人类活动影响的温带森林土壤温室气体排放潜力

CH4 and N2O are the most important greenhouse gas just second to CO2. They are indispensable components of the national greenhouse gas emission budget, also are the main target of greenhouse gas emission reduction.. Nation key ecological projects like reforestation on farmland significantly changed the area and structure of the forests in NorthEast of China. The forest entered into the recovery stage. This will help China to slow down the increasing serious pressure of nonCO2 greenhouse gas emission. Related data and knowledge will help China to meet challenge in climate changes.. Taking the temperate forest in NorthEast of China as the object, This project through the time sequence plot method to establish forest restoration (or development) sequence, by fusion of continuous field measurement, experiment and the process models, to study emission rate and potential of CH4 and N2O of forest influenced by typical human activities. to explore the influence of forest restoration on emission of CH4 and N2o and the mechanisms behind; to construct a process-based CH4 and N2O emission model for temperate forests; to establish a new method for quantitative assessment of the CH4 and N2O emissions in managed forest. The output will help to reduce uncertainties of the greenhouse gas emissions evaluation at large scale and to provide the scientific reference for the nation policy for mitigation of climate change..

CH4和N2O是仅次于CO2的大气温室气体,是温室气体国家排放清单不可或缺的组分和温室气体减排的主要对象。土地利用/覆被变化对温室气体排放有重要影响.退耕还林工程和天然林保护等国家重大生态工程显著改变了东北森林的面积和结构,使其进入恢复性发展阶段,这对减缓我国面临的日益严峻的非CO2温室气体排放压力有显著正面效应,相关数据和知识必对我国应对气候变化有鲜明现实意义.. 本项目以我国温带森林为对象，通过年代序列样地法建立皆伐和退耕还林森林恢复序列，野外连续观测、模拟实验和过程模型相融合,提供典型人类活动影响的不同恢复（或发育）阶段森林CH4和N2O排放速率与潜力,系统探讨森林恢复对CH4和N2O排放影响与机制,构建温带森林CH4和N2O排放综合模型，建立量化非自然生境条件的森林管理下CH4和N2O排放评估方法,为降低大尺度温室气体排放评估不确定性和制订减缓气候变化的国家政策提供科学依据.

CH4和N2O是仅次于CO2的大气温室气体,是温室气体国家排放清单不可或缺的组分和温室气体减排的主要对象。土地利用/覆被变化对温室气体排放有重要影响.退耕还林工程和天然林保护等国家重大生态工程显著改变了东北森林的面积和结构,使其进入恢复性发展阶段,这对减缓我国面临的日益严峻的非CO2温室气体排放压力有显著正面效应,相关数据和知识必对我国应对气候变化有鲜明现实意义。.本项目以我国温带森林为对象，在长白山自然保护区和帽儿山自然保护区通过年代序列样地法建立了3个皆伐和退耕还林森林恢复序列，共计63个样点。连续三年野外原位观测CH4和N2O排放通量探索森林复过程土壤CH4和N2O排放速率与主要调控因子。15N标记室内模拟实验、野外氮添加控制实验和过程模型相融合系统探讨森林恢复对CH4和N2O排放影响机制，数据整合与模型相结合建立了量化非自然生境条件CH4和N2O排放评估方法并评估了排放潜力。研究工作基本按照计划完成。.研究发现（1）土壤温度、pH值和硝酸根离子浓度是影响林地氧化亚氮排放的主要土壤环境因子；土壤温度、pH值和铵根离子浓度是影响甲烷排放的主要土壤环境因子。（2）有机氮直接氧化途径是天然恢复演替序列土壤氧化亚氮排放首要途径，其平均贡献率为35.1~54.5%。有机氮直接氧化途径是退耕还林红松和落叶松发育序列土壤氧化亚氮排放的主要途径，其平均贡献率大于68%。（3）森林恢复可大大降低土壤N2O排放，增强CH4吸收。黑龙江和吉林两省退耕还林森林现实CH4和N2O年排放量分别为-8.48±2.63GgC和7.23±2.12GgN，较无施肥农田CH4和N2O年排放量（分别为6.03±3.07GgC和9.04±2.89GgN）分别下降了171%和20%。如果以原始森林为参照，其CH4和N2O年排放量分别为-30.13±1.88GgC和3.01±0.65GgN，N2O年排放量可下降58%，CH4汇强度可增加255%。黑龙江和吉林两省天然次生林CH4和N2O现实年排放量分别为-123.84±30.95GgC和20.64±7.99GgN，如果以原始森林为参照，若干年后其甲烷汇强度有望增加67%，达到-206.40±51.59GgC,而氧化亚氮排放将下降30%，达到14.45±5.59GgN。.本项目共发表论文24篇，培养研究生13人，三人次获得国家自然科学基金青年项目资助。