兴凯湖退耕还湿地碳固持效应及其再湿响应机理研究

It is one of the key scientific issues on carbon sequestration effect and the mechanism responding to rewetting environment in returning paddy fields to marshlands for understanding of ecosystem function evolution with wetland restoration accurately. It will be clarified clearly on micro and ecosystem scales in our research. It takes the returning paddy fields to marshlands and the adjacent natural marshlands by the lakeside of Xingkai Lake as the research plots. It designs the in-situ observations in fields and microcosm simulated experiments, meanwhile, takes advantages of technologies such as solid-state nuclear magnetic resonance spectroscopy and isotope tracer in soil organic carbon. It reveals the profile difference of the soil total organic carbon and the carbon fractions sensitive to the environmental changes on micro scale, and then clarifies the relationship between molecular characteristics of soil carbon and turnover time. It will indicate the carbon sequestration effect in returning paddy fields to marshlands on ecosystem scale by carbon sequestration and emission from soil and plants, including plant biomass inputs, litter decomposition, greenhouse gases emission, soil organic carbon density and so on in different periods. The rewetting scenarios in horizontal or vertical directions will be designed in fields or stimulated experiment in our experimental building such as soil moisture gradient and dry-wet alternation, nutrient inputs of agricultural drainage or water supply from lake, and rainfall-slope control device. Thus it reveals the mechanism of carbon sequestration responding to rewetting environment from soil microbial community composition and function under rewetting scenarios. The results will have certain scientific significance for the formulation of restoration strategy on returning paddy fields to wetlands.

从微观-生态系统尺度阐明退耕还湿地碳固持效应及其对不同再湿情境的响应机理是准确认识湿地恢复进程中生态系统功能演变的关键科学问题之一。本项目选择黑龙江省兴凯湖小湖西侧的退耕还湿地及邻近自然沼泽湿地，结合野外原位控制实验、室内微宇宙模拟实验，利用固态核磁共振光谱及碳同位素等技术。明确微观尺度上退耕还湿地土壤有机碳环境敏感性指标，进而阐明土壤有机碳分子结构特征与其周转时间的关系；基于野外不同退耕还湿年限植物生物量及枯落物分解、温室气体排放通量和土壤有机碳密度等分析系统碳固定与排放，明确生态系统尺度上退耕还湿地碳固持效应；通过野外实验与室内模拟设置水平或垂向的再湿情境：土壤水分梯度与干湿交替、灌溉退水养分输入或湖水补给、降雨-坡面控制，解析退耕还湿地土壤微生物群落组成和功能，进而揭示退耕还湿地碳输入、输出的再湿响应机理。对于退耕还湿地恢复策略的制定具有一定的科学指示意义。

人类不合理利用导致自然湿地结构破坏、脆弱性加剧，湿地生物地球化学和生态功能衰退、减弱。湿地恢复过程中土壤有机碳库的恢复既是湿地生态功能恢复的重要内容，又是其重要指标。揭示退耕还湿过程中碳固持能力及其变化是目前陆地碳循环研究中的热点与难点问题之一，其消长动态及再湿响应机理也亟待明确。面向这一重要科学问题，本项目以典型退耕还湿地为研究对象，针对湿地水文情势是湿地生态系统区别于其他陆地生态系统的重要特征，本项目阐明了恒定水位与水位周期性波动对不同年份退耕还湿地和自然湿地（对照）温室气体排放的影响及其全球增温潜势的响应；明确了枯落物添加对退耕还湿地和自然湿地温室气体排放的影响及其全球增温潜势差异性；揭示了不同氮沉降梯度下不同年份退耕还湿地和自然湿地温室气体排放的差异及其全球增温潜势变化；进而揭示了湿地开垦对沼泽湿地系统碳固持的影响。本项目从水文-植物-土壤关键地理要素出发，揭示退耕还湿地碳固持效应及其再湿响应机理，对深入理解生态系统恢复过程中的生态功能动态至关重要，也可从机理上为制定退耕还湿地的恢复策略提供科学依据。项目负责人作为第一完成人获吉林省自然科学奖二等奖1项，较好地完成了项目研究任务和成果目标。