and field experiments were to reveal relationships between carbon accreting rate and environmental factors, to assess the acceleration or slowing effects of warming, waterlevel flucation and nitoren input and their interaction on wetland carbon sequestration rates, to find the key factor, porcess and driving mechanisms of environmental factors on carbon sequestration potential under different scenarios. Based on BioMod2 models, the potental wetland distribution areas in Northeast China are predicted in order to estimate carbon sequestration potential change. Results of this projects are import to a deeper appreciation of water-heat-carbon-nitorent interactly circulation processes doubly affected by climate change and nitrogen input, and are with guidence signficance to adapative police establishiment for wetlands.

水热波动及氮输入对北方沼泽湿地碳固定过程影响及其作用机制是目前气候变化研究的热点问题。本项目拟在搜集资料并基于137Cs定年对东北沼泽湿地碳固定速率评估的基础上，选择典型小叶章湿地、毛果苔草湿地及泥炭藓湿地进行原位OTC开顶箱增温控制实验，通过设置不同的增温幅度、水位及氮输入负荷，结合枯落物分解实验，监测湿地生态系统植被（叶、茎、根、枯落物）生物量及其品质、枯落物分解、微生物群落（微生物量碳、氮、磷）的变化及环境参数，分析其与碳固定速率变化之间的关系，评估水热波动及氮输入对湿地生态系统碳固定速率的促进或减缓作用，分析不同情境下影响碳固定速率变化的关键因素、过程及作用机理，基于BioMod2模型预测不同气候变化情景下未来东北湿地潜在分布区变化，评估未来东北湿地固碳潜力及汇碳功能变化。研究结果对深入认识气候变化及氮输入多因子协同作用下湿地水-热-碳-氮耦合循环过程并制定湿地适应性对策意义。

本项目以东北典型沼泽湿地为研究对象，基于面上调查及同位素定年技术，结合遥感与模型推演，估算了东北地区典型沼泽湿地固碳速率在水热波动及氮输入协同作用下的响应机制，评估东北地区典型沼泽湿地固碳潜力。研究表明，典型湿地剖面沉积年龄在70-205年之间变化，平均为124年。近200a来土壤沉积速率在2.28~5.83mm yr-1之间变化，平均沉积速率为3.84±1.25mm yr-1。近200a来沼泽湿地固碳速率在61.60~318.48 gC m-2yr-1之间变化，平均值为164.73±67gC m-2yr-1。黑龙江省地区平均固碳速率为202.4 gC m-2yr-1，该地区每年固碳量为10,409,431t。全球平均固碳速率为185.16g m-2 yr-1。气温与固碳速率之间具有显著负相关关系，降水与固碳速率之间具有极显著正相关关系，气候暖干化—湿地碳固定过程—大气CO2浓度将形成正反馈机制。气候变化的不对称性对湿地固碳速率具有显著影响，增温过程导致的干旱是引起湿地生态系统固碳潜力下降的根本性因素。氮输入湿地固碳潜力具有限制性作用，当氮输入通量低于20gN m-2 yr-1的水平时，氮输入对于固碳速率具有显著的促进作用，而当氮输入高于20gN m-2 yr-1，固碳速率变化不大。磷输入同样对湿地固碳潜力具有促进作用。在过去的几十年中，人类活动时东北地区湿地丧失的主要因素，气候变化对于湿地面积变化具有正效应。东北地区未来气候以暖干化趋势为主，2050年RCP2.6和RCP4.5情境下，湿地面临低风险，而RCP6.0和RCP8.0情境下，湿地面临高风险。预计未来气候变暖将进一步削弱本地区湿地土壤碳汇功能。