嫩江源多年冻土区沼泽湿地径流过程变化对溶解有机质输出特征的影响研究

The Nenjiang sources area is an important distributed region of mire-wetlands in China. The presence of permafrost is closely linked to the hydrological processes and the carbon balance in the mire ecosystem. But recent years, large area of permafrost degradation has occourred due to global climate warming. By now, there are still no answers to the questions that what will be the alterations in surfacial hydrology in the mire, and what is the relation between the hydrological processes and the exporting trends of the dissolved organic matter (DOM) from the mire. Especailly, the questions is most important that how will the alteration in the hydrological processes affect the DOM characteristics in the runoff, and what is the key conrolling factor.There has no enough systematic research on the questions which involve the changing trend of the whole mire ecosystem in the region. My project will research the influences of the alteration in hydrological processes on the exporting characteristics of DOM, both concentration and chemical features, in the mire ecosystem under the condition of permafrost degration with the methods of field comparing observation in parallel to typical runoff observation and simulated experiments. The research will reveal the coupling processes of the hydrological mechanism with physical-chemical mechanism, as well as the key inflencing factor, which lead to the alteration in the DOM export in the runoff.Meanwhile, the futher DOM export potential from mires under the condition of sustained permafrost degradation will be forcasted in the study area. This project will promote the research of carbon exporting in the boreal area in Northeast China, and provide basic data and theoretical foundation to the regional carbon and hydrology management in the future.

东北嫩江源地区是我国沼泽湿地的重要分布区，多年冻土的存在与沼泽湿地水文过程和碳循环过程密切相关。目前，气候变暖已导致该地区多年冻土大面积退化，而沼泽湿地的地表径流特征将发生怎样变化？径流过程与沼泽湿地溶解性有机质（DOM）输出过程有怎样的联系，又将如何影响DOM的年季输出特征？关键的驱动因子是什么？这些涉及到整个多年冻土区沼泽生态系统变化趋势的基本问题尚缺少系统研究。本项目拟选取嫩江原多年冻土区沼泽湿地为研究对象，采用野外对比观测、径流小区连续观测与模拟实验相结合的研究方法，系统研究多年冻土退化过程中沼泽湿地径流过程变化对DOM输出特征（浓度及化学性质）的影响规律，揭示控制DOM输出规律的水文学机制与物理化学机制的耦合过程及关键影响因子，预测区域沼泽湿地DOM径流输出特征的变化趋势和强度，为精确评价冻土退化情势下东北寒区沼泽湿地碳输出趋势和实施区域水资源科学管理提供基础数据和理论支持。

东北嫩江源地区是我国沼泽湿地的重要分布区，多年冻土的存在与沼泽湿地水文过程和碳循环过程密切相关。目前，气候变暖已导致该地区多年冻土大面积退化，而沼泽湿地的地表径流特征将发生怎样变化？径流过程与沼泽湿地溶解性有机质（DOM）输出过程如何影响DOM的输出特征？这些涉及到多年冻土区沼泽变化趋势的基本问题尚无法回答。本项目选取嫩江原多年冻土区沼泽湿地为研究对象，系统研究多年冻土退化过程中沼泽湿地径流过程变化对DOM输出特征的影响规律，揭示控制DOM输出规律的水文学机制与物理化学机制的耦合过程及关键影响因子，预测区域沼泽湿地DOM径流输出特征的变化趋势和强度，为精确评价冻土退化情势下东北寒区沼泽湿地碳输出趋势提供基础数据支持。通过4年的研究，得出以下主要结论：.1）冻土退化导致的活动层融深增加，增大了洪峰径流与枯水期基流中DOM浓度和化学性质差异，但对洪峰期径流影响较小，对枯水期基流径流量和DOM输出通量影响较大；2）估算了嫩江源小流域湿地径流输出DOM通量，生长季内流域DOC和TDC（溶解性总碳）平局浓度为9.64mg/L和14.86 mg/L，TDC输出通量平均为16781t，湿地面积所占流域面积比例是决定TDC输出通量的重要因素；3）DOC与DIC（溶解性无机碳）的来源与径流输出过程具有显著差异，DOC和DIC主要来源与上层有机土壤和下层矿质土壤，其浓度与径流量成显著正相关和指数相关关系，下层土壤在退水过程对DIC贡献显著；4）温度增加导致的小流域季节性水文格局和溶解性碳氮输出通量的季节性规律发生变化，春季融雪径流通量显著增加、夏季洪峰径流通量降低；5）冻土区流域DOC输出浓度随年均温度和冻土活动层深度的增加呈现指数下降的趋势，而DIC浓度却随温度和活动层深度的增加呈现升高的趋势，说明区域尺度上长期冻土退化过程将导致径流输出的DOM浓度降低，溶解性无机组分浓度将逐渐增加。